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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull performance events updates from Ingo Molnar:
"Core perf code updates:
- Convert mmap() related reference counts to refcount_t. This is in
reaction to the recently fixed refcount bugs, which could have been
detected earlier and could have mitigated the bug somewhat (Thomas
Gleixner, Peter Zijlstra)
- Clean up and simplify the callchain code, in preparation for
sframes (Steven Rostedt, Josh Poimboeuf)
Uprobes updates:
- Add support to optimize usdt probes on x86-64, which gives a
substantial speedup (Jiri Olsa)
- Cleanups and fixes on x86 (Peter Zijlstra)
PMU driver updates:
- Various optimizations and fixes to the Intel PMU driver (Dapeng Mi)
Misc cleanups and fixes:
- Remove redundant __GFP_NOWARN (Qianfeng Rong)"
* tag 'perf-core-2025-09-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (57 commits)
selftests/bpf: Fix uprobe_sigill test for uprobe syscall error value
uprobes/x86: Return error from uprobe syscall when not called from trampoline
perf: Skip user unwind if the task is a kernel thread
perf: Simplify get_perf_callchain() user logic
perf: Use current->flags & PF_KTHREAD|PF_USER_WORKER instead of current->mm == NULL
perf: Have get_perf_callchain() return NULL if crosstask and user are set
perf: Remove get_perf_callchain() init_nr argument
perf/x86: Print PMU counters bitmap in x86_pmu_show_pmu_cap()
perf/x86/intel: Add ICL_FIXED_0_ADAPTIVE bit into INTEL_FIXED_BITS_MASK
perf/x86/intel: Change macro GLOBAL_CTRL_EN_PERF_METRICS to BIT_ULL(48)
perf/x86: Add PERF_CAP_PEBS_TIMING_INFO flag
perf/x86/intel: Fix IA32_PMC_x_CFG_B MSRs access error
perf/x86/intel: Use early_initcall() to hook bts_init()
uprobes: Remove redundant __GFP_NOWARN
selftests/seccomp: validate uprobe syscall passes through seccomp
seccomp: passthrough uprobe systemcall without filtering
selftests/bpf: Fix uprobe syscall shadow stack test
selftests/bpf: Change test_uretprobe_regs_change for uprobe and uretprobe
selftests/bpf: Add uprobe_regs_equal test
selftests/bpf: Add optimized usdt variant for basic usdt test
...
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With the introduction of clone3 in commit 7f192e3cd316 ("fork: add
clone3") the effective bit width of clone_flags on all architectures was
increased from 32-bit to 64-bit, with a new type of u64 for the flags.
However, for most consumers of clone_flags the interface was not
changed from the previous type of unsigned long.
While this works fine as long as none of the new 64-bit flag bits
(CLONE_CLEAR_SIGHAND and CLONE_INTO_CGROUP) are evaluated, this is still
undesirable in terms of the principle of least surprise.
Thus, this commit fixes all relevant interfaces of callees to
sys_clone3/copy_process (excluding the architecture-specific
copy_thread) to consistently pass clone_flags as u64, so that
no truncation to 32-bit integers occurs on 32-bit architectures.
Signed-off-by: Simon Schuster <schuster.simon@siemens-energy.com>
Link: https://lore.kernel.org/20250901-nios2-implement-clone3-v2-2-53fcf5577d57@siemens-energy.com
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Putting together all the previously added pieces to support optimized
uprobes on top of 5-byte nop instruction.
The current uprobe execution goes through following:
- installs breakpoint instruction over original instruction
- exception handler hit and calls related uprobe consumers
- and either simulates original instruction or does out of line single step
execution of it
- returns to user space
The optimized uprobe path does following:
- checks the original instruction is 5-byte nop (plus other checks)
- adds (or uses existing) user space trampoline with uprobe syscall
- overwrites original instruction (5-byte nop) with call to user space
trampoline
- the user space trampoline executes uprobe syscall that calls related uprobe
consumers
- trampoline returns back to next instruction
This approach won't speed up all uprobes as it's limited to using nop5 as
original instruction, but we plan to use nop5 as USDT probe instruction
(which currently uses single byte nop) and speed up the USDT probes.
The arch_uprobe_optimize triggers the uprobe optimization and is called after
first uprobe hit. I originally had it called on uprobe installation but then
it clashed with elf loader, because the user space trampoline was added in a
place where loader might need to put elf segments, so I decided to do it after
first uprobe hit when loading is done.
The uprobe is un-optimized in arch specific set_orig_insn call.
The instruction overwrite is x86 arch specific and needs to go through 3 updates:
(on top of nop5 instruction)
- write int3 into 1st byte
- write last 4 bytes of the call instruction
- update the call instruction opcode
And cleanup goes though similar reverse stages:
- overwrite call opcode with breakpoint (int3)
- write last 4 bytes of the nop5 instruction
- write the nop5 first instruction byte
We do not unmap and release uprobe trampoline when it's no longer needed,
because there's no easy way to make sure none of the threads is still
inside the trampoline. But we do not waste memory, because there's just
single page for all the uprobe trampoline mappings.
We do waste frame on page mapping for every 4GB by keeping the uprobe
trampoline page mapped, but that seems ok.
We take the benefit from the fact that set_swbp and set_orig_insn are
called under mmap_write_lock(mm), so we can use the current instruction
as the state the uprobe is in - nop5/breakpoint/call trampoline -
and decide the needed action (optimize/un-optimize) based on that.
Attaching the speed up from benchs/run_bench_uprobes.sh script:
current:
usermode-count : 152.604 ± 0.044M/s
syscall-count : 13.359 ± 0.042M/s
--> uprobe-nop : 3.229 ± 0.002M/s
uprobe-push : 3.086 ± 0.004M/s
uprobe-ret : 1.114 ± 0.004M/s
uprobe-nop5 : 1.121 ± 0.005M/s
uretprobe-nop : 2.145 ± 0.002M/s
uretprobe-push : 2.070 ± 0.001M/s
uretprobe-ret : 0.931 ± 0.001M/s
uretprobe-nop5 : 0.957 ± 0.001M/s
after the change:
usermode-count : 152.448 ± 0.244M/s
syscall-count : 14.321 ± 0.059M/s
uprobe-nop : 3.148 ± 0.007M/s
uprobe-push : 2.976 ± 0.004M/s
uprobe-ret : 1.068 ± 0.003M/s
--> uprobe-nop5 : 7.038 ± 0.007M/s
uretprobe-nop : 2.109 ± 0.004M/s
uretprobe-push : 2.035 ± 0.001M/s
uretprobe-ret : 0.908 ± 0.001M/s
uretprobe-nop5 : 3.377 ± 0.009M/s
I see bit more speed up on Intel (above) compared to AMD. The big nop5
speed up is partly due to emulating nop5 and partly due to optimization.
The key speed up we do this for is the USDT switch from nop to nop5:
uprobe-nop : 3.148 ± 0.007M/s
uprobe-nop5 : 7.038 ± 0.007M/s
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20250720112133.244369-11-jolsa@kernel.org
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Adding new uprobe syscall that calls uprobe handlers for given
'breakpoint' address.
The idea is that the 'breakpoint' address calls the user space
trampoline which executes the uprobe syscall.
The syscall handler reads the return address of the initial call
to retrieve the original 'breakpoint' address. With this address
we find the related uprobe object and call its consumers.
Adding the arch_uprobe_trampoline_mapping function that provides
uprobe trampoline mapping. This mapping is backed with one global
page initialized at __init time and shared by the all the mapping
instances.
We do not allow to execute uprobe syscall if the caller is not
from uprobe trampoline mapping.
The uprobe syscall ensures the consumer (bpf program) sees registers
values in the state before the trampoline was called.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20250720112133.244369-10-jolsa@kernel.org
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Adding support to add special mapping for user space trampoline with
following functions:
uprobe_trampoline_get - find or add uprobe_trampoline
uprobe_trampoline_put - remove or destroy uprobe_trampoline
The user space trampoline is exported as arch specific user space special
mapping through tramp_mapping, which is initialized in following changes
with new uprobe syscall.
The uprobe trampoline needs to be callable/reachable from the probed address,
so while searching for available address we use is_reachable_by_call function
to decide if the uprobe trampoline is callable from the probe address.
All uprobe_trampoline objects are stored in uprobes_state object and are
cleaned up when the process mm_struct goes down. Adding new arch hooks
for that, because this change is x86_64 specific.
Locking is provided by callers in following changes.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20250720112133.244369-9-jolsa@kernel.org
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Making update_ref_ctr call in uprobe_write conditional based
on do_ref_ctr argument. This way we can use uprobe_write for
instruction update without doing ref_ctr_offset update.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250720112133.244369-8-jolsa@kernel.org
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The uprobe_write has special path to restore the original page when we
write original instruction back. This happens when uprobe_write detects
that we want to write anything else but breakpoint instruction.
Moving the detection away and passing it to uprobe_write as argument,
so it's possible to write different instructions (other than just
breakpoint and rest).
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250720112133.244369-7-jolsa@kernel.org
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Adding nbytes argument to uprobe_write and related functions as
preparation for writing whole instructions in following changes.
Also renaming opcode arguments to insn, which seems to fit better.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250720112133.244369-6-jolsa@kernel.org
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Adding uprobe_write function that does what uprobe_write_opcode did
so far, but allows to pass verify callback function that checks the
memory location before writing the opcode.
It will be used in following changes to implement specific checking
logic for instruction update.
The uprobe_write_opcode now calls uprobe_write with verify_opcode as
the verify callback.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250720112133.244369-5-jolsa@kernel.org
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Making copy_from_page global and adding uprobe prefix.
Adding the uprobe prefix to copy_to_page as well for symmetry.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250720112133.244369-4-jolsa@kernel.org
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We are about to add uprobe trampoline, so cleaning up the namespace.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250720112133.244369-3-jolsa@kernel.org
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uprobe_write_opcode()
We already have the VMA, no need to look it up using
get_user_page_vma_remote(). We can now switch to get_user_pages_remote().
Link: https://lkml.kernel.org/r/20250321113713.204682-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <olsajiri@gmail.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Namhyung kim <namhyung@kernel.org>
Cc: Russel King <linux@armlinux.org.uk>
Cc: tongtiangen <tongtiangen@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Jann reported a possible issue when trampoline_check_ip returns
address near the bottom of the address space that is allowed to
call into the syscall if uretprobes are not set up:
https://lore.kernel.org/bpf/202502081235.5A6F352985@keescook/T/#m9d416df341b8fbc11737dacbcd29f0054413cbbf
Though the mmap minimum address restrictions will typically prevent
creating mappings there, let's make sure uretprobe syscall checks
for that.
Fixes: ff474a78cef5 ("uprobe: Add uretprobe syscall to speed up return probe")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250212220433.3624297-1-jolsa@kernel.org
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This patch introduces a flag to track TIF_SIGPENDING is suppress
temporarily during the uprobe single-step. Upon uprobe singlestep is
handled and the flag is confirmed, it could resume the TIF_SIGPENDING
directly without acquiring the siglock in most case, then reducing
contention and improving overall performance.
I've use the script developed by Andrii in [1] to run benchmark. The CPU
used was Kunpeng916 (Hi1616), 4 NUMA nodes, 64 cores@2.4GHz running the
kernel on next tree + the optimization for get_xol_insn_slot() [2].
before-opt
----------
uprobe-nop ( 1 cpus): 0.907 ± 0.003M/s ( 0.907M/s/cpu)
uprobe-nop ( 2 cpus): 1.676 ± 0.008M/s ( 0.838M/s/cpu)
uprobe-nop ( 4 cpus): 3.210 ± 0.003M/s ( 0.802M/s/cpu)
uprobe-nop ( 8 cpus): 4.457 ± 0.003M/s ( 0.557M/s/cpu)
uprobe-nop (16 cpus): 3.724 ± 0.011M/s ( 0.233M/s/cpu)
uprobe-nop (32 cpus): 2.761 ± 0.003M/s ( 0.086M/s/cpu)
uprobe-nop (64 cpus): 1.293 ± 0.015M/s ( 0.020M/s/cpu)
uprobe-push ( 1 cpus): 0.883 ± 0.001M/s ( 0.883M/s/cpu)
uprobe-push ( 2 cpus): 1.642 ± 0.005M/s ( 0.821M/s/cpu)
uprobe-push ( 4 cpus): 3.086 ± 0.002M/s ( 0.771M/s/cpu)
uprobe-push ( 8 cpus): 3.390 ± 0.003M/s ( 0.424M/s/cpu)
uprobe-push (16 cpus): 2.652 ± 0.005M/s ( 0.166M/s/cpu)
uprobe-push (32 cpus): 2.713 ± 0.005M/s ( 0.085M/s/cpu)
uprobe-push (64 cpus): 1.313 ± 0.009M/s ( 0.021M/s/cpu)
uprobe-ret ( 1 cpus): 1.774 ± 0.000M/s ( 1.774M/s/cpu)
uprobe-ret ( 2 cpus): 3.350 ± 0.001M/s ( 1.675M/s/cpu)
uprobe-ret ( 4 cpus): 6.604 ± 0.000M/s ( 1.651M/s/cpu)
uprobe-ret ( 8 cpus): 6.706 ± 0.005M/s ( 0.838M/s/cpu)
uprobe-ret (16 cpus): 5.231 ± 0.001M/s ( 0.327M/s/cpu)
uprobe-ret (32 cpus): 5.743 ± 0.003M/s ( 0.179M/s/cpu)
uprobe-ret (64 cpus): 4.726 ± 0.016M/s ( 0.074M/s/cpu)
after-opt
---------
uprobe-nop ( 1 cpus): 0.985 ± 0.002M/s ( 0.985M/s/cpu)
uprobe-nop ( 2 cpus): 1.773 ± 0.005M/s ( 0.887M/s/cpu)
uprobe-nop ( 4 cpus): 3.304 ± 0.001M/s ( 0.826M/s/cpu)
uprobe-nop ( 8 cpus): 5.328 ± 0.002M/s ( 0.666M/s/cpu)
uprobe-nop (16 cpus): 6.475 ± 0.002M/s ( 0.405M/s/cpu)
uprobe-nop (32 cpus): 4.831 ± 0.082M/s ( 0.151M/s/cpu)
uprobe-nop (64 cpus): 2.564 ± 0.053M/s ( 0.040M/s/cpu)
uprobe-push ( 1 cpus): 0.964 ± 0.001M/s ( 0.964M/s/cpu)
uprobe-push ( 2 cpus): 1.766 ± 0.002M/s ( 0.883M/s/cpu)
uprobe-push ( 4 cpus): 3.290 ± 0.009M/s ( 0.823M/s/cpu)
uprobe-push ( 8 cpus): 4.670 ± 0.002M/s ( 0.584M/s/cpu)
uprobe-push (16 cpus): 5.197 ± 0.004M/s ( 0.325M/s/cpu)
uprobe-push (32 cpus): 5.068 ± 0.161M/s ( 0.158M/s/cpu)
uprobe-push (64 cpus): 2.605 ± 0.026M/s ( 0.041M/s/cpu)
uprobe-ret ( 1 cpus): 1.833 ± 0.001M/s ( 1.833M/s/cpu)
uprobe-ret ( 2 cpus): 3.384 ± 0.003M/s ( 1.692M/s/cpu)
uprobe-ret ( 4 cpus): 6.677 ± 0.004M/s ( 1.669M/s/cpu)
uprobe-ret ( 8 cpus): 6.854 ± 0.005M/s ( 0.857M/s/cpu)
uprobe-ret (16 cpus): 6.508 ± 0.006M/s ( 0.407M/s/cpu)
uprobe-ret (32 cpus): 5.793 ± 0.009M/s ( 0.181M/s/cpu)
uprobe-ret (64 cpus): 4.743 ± 0.016M/s ( 0.074M/s/cpu)
Above benchmark results demonstrates a obivious improvement in the
scalability of trig-uprobe-nop and trig-uprobe-push, the peak throughput
of which are from 4.5M/s to 6.4M/s and 3.3M/s to 5.1M/s individually.
[1] https://lore.kernel.org/all/20240731214256.3588718-1-andrii@kernel.org
[2] https://lore.kernel.org/all/20240727094405.1362496-1-liaochang1@huawei.com
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Liao Chang <liaochang1@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250124093826.2123675-3-liaochang1@huawei.com
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Instead of constantly allocating and freeing very short-lived
struct return_instance, reuse it as much as possible within current
task. For that, store a linked list of reusable return_instances within
current->utask.
The only complication is that ri_timer() might be still processing such
return_instance. And so while the main uretprobe processing logic might
be already done with return_instance and would be OK to immediately
reuse it for the next uretprobe instance, it's not correct to
unconditionally reuse it just like that.
Instead we make sure that ri_timer() can't possibly be processing it by
using seqcount_t, with ri_timer() being "a writer", while
free_ret_instance() being "a reader". If, after we unlink return
instance from utask->return_instances list, we know that ri_timer()
hasn't gotten to processing utask->return_instances yet, then we can be
sure that immediate return_instance reuse is OK, and so we put it
onto utask->ri_pool for future (potentially, almost immediate) reuse.
This change shows improvements both in single CPU performance (by
avoiding relatively expensive kmalloc/free combon) and in terms of
multi-CPU scalability, where you can see that per-CPU throughput doesn't
decline as steeply with increased number of CPUs (which were previously
attributed to kmalloc()/free() through profiling):
BASELINE (latest perf/core)
===========================
uretprobe-nop ( 1 cpus): 1.898 ± 0.002M/s ( 1.898M/s/cpu)
uretprobe-nop ( 2 cpus): 3.574 ± 0.011M/s ( 1.787M/s/cpu)
uretprobe-nop ( 3 cpus): 5.279 ± 0.066M/s ( 1.760M/s/cpu)
uretprobe-nop ( 4 cpus): 6.824 ± 0.047M/s ( 1.706M/s/cpu)
uretprobe-nop ( 5 cpus): 8.339 ± 0.060M/s ( 1.668M/s/cpu)
uretprobe-nop ( 6 cpus): 9.812 ± 0.047M/s ( 1.635M/s/cpu)
uretprobe-nop ( 7 cpus): 11.030 ± 0.048M/s ( 1.576M/s/cpu)
uretprobe-nop ( 8 cpus): 12.453 ± 0.126M/s ( 1.557M/s/cpu)
uretprobe-nop (10 cpus): 14.838 ± 0.044M/s ( 1.484M/s/cpu)
uretprobe-nop (12 cpus): 17.092 ± 0.115M/s ( 1.424M/s/cpu)
uretprobe-nop (14 cpus): 19.576 ± 0.022M/s ( 1.398M/s/cpu)
uretprobe-nop (16 cpus): 22.264 ± 0.015M/s ( 1.391M/s/cpu)
uretprobe-nop (24 cpus): 33.534 ± 0.078M/s ( 1.397M/s/cpu)
uretprobe-nop (32 cpus): 43.262 ± 0.127M/s ( 1.352M/s/cpu)
uretprobe-nop (40 cpus): 53.252 ± 0.080M/s ( 1.331M/s/cpu)
uretprobe-nop (48 cpus): 55.778 ± 0.045M/s ( 1.162M/s/cpu)
uretprobe-nop (56 cpus): 56.850 ± 0.227M/s ( 1.015M/s/cpu)
uretprobe-nop (64 cpus): 62.005 ± 0.077M/s ( 0.969M/s/cpu)
uretprobe-nop (72 cpus): 66.445 ± 0.236M/s ( 0.923M/s/cpu)
uretprobe-nop (80 cpus): 68.353 ± 0.180M/s ( 0.854M/s/cpu)
THIS PATCHSET (on top of latest perf/core)
==========================================
uretprobe-nop ( 1 cpus): 2.253 ± 0.004M/s ( 2.253M/s/cpu)
uretprobe-nop ( 2 cpus): 4.281 ± 0.003M/s ( 2.140M/s/cpu)
uretprobe-nop ( 3 cpus): 6.389 ± 0.027M/s ( 2.130M/s/cpu)
uretprobe-nop ( 4 cpus): 8.328 ± 0.005M/s ( 2.082M/s/cpu)
uretprobe-nop ( 5 cpus): 10.353 ± 0.001M/s ( 2.071M/s/cpu)
uretprobe-nop ( 6 cpus): 12.513 ± 0.010M/s ( 2.086M/s/cpu)
uretprobe-nop ( 7 cpus): 14.525 ± 0.017M/s ( 2.075M/s/cpu)
uretprobe-nop ( 8 cpus): 15.633 ± 0.013M/s ( 1.954M/s/cpu)
uretprobe-nop (10 cpus): 19.532 ± 0.011M/s ( 1.953M/s/cpu)
uretprobe-nop (12 cpus): 21.405 ± 0.009M/s ( 1.784M/s/cpu)
uretprobe-nop (14 cpus): 24.857 ± 0.020M/s ( 1.776M/s/cpu)
uretprobe-nop (16 cpus): 26.466 ± 0.018M/s ( 1.654M/s/cpu)
uretprobe-nop (24 cpus): 40.513 ± 0.222M/s ( 1.688M/s/cpu)
uretprobe-nop (32 cpus): 54.180 ± 0.074M/s ( 1.693M/s/cpu)
uretprobe-nop (40 cpus): 66.100 ± 0.082M/s ( 1.652M/s/cpu)
uretprobe-nop (48 cpus): 70.544 ± 0.068M/s ( 1.470M/s/cpu)
uretprobe-nop (56 cpus): 74.494 ± 0.055M/s ( 1.330M/s/cpu)
uretprobe-nop (64 cpus): 79.317 ± 0.029M/s ( 1.239M/s/cpu)
uretprobe-nop (72 cpus): 84.875 ± 0.020M/s ( 1.179M/s/cpu)
uretprobe-nop (80 cpus): 92.318 ± 0.224M/s ( 1.154M/s/cpu)
For reference, with uprobe-nop we hit the following throughput:
uprobe-nop (80 cpus): 143.485 ± 0.035M/s ( 1.794M/s/cpu)
So now uretprobe stays a bit closer to that performance.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20241206002417.3295533-5-andrii@kernel.org
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In practice, each return_instance will typically contain either zero or
one return_consumer, depending on whether it has any uprobe session
consumer attached or not. It's highly unlikely that more than one uprobe
session consumers will be attached to any given uprobe, so there is no
need to optimize for that case. But the way we currently do memory
allocation and accounting is by pre-allocating the space for 4 session
consumers in contiguous block of memory next to struct return_instance
fixed part. This is unnecessarily wasteful.
This patch changes this to keep struct return_instance fixed-sized with one
pre-allocated return_consumer, while (in a highly unlikely scenario)
allowing for more session consumers in a separate dynamically
allocated and reallocated array.
We also simplify accounting a bit by not maintaining a separate
temporary capacity for consumers array, and, instead, relying on
krealloc() to be a no-op if underlying memory can accommodate a slightly
bigger allocation (but again, it's very uncommon scenario to even have
to do this reallocation).
All this gets rid of ri_size(), simplifies push_consumer() and removes
confusing ri->consumers_cnt re-assignment, while containing this
singular preallocated consumer logic contained within a few simple
preexisting helpers.
Having fixed-sized struct return_instance simplifies and speeds up
return_instance reuse that we ultimately add later in this patch set,
see follow up patches.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20241206002417.3295533-2-andrii@kernel.org
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|
On x86_64, with allmodconfig, struct uprobe_task is 72 bytes long, with a
hole and some padding.
/* size: 72, cachelines: 2, members: 7 */
/* sum members: 64, holes: 1, sum holes: 4 */
/* padding: 4 */
/* forced alignments: 1, forced holes: 1, sum forced holes: 4 */
/* last cacheline: 8 bytes */
Reorder the structure to fill the hole and avoid the padding.
This way, the whole structure fits in a single cacheline and some memory is
saved when it is allocated.
/* size: 64, cachelines: 1, members: 7 */
/* forced alignments: 1 */
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/a9f541d0cedf421f765c77a1fb93d6a979778a88.1730495562.git.christophe.jaillet@wanadoo.fr
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Avoid taking refcount on uprobe in prepare_uretprobe(), instead take
uretprobe-specific SRCU lock and keep it active as kernel transfers
control back to user space.
Given we can't rely on user space returning from traced function within
reasonable time period, we need to make sure not to keep SRCU lock
active for too long, though. To that effect, we employ a timer callback
which is meant to terminate SRCU lock region after predefined timeout
(currently set to 100ms), and instead transfer underlying struct
uprobe's lifetime protection to refcounting.
This fallback to less scalable refcounting after 100ms is a fine
tradeoff from uretprobe's scalability and performance perspective,
because uretprobing *long running* user functions inherently doesn't run
into scalability issues (there is just not enough frequency to cause
noticeable issues with either performance or scalability).
The overall trick is in ensuring synchronization between current thread
and timer's callback fired on some other thread. To cope with that with
minimal logic complications, we add hprobe wrapper which is used to
contain all the synchronization related issues behind a small number of
basic helpers: hprobe_expire() for "downgrading" uprobe from SRCU-protected
state to refcounted state, and a hprobe_consume() and hprobe_finalize()
pair of single-use consuming helpers. Other than that, whatever current
thread's logic is there stays the same, as timer thread cannot modify
return_instance state (or add new/remove old return_instances). It only
takes care of SRCU unlock and uprobe refcounting, which is hidden from
the higher-level uretprobe handling logic.
We use atomic xchg() in hprobe_consume(), which is called from
performance critical handle_uretprobe_chain() function run in the
current context. When uncontended, this xchg() doesn't seem to hurt
performance as there are no other competing CPUs fighting for the same
cache line. We also mark struct return_instance as ____cacheline_aligned
to ensure no false sharing can happen.
Another technical moment. We need to make sure that the list of return
instances can be safely traversed under RCU from timer callback, so we
delay return_instance freeing with kfree_rcu() and make sure that list
modifications use RCU-aware operations.
Also, given SRCU lock survives transition from kernel to user space and
back we need to use lower-level __srcu_read_lock() and
__srcu_read_unlock() to avoid lockdep complaining.
Just to give an impression of a kind of performance improvements this
change brings, below are benchmarking results with and without these
SRCU changes, assuming other uprobe optimizations (mainly RCU Tasks
Trace for entry uprobes, lockless RB-tree lookup, and lockless VMA to
uprobe lookup) are left intact:
WITHOUT SRCU for uretprobes
===========================
uretprobe-nop ( 1 cpus): 2.197 ± 0.002M/s ( 2.197M/s/cpu)
uretprobe-nop ( 2 cpus): 3.325 ± 0.001M/s ( 1.662M/s/cpu)
uretprobe-nop ( 3 cpus): 4.129 ± 0.002M/s ( 1.376M/s/cpu)
uretprobe-nop ( 4 cpus): 6.180 ± 0.003M/s ( 1.545M/s/cpu)
uretprobe-nop ( 8 cpus): 7.323 ± 0.005M/s ( 0.915M/s/cpu)
uretprobe-nop (16 cpus): 6.943 ± 0.005M/s ( 0.434M/s/cpu)
uretprobe-nop (32 cpus): 5.931 ± 0.014M/s ( 0.185M/s/cpu)
uretprobe-nop (64 cpus): 5.145 ± 0.003M/s ( 0.080M/s/cpu)
uretprobe-nop (80 cpus): 4.925 ± 0.005M/s ( 0.062M/s/cpu)
WITH SRCU for uretprobes
========================
uretprobe-nop ( 1 cpus): 1.968 ± 0.001M/s ( 1.968M/s/cpu)
uretprobe-nop ( 2 cpus): 3.739 ± 0.003M/s ( 1.869M/s/cpu)
uretprobe-nop ( 3 cpus): 5.616 ± 0.003M/s ( 1.872M/s/cpu)
uretprobe-nop ( 4 cpus): 7.286 ± 0.002M/s ( 1.822M/s/cpu)
uretprobe-nop ( 8 cpus): 13.657 ± 0.007M/s ( 1.707M/s/cpu)
uretprobe-nop (32 cpus): 45.305 ± 0.066M/s ( 1.416M/s/cpu)
uretprobe-nop (64 cpus): 42.390 ± 0.922M/s ( 0.662M/s/cpu)
uretprobe-nop (80 cpus): 47.554 ± 2.411M/s ( 0.594M/s/cpu)
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241024044159.3156646-3-andrii@kernel.org
|
|
This change allows the uprobe consumer to behave as session which
means that 'handler' and 'ret_handler' callbacks are connected in
a way that allows to:
- control execution of 'ret_handler' from 'handler' callback
- share data between 'handler' and 'ret_handler' callbacks
The session concept fits to our common use case where we do filtering
on entry uprobe and based on the result we decide to run the return
uprobe (or not).
It's also convenient to share the data between session callbacks.
To achive this we are adding new return value the uprobe consumer
can return from 'handler' callback:
UPROBE_HANDLER_IGNORE
- Ignore 'ret_handler' callback for this consumer.
And store cookie and pass it to 'ret_handler' when consumer has both
'handler' and 'ret_handler' callbacks defined.
We store shared data in the return_consumer object array as part of
the return_instance object. This way the handle_uretprobe_chain can
find related return_consumer and its shared data.
We also store entry handler return value, for cases when there are
multiple consumers on single uprobe and some of them are ignored and
some of them not, in which case the return probe gets installed and
we need to have a way to find out which consumer needs to be ignored.
The tricky part is when consumer is registered 'after' the uprobe
entry handler is hit. In such case this consumer's 'ret_handler' gets
executed as well, but it won't have the proper data pointer set,
so we can filter it out.
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20241018202252.693462-3-jolsa@kernel.org
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|
Adding data pointer to both entry and exit consumer handlers and all
its users. The functionality itself is coming in following change.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20241018202252.693462-2-jolsa@kernel.org
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|
With uprobe_unregister() having grown a synchronize_srcu(), it becomes
fairly slow to call. Esp. since both users of this API call it in a
loop.
Peel off the sync_srcu() and do it once, after the loop.
We also need to add uprobe_unregister_sync() into uprobe_register()'s
error handling path, as we need to be careful about returning to the
caller before we have a guarantee that partially attached consumer won't
be called anymore. This is an unlikely slow path and this should be
totally fine to be slow in the case of a failed attach.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Co-developed-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20240903174603.3554182-6-andrii@kernel.org
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|
uprobe->register_rwsem is one of a few big bottlenecks to scalability of
uprobes, so we need to get rid of it to improve uprobe performance and
multi-CPU scalability.
First, we turn uprobe's consumer list to a typical doubly-linked list
and utilize existing RCU-aware helpers for traversing such lists, as
well as adding and removing elements from it.
For entry uprobes we already have SRCU protection active since before
uprobe lookup. For uretprobe we keep refcount, guaranteeing that uprobe
won't go away from under us, but we add SRCU protection around consumer
list traversal.
Lastly, to keep handler_chain()'s UPROBE_HANDLER_REMOVE handling simple,
we remember whether any removal was requested during handler calls, but
then we double-check the decision under a proper register_rwsem using
consumers' filter callbacks. Handler removal is very rare, so this extra
lock won't hurt performance, overall, but we also avoid the need for any
extra protection (e.g., seqcount locks).
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20240903174603.3554182-5-andrii@kernel.org
|
|
It serves no purpose beyond adding unnecessray argument passed to the
filter callback. Just get rid of it, no one is actually using it.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20240903174603.3554182-4-andrii@kernel.org
|
|
This way uprobe_unregister() and uprobe_apply() can use "struct uprobe *"
rather than inode + offset. This simplifies the code and allows to avoid
the unnecessary find_uprobe() + put_uprobe() in these functions.
TODO: uprobe_unregister() still needs get_uprobe/put_uprobe to ensure that
this uprobe can't be freed before up_write(&uprobe->register_rwsem).
Co-developed-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20240801132734.GA8803@redhat.com
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It doesn't make any sense to have 2 versions of _register(). Note that
trace_uprobe_enable(), the only user of uprobe_register(), doesn't need
to check tu->ref_ctr_offset to decide which one should be used, it could
safely pass ref_ctr_offset == 0 to uprobe_register_refctr().
Add this argument to uprobe_register(), update the callers, and kill
uprobe_register_refctr().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240801132728.GA8800@redhat.com
|
|
When tracing user functions with uprobe functionality, it's common to
install the probe (e.g., a BPF program) at the first instruction of the
function. This is often going to be `push %rbp` instruction in function
preamble, which means that within that function frame pointer hasn't
been established yet. This leads to consistently missing an actual
caller of the traced function, because perf_callchain_user() only
records current IP (capturing traced function) and then following frame
pointer chain (which would be caller's frame, containing the address of
caller's caller).
So when we have target_1 -> target_2 -> target_3 call chain and we are
tracing an entry to target_3, captured stack trace will report
target_1 -> target_3 call chain, which is wrong and confusing.
This patch proposes a x86-64-specific heuristic to detect `push %rbp`
(`push %ebp` on 32-bit architecture) instruction being traced. Given
entire kernel implementation of user space stack trace capturing works
under assumption that user space code was compiled with frame pointer
register (%rbp/%ebp) preservation, it seems pretty reasonable to use
this instruction as a strong indicator that this is the entry to the
function. In that case, return address is still pointed to by %rsp/%esp,
so we fetch it and add to stack trace before proceeding to unwind the
rest using frame pointer-based logic.
We also check for `endbr64` (for 64-bit modes) as another common pattern
for function entry, as suggested by Josh Poimboeuf. Even if we get this
wrong sometimes for uprobes attached not at the function entry, it's OK
because stack trace will still be overall meaningful, just with one
extra bogus entry. If we don't detect this, we end up with guaranteed to
be missing caller function entry in the stack trace, which is worse
overall.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20240729175223.23914-1-andrii@kernel.org
|
|
Adding uretprobe syscall instead of trap to speed up return probe.
At the moment the uretprobe setup/path is:
- install entry uprobe
- when the uprobe is hit, it overwrites probed function's return address
on stack with address of the trampoline that contains breakpoint
instruction
- the breakpoint trap code handles the uretprobe consumers execution and
jumps back to original return address
This patch replaces the above trampoline's breakpoint instruction with new
ureprobe syscall call. This syscall does exactly the same job as the trap
with some more extra work:
- syscall trampoline must save original value for rax/r11/rcx registers
on stack - rax is set to syscall number and r11/rcx are changed and
used by syscall instruction
- the syscall code reads the original values of those registers and
restore those values in task's pt_regs area
- only caller from trampoline exposed in '[uprobes]' is allowed,
the process will receive SIGILL signal otherwise
Even with some extra work, using the uretprobes syscall shows speed
improvement (compared to using standard breakpoint):
On Intel (11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz)
current:
uretprobe-nop : 1.498 ± 0.000M/s
uretprobe-push : 1.448 ± 0.001M/s
uretprobe-ret : 0.816 ± 0.001M/s
with the fix:
uretprobe-nop : 1.969 ± 0.002M/s < 31% speed up
uretprobe-push : 1.910 ± 0.000M/s < 31% speed up
uretprobe-ret : 0.934 ± 0.000M/s < 14% speed up
On Amd (AMD Ryzen 7 5700U)
current:
uretprobe-nop : 0.778 ± 0.001M/s
uretprobe-push : 0.744 ± 0.001M/s
uretprobe-ret : 0.540 ± 0.001M/s
with the fix:
uretprobe-nop : 0.860 ± 0.001M/s < 10% speed up
uretprobe-push : 0.818 ± 0.001M/s < 10% speed up
uretprobe-ret : 0.578 ± 0.000M/s < 7% speed up
The performance test spawns a thread that runs loop which triggers
uprobe with attached bpf program that increments the counter that
gets printed in results above.
The uprobe (and uretprobe) kind is determined by which instruction
is being patched with breakpoint instruction. That's also important
for uretprobes, because uprobe is installed for each uretprobe.
The performance test is part of bpf selftests:
tools/testing/selftests/bpf/run_bench_uprobes.sh
Note at the moment uretprobe syscall is supported only for native
64-bit process, compat process still uses standard breakpoint.
Note that when shadow stack is enabled the uretprobe syscall returns
via iret, which is slower than return via sysret, but won't cause the
shadow stack violation.
Link: https://lore.kernel.org/all/20240611112158.40795-4-jolsa@kernel.org/
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
|
|
Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version this program is distributed in the
hope that it will be useful but without any warranty without even
the implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details you
should have received a copy of the gnu general public license along
with this program if not write to the free software foundation inc
59 temple place suite 330 boston ma 02111 1307 usa
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 1334 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070033.113240726@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
|
|
In order to have a separate address space for text poking, we need to
duplicate init_mm early during start_kernel(). This, however, introduces
a problem since uprobes functions are called from dup_mmap(), but
uprobes is still not initialized in this early stage.
Since uprobes initialization is necassary for fork, and since all the
dependant initialization has been done when fork is initialized (percpu
and vmalloc), move uprobes initialization to fork_init(). It does not
seem uprobes introduces any security problem for the poking_mm.
Crash and burn if uprobes initialization fails, similarly to other early
initializations. Change the init_probes() name to probes_init() to match
other early initialization functions name convention.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akpm@linux-foundation.org
Cc: ard.biesheuvel@linaro.org
Cc: deneen.t.dock@intel.com
Cc: kernel-hardening@lists.openwall.com
Cc: kristen@linux.intel.com
Cc: linux_dti@icloud.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190426232303.28381-6-nadav.amit@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
Userspace Statically Defined Tracepoints[1] are dtrace style markers
inside userspace applications. Applications like PostgreSQL, MySQL,
Pthread, Perl, Python, Java, Ruby, Node.js, libvirt, QEMU, glib etc
have these markers embedded in them. These markers are added by developer
at important places in the code. Each marker source expands to a single
nop instruction in the compiled code but there may be additional
overhead for computing the marker arguments which expands to couple of
instructions. In case the overhead is more, execution of it can be
omitted by runtime if() condition when no one is tracing on the marker:
if (reference_counter > 0) {
Execute marker instructions;
}
Default value of reference counter is 0. Tracer has to increment the
reference counter before tracing on a marker and decrement it when
done with the tracing.
Implement the reference counter logic in core uprobe. User will be
able to use it from trace_uprobe as well as from kernel module. New
trace_uprobe definition with reference counter will now be:
<path>:<offset>[(ref_ctr_offset)]
where ref_ctr_offset is an optional field. For kernel module, new
variant of uprobe_register() has been introduced:
uprobe_register_refctr(inode, offset, ref_ctr_offset, consumer)
No new variant for uprobe_unregister() because it's assumed to have
only one reference counter for one uprobe.
[1] https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation
Note: 'reference counter' is called as 'semaphore' in original Dtrace
(or Systemtap, bcc and even in ELF) documentation and code. But the
term 'semaphore' is misleading in this context. This is just a counter
used to hold number of tracers tracing on a marker. This is not really
used for any synchronization. So we are calling it a 'reference counter'
in kernel / perf code.
Link: http://lkml.kernel.org/r/20180820044250.11659-2-ravi.bangoria@linux.ibm.com
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
[Only trace_uprobe.c]
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Song Liu <songliubraving@fb.com>
Tested-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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Add addition argument 'arch_uprobe' to uprobe_write_opcode().
We need this in later set of patches.
Link: http://lkml.kernel.org/r/20180809041856.1547-3-ravi.bangoria@linux.ibm.com
Reviewed-by: Song Liu <songliubraving@fb.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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Signed-off-by: Eric Saint Etienne <eric.saint.etienne@oracle.com>
Signed-off-by: Allen Pais <allen.pais@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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There were still a number of references to my old Red Hat email
address in the kernel source. Remove these while keeping the
Red Hat copyright notices intact.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The previous change documents that cleanup_return_instances()
can't always detect the dead frames, the stack can grow. But
there is one special case which imho worth fixing:
arch_uretprobe_is_alive() can return true when the stack didn't
actually grow, but the next "call" insn uses the already
invalidated frame.
Test-case:
#include <stdio.h>
#include <setjmp.h>
jmp_buf jmp;
int nr = 1024;
void func_2(void)
{
if (--nr == 0)
return;
longjmp(jmp, 1);
}
void func_1(void)
{
setjmp(jmp);
func_2();
}
int main(void)
{
func_1();
return 0;
}
If you ret-probe func_1() and func_2() prepare_uretprobe() hits
the MAX_URETPROBE_DEPTH limit and "return" from func_2() is not
reported.
When we know that the new call is not chained, we can do the
more strict check. In this case "sp" points to the new ret-addr,
so every frame which uses the same "sp" must be dead. The only
complication is that arch_uretprobe_is_alive() needs to know was
it chained or not, so we add the new RP_CHECK_CHAIN_CALL enum
and change prepare_uretprobe() to pass RP_CHECK_CALL only if
!chained.
Note: arch_uretprobe_is_alive() could also re-read *sp and check
if this word is still trampoline_vaddr. This could obviously
improve the logic, but I would like to avoid another
copy_from_user() especially in the case when we can't avoid the
false "alive == T" positives.
Tested-by: Pratyush Anand <panand@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Anton Arapov <arapov@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150721134028.GA4786@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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arch/x86 doesn't care (so far), but as Pratyush Anand pointed
out other architectures might want why arch_uretprobe_is_alive()
was called and use different checks depending on the context.
Add the new argument to distinguish 2 callers.
Tested-by: Pratyush Anand <panand@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Anton Arapov <arapov@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150721134026.GA4779@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Add the x86 specific version of arch_uretprobe_is_alive()
helper. It returns true if the stack frame mangled by
prepare_uretprobe() is still on stack. So if it returns false,
we know that the probed function has already returned.
We add the new return_instance->stack member and change the
generic code to initialize it in prepare_uretprobe, but it
should be equally useful for other architectures.
TODO: this assumes that the probed application can't use
multiple stacks (say sigaltstack). We will try to improve
this logic later.
Tested-by: Pratyush Anand <panand@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Anton Arapov <arapov@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150721134018.GA4766@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Add the new "weak" helper, arch_uretprobe_is_alive(), used by
the next patches. It should return true if this return_instance
is still valid. The arch agnostic version just always returns
true.
The patch exports "struct return_instance" for the architectures
which want to override this hook. We can also cleanup
prepare_uretprobe() if we pass the new return_instance to
arch_uretprobe_hijack_return_addr().
Tested-by: Pratyush Anand <panand@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Anton Arapov <arapov@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150721134016.GA4762@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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For the following interfaces:
set_swbp()
set_orig_insn()
is_swbp_insn()
is_trap_insn()
uprobe_get_swbp_addr()
arch_uprobe_ignore()
arch_uprobe_copy_ixol()
kernel/events/uprobes.c provides default definitions explicitly marked
"weak". Some architectures provide their own definitions intended to
override the defaults, but the "weak" attribute on the declarations applied
to the arch definitions as well, so the linker chose one based on link
order (see 10629d711ed7 ("PCI: Remove __weak annotation from
pcibios_get_phb_of_node decl")).
Remove the "weak" attribute from the declarations so we always prefer a
non-weak definition over the weak one, independent of link order.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
CC: Victor Kamensky <victor.kamensky@linaro.org>
CC: Oleg Nesterov <oleg@redhat.com>
CC: David A. Long <dave.long@linaro.org>
CC: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull more perf updates from Ingo Molnar:
"A second round of perf updates:
- wide reaching kprobes sanitization and robustization, with the hope
of fixing all 'probe this function crashes the kernel' bugs, by
Masami Hiramatsu.
- uprobes updates from Oleg Nesterov: tmpfs support, corner case
fixes and robustization work.
- perf tooling updates and fixes from Jiri Olsa, Namhyung Ki, Arnaldo
et al:
* Add support to accumulate hist periods (Namhyung Kim)
* various fixes, refactorings and enhancements"
* 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (101 commits)
perf: Differentiate exec() and non-exec() comm events
perf: Fix perf_event_comm() vs. exec() assumption
uprobes/x86: Rename arch_uprobe->def to ->defparam, minor comment updates
perf/documentation: Add description for conditional branch filter
perf/x86: Add conditional branch filtering support
perf/tool: Add conditional branch filter 'cond' to perf record
perf: Add new conditional branch filter 'PERF_SAMPLE_BRANCH_COND'
uprobes: Teach copy_insn() to support tmpfs
uprobes: Shift ->readpage check from __copy_insn() to uprobe_register()
perf/x86: Use common PMU interrupt disabled code
perf/ARM: Use common PMU interrupt disabled code
perf: Disable sampled events if no PMU interrupt
perf: Fix use after free in perf_remove_from_context()
perf tools: Fix 'make help' message error
perf record: Fix poll return value propagation
perf tools: Move elide bool into perf_hpp_fmt struct
perf tools: Remove elide setup for SORT_MODE__MEMORY mode
perf tools: Fix "==" into "=" in ui_browser__warning assignment
perf tools: Allow overriding sysfs and proc finding with env var
perf tools: Consider header files outside perf directory in tags target
...
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After instruction write into xol area, on ARM V7
architecture code need to flush dcache and icache to sync
them up for given set of addresses. Having just
'flush_dcache_page(page)' call is not enough - it is
possible to have stale instruction sitting in icache
for given xol area slot address.
Introduce arch_uprobe_ixol_copy weak function
that by default calls uprobes copy_to_page function and
than flush_dcache_page function and on ARM define new one
that handles xol slot copy in ARM specific way
flush_uprobe_xol_access function shares/reuses implementation
with/of flush_ptrace_access function and takes care of writing
instruction to user land address space on given variety of
different cache types on ARM CPUs. Because
flush_uprobe_xol_access does not have vma around
flush_ptrace_access was split into two parts. First that
retrieves set of condition from vma and common that receives
those conditions as flags.
Note ARM cache flush function need kernel address
through which instruction write happened, so instead
of using uprobes copy_to_page function changed
code to explicitly map page and do memcpy.
Note arch_uprobe_copy_ixol function, in similar way as
copy_to_user_page function, has preempt_disable/preempt_enable.
Signed-off-by: Victor Kamensky <victor.kamensky@linaro.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: David A. Long <dave.long@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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If the probed insn triggers a trap, ->si_addr = regs->ip is technically
correct, but this is not what the signal handler wants; we need to pass
the address of the probed insn, not the address of xol slot.
Add the new arch-agnostic helper, uprobe_get_trap_addr(), and change
fill_trap_info() and math_error() to use it. !CONFIG_UPROBES case in
uprobes.h uses a macro to avoid include hell and ensure that it can be
compiled even if an architecture doesn't define instruction_pointer().
Test-case:
#include <signal.h>
#include <stdio.h>
#include <unistd.h>
extern void probe_div(void);
void sigh(int sig, siginfo_t *info, void *c)
{
int passed = (info->si_addr == probe_div);
printf(passed ? "PASS\n" : "FAIL\n");
_exit(!passed);
}
int main(void)
{
struct sigaction sa = {
.sa_sigaction = sigh,
.sa_flags = SA_SIGINFO,
};
sigaction(SIGFPE, &sa, NULL);
asm (
"xor %ecx,%ecx\n"
".globl probe_div; probe_div:\n"
"idiv %ecx\n"
);
return 0;
}
it fails if probe_div() is probed.
Note: show_unhandled_signals users should probably use this helper too,
but we need to cleanup them first.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
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Allow arches to decided to ignore a probe hit. ARM will use this to
only call handlers if the conditions to execute a conditionally executed
instruction are satisfied.
Signed-off-by: David A. Long <dave.long@linaro.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
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1. Don't include asm/uprobes.h unconditionally, we only need
it if CONFIG_UPROBES.
2. Move the definition of "struct xol_area" into uprobes.c.
Perhaps we should simply kill struct uprobes_state, it buys
nothing.
3. Kill the dummy definition of uprobe_get_swbp_addr(), nobody
except handle_swbp() needs it.
4. Purely cosmetic, but move the decl of uprobe_get_swbp_addr()
up, close to other __weak helpers.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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uprobe_task->vaddr is a bit strange. The generic code uses it only
to pass the additional argument to arch_uprobe_pre_xol(), and since
it is always equal to instruction_pointer() this looks even more
strange.
And both utask->vaddr and and utask->autask have the same scope,
they only have the meaning when the task executes the probed insn
out-of-line, so it is safe to reuse both in UTASK_RUNNING state.
This all means that logically ->vaddr belongs to arch_uprobe_task
and we should probably move it there, arch_uprobe_pre_xol() can
record instruction_pointer() itself.
OTOH, it is also used by uprobe_copy_process() and dup_xol_work()
for another purpose, this doesn't look clean and doesn't allow to
move this member into arch_uprobe_task.
This patch adds the union with 2 anonymous structs into uprobe_task.
The first struct is autask + vaddr, this way we "almost" move vaddr
into autask.
The second struct has 2 new members for uprobe_copy_process() paths:
->dup_xol_addr which can be used instead ->vaddr, and ->dup_xol_work
which can be used to avoid kmalloc() and simplify the code.
Note that this union will likely have another member(s), we need
something like "private_data_for_handlers" so that the tracing
handlers could use it to communicate with call_fetch() methods.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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set_swbp() and set_orig_insn() are __weak, but this is pointless
because write_opcode() is static.
Export write_opcode() as uprobe_write_opcode() for the upcoming
arm port, this way it can actually override set_swbp() and use
__opcode_to_mem_arm(bpinsn) instead if UPROBE_SWBP_INSN.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
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Move the function declarations from the arch headers to the common
header, since only the function bodies are architecture-specific.
These changes are from Vincent Rabin's uprobes patch.
[ oleg: update arch/powerpc/include/asm/uprobes.h ]
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: David A. Long <dave.long@linaro.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
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uprobe_copy_process() does nothing if the child shares ->mm with
the forking process, but there is a special case: CLONE_VFORK.
In this case it would be more correct to do dup_utask() but avoid
dup_xol(). This is not that important, the child should not unwind
its stack too much, this can corrupt the parent's stack, but at
least we need this to allow to ret-probe __vfork() itself.
Note: in theory, it would be better to check task_pt_regs(p)->sp
instead of CLONE_VFORK, we need to dup_utask() if and only if the
child can return from the function called by the parent. But this
needs the arch-dependant helper, and I think that nobody actually
does clone(same_stack, CLONE_VM).
Reported-by: Martin Cermak <mcermak@redhat.com>
Reported-by: David Smith <dsmith@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
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linux/uprobes.h declares arch_uprobe_skip_sstep() as a weak function.
But as there is no definition of generic version so when trying to build
uprobes for an architecture that doesn't yet have a arch_uprobe_skip_sstep()
implementation, the vmlinux will try to call arch_uprobe_skip_sstep()
somehwere in Stupidhistan leading to a system crash. We rather want a
proper link error so remove arch_uprobe_skip_sstep().
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
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Unlike the kretprobes we can't trust userspace, thus must have
protection from user space attacks. User-space have "unlimited"
stack, and this patch limits the return probes nestedness as a
simple remedy for it.
Note that this implementation leaks return_instance on siglongjmp
until exit()/exec().
The intention is to have KISS and bare minimum solution for the
initial implementation in order to not complicate the uretprobes
code.
In the future we may come up with more sophisticated solution that
remove this depth limitation. It is not easy task and lays beyond
this patchset.
Signed-off-by: Anton Arapov <anton@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
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When a uprobe with return probe consumer is hit, prepare_uretprobe()
function is invoked. It creates return_instance, hijacks return address
and replaces it with the trampoline.
* Return instances are kept as stack per uprobed task.
* Return instance is chained, when the original return address is
trampoline's page vaddr (e.g. recursive call of the probed function).
Signed-off-by: Anton Arapov <anton@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
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