linux-stable.git/arch/s390/kernel/ftrace.c, branch linux-rolling-stable

Merge tag 's390-6.15-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2025-03-29T18:59:43+00:00

Pull s390 updates from Vasily Gorbik:

 - Add sorting of mcount locations at build time

 - Rework uaccess functions with C exception handling to shorten inline
   assembly size and enable full inlining. This yields near-optimal code
   for small constant copies with a ~40kb kernel size increase

 - Add support for a configurable STRICT_MM_TYPECHECKS which allows to
   generate better code, but also allows to have type checking for debug
   builds

 - Optimize get_lowcore() for common callers with alternatives that
   nearly revert to the pre-relocated lowcore code, while also slightly
   reducing syscall entry and exit time

 - Convert MACHINE_HAS_* checks for single facility tests into cpu_has_*
   style macros that call test_facility(), and for features with
   additional conditions, add a new ALT_TYPE_FEATURE alternative to
   provide a static branch via alternative patching. Also, move machine
   feature detection to the decompressor for early patching and add
   debugging functionality to easily show which alternatives are patched

 - Add exception table support to early boot / startup code to get rid
   of the open coded exception handling

 - Use asm_inline for all inline assemblies with EX_TABLE or ALTERNATIVE
   to ensure correct inlining and unrolling decisions

 - Remove 2k page table leftovers now that s390 has been switched to
   always allocate 4k page tables

 - Split kfence pool into 4k mappings in arch_kfence_init_pool() and
   remove the architecture-specific kfence_split_mapping()

 - Use READ_ONCE_NOCHECK() in regs_get_kernel_stack_nth() to silence
   spurious KASAN warnings from opportunistic ftrace argument tracing

 - Force __atomic_add_const() variants on s390 to always return void,
   ensuring compile errors for improper usage

 - Remove s390's ioremap_wt() and pgprot_writethrough() due to
   mismatched semantics and lack of known users, relying on asm-generic
   fallbacks

 - Signal eventfd in vfio-ap to notify userspace when the guest AP
   configuration changes, including during mdev removal

 - Convert mdev_types from an array to a pointer in vfio-ccw and vfio-ap
   drivers to avoid fake flex array confusion

 - Cleanup trap code

 - Remove references to the outdated linux390@de.ibm.com address

 - Other various small fixes and improvements all over the code

* tag 's390-6.15-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (78 commits)
  s390: Use inline qualifier for all EX_TABLE and ALTERNATIVE inline assemblies
  s390/kfence: Split kfence pool into 4k mappings in arch_kfence_init_pool()
  s390/ptrace: Avoid KASAN false positives in regs_get_kernel_stack_nth()
  s390/boot: Ignore vmlinux.map
  s390/sysctl: Remove "vm/allocate_pgste" sysctl
  s390: Remove 2k vs 4k page table leftovers
  s390/tlb: Use mm_has_pgste() instead of mm_alloc_pgste()
  s390/lowcore: Use lghi instead llilh to clear register
  s390/syscall: Merge __do_syscall() and do_syscall()
  s390/spinlock: Implement SPINLOCK_LOCKVAL with inline assembly
  s390/smp: Implement raw_smp_processor_id() with inline assembly
  s390/current: Implement current with inline assembly
  s390/lowcore: Use inline qualifier for get_lowcore() inline assembly
  s390: Move s390 sysctls into their own file under arch/s390
  s390/syscall: Simplify syscall_get_arguments()
  s390/vfio-ap: Notify userspace that guest's AP config changed when mdev removed
  s390: Remove ioremap_wt() and pgprot_writethrough()
  s390/mm: Add configurable STRICT_MM_TYPECHECKS
  s390/mm: Convert pgste_val() into function
  s390/mm: Convert pgprot_val() into function
  ...

s390/cpufeature: Convert MACHINE_HAS_SEQ_INSN to cpu_has_seq_insn()

2025-03-04T16:18:04+00:00

Convert MACHINE_HAS_... to cpu_has_...() which uses test_facility() instead
of testing the machine_flags lowcore member if the feature is present.

test_facility() generates better code since it results in a static branch
without accessing memory. The branch is patched via alternatives by the
decompressor depending on the availability of the required facility.

Reviewed-by: Vasily Gorbik 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/ftrace: Fix return address recovery of traced function

2025-03-04T16:15:19+00:00

When fgraph is enabled the traced function return address is replaced with
trampoline return_to_handler(). The original return address of the traced
function is saved in per task return stack along with a stack pointer for
reliable stack unwinding via function_graph_enter_regs().

During stack unwinding e.g. for livepatching, ftrace_graph_ret_addr()
identifies the original return address of the traced function with the
saved stack pointer.

With a recent change, the stack pointers passed to ftrace_graph_ret_addr()
and function_graph_enter_regs() do not match anymore, and therefore the
original return address is not found.

Pass the correct stack pointer to function_graph_enter_regs() to fix this.

Fixes: 7495e179b478 ("s390/tracing: Enable HAVE_FTRACE_GRAPH_FUNC")
Reviewed-by: Heiko Carstens 
Signed-off-by: Sumanth Korikkar 
Signed-off-by: Vasily Gorbik

s390/fgraph: Fix to remove ftrace_test_recursion_trylock()

2025-01-29T14:12:31+00:00

Fix to remove ftrace_test_recursion_trylock() from ftrace_graph_func()
because commit d576aec24df9 ("fgraph: Get ftrace recursion lock in
function_graph_enter") has been moved it to function_graph_enter_regs()
already.

Reported-by: Jiri Olsa 
Closes: https://lore.kernel.org/all/Z5O0shrdgeExZ2kF@krava/
Fixes: d576aec24df9 ("fgraph: Get ftrace recursion lock in function_graph_enter")
Signed-off-by: Masami Hiramatsu (Google) 
Tested-by: Jiri Olsa 
Tested-by: Ihor Solodrai 
Reviewed-by: Heiko Carstens 
Link: https://lore.kernel.org/r/173807817692.1854334.2985776940754607459.stgit@devnote2
Signed-off-by: Alexander Gordeev

s390/tracing: Enable HAVE_FTRACE_GRAPH_FUNC

2024-12-26T15:50:05+00:00

Add ftrace_graph_func() which is required for fprobe to access registers.
This also eliminates the need for calling prepare_ftrace_return() from
ftrace_caller().

Cc: Alexei Starovoitov 
Cc: Florent Revest 
Cc: Martin KaFai Lau 
Cc: bpf 
Cc: Alexei Starovoitov 
Cc: Jiri Olsa 
Cc: Alan Maguire 
Cc: Mark Rutland 
Link: https://lore.kernel.org/173519002875.391279.7060964632119674159.stgit@devnote2
Signed-off-by: Sven Schnelle 
Acked-by: Heiko Carstens 
Signed-off-by: Steven Rostedt (Google)

ftrace: Make ftrace_regs abstract from direct use

2024-10-11T00:18:01+00:00

ftrace_regs was created to hold registers that store information to save
function parameters, return value and stack. Since it is a subset of
pt_regs, it should only be used by its accessor functions. But because
pt_regs can easily be taken from ftrace_regs (on most archs), it is
tempting to use it directly. But when running on other architectures, it
may fail to build or worse, build but crash the kernel!

Instead, make struct ftrace_regs an empty structure and have the
architectures define __arch_ftrace_regs and all the accessor functions
will typecast to it to get to the actual fields. This will help avoid
usage of ftrace_regs directly.

Link: https://lore.kernel.org/all/20241007171027.629bdafd@gandalf.local.home/

Cc: "linux-arch@vger.kernel.org" 
Cc: "x86@kernel.org" 
Cc: Mathieu Desnoyers 
Cc: Mark Rutland 
Cc: Will Deacon 
Cc: Huacai Chen 
Cc: WANG Xuerui 
Cc: Michael Ellerman 
Cc: Nicholas Piggin 
Cc: Christophe Leroy 
Cc: Naveen N Rao 
Cc: Madhavan Srinivasan 
Cc: Paul  Walmsley 
Cc: Palmer Dabbelt 
Cc: Albert Ou 
Cc: Heiko Carstens 
Cc: Vasily Gorbik 
Cc: Alexander Gordeev 
Cc: Christian Borntraeger 
Cc: Sven Schnelle 
Cc: Thomas  Gleixner 
Cc: Ingo Molnar 
Cc: Borislav  Petkov 
Cc: Dave Hansen 
Link: https://lore.kernel.org/20241008230628.958778821@goodmis.org
Acked-by: Catalin Marinas 
Signed-off-by: Steven Rostedt (Google) 
Acked-by: Masami Hiramatsu (Google) 
Acked-by: Heiko Carstens  # s390
Signed-off-by: Steven Rostedt (Google)

s390/ftrace: Avoid extra serialization for graph caller patching

2024-08-29T20:56:34+00:00

The only context where ftrace_enable_ftrace_graph_caller()
or ftrace_disable_ftrace_graph_caller() is called also calls
ftrace_arch_code_modify_post_process(), which already performs
text_poke_sync_lock().

ftrace_run_update_code()
	arch_ftrace_update_code()
		ftrace_modify_all_code()
			ftrace_enable_ftrace_graph_caller()/ftrace_disable_ftrace_graph_caller()
	ftrace_arch_code_modify_post_process()
		text_poke_sync_lock()

Remove the redundant serialization.

Reviewed-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/ftrace: Use get/copy_from_kernel_nofault consistently

2024-08-29T20:56:34+00:00

Use get/copy_from_kernel_nofault to access the kernel text consistently.
Replace memcmp() in ftrace_init_nop() to ensure that in case of
inconsistencies in the 'mcount' table, the kernel reports a failure
instead of potentially crashing.

Reviewed-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/ftrace: Avoid trampolines if possible

2024-08-29T20:56:34+00:00

When a sequential instruction fetching facility is present, it is safe
to patch ftrace NOPs in function prologues. All of them are 8-byte
aligned.

Reviewed-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/ftrace: Use kernel ftrace trampoline for modules

2024-08-27T18:16:48+00:00

Now that both the kernel modules area and the kernel image itself are
located within 4 GB, there is no longer a need to maintain a separate
ftrace_plt trampoline. Use the existing trampoline in the kernel.

Reviewed-by: Ilya Leoshkevich 
Reviewed-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik