GCC has supported asm goto since 4.5, and Clang has since version 9.0.0. The minimum supported versions of these tools for the build according to Documentation/process/changes.rst are 5.1 and 11.0.0 respectively. Remove the feature detection script, Kconfig option, and clean up some fallback code that is no longer supported. The removed script was also testing for a GCC specific bug that was fixed in the 4.7 release. Also remove workarounds for bpftrace using clang older than 9.0.0, since other BPF backend fixes are required at this point. Link: https://lore.kernel.org/lkml/CAK7LNATSr=BXKfkdW8f-H5VT_w=xBpT2ZQcZ7rm6JfkdE+QnmA@mail.gmail.com/ Link: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48637 Acked-by: Borislav Petkov <bp@suse.de> Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
To pick the changes in:
43bb9e000ea4c621 ("KVM: x86: Tweak name of MONITOR/MWAIT #UD quirk to make it #UD specific")
94dfc73e7cf4a31d ("treewide: uapi: Replace zero-length arrays with flexible-array members")
bfbcc81bb82cbbad ("KVM: x86: Add a quirk for KVM's "MONITOR/MWAIT are NOPs!" behavior")
b172862241b48499 ("KVM: x86: PIT: Preserve state of speaker port data bit")
ed2351174e38ad4f ("KVM: x86: Extend KVM_{G,S}ET_VCPU_EVENTS to support pending triple fault")
That just rebuilds kvm-stat.c on x86, no change in functionality.
This silences these perf build warning:
Warning: Kernel ABI header at 'tools/arch/x86/include/uapi/asm/kvm.h' differs from latest version at 'arch/x86/include/uapi/asm/kvm.h'
diff -u tools/arch/x86/include/uapi/asm/kvm.h arch/x86/include/uapi/asm/kvm.h
Cc: Chenyi Qiang <chenyi.qiang@intel.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Paul Durrant <pdurrant@amazon.com>
Link: https://lore.kernel.org/lkml/Yv6OMPKYqYSbUxwZ@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
To pick the changes in:
2f4073e08f4cc5a4 ("KVM: VMX: Enable Notify VM exit")
That makes 'perf kvm-stat' aware of this new NOTIFY exit reason, thus
addressing the following perf build warning:
Warning: Kernel ABI header at 'tools/arch/x86/include/uapi/asm/vmx.h' differs from latest version at 'arch/x86/include/uapi/asm/vmx.h'
diff -u tools/arch/x86/include/uapi/asm/vmx.h arch/x86/include/uapi/asm/vmx.h
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Tao Xu <tao3.xu@intel.com>
Link: http://lore.kernel.org/lkml/Yv6LavXMZ+njijpq@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
To pick the changes in:
f5ecfee944934757 ("KVM: s390: resetting the Topology-Change-Report")
None of them trigger any changes in tooling, this time this is just to silence
these perf build warnings:
Warning: Kernel ABI header at 'tools/arch/s390/include/uapi/asm/kvm.h' differs from latest version at 'arch/s390/include/uapi/asm/kvm.h'
diff -u tools/arch/s390/include/uapi/asm/kvm.h arch/s390/include/uapi/asm/kvm.h
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Pierre Morel <pmorel@linux.ibm.com>
Link: http://lore.kernel.org/lkml/YvzwMXzaIzOU4WAY@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
To pick the changes from:
2b1299322016731d ("x86/speculation: Add RSB VM Exit protections")
28a99e95f55c6185 ("x86/amd: Use IBPB for firmware calls")
4ad3278df6fe2b08 ("x86/speculation: Disable RRSBA behavior")
26aae8ccbc197223 ("x86/cpu/amd: Enumerate BTC_NO")
9756bba28470722d ("x86/speculation: Fill RSB on vmexit for IBRS")
3ebc170068885b6f ("x86/bugs: Add retbleed=ibpb")
2dbb887e875b1de3 ("x86/entry: Add kernel IBRS implementation")
6b80b59b35557065 ("x86/bugs: Report AMD retbleed vulnerability")
a149180fbcf336e9 ("x86: Add magic AMD return-thunk")
15e67227c49a5783 ("x86: Undo return-thunk damage")
a883d624aed463c8 ("x86/cpufeatures: Move RETPOLINE flags to word 11")
aae99a7c9ab371b2 ("x86/cpufeatures: Introduce x2AVIC CPUID bit")
6f33a9daff9f0790 ("x86: Fix comment for X86_FEATURE_ZEN")
51802186158c74a0 ("x86/speculation/mmio: Enumerate Processor MMIO Stale Data bug")
This only causes these perf files to be rebuilt:
CC /tmp/build/perf/bench/mem-memcpy-x86-64-asm.o
CC /tmp/build/perf/bench/mem-memset-x86-64-asm.o
And addresses this perf build warning:
Warning: Kernel ABI header at 'tools/arch/x86/include/asm/cpufeatures.h' differs from latest version at 'arch/x86/include/asm/cpufeatures.h'
diff -u tools/arch/x86/include/asm/cpufeatures.h arch/x86/include/asm/cpufeatures.h
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Cc: Wyes Karny <wyes.karny@amd.com>
Link: https://lore.kernel.org/lkml/Yvznmu5oHv0ZDN2w@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
To pick up the changes in:
2b1299322016731d ("x86/speculation: Add RSB VM Exit protections")
4af184ee8b2c0a69 ("tools/power turbostat: dump secondary Turbo-Ratio-Limit")
4ad3278df6fe2b08 ("x86/speculation: Disable RRSBA behavior")
d7caac991feeef1b ("x86/cpu/amd: Add Spectral Chicken")
6ad0ad2bf8a67e27 ("x86/bugs: Report Intel retbleed vulnerability")
c59a1f106f5cd484 ("KVM: x86/pmu: Add IA32_PEBS_ENABLE MSR emulation for extended PEBS")
465932db25f36648 ("x86/cpu: Add new VMX feature, Tertiary VM-Execution control")
027bbb884be006b0 ("KVM: x86/speculation: Disable Fill buffer clear within guests")
51802186158c74a0 ("x86/speculation/mmio: Enumerate Processor MMIO Stale Data bug")
Addressing these tools/perf build warnings:
diff -u tools/arch/x86/include/asm/msr-index.h arch/x86/include/asm/msr-index.h
Warning: Kernel ABI header at 'tools/arch/x86/include/asm/msr-index.h' differs from latest version at 'arch/x86/include/asm/msr-index.h'
That makes the beautification scripts to pick some new entries:
$ tools/perf/trace/beauty/tracepoints/x86_msr.sh > before
$ cp arch/x86/include/asm/msr-index.h tools/arch/x86/include/asm/msr-index.h
$ tools/perf/trace/beauty/tracepoints/x86_msr.sh > after
$ diff -u before after
--- before 2022-08-17 09:05:13.938246475 -0300
+++ after 2022-08-17 09:05:22.221455851 -0300
@@ -161,6 +161,7 @@
[0x0000048f] = "IA32_VMX_TRUE_EXIT_CTLS",
[0x00000490] = "IA32_VMX_TRUE_ENTRY_CTLS",
[0x00000491] = "IA32_VMX_VMFUNC",
+ [0x00000492] = "IA32_VMX_PROCBASED_CTLS3",
[0x000004c1] = "IA32_PMC0",
[0x000004d0] = "IA32_MCG_EXT_CTL",
[0x00000560] = "IA32_RTIT_OUTPUT_BASE",
@@ -212,6 +213,7 @@
[0x0000064D] = "PLATFORM_ENERGY_STATUS",
[0x0000064e] = "PPERF",
[0x0000064f] = "PERF_LIMIT_REASONS",
+ [0x00000650] = "SECONDARY_TURBO_RATIO_LIMIT",
[0x00000658] = "PKG_WEIGHTED_CORE_C0_RES",
[0x00000659] = "PKG_ANY_CORE_C0_RES",
[0x0000065A] = "PKG_ANY_GFXE_C0_RES",
$
Now one can trace systemwide asking to see backtraces to where those
MSRs are being read/written, see this example with a previous update:
# perf trace -e msr:*_msr/max-stack=32/ --filter="msr>=IA32_U_CET && msr<=IA32_INT_SSP_TAB"
^C#
If we use -v (verbose mode) we can see what it does behind the scenes:
# perf trace -v -e msr:*_msr/max-stack=32/ --filter="msr>=IA32_U_CET && msr<=IA32_INT_SSP_TAB"
Using CPUID AuthenticAMD-25-21-0
0x6a0
0x6a8
New filter for msr:read_msr: (msr>=0x6a0 && msr<=0x6a8) && (common_pid != 597499 && common_pid != 3313)
0x6a0
0x6a8
New filter for msr:write_msr: (msr>=0x6a0 && msr<=0x6a8) && (common_pid != 597499 && common_pid != 3313)
mmap size 528384B
^C#
Example with a frequent msr:
# perf trace -v -e msr:*_msr/max-stack=32/ --filter="msr==IA32_SPEC_CTRL" --max-events 2
Using CPUID AuthenticAMD-25-21-0
0x48
New filter for msr:read_msr: (msr==0x48) && (common_pid != 2612129 && common_pid != 3841)
0x48
New filter for msr:write_msr: (msr==0x48) && (common_pid != 2612129 && common_pid != 3841)
mmap size 528384B
Looking at the vmlinux_path (8 entries long)
symsrc__init: build id mismatch for vmlinux.
Using /proc/kcore for kernel data
Using /proc/kallsyms for symbols
0.000 Timer/2525383 msr:write_msr(msr: IA32_SPEC_CTRL, val: 6)
do_trace_write_msr ([kernel.kallsyms])
do_trace_write_msr ([kernel.kallsyms])
__switch_to_xtra ([kernel.kallsyms])
__switch_to ([kernel.kallsyms])
__schedule ([kernel.kallsyms])
schedule ([kernel.kallsyms])
futex_wait_queue_me ([kernel.kallsyms])
futex_wait ([kernel.kallsyms])
do_futex ([kernel.kallsyms])
__x64_sys_futex ([kernel.kallsyms])
do_syscall_64 ([kernel.kallsyms])
entry_SYSCALL_64_after_hwframe ([kernel.kallsyms])
__futex_abstimed_wait_common64 (/usr/lib64/libpthread-2.33.so)
0.030 :0/0 msr:write_msr(msr: IA32_SPEC_CTRL, val: 2)
do_trace_write_msr ([kernel.kallsyms])
do_trace_write_msr ([kernel.kallsyms])
__switch_to_xtra ([kernel.kallsyms])
__switch_to ([kernel.kallsyms])
__schedule ([kernel.kallsyms])
schedule_idle ([kernel.kallsyms])
do_idle ([kernel.kallsyms])
cpu_startup_entry ([kernel.kallsyms])
secondary_startup_64_no_verify ([kernel.kallsyms])
#
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Like Xu <like.xu@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Hoo <robert.hu@linux.intel.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/lkml/YvzbT24m2o5U%2F7+q@kernel.org/
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Pull x86 eIBRS fixes from Borislav Petkov: "More from the CPU vulnerability nightmares front: Intel eIBRS machines do not sufficiently mitigate against RET mispredictions when doing a VM Exit therefore an additional RSB, one-entry stuffing is needed" * tag 'x86_bugs_pbrsb' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/speculation: Add LFENCE to RSB fill sequence x86/speculation: Add RSB VM Exit protections
Pull perf tools updates from Arnaldo Carvalho de Melo:
- Introduce 'perf lock contention' subtool, using new lock contention
tracepoints and using BPF for in kernel aggregation and then
userspace processing using the perf tooling infrastructure for
resolving symbols, target specification, etc.
Since the new lock contention tracepoints don't provide lock names,
get up to 8 stack traces and display the first non-lock function
symbol name as a caller:
$ perf lock report -F acquired,contended,avg_wait,wait_total
Name acquired contended avg wait total wait
update_blocked_a... 40 40 3.61 us 144.45 us
kernfs_fop_open+... 5 5 3.64 us 18.18 us
_nohz_idle_balance 3 3 2.65 us 7.95 us
tick_do_update_j... 1 1 6.04 us 6.04 us
ep_scan_ready_list 1 1 3.93 us 3.93 us
Supports the usual 'perf record' + 'perf report' workflow as well as
a BCC/bpftrace like mode where you start the tool and then press
control+C to get results:
$ sudo perf lock contention -b
^C
contended total wait max wait avg wait type caller
42 192.67 us 13.64 us 4.59 us spinlock queue_work_on+0x20
23 85.54 us 10.28 us 3.72 us spinlock worker_thread+0x14a
6 13.92 us 6.51 us 2.32 us mutex kernfs_iop_permission+0x30
3 11.59 us 10.04 us 3.86 us mutex kernfs_dop_revalidate+0x3c
1 7.52 us 7.52 us 7.52 us spinlock kthread+0x115
1 7.24 us 7.24 us 7.24 us rwlock:W sys_epoll_wait+0x148
2 7.08 us 3.99 us 3.54 us spinlock delayed_work_timer_fn+0x1b
1 6.41 us 6.41 us 6.41 us spinlock idle_balance+0xa06
2 2.50 us 1.83 us 1.25 us mutex kernfs_iop_lookup+0x2f
1 1.71 us 1.71 us 1.71 us mutex kernfs_iop_getattr+0x2c
...
- Add new 'perf kwork' tool to trace time properties of kernel work
(such as softirq, and workqueue), uses eBPF skeletons to collect info
in kernel space, aggregating data that then gets processed by the
userspace tool, e.g.:
# perf kwork report
Kwork Name | Cpu | Total Runtime | Count | Max runtime | Max runtime start | Max runtime end |
----------------------------------------------------------------------------------------------------
nvme0q5:130 | 004 | 1.101 ms | 49 | 0.051 ms | 26035.056403 s | 26035.056455 s |
amdgpu:162 | 002 | 0.176 ms | 9 | 0.046 ms | 26035.268020 s | 26035.268066 s |
nvme0q24:149 | 023 | 0.161 ms | 55 | 0.009 ms | 26035.655280 s | 26035.655288 s |
nvme0q20:145 | 019 | 0.090 ms | 33 | 0.014 ms | 26035.939018 s | 26035.939032 s |
nvme0q31:156 | 030 | 0.075 ms | 21 | 0.010 ms | 26035.052237 s | 26035.052247 s |
nvme0q8:133 | 007 | 0.062 ms | 12 | 0.021 ms | 26035.416840 s | 26035.416861 s |
nvme0q6:131 | 005 | 0.054 ms | 22 | 0.010 ms | 26035.199919 s | 26035.199929 s |
nvme0q19:144 | 018 | 0.052 ms | 14 | 0.010 ms | 26035.110615 s | 26035.110625 s |
nvme0q7:132 | 006 | 0.049 ms | 13 | 0.007 ms | 26035.125180 s | 26035.125187 s |
nvme0q18:143 | 017 | 0.033 ms | 14 | 0.007 ms | 26035.169698 s | 26035.169705 s |
nvme0q17:142 | 016 | 0.013 ms | 1 | 0.013 ms | 26035.565147 s | 26035.565160 s |
enp5s0-rx-0:164 | 006 | 0.004 ms | 4 | 0.002 ms | 26035.928882 s | 26035.928884 s |
enp5s0-tx-0:166 | 008 | 0.003 ms | 3 | 0.002 ms | 26035.870923 s | 26035.870925 s |
--------------------------------------------------------------------------------------------------------
See commit log messages for more examples with extra options to limit
the events time window, etc.
- Add support for new AMD IBS (Instruction Based Sampling) features:
With the DataSrc extensions, the source of data can be decoded among:
- Local L3 or other L1/L2 in CCX.
- A peer cache in a near CCX.
- Data returned from DRAM.
- A peer cache in a far CCX.
- DRAM address map with "long latency" bit set.
- Data returned from MMIO/Config/PCI/APIC.
- Extension Memory (S-Link, GenZ, etc - identified by the CS target
and/or address map at DF's choice).
- Peer Agent Memory.
- Support hardware tracing with Intel PT on guest machines, combining
the traces with the ones in the host machine.
- Add a "-m" option to 'perf buildid-list' to show kernel and modules
build-ids, to display all of the information needed to do external
symbolization of kernel stack traces, such as those collected by
bpf_get_stackid().
- Add arch TSC frequency information to perf.data file headers.
- Handle changes in the binutils disassembler function signatures in
perf, bpftool and bpf_jit_disasm (Acked by the bpftool maintainer).
- Fix building the perf perl binding with the newest gcc in distros
such as fedora rawhide, where some new warnings were breaking the
build as perf uses -Werror.
- Add 'perf test' entry for branch stack sampling.
- Add ARM SPE system wide 'perf test' entry.
- Add user space counter reading tests to 'perf test'.
- Build with python3 by default, if available.
- Add python converter script for the vendor JSON event files.
- Update vendor JSON files for most Intel cores.
- Add vendor JSON File for Intel meteorlake.
- Add Arm Cortex-A78C and X1C JSON vendor event files.
- Add workaround to symbol address reading from ELF files without phdr,
falling back to the previoous equation.
- Convert legacy map definition to BTF-defined in the perf BPF script
test.
- Rework prologue generation code to stop using libbpf deprecated APIs.
- Add default hybrid events for 'perf stat' on x86.
- Add topdown metrics in the default 'perf stat' on the hybrid machines
(big/little cores).
- Prefer sampled CPU when exporting JSON in 'perf data convert'
- Fix ('perf stat CSV output linter') and ("Check branch stack
sampling") 'perf test' entries on s390.
* tag 'perf-tools-for-v6.0-2022-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux: (169 commits)
perf stat: Refactor __run_perf_stat() common code
perf lock: Print the number of lost entries for BPF
perf lock: Add --map-nr-entries option
perf lock: Introduce struct lock_contention
perf scripting python: Do not build fail on deprecation warnings
genelf: Use HAVE_LIBCRYPTO_SUPPORT, not the never defined HAVE_LIBCRYPTO
perf build: Suppress openssl v3 deprecation warnings in libcrypto feature test
perf parse-events: Break out tracepoint and printing
perf parse-events: Don't #define YY_EXTRA_TYPE
tools bpftool: Don't display disassembler-four-args feature test
tools bpftool: Fix compilation error with new binutils
tools bpf_jit_disasm: Don't display disassembler-four-args feature test
tools bpf_jit_disasm: Fix compilation error with new binutils
tools perf: Fix compilation error with new binutils
tools include: add dis-asm-compat.h to handle version differences
tools build: Don't display disassembler-four-args feature test
tools build: Add feature test for init_disassemble_info API changes
perf test: Add ARM SPE system wide test
perf tools: Rework prologue generation code
perf bpf: Convert legacy map definition to BTF-defined
...
tl;dr: The Enhanced IBRS mitigation for Spectre v2 does not work as
documented for RET instructions after VM exits. Mitigate it with a new
one-entry RSB stuffing mechanism and a new LFENCE.
== Background ==
Indirect Branch Restricted Speculation (IBRS) was designed to help
mitigate Branch Target Injection and Speculative Store Bypass, i.e.
Spectre, attacks. IBRS prevents software run in less privileged modes
from affecting branch prediction in more privileged modes. IBRS requires
the MSR to be written on every privilege level change.
To overcome some of the performance issues of IBRS, Enhanced IBRS was
introduced. eIBRS is an "always on" IBRS, in other words, just turn
it on once instead of writing the MSR on every privilege level change.
When eIBRS is enabled, more privileged modes should be protected from
less privileged modes, including protecting VMMs from guests.
== Problem ==
Here's a simplification of how guests are run on Linux' KVM:
void run_kvm_guest(void)
{
// Prepare to run guest
VMRESUME();
// Clean up after guest runs
}
The execution flow for that would look something like this to the
processor:
1. Host-side: call run_kvm_guest()
2. Host-side: VMRESUME
3. Guest runs, does "CALL guest_function"
4. VM exit, host runs again
5. Host might make some "cleanup" function calls
6. Host-side: RET from run_kvm_guest()
Now, when back on the host, there are a couple of possible scenarios of
post-guest activity the host needs to do before executing host code:
* on pre-eIBRS hardware (legacy IBRS, or nothing at all), the RSB is not
touched and Linux has to do a 32-entry stuffing.
* on eIBRS hardware, VM exit with IBRS enabled, or restoring the host
IBRS=1 shortly after VM exit, has a documented side effect of flushing
the RSB except in this PBRSB situation where the software needs to stuff
the last RSB entry "by hand".
IOW, with eIBRS supported, host RET instructions should no longer be
influenced by guest behavior after the host retires a single CALL
instruction.
However, if the RET instructions are "unbalanced" with CALLs after a VM
exit as is the RET in #6, it might speculatively use the address for the
instruction after the CALL in #3 as an RSB prediction. This is a problem
since the (untrusted) guest controls this address.
Balanced CALL/RET instruction pairs such as in step #5 are not affected.
== Solution ==
The PBRSB issue affects a wide variety of Intel processors which
support eIBRS. But not all of them need mitigation. Today,
X86_FEATURE_RSB_VMEXIT triggers an RSB filling sequence that mitigates
PBRSB. Systems setting RSB_VMEXIT need no further mitigation - i.e.,
eIBRS systems which enable legacy IBRS explicitly.
However, such systems (X86_FEATURE_IBRS_ENHANCED) do not set RSB_VMEXIT
and most of them need a new mitigation.
Therefore, introduce a new feature flag X86_FEATURE_RSB_VMEXIT_LITE
which triggers a lighter-weight PBRSB mitigation versus RSB_VMEXIT.
The lighter-weight mitigation performs a CALL instruction which is
immediately followed by a speculative execution barrier (INT3). This
steers speculative execution to the barrier -- just like a retpoline
-- which ensures that speculation can never reach an unbalanced RET.
Then, ensure this CALL is retired before continuing execution with an
LFENCE.
In other words, the window of exposure is opened at VM exit where RET
behavior is troublesome. While the window is open, force RSB predictions
sampling for RET targets to a dead end at the INT3. Close the window
with the LFENCE.
There is a subset of eIBRS systems which are not vulnerable to PBRSB.
Add these systems to the cpu_vuln_whitelist[] as NO_EIBRS_PBRSB.
Future systems that aren't vulnerable will set ARCH_CAP_PBRSB_NO.
[ bp: Massage, incorporate review comments from Andy Cooper. ]
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Co-developed-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Pull uapi flexible array update from Gustavo Silva:
"A treewide patch that replaces zero-length arrays with flexible-array
members in UAPI. This has been baking in linux-next for 5 weeks now.
'-fstrict-flex-arrays=3' is coming and we need to land these changes
to prevent issues like these in the short future:
fs/minix/dir.c:337:3: warning: 'strcpy' will always overflow; destination buffer has size 0, but the source string has length 2 (including NUL byte) [-Wfortify-source]
strcpy(de3->name, ".");
^
Since these are all [0] to [] changes, the risk to UAPI is nearly
zero. If this breaks anything, we can use a union with a new member
name"
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836
* tag 'flexible-array-transformations-UAPI-6.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux:
treewide: uapi: Replace zero-length arrays with flexible-array members