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authorAnand K Mistry <amistry@google.com>2020-12-16 07:42:36 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-12-16 09:46:15 +0300
commitfe719888344ccc7f0046e787a75bb15b6a40b39f (patch)
treed97d5d70dffa9e5954b3895a2d709cd5d4bb5375 /Documentation
parentd2928e8550e541a0a3eb4f486620369f963e5090 (diff)
downloadlinux-fe719888344ccc7f0046e787a75bb15b6a40b39f.tar.xz
proc: provide details on indirect branch speculation
Similar to speculation store bypass, show information about the indirect branch speculation mode of a task in /proc/$pid/status. For testing/benchmarking, I needed to see whether IB (Indirect Branch) speculation (see Spectre-v2) is enabled on a task, to see whether an IBPB instruction should be executed on an address space switch. Unfortunately, this information isn't available anywhere else and currently the only way to get it is to hack the kernel to expose it (like this change). It also helped expose a bug with conditional IB speculation on certain CPUs. Another place this could be useful is to audit the system when using sanboxing. With this change, I can confirm that seccomp-enabled process have IB speculation force disabled as expected when the kernel command line parameter `spectre_v2_user=seccomp`. Since there's already a 'Speculation_Store_Bypass' field, I used that as precedent for adding this one. [amistry@google.com: remove underscores from field name to workaround documentation issue] Link: https://lkml.kernel.org/r/20201106131015.v2.1.I7782b0cedb705384a634cfd8898eb7523562da99@changeid Link: https://lkml.kernel.org/r/20201030172731.1.I7782b0cedb705384a634cfd8898eb7523562da99@changeid Signed-off-by: Anand K Mistry <amistry@google.com> Cc: Anthony Steinhauser <asteinhauser@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Anand K Mistry <amistry@google.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Alexey Gladkov <gladkov.alexey@gmail.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Kees Cook <keescook@chromium.org> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: NeilBrown <neilb@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/proc.rst2
1 files changed, 2 insertions, 0 deletions
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index e5fa972d4c76..2fa69f710e2a 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -210,6 +210,7 @@ read the file /proc/PID/status::
NoNewPrivs: 0
Seccomp: 0
Speculation_Store_Bypass: thread vulnerable
+ SpeculationIndirectBranch: conditional enabled
voluntary_ctxt_switches: 0
nonvoluntary_ctxt_switches: 1
@@ -292,6 +293,7 @@ It's slow but very precise.
NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
Speculation_Store_Bypass speculative store bypass mitigation status
+ SpeculationIndirectBranch indirect branch speculation mode
Cpus_allowed mask of CPUs on which this process may run
Cpus_allowed_list Same as previous, but in "list format"
Mems_allowed mask of memory nodes allowed to this process