Messages in this thread | | | From | Tim Chen <> | Subject | [Patch v2 0/4] Provide options to enable spectre_v2 userspace-userspace protection | Date | Tue, 25 Sep 2018 17:43:55 -0700 |
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I have merged Tom's changes to extend the patchset for AMD cpus, and also added a prctl option to control per process indirect branch speculation per Peter's comments.
Tim
Changes: v2: 1. Extend per process STIBP to AMD cpus 2. Add prctl option to control per process indirect branch speculation 3. Bug fixes and cleanups
This patchset provides an option to apply IBPB and STIBP mitigation to only non-dumpable processes.
Jiri's patch to harden spectre_v2 makes IBPB and STIBP available for general spectre v2 app to app mitigation. IBPB will be issued for switching to an app that's not ptraceable by the previous app and STIBP will be always turned on.
However, leaving STIBP on all the time is expensive for certain applications that have frequent indirect branches. One such application is perlbench in the SpecInt Rate 2006 test suite which shows a 21% reduction in throughput. Other application like bzip2 in the same test suite with minimal indirct branches have only a 0.7% reduction in throughput. IBPB will also impose overhead during context switches.
App to app exploit is in general difficult due to address space layout randomization in apps and the need to know an app's address space layout ahead of time. Users may not wish to incur app to app performance overhead from IBPB and STIBP for general non security sensitive apps and use these mitigations only for non-dumpable apps.
The first patch provides a lite option for spectre_v2 app to app mitigation where IBPB is only issued for security sensitive non-dumpable app. The second patch extends this option where STIBP is only issued for non-dumpable app. The third patch extends per process STIBP update for AMD cpus. The fourth patch adds a prctl option to control per process indirect branch speculation.
Thomas Lendacky (1): x86/speculation: Extend per process STIBP to AMD cpus.
Tim Chen (3): x86/speculation: Option to select app to app mitigation for spectre_v2 x86/speculation: Provide application property based STIBP protection x86/speculation: Add prctl to control indirect branch speculation per process
Documentation/admin-guide/kernel-parameters.txt | 13 ++ Documentation/userspace-api/spec_ctrl.rst | 8 + arch/x86/include/asm/msr-index.h | 3 +- arch/x86/include/asm/nospec-branch.h | 9 ++ arch/x86/include/asm/spec-ctrl.h | 12 ++ arch/x86/include/asm/thread_info.h | 4 +- arch/x86/kernel/cpu/bugs.c | 185 +++++++++++++++++++++++- arch/x86/kernel/process.c | 58 ++++++-- arch/x86/mm/tlb.c | 21 ++- fs/exec.c | 13 +- include/linux/sched.h | 5 + include/linux/sched/coredump.h | 2 +- include/uapi/linux/prctl.h | 1 + kernel/cred.c | 2 +- kernel/sys.c | 2 +- tools/include/uapi/linux/prctl.h | 1 + 16 files changed, 310 insertions(+), 29 deletions(-)
-- 2.9.4
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