Messages in this thread | | | Subject | Re: [PATCH v27 23/31] x86/cet/shstk: Add user-mode shadow stack support | From | "Yu, Yu-cheng" <> | Date | Tue, 20 Jul 2021 10:13:43 -0700 |
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On 7/19/2021 11:23 AM, Edgecombe, Rick P wrote: > On Fri, 2021-05-21 at 15:12 -0700, Yu-cheng Yu wrote: >> Introduce basic shadow stack enabling/disabling/allocation routines. >> A task's shadow stack is allocated from memory with VM_SHADOW_STACK >> flag >> and has a fixed size of min(RLIMIT_STACK, 4GB). >> >> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> >> Cc: Kees Cook <keescook@chromium.org>
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>> diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c >> new file mode 100644 >> index 000000000000..5ea2b494e9f9 >> --- /dev/null >> +++ b/arch/x86/kernel/shstk.c
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>> +int shstk_setup(void) >> +{ >> + struct thread_shstk *shstk = ¤t->thread.shstk; >> + unsigned long addr, size; >> + >> + if (!cpu_feature_enabled(X86_FEATURE_SHSTK)) >> + return -EOPNOTSUPP; > The only caller of this will skip it if > !cpu_feature_enabled(X86_FEATURE_SHSTK), so this is dead logic. Same > pattern in the IBT patch. >
Indeed that is the case. We can simply remove the test of X86_FEATURE_SHSTK.
Thanks, Yu-cheng
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