Messages in this thread | | | Subject | Re: [PATCH v24 9/9] x86/vdso: Add ENDBR to __vdso_sgx_enter_enclave | From | "Yu, Yu-cheng" <> | Date | Mon, 24 May 2021 12:01:29 -0700 |
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On 5/24/2021 11:51 AM, Sean Christopherson wrote: > On Thu, Apr 01, 2021, Yu-cheng Yu wrote: >> ENDBR is a special new instruction for the Indirect Branch Tracking (IBT) >> component of CET. IBT prevents attacks by ensuring that (most) indirect >> branches and function calls may only land at ENDBR instructions. Branches >> that don't follow the rules will result in control flow (#CF) exceptions. >> >> ENDBR is a noop when IBT is unsupported or disabled. Most ENDBR >> instructions are inserted automatically by the compiler, but branch >> targets written in assembly must have ENDBR added manually. >> >> Add ENDBR to __vdso_sgx_enter_enclave() branch targets. > ^ > |- indirect > > After reading the changelog, I was expecting ENDBR on every label. >
Sorry about the confusion.
>> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> >> Cc: Andy Lutomirski <luto@kernel.org> >> Cc: Borislav Petkov <bp@alien8.de> >> Cc: Dave Hansen <dave.hansen@linux.intel.com> >> Cc: Jarkko Sakkinen <jarkko@kernel.org> >> Cc: Peter Zijlstra <peterz@infradead.org> >> --- >> arch/x86/entry/vdso/vsgx.S | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/arch/x86/entry/vdso/vsgx.S b/arch/x86/entry/vdso/vsgx.S >> index 86a0e94f68df..c63eafa54abd 100644 >> --- a/arch/x86/entry/vdso/vsgx.S >> +++ b/arch/x86/entry/vdso/vsgx.S >> @@ -4,6 +4,7 @@ >> #include <asm/export.h> >> #include <asm/errno.h> >> #include <asm/enclu.h> >> +#include <asm/vdso.h> >> >> #include "extable.h" >> >> @@ -27,6 +28,7 @@ >> SYM_FUNC_START(__vdso_sgx_enter_enclave) >> /* Prolog */ >> .cfi_startproc >> + ENDBR >> push %rbp >> .cfi_adjust_cfa_offset 8 >> .cfi_rel_offset %rbp, 0 >> @@ -62,6 +64,7 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave) >> .Lasync_exit_pointer: >> .Lenclu_eenter_eresume: >> enclu >> + ENDBR > > It would be better to move this below the comment about EEXIT. As is, it looks > like a misplaced annotation on the AEP. The AEP doesn't need ENDBR, it's the > EEXIT target that needs ENDBR because EEXIT is treated as an indirect branch. > > Might also be helpful for future readers to explicitly state in the changelog > that EEXIT is considered an indirect branch. > > I.e. > >> /* EEXIT jumps here unless the enclave is doing something fancy. */ > ENDBR >> mov SGX_ENCLAVE_OFFSET_OF_RUN(%rbp), %rbx >> @@ -91,6 +94,7 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave) >> jmp .Lout >> >> .Lhandle_exception: >> + ENDBR >> mov SGX_ENCLAVE_OFFSET_OF_RUN(%rbp), %rbx >> >> /* Set the exception info. */
Thanks, I will fix that.
Yu-cheng
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