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| author | Peter Zijlstra <peterz@infradead.org> | 2021-10-26 14:01:41 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-10-28 23:25:27 +0200 |
| commit | 1a6f74429c42a3854980359a758e222005712aee (patch) | |
| tree | 0168b8c980de23edda42aedacfb8d670cf816ba1 /arch/x86/lib | |
| parent | 6fda8a38865607db739be3e567a2387376222dbd (diff) | |
| download | linux-1a6f74429c42a3854980359a758e222005712aee.tar.gz | |
x86/retpoline: Create a retpoline thunk array
Stick all the retpolines in a single symbol and have the individual thunks as inner labels, this should guarantee thunk order and layout. Previously there were 16 (or rather 15 without rsp) separate symbols and a toolchain might reasonably expect it could displace them however it liked, with disregard for their relative position. However, now they're part of a larger symbol. Any change to their relative position would disrupt this larger _array symbol and thus not be sound. This is the same reasoning used for data symbols. On their own there is no guarantee about their relative position wrt to one aonther, but we're still able to do arrays because an array as a whole is a single larger symbol. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Tested-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/r/20211026120310.169659320@infradead.org
Diffstat (limited to 'arch/x86/lib')
| -rw-r--r-- | arch/x86/lib/retpoline.S | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S index 4c910fa92086..cf0b39f97adc 100644 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -28,16 +28,14 @@ .macro THUNK reg - .align 32 - -SYM_FUNC_START(__x86_indirect_thunk_\reg) + .align RETPOLINE_THUNK_SIZE +SYM_INNER_LABEL(__x86_indirect_thunk_\reg, SYM_L_GLOBAL) + UNWIND_HINT_EMPTY ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \ __stringify(RETPOLINE \reg), X86_FEATURE_RETPOLINE, \ __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_AMD -SYM_FUNC_END(__x86_indirect_thunk_\reg) - .endm /* @@ -55,10 +53,16 @@ SYM_FUNC_END(__x86_indirect_thunk_\reg) #define __EXPORT_THUNK(sym) _ASM_NOKPROBE(sym); EXPORT_SYMBOL(sym) #define EXPORT_THUNK(reg) __EXPORT_THUNK(__x86_indirect_thunk_ ## reg) + .align RETPOLINE_THUNK_SIZE +SYM_CODE_START(__x86_indirect_thunk_array) + #define GEN(reg) THUNK reg #include <asm/GEN-for-each-reg.h> #undef GEN + .align RETPOLINE_THUNK_SIZE +SYM_CODE_END(__x86_indirect_thunk_array) + #define GEN(reg) EXPORT_THUNK(reg) #include <asm/GEN-for-each-reg.h> #undef GEN |