diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2021-03-26 16:12:15 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2021-04-02 12:47:28 +0200 |
| commit | 9bc0bb50727c8ac69fbb33fb937431cf3518ff37 (patch) | |
| tree | 586a82e95847ae6c3f393728fb074b1d6df9ae71 /arch/x86/lib | |
| parent | 50e7b4a1a1b264fc7df0698f2defb93cadf19a7b (diff) | |
objtool/x86: Rewrite retpoline thunk calls
When the compiler emits: "CALL __x86_indirect_thunk_\reg" for an
indirect call, have objtool rewrite it to:
ALTERNATIVE "call __x86_indirect_thunk_\reg",
"call *%reg", ALT_NOT(X86_FEATURE_RETPOLINE)
Additionally, in order to not emit endless identical
.altinst_replacement chunks, use a global symbol for them, see
__x86_indirect_alt_*.
This also avoids objtool from having to do code generation.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/20210326151300.320177914@infradead.org
Diffstat (limited to 'arch/x86/lib')
| -rw-r--r-- | arch/x86/lib/retpoline.S | 41 |
1 files changed, 40 insertions, 1 deletions
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S index d2c0d14c1e22..4d32cb06ffd5 100644 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -10,6 +10,8 @@ #include <asm/unwind_hints.h> #include <asm/frame.h> + .section .text.__x86.indirect_thunk + .macro RETPOLINE reg ANNOTATE_INTRA_FUNCTION_CALL call .Ldo_rop_\@ @@ -25,9 +27,9 @@ .endm .macro THUNK reg - .section .text.__x86.indirect_thunk .align 32 + SYM_FUNC_START(__x86_indirect_thunk_\reg) ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \ @@ -39,6 +41,32 @@ SYM_FUNC_END(__x86_indirect_thunk_\reg) .endm /* + * This generates .altinstr_replacement symbols for use by objtool. They, + * however, must not actually live in .altinstr_replacement since that will be + * discarded after init, but module alternatives will also reference these + * symbols. + * + * Their names matches the "__x86_indirect_" prefix to mark them as retpolines. + */ +.macro ALT_THUNK reg + + .align 1 + +SYM_FUNC_START_NOALIGN(__x86_indirect_alt_call_\reg) + ANNOTATE_RETPOLINE_SAFE +1: call *%\reg +2: .skip 5-(2b-1b), 0x90 +SYM_FUNC_END(__x86_indirect_alt_call_\reg) + +SYM_FUNC_START_NOALIGN(__x86_indirect_alt_jmp_\reg) + ANNOTATE_RETPOLINE_SAFE +1: jmp *%\reg +2: .skip 5-(2b-1b), 0x90 +SYM_FUNC_END(__x86_indirect_alt_jmp_\reg) + +.endm + +/* * Despite being an assembler file we can't just use .irp here * because __KSYM_DEPS__ only uses the C preprocessor and would * only see one instance of "__x86_indirect_thunk_\reg" rather @@ -61,3 +89,14 @@ SYM_FUNC_END(__x86_indirect_thunk_\reg) #define GEN(reg) EXPORT_THUNK(reg) #include <asm/GEN-for-each-reg.h> +#undef GEN +#define GEN(reg) ALT_THUNK reg +#include <asm/GEN-for-each-reg.h> + +#undef GEN +#define GEN(reg) __EXPORT_THUNK(__x86_indirect_alt_call_ ## reg) +#include <asm/GEN-for-each-reg.h> + +#undef GEN +#define GEN(reg) __EXPORT_THUNK(__x86_indirect_alt_jmp_ ## reg) +#include <asm/GEN-for-each-reg.h> |