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| author | Peter Zijlstra <peterz@infradead.org> | 2020-04-16 14:34:26 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2020-04-30 20:14:34 +0200 |
| commit | cc1ac9c792810b93783a7de344f428922af8d98c (patch) | |
| tree | 33da496a06b118211f1178a55f3d30d51f96abec /arch/x86/lib | |
| parent | 34fdce6981b96920ced4e0ee56e9db3fb03a33f0 (diff) | |
| download | linux-cc1ac9c792810b93783a7de344f428922af8d98c.tar.bz2 | |
x86/retpoline: Fix retpoline unwind
Currently objtool cannot understand retpolines, and thus cannot
generate ORC unwind information for them. This means that we cannot
unwind from the middle of a retpoline.
The recent ANNOTATE_INTRA_FUNCTION_CALL and UNWIND_HINT_RET_OFFSET
support in objtool enables it to understand the basic retpoline
construct. A further problem is that the ORC unwind information is
alternative invariant; IOW. every alternative should have the same
ORC, retpolines obviously violate this. This means we need to
out-of-line them.
Since all GCC generated code already uses out-of-line retpolines, this
should not affect performance much, if anything.
This will enable objtool to generate valid ORC data for the
out-of-line copies, which means we can correctly and reliably unwind
through a retpoline.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200428191700.210835357@infradead.org
Diffstat (limited to 'arch/x86/lib')
| -rw-r--r-- | arch/x86/lib/retpoline.S | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S index 9cc5480300c9..b4c43a9b1483 100644 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -7,15 +7,31 @@ #include <asm/alternative-asm.h> #include <asm/export.h> #include <asm/nospec-branch.h> +#include <asm/unwind_hints.h> +#include <asm/frame.h> .macro THUNK reg .section .text.__x86.indirect_thunk + .align 32 SYM_FUNC_START(__x86_indirect_thunk_\reg) - CFI_STARTPROC - JMP_NOSPEC %\reg - CFI_ENDPROC + JMP_NOSPEC \reg SYM_FUNC_END(__x86_indirect_thunk_\reg) + +SYM_FUNC_START_NOALIGN(__x86_retpoline_\reg) + ANNOTATE_INTRA_FUNCTION_CALL + call .Ldo_rop_\@ +.Lspec_trap_\@: + UNWIND_HINT_EMPTY + pause + lfence + jmp .Lspec_trap_\@ +.Ldo_rop_\@: + mov %\reg, (%_ASM_SP) + UNWIND_HINT_RET_OFFSET + ret +SYM_FUNC_END(__x86_retpoline_\reg) + .endm /* @@ -32,6 +48,7 @@ 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) +#define EXPORT_RETPOLINE(reg) __EXPORT_THUNK(__x86_retpoline_ ## reg) #undef GEN #define GEN(reg) THUNK reg @@ -41,3 +58,6 @@ 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) EXPORT_RETPOLINE(reg) +#include <asm/GEN-for-each-reg.h> |