From: Peter Zijlstra peterz@infradead.org
commit 089dd8e53126ebaf506e2dc0bf89d652c36bfc12 upstream.
Change FILL_RETURN_BUFFER so that objtool groks it and can generate correct ORC unwind information.
- Since ORC is alternative invariant; that is, all alternatives should have the same ORC entries, the __FILL_RETURN_BUFFER body can not be part of an alternative.
Therefore, move it out of the alternative and keep the alternative as a sort of jump_label around it.
- Use the ANNOTATE_INTRA_FUNCTION_CALL annotation to white-list these 'funny' call instructions to nowhere.
- Use UNWIND_HINT_EMPTY to 'fill' the speculation traps, otherwise objtool will consider them unreachable.
- Move the RSP adjustment into the loop, such that the loop has a deterministic stack layout.
Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Alexandre Chartre alexandre.chartre@oracle.com Acked-by: Josh Poimboeuf jpoimboe@redhat.com Link: https://lkml.kernel.org/r/20200428191700.032079304@infradead.org [cascardo: fixup because of backport of ba6e31af2be96c4d0536f2152ed6f7b6c11bca47 ("x86/speculation: Add LFENCE to RSB fill sequence")] [cascardo: no intra-function call validation support] [cascardo: avoid UNWIND_HINT_EMPTY because of svm] Signed-off-by: Thadeu Lima de Souza Cascardo cascardo@canonical.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/nospec-branch.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
--- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -4,11 +4,13 @@ #define _ASM_X86_NOSPEC_BRANCH_H_
#include <linux/static_key.h> +#include <linux/frame.h>
#include <asm/alternative.h> #include <asm/alternative-asm.h> #include <asm/cpufeatures.h> #include <asm/msr-index.h> +#include <asm/unwind_hints.h>
/* * This should be used immediately before a retpoline alternative. It tells @@ -60,9 +62,9 @@ lfence; \ jmp 775b; \ 774: \ + add $(BITS_PER_LONG/8) * 2, sp; \ dec reg; \ jnz 771b; \ - add $(BITS_PER_LONG/8) * nr, sp; \ /* barrier for jnz misprediction */ \ lfence; #else @@ -154,10 +156,8 @@ */ .macro FILL_RETURN_BUFFER reg:req nr:req ftr:req #ifdef CONFIG_RETPOLINE - ANNOTATE_NOSPEC_ALTERNATIVE - ALTERNATIVE "jmp .Lskip_rsb_@", \ - __stringify(__FILL_RETURN_BUFFER(\reg,\nr,%_ASM_SP)) \ - \ftr + ALTERNATIVE "jmp .Lskip_rsb_@", "", \ftr + __FILL_RETURN_BUFFER(\reg,\nr,%_ASM_SP) .Lskip_rsb_@: #endif .endm