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x86/nospec, objtool: Introduce ANNOTATE_IGNORE_ALTERNATIVE

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To facillitate other usage of ignoring alternatives; rename
ANNOTATE_NOSPEC_IGNORE to ANNOTATE_IGNORE_ALTERNATIVE.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2019-03-18 14:33:07 +01:00 committed by Ingo Molnar
parent b69656fa7e
commit ff05ab2305
4 changed files with 34 additions and 23 deletions
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11
arch/x86/include/asm/alternative-asm.h
View File

@ -19,6 +19,17 @@
.endm
#endif
/*
* objtool annotation to ignore the alternatives and only consider the original
* instruction(s).
*/
.macro ANNOTATE_IGNORE_ALTERNATIVE
.Lannotate_\@:
.pushsection .discard.ignore_alts
.long .Lannotate_\@ - .
.popsection
.endm
/*
* Issue one struct alt_instr descriptor entry (need to put it into
* the section .altinstructions, see below). This entry contains

10
arch/x86/include/asm/alternative.h
View File

@ -45,6 +45,16 @@
#define LOCK_PREFIX ""
#endif
/*
* objtool annotation to ignore the alternatives and only consider the original
* instruction(s).
*/
#define ANNOTATE_IGNORE_ALTERNATIVE \
"999:\n\t" \
".pushsection .discard.ignore_alts\n\t" \
".long 999b - .\n\t" \
".popsection\n\t"
struct alt_instr {
s32 instr_offset; /* original instruction */
s32 repl_offset; /* offset to replacement instruction */

28
arch/x86/include/asm/nospec-branch.h
View File

@ -10,6 +10,15 @@
#include <asm/cpufeatures.h>
#include <asm/msr-index.h>
/*
* This should be used immediately before a retpoline alternative. It tells
* objtool where the retpolines are so that it can make sense of the control
* flow by just reading the original instruction(s) and ignoring the
* alternatives.
*/
#define ANNOTATE_NOSPEC_ALTERNATIVE \
ANNOTATE_IGNORE_ALTERNATIVE
/*
* Fill the CPU return stack buffer.
*
@ -56,19 +65,6 @@
#ifdef __ASSEMBLY__
/*
* This should be used immediately before a retpoline alternative. It tells
* objtool where the retpolines are so that it can make sense of the control
* flow by just reading the original instruction(s) and ignoring the
* alternatives.
*/
.macro ANNOTATE_NOSPEC_ALTERNATIVE
.Lannotate_\@:
.pushsection .discard.nospec
.long .Lannotate_\@ - .
.popsection
.endm
/*
* This should be used immediately before an indirect jump/call. It tells
* objtool the subsequent indirect jump/call is vouched safe for retpoline
@ -152,12 +148,6 @@
#else /* __ASSEMBLY__ */
#define ANNOTATE_NOSPEC_ALTERNATIVE \
"999:\n\t" \
".pushsection .discard.nospec\n\t" \
".long 999b - .\n\t" \
".popsection\n\t"
#define ANNOTATE_RETPOLINE_SAFE \
"999:\n\t" \
".pushsection .discard.retpoline_safe\n\t" \

8
tools/objtool/check.c
View File

@ -457,13 +457,13 @@ static void add_ignores(struct objtool_file *file)
* But it at least allows objtool to understand the control flow *around* the
* retpoline.
*/
static int add_nospec_ignores(struct objtool_file *file)
static int add_ignore_alternatives(struct objtool_file *file)
{
struct section *sec;
struct rela *rela;
struct instruction *insn;
sec = find_section_by_name(file->elf, ".rela.discard.nospec");
sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
if (!sec)
return 0;
@ -475,7 +475,7 @@ static int add_nospec_ignores(struct objtool_file *file)
insn = find_insn(file, rela->sym->sec, rela->addend);
if (!insn) {
WARN("bad .discard.nospec entry");
WARN("bad .discard.ignore_alts entry");
return -1;
}
@ -1239,7 +1239,7 @@ static int decode_sections(struct objtool_file *file)
add_ignores(file);
ret = add_nospec_ignores(file);
ret = add_ignore_alternatives(file);
if (ret)
return ret;