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objtool: Generate ORC data for __pfx code

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Allow unwinding from prefix code by copying the CFI from the starting
instruction of the corresponding function.  Even when the NOPs are
replaced, they're still stack-invariant instructions so the same ORC
entry can be reused everywhere.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/bc3344e51f3e87102f1301a0be0f72a7689ea4a4.1681331135.git.jpoimboe@kernel.org
This commit is contained in:
Josh Poimboeuf 2023-04-12 13:26:15 -07:00 committed by Peter Zijlstra
parent 4a2c3448ed
commit 5743654f5e
1 changed files with 14 additions and 0 deletions
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14
tools/objtool/check.c
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@ -4117,6 +4117,7 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
{
struct instruction *insn, *prev;
struct cfi_state *cfi;
insn = find_insn(file, func->sec, func->offset);
if (!insn)
@ -4145,6 +4146,19 @@ static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
if (!prev)
return -1;
if (!insn->cfi) {
/*
* This can happen if stack validation isn't enabled or the
* function is annotated with STACK_FRAME_NON_STANDARD.
*/
return 0;
}
/* Propagate insn->cfi to the prefix code */
cfi = cfi_hash_find_or_add(insn->cfi);
for (; prev != insn; prev = next_insn_same_sec(file, prev))
prev->cfi = cfi;
return 0;
}