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x86/ftrace: Rebalance RSB

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ftrace_regs_caller() uses a PUSH;RET pattern to tail-call into a
direct-call function, this unbalances the RSB, fix that.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111148.823216933@infradead.org
This commit is contained in:
Peter Zijlstra 2022-09-15 13:11:36 +02:00
parent eac828eaef
commit 36b64f1012
1 changed files with 11 additions and 0 deletions
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11
arch/x86/kernel/ftrace_64.S
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@ -271,6 +271,17 @@ SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL)
/* Restore flags */
popfq
UNWIND_HINT_FUNC
/*
* The above left an extra return value on the stack; effectively
* doing a tail-call without using a register. This PUSH;RET
* pattern unbalances the RSB, inject a pointless CALL to rebalance.
*/
ANNOTATE_INTRA_FUNCTION_CALL
CALL .Ldo_rebalance
int3
.Ldo_rebalance:
add $8, %rsp
RET
SYM_FUNC_END(ftrace_regs_caller)