The following commit has been merged into the x86/core branch of tip: Commit-ID: 36b64f101219dd9e6e4f0ea880b64e8a90da547b Gitweb: https://git.kernel.org/tip/36b64f101219dd9e6e4f0ea880b64e8a90da547b Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Thu, 15 Sep 2022 13:11:36 +02:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Mon, 17 Oct 2022 16:41:19 +02:00 x86/ftrace: Rebalance RSB 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@xxxxxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220915111148.823216933@xxxxxxxxxxxxx --- arch/x86/kernel/ftrace_64.S | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S index a90c55a..b5b54f5 100644 --- a/arch/x86/kernel/ftrace_64.S +++ b/arch/x86/kernel/ftrace_64.S @@ -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)
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