Commit 36b64f10 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111148.823216933@infradead.org
parent eac828ea

arch/x86/kernel/ftrace_64.S

+11 −0
Original line number Diff line number Diff line
@@ -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)