Commit 1f001e9d authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Borislav Petkov
Browse files

x86/ftrace: Use alternative RET encoding 



Use the return thunk in ftrace trampolines, if needed.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
parent ee88d363

arch/x86/kernel/ftrace.c

+5 −2
Original line number Diff line number Diff line
@@ -301,7 +301,7 @@ union ftrace_op_code_union { 
	} __attribute__((packed));

};



#define RET_SIZE		1 + IS_ENABLED(CONFIG_SLS)

#define RET_SIZE		(IS_ENABLED(CONFIG_RETPOLINE) ? 5 : 1 + IS_ENABLED(CONFIG_SLS))



static unsigned long

create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
@@ -357,7 +357,10 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) 
		goto fail;



	ip = trampoline + size;

	memcpy(ip, retq, RET_SIZE);

	if (cpu_feature_enabled(X86_FEATURE_RETHUNK))

		__text_gen_insn(ip, JMP32_INSN_OPCODE, ip, &__x86_return_thunk, JMP32_INSN_SIZE);

	else

		memcpy(ip, retq, sizeof(retq));



	/* No need to test direct calls on created trampolines */

	if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {