Commit 770ae1b7 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

x86/returnthunk: Allow different return thunks 



In preparation for call depth tracking on Intel SKL CPUs, make it possible
to patch in a SKL specific return thunk.

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/20220915111147.680469665@infradead.org
parent eaf44c81

arch/x86/include/asm/nospec-branch.h

+6 −0
Original line number Diff line number Diff line
@@ -208,6 +208,12 @@ extern void __x86_return_thunk(void); 
extern void zen_untrain_ret(void);

extern void entry_ibpb(void);



#ifdef CONFIG_CALL_THUNKS

extern void (*x86_return_thunk)(void);

#else

#define x86_return_thunk	(&__x86_return_thunk)

#endif



#ifdef CONFIG_RETPOLINE



#define GEN(reg) \

arch/x86/kernel/alternative.c

+13 −4
Original line number Diff line number Diff line
@@ -518,6 +518,11 @@ void __init_or_module noinline apply_retpolines(s32 *start, s32 *end) 
}



#ifdef CONFIG_RETHUNK



#ifdef CONFIG_CALL_THUNKS

void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk;

#endif



/*

 * Rewrite the compiler generated return thunk tail-calls.

 *
@@ -533,14 +538,18 @@ static int patch_return(void *addr, struct insn *insn, u8 *bytes) 
{

	int i = 0;



	if (cpu_feature_enabled(X86_FEATURE_RETHUNK))

	if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) {

		if (x86_return_thunk == __x86_return_thunk)

			return -1;



		i = JMP32_INSN_SIZE;

		__text_gen_insn(bytes, JMP32_INSN_OPCODE, addr, x86_return_thunk, i);

	} else {

		bytes[i++] = RET_INSN_OPCODE;

	}



	for (; i < insn->length;)

		bytes[i++] = INT3_INSN_OPCODE;



	return i;

}

arch/x86/kernel/ftrace.c

+1 −1
Original line number Diff line number Diff line
@@ -359,7 +359,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) 


	ip = trampoline + size;

	if (cpu_feature_enabled(X86_FEATURE_RETHUNK))

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

		__text_gen_insn(ip, JMP32_INSN_OPCODE, ip, x86_return_thunk, JMP32_INSN_SIZE);

	else

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

arch/x86/kernel/static_call.c

+1 −1
Original line number Diff line number Diff line
@@ -52,7 +52,7 @@ static void __ref __static_call_transform(void *insn, enum insn_type type, 


	case RET:

		if (cpu_feature_enabled(X86_FEATURE_RETHUNK))

			code = text_gen_insn(JMP32_INSN_OPCODE, insn, &__x86_return_thunk);

			code = text_gen_insn(JMP32_INSN_OPCODE, insn, x86_return_thunk);

		else

			code = &retinsn;

		break;

arch/x86/net/bpf_jit_comp.c

+1 −1
Original line number Diff line number Diff line
@@ -432,7 +432,7 @@ static void emit_return(u8 **pprog, u8 *ip) 
	u8 *prog = *pprog;



	if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) {

		emit_jump(&prog, &__x86_return_thunk, ip);

		emit_jump(&prog, x86_return_thunk, ip);

	} else {

		EMIT1(0xC3);		/* ret */

		if (IS_ENABLED(CONFIG_SLS))