Commit 0ad90b41 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Zheng Zengkai
Browse files

static_call/x86: Add __static_call_return0() 

mainline inclusion
from mainline-5.12-rc1
commit 3f2a8fc4
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I410UT
CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3f2a8fc4b15de18644e8a80a09edda168676e22c



---------------------------

Provide a stub function that return 0 and wire up the static call site
patching to replace the CALL with a single 5 byte instruction that
clears %RAX, the return value register.

The function can be cast to any function pointer type that has a
single %RAX return (including pointers). Also provide a version that
returns an int for convenience. We are clearing the entire %RAX register
in any case, whether the return value is 32 or 64 bits, since %RAX is
always a scratch register anyway.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210118141223.123667-2-frederic@kernel.org


Signed-off-by: default avatarMa Junhai <majunhai2@huawei.com>
Reviewed-by: default avatarChen Hui <judy.chenhui@huawei.com>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
parent 4ffe31e2

arch/x86/kernel/static_call.c

+15 −2
Original line number Diff line number Diff line
@@ -11,14 +11,26 @@ enum insn_type { 
	RET = 3,  /* tramp / site cond-tail-call */

};



/*

 * data16 data16 xorq %rax, %rax - a single 5 byte instruction that clears %rax

 * The REX.W cancels the effect of any data16.

 */

static const u8 xor5rax[] = { 0x66, 0x66, 0x48, 0x31, 0xc0 };



static void __ref __static_call_transform(void *insn, enum insn_type type, void *func)

{

	const void *emulate = NULL;

	int size = CALL_INSN_SIZE;

	const void *code;



	switch (type) {

	case CALL:

		code = text_gen_insn(CALL_INSN_OPCODE, insn, func);

		if (func == &__static_call_return0) {

			emulate = code;

			code = &xor5rax;

		}



		break;



	case NOP:
@@ -41,7 +53,7 @@ static void __ref __static_call_transform(void *insn, enum insn_type type, void 
	if (unlikely(system_state == SYSTEM_BOOTING))

		return text_poke_early(insn, code, size);



	text_poke_bp(insn, code, size, NULL);

	text_poke_bp(insn, code, size, emulate);

}



static void __static_call_validate(void *insn, bool tail)
@@ -54,7 +66,8 @@ static void __static_call_validate(void *insn, bool tail) 
			return;

	} else {

		if (opcode == CALL_INSN_OPCODE ||

		    !memcmp(insn, ideal_nops[NOP_ATOMIC5], 5))

		    !memcmp(insn, ideal_nops[NOP_ATOMIC5], 5) ||

		    !memcmp(insn, xor5rax, 5))

			return;

	}

include/linux/static_call.h

+12 −0
Original line number Diff line number Diff line
@@ -148,6 +148,8 @@ extern void __static_call_update(struct static_call_key *key, void *tramp, void 
extern int static_call_mod_init(struct module *mod);

extern int static_call_text_reserved(void *start, void *end);



extern long __static_call_return0(void);



#define DEFINE_STATIC_CALL(name, _func)					\

	DECLARE_STATIC_CALL(name, _func);				\

	struct static_call_key STATIC_CALL_KEY(name) = {		\
@@ -219,6 +221,11 @@ static inline int static_call_text_reserved(void *start, void *end) 
	return 0;

}



static inline long __static_call_return0(void)

{

	return 0;

}



#define EXPORT_STATIC_CALL(name)					\

	EXPORT_SYMBOL(STATIC_CALL_KEY(name));				\

	EXPORT_SYMBOL(STATIC_CALL_TRAMP(name))
@@ -240,6 +247,11 @@ struct static_call_key { 
	void *func;

};



static inline long __static_call_return0(void)

{

	return 0;

}



#define DEFINE_STATIC_CALL(name, _func)					\

	DECLARE_STATIC_CALL(name, _func);				\

	struct static_call_key STATIC_CALL_KEY(name) = {		\

kernel/static_call.c

+5 −0
Original line number Diff line number Diff line
@@ -496,6 +496,11 @@ int __init static_call_init(void) 
}

early_initcall(static_call_init);



long __static_call_return0(void)

{

	return 0;

}



#ifdef CONFIG_STATIC_CALL_SELFTEST



static int func_a(int x)