Commit db7adcfd authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

x86/alternatives: Introduce int3_emulate_jcc() 



Move the kprobe Jcc emulation into int3_emulate_jcc() so it can be
used by more code -- specifically static_call() will need this.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20230123210607.057678245@infradead.org
parent 5d1dd961

arch/x86/include/asm/text-patching.h

+31 −0
Original line number Diff line number Diff line
@@ -184,6 +184,37 @@ void int3_emulate_ret(struct pt_regs *regs) 
	unsigned long ip = int3_emulate_pop(regs);

	int3_emulate_jmp(regs, ip);

}



static __always_inline

void int3_emulate_jcc(struct pt_regs *regs, u8 cc, unsigned long ip, unsigned long disp)

{

	static const unsigned long jcc_mask[6] = {

		[0] = X86_EFLAGS_OF,

		[1] = X86_EFLAGS_CF,

		[2] = X86_EFLAGS_ZF,

		[3] = X86_EFLAGS_CF | X86_EFLAGS_ZF,

		[4] = X86_EFLAGS_SF,

		[5] = X86_EFLAGS_PF,

	};



	bool invert = cc & 1;

	bool match;



	if (cc < 0xc) {

		match = regs->flags & jcc_mask[cc >> 1];

	} else {

		match = ((regs->flags & X86_EFLAGS_SF) >> X86_EFLAGS_SF_BIT) ^

			((regs->flags & X86_EFLAGS_OF) >> X86_EFLAGS_OF_BIT);

		if (cc >= 0xe)

			match = match || (regs->flags & X86_EFLAGS_ZF);

	}



	if ((match && !invert) || (!match && invert))

		ip += disp;



	int3_emulate_jmp(regs, ip);

}



#endif /* !CONFIG_UML_X86 */



#endif /* _ASM_X86_TEXT_PATCHING_H */

arch/x86/kernel/kprobes/core.c

+8 −30
Original line number Diff line number Diff line
@@ -460,50 +460,26 @@ static void kprobe_emulate_call(struct kprobe *p, struct pt_regs *regs) 
}

NOKPROBE_SYMBOL(kprobe_emulate_call);



static nokprobe_inline

void __kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs, bool cond)

static void kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs)

{

	unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;



	if (cond)

	ip += p->ainsn.rel32;

	int3_emulate_jmp(regs, ip);

}



static void kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs)

{

	__kprobe_emulate_jmp(p, regs, true);

}

NOKPROBE_SYMBOL(kprobe_emulate_jmp);



static const unsigned long jcc_mask[6] = {

	[0] = X86_EFLAGS_OF,

	[1] = X86_EFLAGS_CF,

	[2] = X86_EFLAGS_ZF,

	[3] = X86_EFLAGS_CF | X86_EFLAGS_ZF,

	[4] = X86_EFLAGS_SF,

	[5] = X86_EFLAGS_PF,

};



static void kprobe_emulate_jcc(struct kprobe *p, struct pt_regs *regs)

{

	bool invert = p->ainsn.jcc.type & 1;

	bool match;

	unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;



	if (p->ainsn.jcc.type < 0xc) {

		match = regs->flags & jcc_mask[p->ainsn.jcc.type >> 1];

	} else {

		match = ((regs->flags & X86_EFLAGS_SF) >> X86_EFLAGS_SF_BIT) ^

			((regs->flags & X86_EFLAGS_OF) >> X86_EFLAGS_OF_BIT);

		if (p->ainsn.jcc.type >= 0xe)

			match = match || (regs->flags & X86_EFLAGS_ZF);

	}

	__kprobe_emulate_jmp(p, regs, (match && !invert) || (!match && invert));

	int3_emulate_jcc(regs, p->ainsn.jcc.type, ip, p->ainsn.rel32);

}

NOKPROBE_SYMBOL(kprobe_emulate_jcc);



static void kprobe_emulate_loop(struct kprobe *p, struct pt_regs *regs)

{

	unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;

	bool match;



	if (p->ainsn.loop.type != 3) {	/* LOOP* */
@@ -531,7 +507,9 @@ static void kprobe_emulate_loop(struct kprobe *p, struct pt_regs *regs) 
	else if (p->ainsn.loop.type == 1)	/* LOOPE */

		match = match && (regs->flags & X86_EFLAGS_ZF);



	__kprobe_emulate_jmp(p, regs, match);

	if (match)

		ip += p->ainsn.rel32;

	int3_emulate_jmp(regs, ip);

}

NOKPROBE_SYMBOL(kprobe_emulate_loop);