From: Peter Zijlstra <peterz@infradead.org>

Date: Mon, 23 Jan 2023 21:59:16 +0100

Subject: [PATCH] x86/alternatives: Introduce int3_emulate_jcc()

References: bsc#1012628

Patch-mainline: 6.2.1

Git-commit: db7adcfd1cec4e95155e37bc066fddab302c6340

commit db7adcfd1cec4e95155e37bc066fddab302c6340 upstream.

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: Peter Zijlstra (Intel) <peterz@infradead.org>

Signed-off-by: Ingo Molnar <mingo@kernel.org>

Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Link: https://lore.kernel.org/r/20230123210607.057678245@infradead.org

Cc: Nathan Chancellor <nathan@kernel.org>

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Jiri Slaby <jslaby@suse.cz>

---

 arch/x86/include/asm/text-patching.h | 31 +++++++++++++++++++++++

 arch/x86/kernel/kprobes/core.c       | 38 ++++++----------------------

 2 files changed, 39 insertions(+), 30 deletions(-)

diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h

index f4b87f08..29832c33 100644

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

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

@@ -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 */

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c

index 695873c0..0ce969ae 100644

--- a/arch/x86/kernel/kprobes/core.c

+++ b/arch/x86/kernel/kprobes/core.c

@@ -464,50 +464,26 @@ 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;

+	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* */

@@ -535,7 +511,9 @@ 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);

-- 

2.35.3