lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-Id: <1198807702.6323.37.camel@brick>
Date:	Thu, 27 Dec 2007 18:08:22 -0800
From:	Harvey Harrison <harvey.harrison@...il.com>
To:	Masami Hiramatsu <mhiramat@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] x86: kprobes change kprobe_handler flow

Make the control flow of kprobe_handler more obvious.

Collapse the separate if blocks/gotos with if/else blocks
this unifies the duplication of the check for a breakpoint
instruction race with another cpu.

Create two jump targets:
	preempt_out: re-enables preemption before returning ret
	out: only returns ret

Signed-off-by: Harvey Harrison <harvey.harrison@...il.com>
---
Masami, noticed a small bug in the previous version in the !p
case when the breakpoint was the kernel's.  Please review this
version.

 arch/x86/kernel/kprobes.c |   60 +++++++++++++++++++++------------------------
 1 files changed, 28 insertions(+), 32 deletions(-)

diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 4e33329..f8c7ac1 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -480,32 +480,28 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
 	preempt_disable();
 	kcb = get_kprobe_ctlblk();
 
-	/* Check we're not actually recursing */
-	if (kprobe_running()) {
-		p = get_kprobe(addr);
-		if (p) {
+	p = get_kprobe(addr);
+	if (p) {
+		/* Check we're not actually recursing */
+		if (kprobe_running()) {
 			ret = reenter_kprobe(p, regs, kcb);
 			if (kcb->kprobe_status == KPROBE_REENTER)
-				return 1;
+			{
+				ret = 1;
+				goto out;
+			}
+			goto preempt_out;
 		} else {
-			if (*addr != BREAKPOINT_INSTRUCTION) {
-			/* The breakpoint instruction was removed by
-			 * another cpu right after we hit, no further
-			 * handling of this interrupt is appropriate
-			 */
-				regs->ip = (unsigned long)addr;
+			set_current_kprobe(p, regs, kcb);
+			kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+			if (p->pre_handler && p->pre_handler(p, regs))
+			{
+				/* handler set things up, skip ss setup */
 				ret = 1;
-				goto no_kprobe;
+				goto out;
 			}
-			p = __get_cpu_var(current_kprobe);
-			if (p->break_handler && p->break_handler(p, regs))
-				goto ss_probe;
 		}
-		goto no_kprobe;
-	}
-
-	p = get_kprobe(addr);
-	if (!p) {
+	} else {
 		if (*addr != BREAKPOINT_INSTRUCTION) {
 			/*
 			 * The breakpoint instruction was removed right
@@ -518,34 +514,34 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
 			 */
 			regs->ip = (unsigned long)addr;
 			ret = 1;
+			goto preempt_out;
+		}
+		if (kprobe_running()) {
+			p = __get_cpu_var(current_kprobe);
+			if (p->break_handler && p->break_handler(p, regs))
+				goto ss_probe;
 		}
 		/* Not one of ours: let kernel handle it */
-		goto no_kprobe;
+		goto preempt_out;
 	}
 
-	set_current_kprobe(p, regs, kcb);
-	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
-
-	if (p->pre_handler && p->pre_handler(p, regs))
-		/* handler has already set things up, so skip ss setup */
-		return 1;
-
 ss_probe:
+	ret = 1;
 #if !defined(CONFIG_PREEMPT) || defined(CONFIG_PM)
 	if (p->ainsn.boostable == 1 && !p->post_handler) {
 		/* Boost up -- we can execute copied instructions directly */
 		reset_current_kprobe();
 		regs->ip = (unsigned long)p->ainsn.insn;
-		preempt_enable_no_resched();
-		return 1;
+		goto preempt_out;
 	}
 #endif
 	prepare_singlestep(p, regs);
 	kcb->kprobe_status = KPROBE_HIT_SS;
-	return 1;
+	goto out;
 
-no_kprobe:
+preempt_out:
 	preempt_enable_no_resched();
+out:
 	return ret;
 }
 
-- 
1.5.4.rc2.1097.gb6e0d



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ