linux-kernel - [PATCH 8/7] uprobes: Fix arch_uprobe_disable_step() && UTASK_SSTEP

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Message-ID: <20120908170623.GB19311@redhat.com>
Date:	Sat, 8 Sep 2012 19:06:23 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Roland McGrath <roland@...k.frob.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 8/7] uprobes: Fix arch_uprobe_disable_step() &&
	UTASK_SSTEP_TRAPPED interaction

arch_uprobe_disable_step() should also take UTASK_SSTEP_TRAPPED into
account. In this case the probed insn was not executed, we need to
clear X86_EFLAGS_TF if it was set by us and that is all.

Again, this code will look more clean when we move it into
arch_uprobe_post_xol() and arch_uprobe_abort_xol().

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 arch/x86/kernel/uprobes.c |   14 ++++++++++----
 1 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 7e993d1..9538f00 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -706,14 +706,20 @@ void arch_uprobe_disable_step(struct arch_uprobe *auprobe)
 {
 	struct task_struct *task = current;
 	struct arch_uprobe_task	*autask	= &task->utask->autask;
+	bool trapped = (task->utask->state == UTASK_SSTEP_TRAPPED);
 	struct pt_regs *regs = task_pt_regs(task);
 	/*
 	 * The state of TIF_BLOCKSTEP was not saved so we can get an extra
 	 * SIGTRAP if we do not clear TF. We need to examine the opcode to
 	 * make it right.
 	 */
-	if (autask->saved_tf)
-		send_sig(SIGTRAP, task, 0);
-	else if (!(auprobe->fixups & UPROBE_FIX_SETF))
-		regs->flags &= ~X86_EFLAGS_TF;
+	if (unlikely(trapped)) {
+		if (!autask->saved_tf)
+			regs->flags &= ~X86_EFLAGS_TF;
+	} else {
+		if (autask->saved_tf)
+			send_sig(SIGTRAP, task, 0);
+		else if (!(auprobe->fixups & UPROBE_FIX_SETF))
+			regs->flags &= ~X86_EFLAGS_TF;
+	}
 }
-- 
1.5.5.1


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