linux-kernel - [PATCH 8/X] uprobes: kill sstep

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Date:	Wed, 19 Oct 2011 23:52:06 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Hugh Dickins <hughd@...gle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 8/X] uprobes: kill sstep_complete()

Kill sstep_complete(), change uprobe_notify_resume() to use post_xol()
unconditionally.

As we already discussed, it is wrong to assume that regs->ip always
changes after the step. rep or jmp/call to self for example. We know
that this task has already done the step, we can rely on DIE_DEBUG
notification.
---
 kernel/uprobes.c |   37 +++++++++----------------------------
 1 files changed, 9 insertions(+), 28 deletions(-)

diff --git a/kernel/uprobes.c b/kernel/uprobes.c
index a323e0a..135b9a2 100644
--- a/kernel/uprobes.c
+++ b/kernel/uprobes.c
@@ -1321,24 +1321,6 @@ static int pre_ssout(struct uprobe *uprobe, struct pt_regs *regs,
 }
 
 /*
- * Verify from Instruction Pointer if singlestep has indeed occurred.
- * If Singlestep has occurred, then do post singlestep fix-ups.
- */
-static bool sstep_complete(struct uprobe *uprobe, struct pt_regs *regs)
-{
-	unsigned long vaddr = instruction_pointer(regs);
-
-	/*
-	 * If we have executed out of line, Instruction pointer
-	 * cannot be same as virtual address of XOL slot.
-	 */
-	if (vaddr == current->utask->xol_vaddr)
-		return false;
-	post_xol(uprobe, regs);
-	return true;
-}
-
-/*
  * uprobe_notify_resume gets called in task context just before returning
  * to userspace.
  *
@@ -1374,7 +1356,7 @@ void uprobe_notify_resume(struct pt_regs *regs)
 			if (!utask)
 				goto cleanup_ret;
 		}
-		/* TODO Start queueing signals. */
+
 		utask->active_uprobe = u;
 		handler_chain(u, regs);
 		utask->state = UTASK_SSTEP;
@@ -1385,15 +1367,14 @@ void uprobe_notify_resume(struct pt_regs *regs)
 			goto cleanup_ret;
 	} else if (utask->state == UTASK_SSTEP) {
 		u = utask->active_uprobe;
-		if (sstep_complete(u, regs)) {
-			put_uprobe(u);
-			utask->active_uprobe = NULL;
-			utask->state = UTASK_RUNNING;
-			user_disable_single_step(current);
-			xol_free_insn_slot(current);
-
-			/* TODO Stop queueing signals. */
-		}
+
+		post_xol(u, regs);	/* TODO: check result? */
+
+		put_uprobe(u);
+		utask->active_uprobe = NULL;
+		utask->state = UTASK_RUNNING;
+		user_disable_single_step(current);
+		xol_free_insn_slot(current);
 	}
 	return;
 
-- 
1.5.5.1


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