Patch "hw_breakpoints, powerpc: Fix CONFIG_HAVE_HW_BREAKPOINT off-case in ptrace_set_debugreg()" has been added to the 2.6.38-stable tree

This is a note to let you know that I've just added the patch titled

hw_breakpoints, powerpc: Fix CONFIG_HAVE_HW_BREAKPOINT off-case in ptrace_set_debugreg()

to the 2.6.38-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
hw_breakpoints-powerpc-fix-config_have_hw_breakpoint-off-case-in-ptrace_set_debugreg.patch
and it can be found in the queue-2.6.38 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Frederic Weisbecker <[email protected]>
Date: Fri, 6 May 2011 01:53:18 +0200
Subject: hw_breakpoints, powerpc: Fix CONFIG_HAVE_HW_BREAKPOINT off-case in ptrace_set_debugreg()

From: Frederic Weisbecker <[email protected]>

commit 925f83c085e1bb08435556c5b4844a60de002e31 upstream.

We make use of ptrace_get_breakpoints() / ptrace_put_breakpoints() to protect ptrace_set_debugreg() even if CONFIG_HAVE_HW_BREAKPOINT if off. However in this case, these APIs are not implemented.

To fix this, push the protection down inside the relevant ifdef. Best would be to export the code inside CONFIG_HAVE_HW_BREAKPOINT into a standalone function to cleanup the ifdefury there and call the breakpoint ref API inside. But as it is more invasive, this should be rather made in an -rc1.

Fixes this build error:

arch/powerpc/kernel/ptrace.c:1594: error: implicit declaration of function 'ptrace_get_breakpoints' make[2]: ***

---
 arch/powerpc/kernel/ptrace.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

@@ -924,12 +924,16 @@ int ptrace_set_debugreg(struct task_stru
 	if (data && !(data & DABR_TRANSLATION))
 		return -EIO;
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
+	if (ptrace_get_breakpoints(task) < 0)
+		return -ESRCH;
+
 	bp = thread->ptrace_bps[0];
 	if ((!data) || !(data & (DABR_DATA_WRITE | DABR_DATA_READ))) {
 		if (bp) {
 			unregister_hw_breakpoint(bp);
 			thread->ptrace_bps[0] = NULL;
 		}
+		ptrace_put_breakpoints(task);
 		return 0;
 	}
 	if (bp) {

@@ -939,9 +943,12 @@ int ptrace_set_debugreg(struct task_stru
 					(DABR_DATA_WRITE | DABR_DATA_READ),
 							&attr.bp_type);
 		ret =  modify_user_hw_breakpoint(bp, &attr);
-		if (ret)
+		if (ret) {
+			ptrace_put_breakpoints(task);
 			return ret;
+		}
 		thread->ptrace_bps[0] = bp;
+		ptrace_put_breakpoints(task);
 		thread->dabr = data;
 		return 0;
 	}

@@ -956,9 +963,12 @@ int ptrace_set_debugreg(struct task_stru
 							ptrace_triggered, task);
 	if (IS_ERR(bp)) {
 		thread->ptrace_bps[0] = NULL;
+		ptrace_put_breakpoints(task);
 		return PTR_ERR(bp);
 	}
 
+	ptrace_put_breakpoints(task);
+
 #endif /* CONFIG_HAVE_HW_BREAKPOINT */
 
 	/* Move contents to the DABR register */

Patches currently in stable-queue which might be from [email protected] are

queue-2.6.38/ptrace-prepare-to-fix-racy-accesses-on-task-breakpoints.patch queue-2.6.38/hw_breakpoints-powerpc-fix-config_have_hw_breakpoint-off-case-in-ptrace_set_debugreg.patch queue-2.6.38/x86-hw_breakpoints-fix-racy-access-to-ptrace-breakpoints.patch