linux-kernel - [v2][PATCH 3/3] powerpc/kgdb: restore current_thread

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-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1345687820-5248-3-git-send-email-tiejun.chen@windriver.com>
Date:	Thu, 23 Aug 2012 10:10:20 +0800
From:	Tiejun Chen <tiejun.chen@...driver.com>
To:	<benh@...nel.crashing.org>
CC:	<jason.wessel@...driver.com>, <linuxppc-dev@...ts.ozlabs.org>,
	<linux-kernel@...r.kernel.org>
Subject: [v2][PATCH 3/3] powerpc/kgdb: restore current_thread_info properly

For powerpc BooKE and e200, singlestep is handled on the critical/dbg
exception stack. This causes current_thread_info() to fail for kgdb
internal, so previously We work around this issue by copying
the thread_info from the kernel stack before calling kgdb_handle_exception,
and copying it back afterwards.

But actually we don't do this properly. We should backup current_thread_info
then restore that when exit.

Signed-off-by: Tiejun Chen <tiejun.chen@...driver.com>
---
v2: fix a typo in patch head description.

 arch/powerpc/kernel/kgdb.c |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
index 05adb69..c470a40 100644
--- a/arch/powerpc/kernel/kgdb.c
+++ b/arch/powerpc/kernel/kgdb.c
@@ -25,6 +25,7 @@
 #include <asm/processor.h>
 #include <asm/machdep.h>
 #include <asm/debug.h>
+#include <linux/slab.h>
 
 /*
  * This table contains the mapping between PowerPC hardware trap types, and
@@ -153,6 +154,8 @@ static int kgdb_handle_breakpoint(struct pt_regs *regs)
 static int kgdb_singlestep(struct pt_regs *regs)
 {
 	struct thread_info *thread_info, *exception_thread_info;
+	struct thread_info *backup_current_thread_info = \
+		(struct thread_info *)kmalloc(sizeof(struct thread_info), GFP_KERNEL);
 
 	if (user_mode(regs))
 		return 0;
@@ -170,13 +173,17 @@ static int kgdb_singlestep(struct pt_regs *regs)
 	thread_info = (struct thread_info *)(regs->gpr[1] & ~(THREAD_SIZE-1));
 	exception_thread_info = current_thread_info();
 
-	if (thread_info != exception_thread_info)
+	if (thread_info != exception_thread_info) {
+		/* Save the original current_thread_info. */
+		memcpy(backup_current_thread_info, exception_thread_info, sizeof *thread_info);
 		memcpy(exception_thread_info, thread_info, sizeof *thread_info);
+	}
 
 	kgdb_handle_exception(0, SIGTRAP, 0, regs);
 
 	if (thread_info != exception_thread_info)
-		memcpy(thread_info, exception_thread_info, sizeof *thread_info);
+		/* Restore current_thread_info lastly. */
+		memcpy(exception_thread_info, backup_current_thread_info, sizeof *thread_info);
 
 	return 1;
 }
-- 
1.5.6

--
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/