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authorIngo Molnar <mingo@elte.hu>2006-11-17 05:57:49 +0100
committerLinus Torvalds <torvalds@woody.osdl.org>2006-11-17 08:20:09 -0800
commit0796bdb7e9e4a48b401f4fba1ee5dc79a45528ef (patch)
treefe7a37931bc1f2ac79b61102d190277f9a1c039e
parent4be703906cffd5902028d20626e636ba21fb0b61 (diff)
[PATCH] x86_64: stack unwinder crash fix
the new dwarf2 unwinder crashes while trying to dump the stack: Leftover inexact backtrace: Unable to handle kernel paging request at ffffffff82800000 RIP: [<ffffffff8026cf26>] dump_trace+0x35b/0x3d2 PGD 203027 PUD 205027 PMD 0 Oops: 0000 [2] PREEMPT SMP CPU 0 Modules linked in: Pid: 30, comm: khelper Not tainted 2.6.19-rc6-rt1 #11 RIP: 0010:[<ffffffff8026cf26>] [<ffffffff8026cf26>] dump_trace+0x35b/0x3d2 RSP: 0000:ffff81003fb9d848 EFLAGS: 00010006 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff805b3520 RDI: 0000000000000000 RBP: ffffffff827ffff9 R08: ffffffff80aad000 R09: 0000000000000005 R10: ffffffff80aae000 R11: ffffffff8037961b R12: ffff81003fb9d858 R13: 0000000000000000 R14: ffffffff80598460 R15: ffffffff80ab1fc0 FS: 0000000000000000(0000) GS:ffffffff806c4200(0000) knlGS:0000000000000000 CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b CR2: ffffffff82800000 CR3: 0000000000201000 CR4: 00000000000006e0 this crash happened because it did not sanitize the dwarf2 data it got, and got an unaligned stack pointer - which happily walked past the process stack (and eventually reached the end of kernel memory and pagefaulted there) due to this naive iteration condition: HANDLE_STACK (((long) stack & (THREAD_SIZE-1)) != 0); note that i386 is alot more conservative when it comes to trusting stack pointers: static inline int valid_stack_ptr(struct thread_info *tinfo, void *p) { return p > (void *)tinfo && p < (void *)tinfo + THREAD_SIZE - 3; } but the x86_64 code did not take this bit of i386 code. The fix is to align the stack pointer. Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Andi Kleen <ak@suse.de> Cc: Jan Beulich <jbeulich@novell.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/x86_64/kernel/traps.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index 7819022a8db..a153d0a01b7 100644
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -290,6 +290,12 @@ void dump_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s
if (tsk && tsk != current)
stack = (unsigned long *)tsk->thread.rsp;
}
+ /*
+ * Align the stack pointer on word boundary, later loops
+ * rely on that (and corruption / debug info bugs can cause
+ * unaligned values here):
+ */
+ stack = (unsigned long *)((unsigned long)stack & ~(sizeof(long)-1));
/*
* Print function call entries within a stack. 'cond' is the