[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>