When an interrupt occurs in userspace, we can call trace_hardirqs_on/off()
With one level stack. But if we have irqsoff tracing enabled,
it checks both CALLER_ADDR0 and CALLER_ADDR1. The second call
goes two stack frames up. If this is from user space, then there may
not exist a second stack.
Add a second stack when calling trace_hardirqs_on/off() otherwise
the following oops might occur:
Oops: Kernel access of bad area, sig: 11 [#1]
PREEMPT SMP NR_CPUS=2 PA Semi PWRficient
last sysfs file: /sys/block/sda/size
Modules linked in: ohci_hcd ehci_hcd usbcore
NIP: c0000000000e1c00 LR: c0000000000034d4 CTR: 000000011012c440
REGS: c00000003e2f3af0 TRAP: 0300 Not tainted (2.6.37-rc6+)
MSR: 9000000000001032 <ME,IR,DR> CR: 48044444 XER: 20000000
DAR: 00000001ffb9db50, DSISR: 0000000040000000
TASK = c00000003e1a00a0[2088] 'emacs' THREAD: c00000003e2f0000 CPU: 1
GPR00: 0000000000000001 c00000003e2f3d70 c00000000084e0d0 c0000000008816e8
GPR04: 000000001034c678 000000001032e8f9 0000000010336540 0000000040020000
GPR08: 0000000040020000 00000001ffb9db40 c00000003e2f3e30 0000000060000000
GPR12: 100000000000f032 c00000000fff0280 000000001032e8c9 0000000000000008
GPR16: 00000000105be9c0 00000000105be950 00000000105be9b0 00000000105be950
GPR20: 00000000ffb9dc50 00000000ffb9dbf0 00000000102f0000 00000000102f0000
GPR24: 00000000102e0000 00000000102f0000 0000000010336540 c0000000009ded38
GPR28: 00000000102e0000 c0000000000034d4 c0000000007ccb10 c00000003e2f3d70
NIP [c0000000000e1c00] .trace_hardirqs_off+0xb0/0x1d0
LR [c0000000000034d4] decrementer_common+0xd4/0x100
Call Trace:
[c00000003e2f3d70] [c00000003e2f3e30] 0xc00000003e2f3e30 (unreliable)
[c00000003e2f3e30] [c0000000000034d4] decrementer_common+0xd4/0x100
Instruction dump:
81690000 7f8b0000 419e0018 f84a0028 60000000 60000000 60000000 e95f0000
80030000 e92a0000 eb6301f8 2f800000 <eb890010> 41fe00dc a06d000a eb1e8050
---[ end trace 4ec7fd2be9240928 ]---
Reported-by: Joerg Sommer <joerg@alea.gnuu.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3cb5f1a3e5