Re: Re: Re: [PATCH RFC 2/6] arm64: Kprobes with single stepping support

From: Sandeepa Prabhu
Date: Wed Nov 13 2013 - 02:08:31 EST

On 13 November 2013 12:25, Sandeepa Prabhu <sandeepa.prabhu@xxxxxxxxxx> wrote:
>>>> I'm unsure about arm64's debug feature behavior, what does happen when
>>>> it performs a single-step on sw-breakpoint?
>>>>
>>>>> Sandeepa: I think you need to retry Masami's test on the arm64 model, since
>>>>> I'm fairly sure it won't work as expected without some additional code.
>>>>
>>>> OK, anyway, for testing same one, we need to port ftrace first. So the next
>>
>> Sorry for confusion, s/next/fallback is what I meant. Making a kprobe module
>> can be done without ftrace port.
>>
>>>> plan is to make a kprobe module to put a probe (which just printk something)
>>>> on a specific function (e.g. vfs_symlink), and run perf record with
>>>> hw-breakpoint as below
>>>>
>>>> $ perf record -e "mem:0xXXXXXX:k" ln -s /dev/null /tmp/foo
>>>>
>>>> Note that 0xXXXXXX is the address of vfs_symlink.
>>>>
>>>> After that, you can see the message in dmesg and also check the perf result
>>>> with "sudo perf script --dump" (you can find a PERF_RECORD_SAMPLE entry if
>>>> it works)
Hi Will, Masami,

I am not sure of 'perf' right now (my minimal rootfs doesn't have) but
I tried to test hardware breakpoints using sample modules
"samples/hw_breakpoint/" on arm64 upstream branch. This should use
same kernel api as perf I believe.

1. Placing watchpoint ( attr.bp_type = HW_BREAKPOINT_W |
HW_BREAKPOINT_R) upon vfs_symlink symbol, but seems watch-point is not
triggering at all.
2. Placing text breakpoint (modified sample module with attr.bp_type
= HW_BREAKPOINT_X) upon vfs_symlink, and run "ln -s /dev/null
/tmp/foo". This time, breakpoint hit but exception is re-cursing
infinitely!

I have attached the kernel logs for reference. So wanted to check if
hw breakpoint/watch-points are working on the upstream branch? Has it
been tested recently with sample modules or perf/ptrace?

Thanks,
Sandeepa
Initializing cgroup subsys cpu
Linux version 3.12.0-rc4+ (sandeepa@linaro-workstation) (gcc version 4.7.3 20130328 (prerelease) (crosstool-NG linaro-1.13.1-4.7-2013.04-20130415 - Linaro GCC 2013.04) ) #24 SMP PREEMPT Wed Nov 13 12:04:03 IST 2013
CPU: AArch64 Processor [410fd0f0] revision 0
Machine: RTSM_VE_AEMv8A
bootconsole [earlycon0] enabled
PERCPU: Embedded 10 pages/cpu @ffffffc87ffa8000 s11776 r8192 d20992 u40960
Built 1 zonelists in Zone order, mobility grouping on. Total pages: 1034240
Kernel command line: console=ttyAMA0 root=/dev/mmcblk0p2 earlyprintk=pl011,0x1c090000 consolelog=9 rw
PID hash table entries: 4096 (order: 3, 32768 bytes)
Dentry cache hash table entries: 524288 (order: 10, 4194304 bytes)
Inode-cache hash table entries: 262144 (order: 9, 2097152 bytes)
software IO TLB [mem 0x8f8000000-0x8fc000000] (64MB) mapped at [ffffffc878000000-ffffffc87bffffff]
Memory: 4058384K/4194304K available (3347K kernel code, 211K rwdata, 1164K rodata, 171K init, 154K bss, 135920K reserved)
Virtual kernel memory layout:
vmalloc : 0xffffff8000000000 - 0xffffffbbffff0000 (245759 MB)
vmemmap : 0xffffffbc01c00000 - 0xffffffbc1f800000 ( 476 MB)
modules : 0xffffffbffc000000 - 0xffffffc000000000 ( 64 MB)
memory : 0xffffffc000000000 - 0xffffffc880000000 ( 34816 MB)
.init : 0xffffffc0004e9000 - 0xffffffc000513e00 ( 172 kB)
.text : 0xffffffc000080000 - 0xffffffc0004e8cf4 ( 4516 kB)
.data : 0xffffffc000514000 - 0xffffffc000548e80 ( 212 kB)
SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1
Preemptible hierarchical RCU implementation.
RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=4.
NR_IRQS:64 nr_irqs:64 0
Architected cp15 timer(s) running at 100.00MHz (phys).
Console: colour dummy device 80x25
Calibrating delay loop (skipped), value calculated using timer frequency.. 200.00 BogoMIPS (lpj=1000000)
pid_max: default: 32768 minimum: 301
Mount-cache hash table entries: 256
hw perfevents: enabled with arm/armv8-pmuv3 PMU driver, 9 counters available
CPU1: Booted secondary processor
CPU2: Booted secondary processor
CPU3: Booted secondary processor
Brought up 4 CPUs
SMP: Total of 4 processors activated.
devtmpfs: initialized
atomic64 test passed
NET: Registered protocol family 16
of_amba_device_create(): amba_device_add() failed (-19) for /smb/motherboard/iofpga@3,00000000/sysctl@020000
vdso: 2 pages (1 code, 1 data) at base ffffffc000519000
hw-breakpoint: found 16 breakpoint and 16 watchpoint registers.
Serial: AMBA PL011 UART driver
1c090000.uart: ttyAMA0 at MMIO 0x1c090000 (irq = 37, base_baud = 0) is a PL011 rev2
console [ttyAMA0] enabled, bootconsole disabled
console [ttyAMA0] enabled, bootconsole disabled
1c0a0000.uart: ttyAMA1 at MMIO 0x1c0a0000 (irq = 38, base_baud = 0) is a PL011 rev2
1c0b0000.uart: ttyAMA2 at MMIO 0x1c0b0000 (irq = 39, base_baud = 0) is a PL011 rev2
1c0c0000.uart: ttyAMA3 at MMIO 0x1c0c0000 (irq = 40, base_baud = 0) is a PL011 rev2
bio: create slab <bio-0> at 0
SCSI subsystem initialized
Switched to clocksource arch_sys_counter
NET: Registered protocol family 2
TCP established hash table entries: 32768 (order: 7, 524288 bytes)
TCP bind hash table entries: 32768 (order: 7, 524288 bytes)
TCP: Hash tables configured (established 32768 bind 32768)
TCP: reno registered
UDP hash table entries: 2048 (order: 4, 65536 bytes)
UDP-Lite hash table entries: 2048 (order: 4, 65536 bytes)
NET: Registered protocol family 1
RPC: Registered named UNIX socket transport module.
RPC: Registered udp transport module.
RPC: Registered tcp transport module.
RPC: Registered tcp NFSv4.1 backchannel transport module.
Unpacking initramfs...
Freeing initrd memory: 936K (ffffffc010000000 - ffffffc0100ea000)
fuse init (API version 7.22)
msgmni has been set to 7928
io scheduler noop registered
io scheduler cfq registered (default)
Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
smc91x: not found (-19).
mousedev: PS/2 mouse device common for all mice
TCP: cubic registered
NET: Registered protocol family 17
<NUL>Freeing unused kernel memory: 168K (ffffffc0004e9000 - ffffffc000513000)
Wed Nov 18 01:00:00 UTC 2009
sh: can't access tty; job control turned off
/ #
/ #
/ #
/ #
/ # insm
/ # insmod kpda
/ # insmod data_
/ # insmod data_breakpoint.ko fksym=vfs_symlink
HW Breakpoint for vfs_symlink write installed
/ #
/ #
/ #
/ # ln -=s s /de
/ # ln -s /dev
/ # ln -s /dev/null /tmp/a
/ #
/ # ln -s /dev/null /tmp/anb
/ # ls /tm
/ # ls /tmp/
a b log
/ #
/ #
/ #
/ #
/ # ls /tmp/ -al
total 0
drwxrwxrwt 3 0 0 100 Nov 18 01:00 .
drwxrwxr-x 12 1000 1000 0 Nov 18 01:00 ..
lrwxrwxrwx 1 0 0 9 Nov 18 01:00 a -> /dev/null
lrwxrwxrwx 1 0 0 9 Nov 18 01:00 b -> /dev/null
drwxrwxrwx 2 0 0 40 Nov 18 01:00 log
/ # dmesg
Initializing cgroup subsys cpu
Linux version 3.12.0-rc4+ (sandeepa@linaro-workstation) (gcc version 4.7.3 20130328 (prerelease) (crosstool-NG linaro-1.13.1-4.7-2013.04-20130415 - Linaro GCC 2013.04) ) #24 SMP PREEMPT Wed Nov 13 12:04:03 IST 2013
CPU: AArch64 Processor [410fd0f0] revision 0
Machine: RTSM_VE_AEMv8A
bootconsole [earlycon0] enabled
On node 0 totalpages: 1048576
DMA32 zone: 7168 pages used for memmap
DMA32 zone: 0 pages reserved
DMA32 zone: 524288 pages, LIFO batch:31
Normal zone: 7168 pages used for memmap
Normal zone: 524288 pages, LIFO batch:31
PERCPU: Embedded 10 pages/cpu @ffffffc87ffa8000 s11776 r8192 d20992 u40960
pcpu-alloc: s11776 r8192 d20992 u40960 alloc=10*4096
pcpu-alloc: [0] 0 [0] 1 [0] 2 [0] 3
Built 1 zonelists in Zone order, mobility grouping on. Total pages: 1034240
Kernel command line: console=ttyAMA0 root=/dev/mmcblk0p2 earlyprintk=pl011,0x1c090000 consolelog=9 rw
PID hash table entries: 4096 (order: 3, 32768 bytes)
Dentry cache hash table entries: 524288 (order: 10, 4194304 bytes)
Inode-cache hash table entries: 262144 (order: 9, 2097152 bytes)
software IO TLB [mem 0x8f8000000-0x8fc000000] (64MB) mapped at [ffffffc878000000-ffffffc87bffffff]
Memory: 4058384K/4194304K available (3347K kernel code, 211K rwdata, 1164K rodata, 171K init, 154K bss, 135920K reserved)
Virtual kernel memory layout:
vmalloc : 0xffffff8000000000 - 0xffffffbbffff0000 (245759 MB)
vmemmap : 0xffffffbc01c00000 - 0xffffffbc1f800000 ( 476 MB)
modules : 0xffffffbffc000000 - 0xffffffc000000000 ( 64 MB)
memory : 0xffffffc000000000 - 0xffffffc880000000 ( 34816 MB)
.init : 0xffffffc0004e9000 - 0xffffffc000513e00 ( 172 kB)
.text : 0xffffffc000080000 - 0xffffffc0004e8cf4 ( 4516 kB)
.data : 0xffffffc000514000 - 0xffffffc000548e80 ( 212 kB)
SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1
Preemptible hierarchical RCU implementation.
RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=4.
NR_IRQS:64 nr_irqs:64 0
Architected cp15 timer(s) running at 100.00MHz (phys).
Console: colour dummy device 80x25
Calibrating delay loop (skipped), value calculated using timer frequency.. 200.00 BogoMIPS (lpj=1000000)
pid_max: default: 32768 minimum: 301
Mount-cache hash table entries: 256
hw perfevents: enabled with arm/armv8-pmuv3 PMU driver, 9 counters available
CPU1: Booted secondary processor
CPU2: Booted secondary processor
CPU3: Booted secondary processor
Brought up 4 CPUs
SMP: Total of 4 processors activated.
devtmpfs: initialized
atomic64 test passed
NET: Registered protocol family 16
of_amba_device_create(): amba_device_add() failed (-19) for /smb/motherboard/iofpga@3,00000000/sysctl@020000
vdso: 2 pages (1 code, 1 data) at base ffffffc000519000
hw-breakpoint: found 16 breakpoint and 16 watchpoint registers.
Serial: AMBA PL011 UART driver
1c090000.uart: ttyAMA0 at MMIO 0x1c090000 (irq = 37, base_baud = 0) is a PL011 rev2
console [ttyAMA0] enabled, bootconsole disabled
1c0a0000.uart: ttyAMA1 at MMIO 0x1c0a0000 (irq = 38, base_baud = 0) is a PL011 rev2
1c0b0000.uart: ttyAMA2 at MMIO 0x1c0b0000 (irq = 39, base_baud = 0) is a PL011 rev2
1c0c0000.uart: ttyAMA3 at MMIO 0x1c0c0000 (irq = 40, base_baud = 0) is a PL011 rev2
bio: create slab <bio-0> at 0
SCSI subsystem initialized
Switched to clocksource arch_sys_counter
NET: Registered protocol family 2
TCP established hash table entries: 32768 (order: 7, 524288 bytes)
TCP bind hash table entries: 32768 (order: 7, 524288 bytes)
TCP: Hash tables configured (established 32768 bind 32768)
TCP: reno registered
UDP hash table entries: 2048 (order: 4, 65536 bytes)
UDP-Lite hash table entries: 2048 (order: 4, 65536 bytes)
NET: Registered protocol family 1
RPC: Registered named UNIX socket transport module.
RPC: Registered udp transport module.
RPC: Registered tcp transport module.
RPC: Registered tcp NFSv4.1 backchannel transport module.
Unpacking initramfs...
Freeing initrd memory: 936K (ffffffc010000000 - ffffffc0100ea000)
fuse init (API version 7.22)
msgmni has been set to 7928
io scheduler noop registered
io scheduler cfq registered (default)
Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
smc91x: not found (-19).
mousedev: PS/2 mouse device common for all mice
TCP: cubic registered
NET: Registered protocol family 17
Freeing unused kernel memory: 168K (ffffffc0004e9000 - ffffffc000513000)
HW Breakpoint for vfs_symlink write installed
/ #
/ #
/ #
/ # rmm
/ # rmmod da
/ # rmmod data_
/ # rmmod data_breakpoint.ko 
HW Breakpoint for vfs_symlink write uninstalled
/ #
/ #
/ #
/ #
/ # insm
/ # insmod te
/ # insmod text_breakpoint.ko ksym=bfsvfs_symlink
HW Breakpoint for vfs_symlink write installed
/ #
/ #
/ #
/ #
/ #
/ #
/ #
/ #
/ # insmod text_breakpoint.ko ksym=vfs_symlink
/ # rmmod data_breakpoint.ko 
/ # dmesg
/ # ls /tmp/ -al
/ # ls /tmp/
/ # ln -s /dev/null /tmp/b
/ # ln -s /dev/null /tmp/ac
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 7fd27ce0 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d00 ffffffc0 00159670 ffffffc0 7784ec00 ffffffc8 7f81f180 ffffffc0
7d00: 7fd27d20 ffffffc0 0013e010 ffffffc0 7784ec00 ffffffc8 00000000 00000000
7d20: 7fd27d40 ffffffc0 0013ec5c ffffffc0 00000600 00000000 7f81f180 ffffffc0
7d40: 7fd27d70 ffffffc0 0013ec88 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 7fd27ce0 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d00 ffffffc0 00159670 ffffffc0 7784ec00 ffffffc8 7f81f180 ffffffc0
7d00: 7fd27d20 ffffffc0 0013e010 ffffffc0 7784ec00 ffffffc8 00000000 00000000
7d20: 7fd27d40 ffffffc0 0013ec5c ffffffc0 00000600 00000000 7f81f180 ffffffc0
7d40: 7fd27d70 ffffffc0 0013ec88 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 7fd27ce0 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d00 ffffffc0 00159670 ffffffc0 7784ec00 ffffffc8 7f81f180 ffffffc0
7d00: 7fd27d20 ffffffc0 0013e010 ffffffc0 7784ec00 ffffffc8 00000000 00000000
7d20: 7fd27d40 ffffffc0 0013ec5c ffffffc0 00000600 00000000 7f81f180 ffffffc0
7d40: 7fd27d70 ffffffc0 0013ec88 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 7fd27ce0 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d00 ffffffc0 00159670 ffffffc0 7784ec00 ffffffc8 7f81f180 ffffffc0
7d00: 7fd27d20 ffffffc0 0013e010 ffffffc0 7784ec00 ffffffc8 00000000 00000000
7d20: 7fd27d40 ffffffc0 0013ec5c ffffffc0 00000600 00000000 7f81f180 ffffffc0
7d40: 7fd27d70 ffffffc0 0013ec88 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 00512000 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d20 ffffffc0 00081294 ffffffc0 0000200c ffffff80 7fd27d50 ffffffc0
7d00: 00548d84 ffffffc0 00491788 ffffffc0 005132c0 ffffffc0 003bbaa0 ffffffc0
7d20: 7fd27d30 ffffffc0 003bbaac ffffffc0 7fd27e70 ffffffc0 00083630 ffffffc0
7d40: 7784ec00 ffffffc8 0013f9d8 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 00512000 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d20 ffffffc0 00081294 ffffffc0 0000200c ffffff80 7fd27d50 ffffffc0
7d00: 00548d84 ffffffc0 00491788 ffffffc0 005132c0 ffffffc0 003bbaa0 ffffffc0
7d20: 7fd27d30 ffffffc0 003bbaac ffffffc0 7fd27e70 ffffffc0 00083630 ffffffc0
7d40: 7784ec00 ffffffc8 0013f9d8 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 00512000 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d20 ffffffc0 00081294 ffffffc0 0000200c ffffff80 7fd27d50 ffffffc0
7d00: 00548d84 ffffffc0 00491788 ffffffc0 005132c0 ffffffc0 003bbaa0 ffffffc0
7d20: 7fd27d30 ffffffc0 003bbaac ffffffc0 7fd27e70 ffffffc0 00083630 ffffffc0
7d40: 7784ec00 ffffffc8 0013f9d8 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 00512000 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d20 ffffffc0 00081294 ffffffc0 0000200c ffffff80 7fd27d50 ffffffc0
7d00: 00548d84 ffffffc0 00491788 ffffffc0 005132c0 ffffffc0 003bbaa0 ffffffc0
7d20: 7fd27d30 ffffffc0 003bbaac ffffffc0 7fd27e70 ffffffc0 00083630 ffffffc0
7d40: 7784ec00 ffffffc8 0013f9d8 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 00512000 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d20 ffffffc0 00081294 ffffffc0 0000200c ffffff80 7fd27d50 ffffffc0
7d00: 00548d84 ffffffc0 00491788 ffffffc0 005132c0 ffffffc0 003bbaa0 ffffffc0
7d20: 7fd27d30 ffffffc0 003bbaac ffffffc0 7fd27e70 ffffffc0 00083630 ffffffc0
7d40: 7784ec00 ffffffc8 0013f9d8 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 00512000 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d20 ffffffc0 00081294 ffffffc0 0000200c ffffff80 7fd27d50 ffffffc0
7d00: 0055b8c0 ffffffc0 00002010 ffffff80 80000145 00000000 003bbaa0 ffffffc0
7d20: 7fd27e70 ffffffc0 000835c0 ffffffc0 7784ec00 ffffffc8 7fd44000 ffffffc0
7d40: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 00512000 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d20 ffffffc0 00081294 ffffffc0 0000200c ffffff80 7fd27d50 ffffffc0
7d00: 0055b8c0 ffffffc0 00002010 ffffff80 80000145 00000000 003bbaa0 ffffffc0
7d20: 7fd27e70 ffffffc0 000835c0 ffffffc0 7784ec00 ffffffc8 7fd44000 ffffffc0
7d40: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 00512000 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d20 ffffffc0 00081294 ffffffc0 0000200c ffffff80 7fd27d50 ffffffc0
7d00: 0055b8c0 ffffffc0 00002010 ffffff80 80000145 00000000 003bbaa0 ffffffc0
7d20: 7fd27e70 ffffffc0 000835c0 ffffffc0 7784ec00 ffffffc8 7fd44000 ffffffc0
7d40: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 00512000 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d20 ffffffc0 00081294 ffffffc0 0000200c ffffff80 7fd27d50 ffffffc0
7d00: 0055b8c0 ffffffc0 00002010 ffffff80 80000145 00000000 003bbaa0 ffffffc0
7d20: 7fd27e70 ffffffc0 000835c0 ffffffc0 7784ec00 ffffffc8 7fd44000 ffffffc0
7d40: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24
Call trace:
[<ffffffc00008718c>] dump_backtrace+0x0/0x12c
[<ffffffc0000872cc>] show_stack+0x14/0x1c
[<ffffffc0003b88e4>] dump_stack+0x70/0xac
[<ffffffbffc004020>] $x+0x20/0x34 [text_breakpoint]
[<ffffffc0000f8d40>] __perf_event_overflow+0xa4/0x214
[<ffffffc0000f9604>] perf_swevent_overflow+0x50/0x84
[<ffffffc0000f96f4>] perf_swevent_event+0xbc/0xc0
[<ffffffc0000f9938>] perf_bp_event+0x6c/0x78
[<ffffffc00008fd90>] breakpoint_handler+0xec/0x1d8
[<ffffffc0000811ec>] do_debug_exception+0x40/0xac
Exception stack(0xffffffc07fd27cb0 to 0xffffffc07fd27dd0)
7ca0: 7784ec00 ffffffc8 7fd44000 ffffffc0
7cc0: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 00512000 ffffffc0 00148400 ffffffc0
7ce0: 7fd27d20 ffffffc0 00081294 ffffffc0 0000200c ffffff80 7fd27d50 ffffffc0
7d00: 0055b8c0 ffffffc0 00002010 ffffff80 80000145 00000000 003bbaa0 ffffffc0
7d20: 7fd27e70 ffffffc0 000835c0 ffffffc0 7784ec00 ffffffc8 7fd44000 ffffffc0
7d40: 7fd27e70 ffffffc0 0013f9d8 ffffffc0 77784048 ffffffc8 7784ec00 ffffffc8
7d60: 7fd44020 ffffffc0 000003ea 00000000 7f81f180 ffffffc0 00556e58 ffffffc0
7d80: 7fd42000 ffffffc0 7fd42000 ffffffc0 00000000 00000000 ffb0c278 00000000
7da0: 00000001 00000000 00000000 00000000 00000000 00000000 ffb0c268 00000000
7dc0: 0007ee24 00000000 00000000 00000000
[<ffffffc0000834ac>] el1_dbg+0x10/0x60
[<ffffffc000143dc4>] SyS_symlink+0x14/0x1c
Dump stack from sample_hbp_handler
vfs_symlink value is changed
CPU: 2 PID: 463 Comm: ln Not tainted 3.12.0-rc4+ #24