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SubjectRe: [PATCH] kprobes: bugfix: checks kprobes_all_disarmed in unoptimized_kprobe().
On 2015/1/19 17:05, Masami Hiramatsu wrote:
> Hi Wang,
>
> I've found a problem on this patch, since kprobes calls unoptioize_kprobe
> with kprobes_all_disarmed=true when trying to disable all kprobes, this
> cause a serious problem.
>
> Moreover, I couldn't reproduce your reported bug on my 3.19-rc4 kernel.
> Could you test it again?
>

I tested it again based on 3.19-rc5 and found that the problem still exists.
My testing is based on QEMU.

First I tested my kprobeopt for ARM, then on x86_64. The test results are pasted
at the bottom of this mail. Commands after 'gdb attaches to QEMU' is my actions
on a gdb console attached to QEMU; commands after 'inside virtual machine' is
what I do in Linux run under QEMU.



** ARM result **

------ gdb attaches to QEMU -------
(gdb) x/3i sys_open
0xc013619c <SyS_open>: mov r12, sp <--- *original insn*
0xc01361a0 <SyS_open+4>: push {r11, r12, lr, pc}
0xc01361a4 <SyS_open+8>: sub r11, r12, #4

------ inside virtual machine -------
# echo 'p:myprobe sys_open' > /sys/kernel/debug/tracing/kprobe_events
# echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable

------ gdb attaches to QEMU -------
cpu_v7_do_idle () at /home/w00229757/kernel-hydrogen/arch/arm/mm/proc-v7.S:74
74 ret lr
(gdb) x/3i sys_open
0xc013619c <SyS_open>: b 0xbf000000 <--- *optimized*
0xc01361a0 <SyS_open+4>: push {r11, r12, lr, pc}
0xc01361a4 <SyS_open+8>: sub r11, r12, #4
(gdb) c

------ inside virtual machine -------
# echo 0 > /sys/kernel/debug/kprobes/enabled

------ gdb attaches to QEMU -------
cpu_v7_do_idle () at /home/w00229757/kernel-hydrogen/arch/arm/mm/proc-v7.S:74
74 ret lr
(gdb) x/3i sys_open
0xc013619c <SyS_open>: ; <UNDEFINED> instruction: 0xe7f001f8 <--- *BREAKPOINT*
0xc01361a0 <SyS_open+4>: push {r11, r12, lr, pc}
0xc01361a4 <SyS_open+8>: sub r11, r12, #4
(gdb) c



** x86_64 result **

------ gdb attaches to QEMU -------
(gdb) x/10i sys_open
0xffffffff81184fe0 <SyS_open>: data32 data32 data32 xchg %ax,%ax
0xffffffff81184fe5 <SyS_open+5>: push %rbp
0xffffffff81184fe6 <SyS_open+6>: movzwl %dx,%ecx
0xffffffff81184fe9 <SyS_open+9>: mov %esi,%edx
0xffffffff81184feb <SyS_open+11>: mov %rsp,%rbp
0xffffffff81184fee <SyS_open+14>: mov %rdi,%rsi
0xffffffff81184ff1 <SyS_open+17>: or $0x80,%dh
0xffffffff81184ff4 <SyS_open+20>: mov $0xffffff9c,%edi
0xffffffff81184ff9 <SyS_open+25>: callq 0xffffffff81184da0 <do_sys_open>
0xffffffff81184ffe <SyS_open+30>: pop %rbp
(gdb) c
Continuing


------ inside virtual machine -------
# echo 'p:myprobe sys_open+20' > /sys/kernel/debug/tracing/kprobe_events
# echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable

------ gdb attaches to QEMU -------
(gdb) x/10i sys_open
0xffffffff81184fe0 <SyS_open>: data32 data32 data32 xchg %ax,%ax
0xffffffff81184fe5 <SyS_open+5>: push %rbp
0xffffffff81184fe6 <SyS_open+6>: movzwl %dx,%ecx
0xffffffff81184fe9 <SyS_open+9>: mov %esi,%edx
0xffffffff81184feb <SyS_open+11>: mov %rsp,%rbp
0xffffffff81184fee <SyS_open+14>: mov %rdi,%rsi
0xffffffff81184ff1 <SyS_open+17>: or $0x80,%dh
0xffffffff81184ff4 <SyS_open+20>: jmpq 0xffffffffa0002000 <--- *optimized*
0xffffffff81184ff9 <SyS_open+25>: callq 0xffffffff81184da0 <do_sys_open>
0xffffffff81184ffe <SyS_open+30>: pop %rbp
(gdb) c
Continuing.

------ inside virtual machine -------
# echo 0 > /sys/kernel/debug/kprobes/enabled

------ gdb attaches to QEMU -------
(gdb) x/10i sys_open
0xffffffff81184fe0 <SyS_open>: data32 data32 data32 xchg %ax,%ax
0xffffffff81184fe5 <SyS_open+5>: push %rbp
0xffffffff81184fe6 <SyS_open+6>: movzwl %dx,%ecx
0xffffffff81184fe9 <SyS_open+9>: mov %esi,%edx
0xffffffff81184feb <SyS_open+11>: mov %rsp,%rbp
0xffffffff81184fee <SyS_open+14>: mov %rdi,%rsi
0xffffffff81184ff1 <SyS_open+17>: or $0x80,%dh
0xffffffff81184ff4 <SyS_open+20>: int3 <-- **BREAKPOINT**
0xffffffff81184ff5 <SyS_open+21>: pushfq
0xffffffff81184ff6 <SyS_open+22>: (bad)
(gdb)




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