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how to show text symbols of command output #112
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Not reproducible at my end.
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k-hagio
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Dec 9, 2022
We met "bt" command on KASAN kernel vmcore display truncated backtraces like this: crash> bt PID: 4131 TASK: ffff8001521df000 CPU: 3 COMMAND: "bash" #0 [ffff2000224b0cb0] machine_kexec_prepare at ffff2000200bff4c After digging the root cause, it turns out that arm64_in_kdump_text() found wrong bt->bptr at "machine_kexec" branch. Disassemble machine_kexec() of KASAN vmlinux (gcc 7.3.0): crash> dis -x machine_kexec 0xffff2000200bff50 <machine_kexec>: stp x29, x30, [sp,#-208]! 0xffff2000200bff54 <machine_kexec+0x4>: mov x29, sp 0xffff2000200bff58 <machine_kexec+0x8>: stp x19, x20, [sp,#16] 0xffff2000200bff5c <machine_kexec+0xc>: str x24, [sp,#56] 0xffff2000200bff60 <machine_kexec+0x10>: str x26, [sp,#72] 0xffff2000200bff64 <machine_kexec+0x14>: mov x2, #0x8ab3 0xffff2000200bff68 <machine_kexec+0x18>: add x1, x29, #0x70 0xffff2000200bff6c <machine_kexec+0x1c>: lsr x1, x1, #3 0xffff2000200bff70 <machine_kexec+0x20>: movk x2, #0x41b5, lsl #16 0xffff2000200bff74 <machine_kexec+0x24>: mov x19, #0x200000000000 0xffff2000200bff78 <machine_kexec+0x28>: adrp x3, 0xffff2000224b0000 0xffff2000200bff7c <machine_kexec+0x2c>: movk x19, #0xdfff, lsl #48 0xffff2000200bff80 <machine_kexec+0x30>: add x3, x3, #0xcb0 0xffff2000200bff84 <machine_kexec+0x34>: add x4, x1, x19 0xffff2000200bff88 <machine_kexec+0x38>: stp x2, x3, [x29,#112] 0xffff2000200bff8c <machine_kexec+0x3c>: adrp x2, 0xffff2000200bf000 <swsusp_arch_resume+0x1e8> 0xffff2000200bff90 <machine_kexec+0x40>: add x2, x2, #0xf50 0xffff2000200bff94 <machine_kexec+0x44>: str x2, [x29,#128] 0xffff2000200bff98 <machine_kexec+0x48>: mov w2, #0xf1f1f1f1 0xffff2000200bff9c <machine_kexec+0x4c>: str w2, [x1,x19] 0xffff2000200bffa0 <machine_kexec+0x50>: mov w2, #0xf200 0xffff2000200bffa4 <machine_kexec+0x54>: mov w1, #0xf3f3f3f3 0xffff2000200bffa8 <machine_kexec+0x58>: movk w2, #0xf2f2, lsl #16 0xffff2000200bffac <machine_kexec+0x5c>: stp w2, w1, [x4,#4] We notice that: 1. machine_kexec() start address is 0xffff2000200bff50 2. the instruction at machine_kexec+0x44 stores the same value 0xffff2000200bff50 (comes from 0xffff2000200bf000 + 0xf50) into stack postion [x29,#128]. When arm64_in_kdump_text() searches for LR from stack, it met 0xffff2000200bff50 firstly, so got wrong bt->bptr. We know that the real LR is always greater than the start address of a function, so let's fix it by changing the search conditon to (*ptr > xxx_start) && (*ptr < xxx_end). Signed-off-by: Ding Hui <[email protected]>
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It will be helpful if crash could show the corresponding symbols of command output
for example
But I can NOT get the symbols when running the same CLI on my own server:
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