Messages in this thread | | | From | He Kuang <> | Subject | [bug] wrong result of android callchain | Date | Tue, 5 Jan 2016 17:14:37 +0800 |
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I found a wrong result of aarch64 callchain when using perf script on a android phone.
Here's the callchain record fragment from the output of perf script:
init 369 [002] 339.970607: raw_syscalls:sys_enter: NR 22 (b, 7fd9e360a0, 10, ffffffff, 0, 8) ... 230ac [unknown] (/system/lib64/libsurfaceflinger.so) 11a0 main (/system/bin/surfaceflinger) 1c3fc __libc_init (/system/lib64/libc.so) fd0 _start (/system/bin/surfaceflinger) 29ec __dl__start (/system/bin/linker64)
The fault occured in the '[unknown]' line, from objdump result of /system/bin/surfaceflinger, we can see the branch instruction before 0x11a0:
# objdump /system/bin/surfaceflinger 1198: f9400fe0 ldr x0, [sp,#24] 119c: 97ffff05 bl db0 <_ZN7android14SurfaceFlinger3runEv@plt> 11a0: f9400be8 ldr x8, [sp,#16] 11a4: b40000c8 cbz x8, 11bc <main+0x150>
The function '_ZN7android14SurfaceFlinger3runEv' is located at 0x3a094 ~ 0x3a0ac in libsurfaceflinger.so, but perf misparsed that value to 0x230ac:
# objdump libsurfaceflinger.so 000000000003a094 <_ZN7android14SurfaceFlinger3runEv>: 3a094: a9be4ff4 stp x20, x19, [sp,#-32]! 3a098: a9017bfd stp x29, x30, [sp,#16] 3a09c: 910043fd add x29, sp, #0x10 3a0a0: 910c0013 add x19, x0, #0x300 3a0a4: aa1303e0 mov x0, x19 3a0a8: 97fff12f bl 36564 <_ZN7android12MessageQueue11waitMessageEv> 3a0ac: 17fffffe b 3a0a4 <_ZN7android14SurfaceFlinger3runEv+0x10>
There's a difference of 0x17000 between those two offsets, it seems that this value is the VirtAddr of this dynamic library.
# readelf -a libsurfaceflinger.so Program Headers: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flags Align LOAD 0x0000000000000000 0x0000000000017000 0x0000000000017000 0x0000000000057258 0x0000000000057258 R E 1000
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