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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
