On Tue, Jan 05, 2016 at 11:20:55AM +0100, Peter Zijlstra wrote: > On Tue, Jan 05, 2016 at 05:14:37PM +0800, He Kuang wrote: > > I found a wrong result of aarch64 callchain when using perf script on > > a android phone. > > Might help to include the AARGH64 people then.. seeing I have no clue > about all that. Cc's added, email preserved etc..
It looks like the issue is in the perf tool, where it fails to resolve the address to a symbol correctly. > > > > 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 This reminds me of: http://lkml.kernel.org/r/1435162623-20075-1-git-send-email-will.dea...@arm.com but that was all vdso-specific. Can you look at what gets passed to objdump? Will -- 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/
