Messages in this thread | | | Date | Fri, 13 Apr 2018 14:20:35 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH 17/17] perf annotate: Handle variables in 'sub', 'or' and many other instructions |
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Em Fri, Apr 13, 2018 at 09:20:43AM -0700, Andi Kleen escreveu: > On Fri, Apr 13, 2018 at 11:01:11AM -0300, Arnaldo Carvalho de Melo wrote: > > From: Arnaldo Carvalho de Melo <acme@redhat.com>
> > Just like is done for 'mov' and others that can have as source or > > targets variables resolved by objdump, to make them more compact: > > > > - orb $0x4,0x224d71(%rip) # 226ca4 <_rtld_global+0xca4> > > + orb $0x4,_rtld_global+0xca4
> That's not equivalent. It could be non rip relative too. You would need > to keep at least the (%rip).
So, the function is _dl_start in /lib64/ld-2.26.so, the objdump output is:
0000000000001b10 <_dl_start>: <SNIP> 1d1f: 0f 84 ab 00 00 00 je 1dd0 <_dl_start+0x2c0> 1d25: 48 8d 3d 64 3c 22 00 lea 0x223c64(%rip),%rdi # 225990 <_rtld_global+0x990> 1d2c: 80 0d 71 3f 22 00 04 orb $0x4,0x223f71(%rip) # 225ca4 <_rtld_global+0xca4> 1d33: e8 78 92 00 00 callq afb0 <_dl_setup_hash> <SNIP>
Then...
21: 0000000000225000 3960 OBJECT GLOBAL DEFAULT 20 _rtld_global@@GLIBC_PRIVATE
0x225ca4 = 0x225000 + 0x0xca4
And that is equal to 0x1d33 + 0x223f71
What do I miss? Or where is it that I'm misinterpreting the calculations that objdump did in its output?
This is just to make things compact, on the TUI if one wants to see the original its just a matter of pressing 'o', i.e. that line appears by default as:
perf annotate _dl_start press HOME press /orb <SNIP> │215: lea _rtld_global+0x990,%rdi │ orb $0x4,_rtld_global+0xca4 │ → callq _dl_setup_hash <SNIP>
press 'o', to see details, i.e. was this encoded as rip-relative?
<SNIP> │1f25: lea 0x224a64(%rip),%rdi # 226990 <_rtld_global+0x990> │1f2c: orb $0x4,0x224d71(%rip) # 226ca4 <_rtld_global+0xca4> │1f33: → callq b080 <_dl_setup_hash> <SNIP>
Now, if we have a non-rip relative orb, lemme search one with:
perf annotate --stdio2 /orb
There, we have one in the kernel's sys_pselect6:
perf annotate sys_pselect6 /orb │ mov %gs:0x15b40,%rax │ orb $0x4,0x490(%rax) │ mov %rdx,0x718(%rax) │ mov (%rax),%rdx
No variables resolved, nothing done, press 'o' to see the original objdump disassembled line:
│ffffffff8128af29: mov %gs:0x15b40,%rax │ffffffff8128af32: orb $0x4,0x490(%rax) │ffffffff8128af39: mov %rdx,0x718(%rax) │ffffffff8128af40: mov (%rax),%rdx
About something mildly related: what do you think about this: http://ref.x86asm.net/, there is a xml file there[1] I'm thinking about using, if available on the developer's HOME or some other standard place, to provide help about the instructions :-)
- Arnaldo
[1] http://ref.x86asm.net/x86reference.xml
look for <mnem>PUNPCKHQDQ</mnem>
<entry r="yes"> <pref>66</pref> <proc_start>10</proc_start> <syntax> <mnem>PUNPCKHQDQ</mnem> <dst> <a>V</a> <t>dq</t> </dst> <src> <a>W</a> <t>dq</t> </src> </syntax> <instr_ext>sse2</instr_ext> <grp1>simdint</grp1> <grp2>shunpck</grp2> <note> <brief>Unpack High Data</brief> </note> </entry>
8-)
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