From: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
To: Brian Downing <bdowning@lavos.net>
Cc: linux-perf-users@vger.kernel.org
Subject: Re: perf adjusting symbols incorrectly with split debuginfo?
Date: Tue, 23 Nov 2010 10:53:37 -0200 [thread overview]
Message-ID: <20101123125337.GB11101@ghostprotocols.net> (raw)
In-Reply-To: <20101123065029.GG18897@glaurung.lavos.net>
Em Tue, Nov 23, 2010 at 06:50:30AM +0000, Brian Downing escreveu:
> I am trying to run perf on a system with split debuginfo. I'm creating the
> debuginfo by:
>
> objcopy --only-keep-debug file /usr/lib/debug/path/to/file
> strip file
> objcopy --add-gnu-debuglink=/usr/lib/debug/path/to/file file
>
> The problem is that perf seems to want to use the section header's load
> address and file offset fields to figure out what to adjust the symbol
> by, in this code:
There is a patch that deals with split debuginfo:
"perf symbols: fix symbol offset breakage with separated debug"
https://patchwork.kernel.org/patch/347491/
Can you please try it and report your results?
- Arnaldo
> if (curr_dso->adjust_symbols) {
> pr_debug4("%s: adjusting symbol: st_value: %#Lx "
> "sh_addr: %#Lx sh_offset: %#Lx\n", __func__,
> (u64)sym.st_value, (u64)shdr.sh_addr,
> (u64)shdr.sh_offset);
> sym.st_value -= shdr.sh_addr - shdr.sh_offset;
> }
>
> If it were reading the real binary this would work fine:
>
> $ powerpc-unknown-linux-gnu-readelf --sections ./ppc5lua
> There are 29 section headers, starting at offset 0x2712c:
>
> Section Headers:
> [Nr] Name Type Addr Off Size ES Flg Lk Inf Al
> [ 0] NULL 00000000 000000 000000 00 0 0 0
> [ 1] .interp PROGBITS 10000174 000174 00000d 00 A 0 0 1
> [ 2] .note.ABI-tag NOTE 10000184 000184 000020 00 A 0 0 4
> ...
> [12] .text PROGBITS 10003410 003410 0207c0 00 AX 0 0 4
>
> 10003410 - 3410 = 10000000, which is correct.
>
> Unfortunately it instead finds and reads the debuginfo, where this is:
>
> $ powerpc-unknown-linux-gnu-readelf --sections ./ppc5luadebug
> There are 31 section headers, starting at offset 0x2ec:
>
> Section Headers:
> [Nr] Name Type Addr Off Size ES Flg Lk Inf Al
> [ 0] NULL 00000000 000000 000000 00 0 0 0
> [ 1] .interp NOBITS 10000174 000174 00000d 00 A 0 0 1
> [ 2] .note.ABI-tag NOTE 10000184 000177 000020 00 A 0 0 4
> ...
> [12] .text NOBITS 10003410 000197 0207c0 00 AX 0 0 4
>
> Needless to say it's not okay if adjusted with that offset.
>
> Fixing this seems like it would be rather hard, since it currently only
> reads one ELF file, namely, the one with the symbols. Is there another
> way I can do split debuginfo that will make perf work, yet not duplicate
> the actual code in two places?
>
> Thanks,
> -bcd
> --
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prev parent reply other threads:[~2010-11-23 12:53 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-23 6:50 perf adjusting symbols incorrectly with split debuginfo? Brian Downing
2010-11-23 12:53 ` Arnaldo Carvalho de Melo [this message]
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