Re: perf adjusting symbols incorrectly with split debuginfo?

[Arnaldo Carvalho de Melo <acme@ghostprotocols.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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