Re: missing mmap events in perf profiles without dwarf callgraph

[Milian Wolff <mail@milianw.de>]

[-- Attachment #1: Type: text/plain, Size: 1238 bytes --]

On Dienstag, 19. Januar 2021 10:36:11 CET Namhyung Kim wrote:
> Hi Milian,
> 
> On Tue, Jan 19, 2021 at 5:11 PM Milian Wolff <mail@milianw.de> wrote:
> > On Donnerstag, 14. Januar 2021 09:56:36 CET Namhyung Kim wrote:
> > > What I noticed is ss->adjust_symbols which is set for user DSOs.  It
> > > does
> > > 
> > >   sym.st_value -= shdr.sh_addr - shdr.sh_offset
> > > 
> > > Maybe your program's section header has different values?
> > 
> > Hey Namhyung,
> > 
> > how would I figure that one out? Isn't that data shown in the readelf
> > output above? Put differently: Could someone else maybe show his readelf
> > output so we can compare?
> 
> I mean the below.  In my case, address and offset of the .text section are
> same as 0x1080.

Ah, indeed for me it's not the same - there's the discrepancy of 0x1000 again:

  [13] .text             PROGBITS         0000000000001610  00000610
       0000000000000185  0000000000000000  AX       0     0     16

Thanks, that gives me a (complicated) path forward. We'd have to essentially 
load the elf file, find this offset, and then take it into account when 
telling elfutils where the file was actually mapped to originally.

Cheers

-- 
Milian Wolff
mail@milianw.de
http://milianw.de

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 833 bytes --]