Re: [lmi] perf

[Greg Chicares]

On 2020-09-29 17:02, Vadim Zeitlin wrote:
> On Tue, 29 Sep 2020 16:33:20 +0000 Greg Chicares <gchicares@sbcglobal.net> 
> wrote:
> 
> GC> On 2020-09-29 11:22, Vadim Zeitlin wrote:
> GC> > On Tue, 29 Sep 2020 08:51:38 +0000 Greg Chicares 
> <gchicares@sbcglobal.net> wrote:
> GC> [...]
> GC> > GC> >  If you do have the symbols, at the very least you would be able 
> to decode
> GC> > GC> > the address manually using "addr2line -f -e 
> /lib/x86_64-linux-gnu/libm.so".
> GC> > GC> 
> GC> > GC> addr2line: /lib/x86_64-linux-gnu/libm.so: file format not recognized
> GC> > 
> GC> >  Hmm, what is this file? It could be a linker script, I guess. I should
> GC> > have written libm-2.29.so in full.
> GC> 
> GC> /opt/lmi/src/lmi[0]$file /lib/x86_64-linux-gnu/libm.so
> GC> /lib/x86_64-linux-gnu/libm.so: ASCII text
> GC> /opt/lmi/src/lmi[0]$cat /lib/x86_64-linux-gnu/libm.so
> GC> /* GNU ld script
> GC> */
> GC> OUTPUT_FORMAT(elf64-x86-64)
> GC> GROUP ( /lib/x86_64-linux-gnu/libm.so.6  AS_NEEDED ( 
> /usr/lib/x86_64-linux-gnu/libmvec_nonshared.a 
> /lib/x86_64-linux-gnu/libmvec.so.1 ) )
> 
>  OK, so it is a linker script. The real library is libm.so.6.
> 
> GC> Trying it anyway, without installing a debug-symbols package,
> GC> it seemed to freeze, so I hit Enter a couple times before Ctrl-C:
> 
>  Oh, sorry, I feel really stupid, but I should have mentioned that add2line
> takes the address you want to map either as command line argument or from
> stdin. I.e. you should have given it 0x000000000001b1c9 (it does understand
> hex) as the last argument -- I was just too lazy to type this one.

I used to know that. But then I found myself using addr2line too much,
and was eager to forget. Anyway:

$addr2line -f -e /lib/x86_64-linux-gnu/libm-2.29.so 0x000000000001b1c9
expm1f64x
??:?

which is no surprise.

> GC> But right now I'm trapped in a morass of dependencies.
> [...]
> 
>  Yes, we definitely should do something to get you out of it quickly. I
> still haven't really started on lib{xml2,xslt} submodules, but I'll do this
> right now (well, after answering your other email).

Ura, ura, ura!