Em Wed, Mar 24, 2010 at 08:20:10PM +0200, Avi Kivity escreveu: > On 03/24/2010 07:47 PM, Arnaldo Carvalho de Melo wrote: >> Em Wed, Mar 24, 2010 at 06:09:30PM +0200, Avi Kivity escreveu: >> >>> Doesn't perf already has a dependency on naming conventions for finding >>> debug information? >>> >> It looks at several places, from most symbol rich (/usr/lib/debug/, aka >> -debuginfo packages, where we have full symtabs) to poorest (the >> packaged binary, where we may just have a .dynsym). >> >> In an ideal world, it would just get the build-id (a SHA1 cookie that is >> in an ELF session inserted in every binary (aka DSOs), kernel module, >> kallsyms or vmlinux file) and use that to look first in a local cache >> (implemented in perf for a long time already) or in some symbol server. >> >> For instance, for a random perf.data file I collected here in my machine >> I have: >> >> [acme@doppio linux-2.6-tip]$ perf buildid-list | grep libpthread >> 5c68f7afeb33309c78037e374b0deee84dd441f6 /lib64/libpthread-2.10.2.so >> [acme@doppio linux-2.6-tip]$ >> >> So I don't have to access /lib64/libpthread-2.10.2.so directly, nor some >> convention to get a debuginfo in a local file like: >> >> /usr/lib/debug/lib64/libpthread-2.10.2.so.debug >> >> Instead the tools look at: >> >> [acme@doppio linux-2.6-tip]$ l ~/.debug/.build-id/5c/68f7afeb33309c78037e374b0deee84dd441f6 >> lrwxrwxrwx 1 acme acme 73 2010-01-06 18:53 /home/acme/.debug/.build-id/5c/68f7afeb33309c78037e374b0deee84dd441f6 -> ../../lib64/libpthread-2.10.2.so/5c68f7afeb33309c78037e374b0deee84dd441f6* >> >> To find the file for that specific build-id, not the one installed in my >> machine (or on the different machine, of a different architecture) that >> may be completely unrelated, a new one, or one for a different arch. > Thanks. I believe qemu could easily act as a symbol server for this use > case. Agreed, but it doesn't even have to :-) We just need to get the build-id in the PERF_RECORD_MMAP event somehow and then get this symbol from elsewhere, say the same DVD/RHN channel/Debian Repository/embedded developer toolkit image not stripped/whatever. Or it may already be in the local cache from last week's perf report session :-) - Arnaldo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
