Arnaldo Carvalho de Melo <[email protected]> writes: > Em Tue, Jul 26, 2016 at 10:14:18PM +0200, Christian Borntraeger escreveu: >> On 07/26/2016 09:50 PM, Arnaldo Carvalho de Melo wrote: >> > Em Thu, Jul 21, 2016 at 11:10:51AM +0800, Song Shan Gong escreveu: >> >> At preset, when creating module's map, perf gets 'start' address by >> >> parsing >> >> '/proc/modules', but it's module base address, isn't the start address of >> >> '.text' section. In most archs, it's OK. But for s390, it places 'GOT' and >> >> 'PLT' relocations before '.text' section. So there exists an offset >> >> between >> >> module base address and '.text' section, which will incur wrong symbol >> >> resolution for modules. >> > >> > I'll apply this as it fixes the problem for you and we need to get fixes >> > in ASAP to get this into 4.8, but why can't we just use your method for >> > all arches and get rid of this arch__ hook? I.e. if I look here in my >> > x86_64 notebook I see: >> > >> > [acme@jouet linux]$ cat /sys/module/tun/sections/.text >> > 0xffffffffc0af2000 >> > [acme@jouet linux]$ grep tun /proc/modules >> > tun 28672 4 vhost_net, Live 0xffffffffc0af2000 >> > [acme@jouet linux]$ >> > >> > So I could as well use what is in /sys/module/tun/sections/.text instead >> > of reading it from /proc/modules and, in s390, reading it from >> > /sys/module/tun/sections/.text. >> > >> > Do you see any problem with using this approach for _all_ arches? >> >> I think it should work well for _all_ arches but it will probably be >> hard to test this without help. > > Well, we could check for the cases we don't know, i.e. read from both > and warn about cases where it is different, except for s390 where we now > which is the right one to pick. > >> I wouldn't be surprised if other architectures than s390 actually have >> the same issue, so doing this for everybody might atually fix this somewhere >> else. > > Would be nice to get info from other arch people, Michael, how this goes > on ppc?
It doesn't look like this is a problem on powerpc - at least I haven't heard of it. Looking at a system I have here, for all modules (26) the value in /proc/modules matches the .text section in /sys. So I think using /sys should be fine for us. cheers
