Arnaldo Carvalho de Melo <[email protected]> writes: > Em Wed, Jul 12, 2017 at 08:40:57PM +1000, Michael Ellerman escreveu: >> Arnaldo Carvalho de Melo <[email protected]> writes: >> >> > Em Tue, Jul 11, 2017 at 04:38:28PM -0300, Arnaldo Carvalho de Melo >> > escreveu: >> >> Em Tue, Jul 11, 2017 at 04:03:04PM -0300, Arnaldo Carvalho de Melo >> >> escreveu: >> >> > Em Fri, Jul 07, 2017 at 02:17:25PM +0200, Thomas-Mich Richter escreveu: >> >> > > On 07/06/2017 02:35 PM, Thomas-Mich Richter wrote: >> >> > > It determines the kernel starts at address 1<<63 and loads the kernel >> >> > > address mapping. >> >> > > On s390x >> >> > > - The kernel starts at 0x0 (value of map->start) and thus all checks >> >> > > in function >> >> > > thread__find_addr_map() fail and no symbol is found for the >> >> > > specified addresses >> >> > > because the kernel starts at 0x8000000000000000. Which is wrong the >> >> > > kernel start at 0x0. >> > >> >> > Hi Thomas, really nice debugging session! >> > >> >> > I'm trying the one-liner below, Adrian, can you please check this and >> >> > provide an ack? I think that that comment about the address that it will >> >> > default when map__load() fails needs rewriting in light of Thomas >> >> > comments about other arches (see further below)? >> > >> >> > I did a quick check of machine->kernel_start usage in Intel PT and since >> >> > on x86 that assumption about partitioning the address space holds, no >> >> > problem should be introduced by the one-liner fix, right? >> > >> >> Argh, this is also broken: >> > >> >> static inline bool machine__kernel_ip(struct machine *machine, u64 ip) >> >> { >> >> u64 kernel_start = machine__kernel_start(machine); >> >> >> >> return ip >= kernel_start; >> >> } >> >> >> >> We can't judge if a address is in the kernel like that :-\ >> > >> > So, this is used by: >> > >> > [acme@jouet linux]$ find tools/ -name "*.[ch]" | xargs grep -w >> > machine__kernel_ip >> > tools/perf/builtin-script.c: kernel = machine__kernel_ip(machine, >> > start); >> > tools/perf/builtin-script.c: if (kernel != >> > machine__kernel_ip(machine, end)) { >> > >> > That is just for "brstackinsn", would that make sense for Sparc, S/390? >> > >> > tools/perf/util/intel-bts.c: if (machine__kernel_ip(machine, ip)) >> > tools/perf/util/intel-bts.c: if >> > (!machine__kernel_ip(btsq->bts->machine, branch->from) && >> > tools/perf/util/intel-bts.c: >> > machine__kernel_ip(btsq->bts->machine, branch->to) && >> > >> > Intel specific stuff, so should be ok. >> > >> > tools/perf/util/event.c: machine__kernel_ip(machine, >> > al->addr)) { >> > >> > For this last one, that affects all arches, I think we can just remove >> > this check and look at the kernel when not finding it anywhere else? >> > >> > diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c >> > index dc5c3bb69d73..8e435baaae6a 100644 >> > --- a/tools/perf/util/event.c >> > +++ b/tools/perf/util/event.c >> > @@ -1432,8 +1432,7 @@ void thread__find_addr_map(struct thread *thread, u8 >> > cpumode, >> > * in the whole kernel symbol list. >> > */ >> > if (cpumode == PERF_RECORD_MISC_USER && machine && >> > - mg != &machine->kmaps && >> > - machine__kernel_ip(machine, al->addr)) { >> > + mg != &machine->kmaps) { >> > mg = &machine->kmaps; >> > load_map = true; >> > goto try_again; >> >> Am I reading this right? We have a sample that claims to be in >> userspace, but was not found in any symbol map, so we try looking for it >> in the kernel map. >> >> And the change is that previously we checked if the address was >= (1 << 63), >> whereas after we don't bother. >> >> Seems harmless™. > > Thanks, will take that as an Acked-by:, ok?
Seems-harmless-but-will-probably-break-something-obscure-by: ... :) Sure. Acked-by: Michael Ellerman <[email protected]> (powerpc) cheers
