Messages in this thread Patch in this message | | | Date | Wed, 23 Sep 2015 09:14:44 +0800 | From | "Wangnan (F)" <> | Subject | Re: [PATCH] perf probe: Fix module probing with shortname |
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On 2015/9/22 21:35, Arnaldo Carvalho de Melo wrote: > Em Tue, Sep 22, 2015 at 03:34:32AM +0000, Wang Nan escreveu: >> After commit 3d39ac538629e4f00a6e1c38d46346f1b8e69505 ("perf machine: >> No need to have two DSOs lists"), perf probe with module short name doesn't >> work again. For example: >> >> # lsmod | grep e1000e >> e1000e 233472 0 >> >> # cat /proc/modules | grep e1000e >> e1000e 233472 0 - Live 0xffffffffa0073000 >> >> # cat /proc/kallsyms | grep '\<e1000e_up\>' >> ffffffffa0093860 t e1000e_up[e1000e] >> >> # perf probe -v -m e1000e --add e1000e_up >> probe-definition(0): e1000e_up >> symbol:e1000e_up file:(null) line:0 offset:0 return:0 lazy:(null) >> 0 arguments >> Failed to find module e1000e. >> Could not open debuginfo. Try to use symbols. >> Looking at the vmlinux_path (7 entries long) >> Using /lib/modules/4.2.0-rc7+/build/vmlinux for symbols >> e1000e_up is out of .text, skip it. >> Error: Failed to add events. Reason: No such file or directory (Code: -2) >> >> This is caused by a misunderstood of dso->kernel in kernel_get_module_dso() >> that, for kernel module, dso->kernel is DSO_TYPE_USER. dso->kernel is DSO_TYPE_KERNEL >> iff dso is vmlinux. > Kernel modules having DSO_TYPE_USER seems to be the bug, no? I'll try to > check that...
I also noticed this problem when I working on commit 1f121b03d058dd07199d8924373d3c52a207f63b ("perf tools: Deal with kernel module names in '[]' correctly") ;)
It should be bug, but I think fixing it is costy. Here's an assumption that, if dso->kernel is not zero, the dso should be vmlinux (not kernel module):
$ grep 'dso.>kernel)' ./tools/perf/ -r ./tools/perf/builtin-inject.c: if (dso->kernel) ./tools/perf/util/symbol.c: if (dso->kernel) { ./tools/perf/util/symbol-elf.c: if (dso->kernel) ./tools/perf/util/symbol-elf.c: if (remap_kernel && dso->kernel) { ./tools/perf/util/event.c: if (pos->dso->kernel) ./tools/perf/util/probe-event.c: if (dso->kernel) ./tools/perf/util/map.c: * map->dso->kernel) before calling __map__is_{kernel,kmodule}()) ./tools/perf/util/map.c: if (!map->dso || !map->dso->kernel) { ./tools/perf/builtin-top.c: if (!map->dso->kernel)
So care must be taken.
Another solution seems simpler: we can redefine the meaning of enum dso_kernel_type like this:
# find ./tools/perf/ -type f | xargs -n1 sed -i 's/DSO_TYPE_USER/DSO_TYPE_NOT_VMLINUX/g' # find ./tools/perf/ -type f | xargs -n1 sed -i 's/DSO_TYPE_KERNEL/DSO_TYPE_VMLINUX/g' # find ./tools/perf/ -type f | xargs -n1 sed -i 's/DSO_TYPE_GUEST_KERNEL/DSO_TYPE_GUEST_VMLINUX/g'
By fixing the name of DSO_TYPE_USER, kernel module with DSO_TYPE_NOT_VMLINUX seems not so buggy. (Please choose a better name...)
What's your opinion?
Thank you.
> - Arnaldo > >> This patch fix 'perf probe -m' with an ad-hoc way. >> >> After this patch: >> >> # perf probe -v -m e1000e --add e1000e_up >> probe-definition(0): e1000e_up >> symbol:e1000e_up file:(null) line:0 offset:0 return:0 lazy:(null) >> 0 arguments >> Open Debuginfo file: /lib/modules/4.2.0-rc7+/kernel/drivers/net/ethernet/intel/e1000e/e1000e.ko >> Try to find probe point from debuginfo. >> Matched function: e1000e_up >> Probe point found: e1000e_up+0 >> Found 1 probe_trace_events. >> Opening /sys/kernel/debug/tracing//kprobe_events write=1 >> Writing event: p:probe/e1000e_up e1000e:e1000e_up+0 >> Added new event: >> probe:e1000e_up (on e1000e_up in e1000e) >> >> You can now use it in all perf tools, such as: >> >> perf record -e probe:e1000e_up -aR sleep 1 >> >> # perf probe -l >> Failed to find debug information for address ffffffffa0093860 >> probe:e1000e_up (on e1000e_up in e1000e) >> >> Signed-off-by: Wang Nan <wangnan0@huawei.com> >> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> >> Cc: Namhyung Kim <namhyung@kernel.org> >> Cc: Jiri Olsa <jolsa@redhat.com> >> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> >> --- >> >> I think there may be other places where dso->kernel is misused. >> machine__process_kernel_mmap_event() may be one of them. If I understand >> correctly, 'dso->kernel && is_kernel_module(dso->long_name)' should always >> false theoretically. However, I don't have enough time to check whether that >> code really cause problem. >> >> --- >> tools/perf/util/probe-event.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c >> index 2b78e8f..c7d6d3d 100644 >> --- a/tools/perf/util/probe-event.c >> +++ b/tools/perf/util/probe-event.c >> @@ -270,7 +270,7 @@ static int kernel_get_module_dso(const char *module, struct dso **pdso) >> >> if (module) { >> list_for_each_entry(dso, &host_machine->dsos.head, node) { >> - if (!dso->kernel) >> + if (dso->kernel) >> continue; >> if (strncmp(dso->short_name + 1, module, >> dso->short_name_len - 2) == 0) >> -- >> 1.8.3.4
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