Hi Arnaldo, Could you wait for pulling this series? I've found that this series has an obvious bug on kaslr enabled kernel. I'll fix that by using the relative address from _stext for kprobes.
Thank you, (2014/01/23 11:29), Masami Hiramatsu wrote: > Hi, > > Here is a series of patches for handling local functions > correctly in perf-probe. > > Issue 1) > Current perf-probe can't handle probe-points for kprobes, > since it uses symbol-based probe definition. The symbol > based definition is easy to read and robust for differnt > kernel and modules. However, when user gives a local > function name which has several different instances, > it may put probes on wrong (or unexpected) address. > On the other hand, since uprobe events are based on the > actual address, it can avoid this issue. > > E.g. > In the case to probe t_show local functions (which has > 4 different instances. > ---- > # grep " t_show\$" /proc/kallsyms > ffffffff810d9720 t t_show > ffffffff810e2e40 t t_show > ffffffff810ece30 t t_show > ffffffff810f4ad0 t t_show > # ./perf probe -f t_show \$vars > Added new events: > probe:t_show (on t_show with $vars) > probe:t_show_1 (on t_show with $vars) > probe:t_show_2 (on t_show with $vars) > probe:t_show_3 (on t_show with $vars) > > You can now use it in all perf tools, such as: > > perf record -e probe:t_show_3 -aR sleep 1 > ---- > OK, we have 4 different t_show()s. All functions have > different arguments as below; > ---- > # cat /sys/kernel/debug/tracing/kprobe_events > p:probe/t_show t_show m=%di:u64 v=%si:u64 > p:probe/t_show_1 t_show m=%di:u64 v=%si:u64 t=%si:u64 > p:probe/t_show_2 t_show m=%di:u64 v=%si:u64 fmt=%si:u64 > p:probe/t_show_3 t_show m=%di:u64 v=%si:u64 file=%si:u64 > ---- > However, all of them have been put on the *same* address. > ---- > # cat /sys/kernel/debug/kprobes/list > ffffffff810d9720 k t_show+0x0 [DISABLED] > ffffffff810d9720 k t_show+0x0 [DISABLED] > ffffffff810d9720 k t_show+0x0 [DISABLED] > ffffffff810d9720 k t_show+0x0 [DISABLED] > ---- > oops... > > Issue 2) > With the debuginfo, issue 1 can be solved by using > address-based probe definition instead of symbol-based. > However, without debuginfo, perf-probe can only use > symbol-map in the binary (or kallsyms). The map provides > symbol find methods, but it returns only the first matched > symbol. To put probes on all functions which have given > symbol, we need a symbol-list iterator for the map. > > E.g. (built perf with NO_DWARF=1) > In the case to probe t_show and identity__map_ip in perf. > ---- > # ./perf probe -a t_show > Added new event: > probe:t_show (on t_show) > > You can now use it in all perf tools, such as: > > perf record -e probe:t_show -aR sleep 1 > > # ./perf probe -x perf -a identity__map_ip > no symbols found in /kbuild/ksrc/linux-3/tools/perf/perf, maybe install a > debug package? > Failed to load map. > Error: Failed to add events. (-22) > ---- > oops..... > > > Solutions) > To solve the issue 1, this series changes perf probe to > use address-based probe definition. This means that we > also need to fix the --list options to analyze probe > addresses instead of symbols (and that has been done > in this series). > > E.g. with this series; > ---- > # ./perf probe -f t_show \$vars > Added new events: > probe:t_show (on t_show with $vars) > probe:t_show_1 (on t_show with $vars) > probe:t_show_2 (on t_show with $vars) > probe:t_show_3 (on t_show with $vars) > > You can now use it in all perf tools, such as: > > perf record -e probe:t_show_3 -aR sleep 1 > > # cat /sys/kernel/debug/tracing/kprobe_events > p:probe/t_show 0xffffffff810d9720 m=%di:u64 v=%si:u64 > p:probe/t_show_1 0xffffffff810e2e40 m=%di:u64 v=%si:u64 t=%si:u64 > p:probe/t_show_2 0xffffffff810ece30 m=%di:u64 v=%si:u64 fmt=%si:u64 > p:probe/t_show_3 0xffffffff810f4ad0 m=%di:u64 v=%si:u64 file=%si:u64 > > # cat /sys/kernel/debug/kprobes/list > ffffffff810e2e40 k t_show+0x0 [DISABLED] > ffffffff810ece30 k t_show+0x0 [DISABLED] > ffffffff810f4ad0 k t_show+0x0 [DISABLED] > ffffffff810d9720 k t_show+0x0 [DISABLED] > ---- > This time we can see the events are set in different > addresses. > > And for the issue 2, the last patch introduces symbol > iterators for map, dso and symbols (since the symbol > list is the symbols and it is included dso, and perf > probe accesses dso via map). > > E.g. with this series (built perf with NO_DWARF=1); > ---- > # ./perf probe -a t_show > Added new events: > probe:t_show (on t_show) > probe:t_show_1 (on t_show) > probe:t_show_2 (on t_show) > probe:t_show_3 (on t_show) > > You can now use it in all perf tools, such as: > > perf record -e probe:t_show_3 -aR sleep 1 > > # ./perf probe -x perf -a identity__map_ip > Added new events: > probe_perf:identity__map_ip (on identity__map_ip in > /kbuild/ksrc/linux-3/tools/perf/perf) > probe_perf:identity__map_ip_1 (on identity__map_ip in > /kbuild/ksrc/linux-3/tools/perf/perf) > probe_perf:identity__map_ip_2 (on identity__map_ip in > /kbuild/ksrc/linux-3/tools/perf/perf) > probe_perf:identity__map_ip_3 (on identity__map_ip in > /kbuild/ksrc/linux-3/tools/perf/perf) > > You can now use it in all perf tools, such as: > > perf record -e probe_perf:identity__map_ip_3 -aR sleep 1 > ---- > Now, even without the debuginfo, both the kprobe and > uprobe are set 4 different places correctly. > > BTW, while testing above, I've found some bugs and > another minor issue; perf-probe doesn't show the > modules and binaries in which probes are set. > I've also fixed it in this series as below. > > Without the fix; > > # ./perf probe -m drm drm_av_sync_delay > # ./perf probe -x perf dso__load_vmlinux > > # ./perf probe -l > probe:drm_av_sync_delay (on drm_av_sync_delay) > probe_perf:dso__load_vmlinux (on 0x000000000006d110) > > With this fix; > > # ./perf probe -l > probe:drm_av_sync_delay (on drm_av_sync_delay in drm) > probe_perf:dso__load_vmlinux (on 0x000000000006d110 in > /kbuild/ksrc/linux-3/tools/perf/perf) > > > TODO: > - Support local functions in modules. This requires kernel > side enhancement to allow setting probes by the relative > addresses in modules too. > - Uprobe-event MUST traces the change of given binary even > when the event is disabled. I've found that user can replace > the target binary after setting events and the events can be > enabled on the different instructions... > > --- > > Masami Hiramatsu (8): > [BUGFIX] perf-probe: Fix to do exit call for symbol maps > [BUGFIX] perf-tools: Load map before using map->map_ip > perf-probe: Show in what binaries/modules probes are set > perf-probe: Use the actual address instead of the symbol name > perf-probe: Show source level information for address only kprobes > perf-probe: Show symbol+offset for address only kprobes > perf-probe: Show source-level or symbol-level info for uprobes > perf-probe: Allow to add events on the local functions > > > tools/perf/util/dso.h | 10 + > tools/perf/util/map.c | 3 > tools/perf/util/map.h | 10 + > tools/perf/util/probe-event.c | 661 > ++++++++++++++++++++++------------------- > tools/perf/util/symbol.h | 11 + > 5 files changed, 387 insertions(+), 308 deletions(-) > -- Masami HIRAMATSU IT Management Research Dept. 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