Hi, > Powerpc has Global Entry Point and Local Entry Point for functions. > LEP catches call from both the GEP and the LEP. Symbol table of ELF > contains GEP and Offset from which we can calculate LEP, but debuginfo > does not have LEP info. > > Currently, perf prioritize symbol table over dwarf to probe on LEP > for ppc64le. But when user tries to probe with function parameter, > we fall back to using dwarf(i.e. GEP) and when function called via > LEP, probe will never hit.
This patch causes a build failure for me on ppc64le: libperf.a(libperf-in.o): In function `arch__post_process_probe_trace_events': tools/perf/arch/powerpc/util/sym-handling.c:109: undefined reference to `get_target_map' Anton > For example: > $ objdump -d vmlinux > ... > do_sys_open(): > c0000000002eb4a0: e8 00 4c 3c addis r2,r12,232 > c0000000002eb4a4: 60 00 42 38 addi r2,r2,96 > c0000000002eb4a8: a6 02 08 7c mflr r0 > c0000000002eb4ac: d0 ff 41 fb std r26,-48(r1) > > $ sudo ./perf probe do_sys_open > $ sudo cat /sys/kernel/debug/tracing/kprobe_events > p:probe/do_sys_open _text+3060904 > > $ sudo ./perf probe 'do_sys_open filename:string' > $ sudo cat /sys/kernel/debug/tracing/kprobe_events > p:probe/do_sys_open _text+3060896 filename_string=+0(%gpr4):string > > For second case, perf probed on GEP. So when function will be called > via LEP, probe won't hit. > > $ sudo ./perf record -a -e probe:do_sys_open ls > [ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.195 MB perf.data ] > > To resolve this issue, let's not prioritize symbol table, let perf > decide what it wants to use. Perf is already converting GEP to LEP > when it uses symbol table. When perf uses debuginfo, let it find > LEP offset form symbol table. This way we fall back to probe on LEP > for all cases. > > After patch: > $ sudo ./perf probe 'do_sys_open filename:string' > $ sudo cat /sys/kernel/debug/tracing/kprobe_events > p:probe/do_sys_open _text+3060904 filename_string=+0(%gpr4):string > > $ sudo ./perf record -a -e probe:do_sys_open ls > [ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.197 MB perf.data (11 samples) > ] > > Signed-off-by: Ravi Bangoria <[email protected]> > --- > tools/perf/arch/powerpc/util/sym-handling.c | 27 > +++++++++++++++++---- tools/perf/util/probe-event.c | > 37 ++++++++++++++++------------- > tools/perf/util/probe-event.h | 6 ++++- 3 files > changed, 49 insertions(+), 21 deletions(-) > > diff --git a/tools/perf/arch/powerpc/util/sym-handling.c > b/tools/perf/arch/powerpc/util/sym-handling.c index c6d0f91..8d4dc97 > 100644 --- a/tools/perf/arch/powerpc/util/sym-handling.c > +++ b/tools/perf/arch/powerpc/util/sym-handling.c > @@ -54,10 +54,6 @@ int arch__compare_symbol_names(const char *namea, > const char *nameb) #endif > > #if defined(_CALL_ELF) && _CALL_ELF == 2 > -bool arch__prefers_symtab(void) > -{ > - return true; > -} > > #ifdef HAVE_LIBELF_SUPPORT > void arch__sym_update(struct symbol *s, GElf_Sym *sym) > @@ -100,4 +96,27 @@ void arch__fix_tev_from_maps(struct > perf_probe_event *pev, tev->point.offset += lep_offset; > } > } > + > +void arch__post_process_probe_trace_events(struct perf_probe_event > *pev, > + int ntevs) > +{ > + struct probe_trace_event *tev; > + struct map *map; > + struct symbol *sym = NULL; > + struct rb_node *tmp; > + int i = 0; > + > + map = get_target_map(pev->target, pev->uprobes); > + if (!map || map__load(map, NULL) < 0) > + return; > + > + for (i = 0; i < ntevs; i++) { > + tev = &pev->tevs[i]; > + map__for_each_symbol(map, sym, tmp) { > + if (map->unmap_ip(map, sym->start) == > tev->point.address) > + arch__fix_tev_from_maps(pev, tev, > map, sym); > + } > + } > +} > + > #endif > diff --git a/tools/perf/util/probe-event.c > b/tools/perf/util/probe-event.c index 4e215e7..5efa535 100644 > --- a/tools/perf/util/probe-event.c > +++ b/tools/perf/util/probe-event.c > @@ -178,7 +178,7 @@ static struct map *kernel_get_module_map(const > char *module) return NULL; > } > > -static struct map *get_target_map(const char *target, bool user) > +struct map *get_target_map(const char *target, bool user) > { > /* Init maps of given executable or kernel */ > if (user) > @@ -703,19 +703,32 @@ post_process_kernel_probe_trace_events(struct > probe_trace_event *tevs, return skipped; > } > > +void __weak > +arch__post_process_probe_trace_events(struct perf_probe_event *pev > __maybe_unused, > + int ntevs __maybe_unused) > +{ > +} > + > /* Post processing the probe events */ > -static int post_process_probe_trace_events(struct probe_trace_event > *tevs, +static int post_process_probe_trace_events(struct > perf_probe_event *pev, > + struct probe_trace_event > *tevs, int ntevs, const char *module, > bool uprobe) > { > - if (uprobe) > - return add_exec_to_probe_trace_events(tevs, ntevs, > module); > + int ret; > > - if (module) > + if (uprobe) > + ret = add_exec_to_probe_trace_events(tevs, ntevs, > module); > + else if (module) > /* Currently ref_reloc_sym based probe is not for > drivers */ > - return add_module_to_probe_trace_events(tevs, ntevs, > module); > + ret = add_module_to_probe_trace_events(tevs, ntevs, > module); > + else > + ret = post_process_kernel_probe_trace_events(tevs, > ntevs); > - return post_process_kernel_probe_trace_events(tevs, ntevs); > + if (ret >= 0) > + arch__post_process_probe_trace_events(pev, ntevs); > + > + return ret; > } > > /* Try to find perf_probe_event with debuginfo */ > @@ -756,7 +769,7 @@ static int try_to_find_probe_trace_events(struct > perf_probe_event *pev, > if (ntevs > 0) { /* Succeeded to find trace events */ > pr_debug("Found %d probe_trace_events.\n", ntevs); > - ret = post_process_probe_trace_events(*tevs, ntevs, > + ret = post_process_probe_trace_events(pev, *tevs, > ntevs, pev->target, pev->uprobes); > if (ret < 0 || ret == ntevs) { > clear_probe_trace_events(*tevs, ntevs); > @@ -2943,8 +2956,6 @@ errout: > return err; > } > > -bool __weak arch__prefers_symtab(void) { return false; } > - > /* Concatinate two arrays */ > static void *memcat(void *a, size_t sz_a, void *b, size_t sz_b) > { > @@ -3165,12 +3176,6 @@ static int > convert_to_probe_trace_events(struct perf_probe_event *pev, if (ret > > 0 || pev->sdt) /* SDT can be found only in the cache */ return > ret == 0 ? -ENOENT : ret; /* Found in probe cache */ > - if (arch__prefers_symtab() > && !perf_probe_event_need_dwarf(pev)) { > - ret = find_probe_trace_events_from_map(pev, tevs); > - if (ret > 0) > - return ret; /* Found in symbol table */ > - } > - > /* Convert perf_probe_event with debuginfo */ > ret = try_to_find_probe_trace_events(pev, tevs); > if (ret != 0) > diff --git a/tools/perf/util/probe-event.h > b/tools/perf/util/probe-event.h index e18ea9f..f4f45db 100644 > --- a/tools/perf/util/probe-event.h > +++ b/tools/perf/util/probe-event.h > @@ -158,7 +158,6 @@ int show_line_range(struct line_range *lr, const > char *module, bool user); int show_available_vars(struct > perf_probe_event *pevs, int npevs, struct strfilter *filter); > int show_available_funcs(const char *module, struct strfilter > *filter, bool user); -bool arch__prefers_symtab(void); > void arch__fix_tev_from_maps(struct perf_probe_event *pev, > struct probe_trace_event *tev, struct > map *map, struct symbol *sym); > @@ -173,4 +172,9 @@ int e_snprintf(char *str, size_t size, const char > *format, ...) int copy_to_probe_trace_arg(struct probe_trace_arg > *tvar, struct perf_probe_arg *pvar); > > +struct map *get_target_map(const char *target, bool user); > + > +void arch__post_process_probe_trace_events(struct perf_probe_event > *pev, > + int ntevs); > + > #endif /*_PROBE_EVENT_H */
