> From: Wang Nan [mailto:[email protected]] > > It should be useful to allow 'perf probe' probe at absolute offset of > a target. For example, when (u)probing at a instruction of a shared > object in a embedded system where debuginfo is not avaliable but we > know the offset of that instruction by manually digging. > > This patch enables following perf probe command syntax: > > # perf probe 0xffffffff811e6615 > > And > > # perf probe /lib/x86_64-linux-gnu/libc-2.19.so 0xeb860 > > In the above example, we don't need a anchor symbol, so it is possible > to compute absolute addresses using other methods and then use > 'perf probe' to create the probing points.
OK, this looks good :) > > This patch also fix a bug that, when offset is provided but function is > skipped, parse_perf_probe_point() will give function a "" string, so > the checking code at the end of this function is not used. For example: > > # perf probe +0x1234 > Failed to find symbol in kernel > Error: Failed to add events. > > After this patch: > > # perf probe +0x1234 > Semantic error :Offset requires an entry function. > Error: Command Parse Error. Hmm, could you please split the bugfix from feature addition patch? Thank you, > > v1 -> v2: > Drop the leading '+' in cmdline; > Allow uprobing at offset 0x0; > Improve 'perf probe -l' result when uprobe at area without debuginfo. > > Test result: > > # perf probe 0xffffffff8119d175 %ax > # perf probe sys_write %ax > # perf probe /lib64/libc-2.18.so 0x0 %ax > # perf probe /lib64/libc-2.18.so 0x5 %ax > # perf probe /lib64/libc-2.18.so 0xd8e40 %ax > # perf probe /lib64/libc-2.18.so __write %ax > # perf probe /lib64/libc-2.18.so 0xd8e49 %ax > # cat /sys/kernel/debug/tracing/uprobe_events > > p:probe_libc/abs_0 /lib64/libc-2.18.so:0x (null) arg1=%ax > p:probe_libc/abs_5 /lib64/libc-2.18.so:0x0000000000000005 arg1=%ax > p:probe_libc/abs_d8e40 /lib64/libc-2.18.so:0x00000000000d8e40 arg1=%ax > p:probe_libc/__write /lib64/libc-2.18.so:0x00000000000d8e40 arg1=%ax > p:probe_libc/abs_d8e49 /lib64/libc-2.18.so:0x00000000000d8e49 arg1=%ax > > # cat /sys/kernel/debug/tracing/kprobe_events > > p:probe/abs_ffffffff8119d175 0xffffffff8119d175 arg1=%ax > p:probe/sys_write _text+1692016 arg1=%ax > > # perf probe -l > > Failed to find debug information for address 5 > probe:abs_ffffffff8119d175 (on sys_write+5 with arg1) > probe:sys_write (on sys_write with arg1) > probe_libc:__write (on @unix/syscall-template.S:81 in > /lib64/libc-2.18.so with arg1) > probe_libc:abs_0 (on 0x0 in /lib64/libc-2.18.so with arg1) > probe_libc:abs_5 (on 0x5 in /lib64/libc-2.18.so with arg1) > probe_libc:abs_d8e40 (on @unix/syscall-template.S:81 in > /lib64/libc-2.18.so with arg1) > probe_libc:abs_d8e49 (on __GI___libc_write+9 in /lib64/libc-2.18.so with > arg1) > > Signed-off-by: Wang Nan <[email protected]> > Cc: Arnaldo Carvalho de Melo <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Masami Hiramatsu <[email protected]> > Cc: Namhyung Kim <[email protected]> > Cc: Steven Rostedt <[email protected]> > --- > tools/perf/util/probe-event.c | 172 > ++++++++++++++++++++++++++++++++++++++--- > tools/perf/util/probe-event.h | 4 + > tools/perf/util/probe-finder.c | 21 +---- > 3 files changed, 170 insertions(+), 27 deletions(-) > > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c > index 3ce223d..b94a8d7 100644 > --- a/tools/perf/util/probe-event.c > +++ b/tools/perf/util/probe-event.c > @@ -1196,15 +1196,37 @@ static int parse_perf_probe_point(char *arg, struct > perf_probe_event *pev) > *ptr++ = '\0'; > } > > - tmp = strdup(arg); > - if (tmp == NULL) > - return -ENOMEM; > + if (arg[0] == '\0') > + tmp = NULL; > + else { > + tmp = strdup(arg); > + if (tmp == NULL) > + return -ENOMEM; > + } > > if (file_spec) > pp->file = tmp; > - else > + else { > pp->function = tmp; > > + /* > + * Keep pp->function even if this is absolute address, > + * so it can mark whether abs_address is valid. > + * Which make 'perf probe lib.bin 0x0' possible. > + * > + * Note that checking length of tmp is not needed > + * because when we access tmp[1] we know tmp[0] is '0', > + * so tmp[1] should always valid (but could be '\0'). > + */ > + if (tmp && !strncmp(tmp, "0x", 2)) { > + pp->abs_address = strtoul(pp->function, &tmp, 0); > + if (*tmp != '\0') { > + semantic_error("Invalid absolute address.\n"); > + return -EINVAL; > + } > + } > + } > + > /* Parse other options */ > while (ptr) { > arg = ptr; > @@ -1802,14 +1824,29 @@ char *synthesize_probe_trace_command(struct > probe_trace_event *tev) > if (len <= 0) > goto error; > > - /* Uprobes must have tp->address and tp->module */ > - if (tev->uprobes && (!tp->address || !tp->module)) > + /* Uprobes must have tp->module */ > + if (tev->uprobes && !tp->module) > goto error; > + /* > + * If tp->address == 0, then this point must be a > + * absolute address uprobe. > + * try_to_find_absolute_address() should have made > + * tp->symbol to "0x0". > + */ > + if (tev->uprobes && !tp->address) { > + if (!tp->symbol || strcmp(tp->symbol, "0x0")) > + goto error; > + } > > /* Use the tp->address for uprobes */ > if (tev->uprobes) > ret = e_snprintf(buf + len, MAX_CMDLEN - len, "%s:0x%lx", > tp->module, tp->address); > + else if (!strncmp(tp->symbol, "0x", 2)) > + /* Absolute address. See try_to_find_absolute_address() */ > + ret = e_snprintf(buf + len, MAX_CMDLEN - len, "%s%s0x%lx", > + tp->module ?: "", tp->module ? ":" : "", > + tp->address); > else > ret = e_snprintf(buf + len, MAX_CMDLEN - len, "%s%s%s+%lu", > tp->module ?: "", tp->module ? ":" : "", > @@ -1872,8 +1909,8 @@ out: > } > > static int convert_to_perf_probe_point(struct probe_trace_point *tp, > - struct perf_probe_point *pp, > - bool is_kprobe) > + struct perf_probe_point *pp, > + bool is_kprobe) > { > char buf[128]; > int ret; > @@ -2334,7 +2371,9 @@ static int probe_trace_event__set_name(struct > probe_trace_event *tev, > if (pev->event) > event = pev->event; > else > - if (pev->point.function && !strisglob(pev->point.function)) > + if (pev->point.function && > + (strncmp(pev->point.function, "0x", 2) != 0) && > + !strisglob(pev->point.function)) > event = pev->point.function; > else > event = tev->point.realname; > @@ -2604,6 +2643,98 @@ err_out: > goto out; > } > > +static int try_to_find_absolute_address(struct perf_probe_event *pev, > + struct probe_trace_event **tevs) > +{ > + struct perf_probe_point *pp = &pev->point; > + struct probe_trace_event *tev; > + struct probe_trace_point *tp; > + int i, err; > + > + if (!(pev->point.function && !strncmp(pev->point.function, "0x", 2))) > + return -EINVAL; > + if (perf_probe_event_need_dwarf(pev)) > + return -EINVAL; > + > + /* > + * This is 'perf probe /lib/libc.so 0xabcd'. Try to probe at > + * absolute address. > + * > + * Only one tev can be generated by this. > + */ > + *tevs = zalloc(sizeof(*tev)); > + if (!*tevs) > + return -ENOMEM; > + > + tev = *tevs; > + tp = &tev->point; > + > + /* > + * Don't use tp->offset, use address directly, because > + * in synthesize_probe_trace_command() address cannot be > + * zero. > + */ > + tp->address = pev->point.abs_address; > + tp->retprobe = pp->retprobe; > + tev->uprobes = pev->uprobes; > + > + err = -ENOMEM; > + /* > + * Give it a '0x' leading symbol name. > + * In __add_probe_trace_events, a NULL symbol is interpreted as > + * invalud. > + */ > + if (asprintf(&tp->symbol, "0x%lx", tp->address) < 0) > + goto errout; > + > + /* For kprobe, check range */ > + if ((!tev->uprobes) && > + (kprobe_warn_out_range(tev->point.symbol, > + tev->point.address))) { > + err = -EACCES; > + goto errout; > + } > + > + if (asprintf(&tp->realname, "abs_%lx", tp->address) < 0) > + goto errout; > + > + if (pev->target) { > + tp->module = strdup(pev->target); > + if (!tp->module) > + goto errout; > + } > + > + if (tev->group) { > + tev->group = strdup(pev->group); > + if (!tev->group) > + goto errout; > + } > + > + if (pev->event) { > + tev->event = strdup(pev->event); > + if (!tev->event) > + goto errout; > + } > + > + tev->nargs = pev->nargs; > + tev->args = zalloc(sizeof(struct probe_trace_arg) * tev->nargs); > + if (!tev->args) { > + err = -ENOMEM; > + goto errout; > + } > + for (i = 0; i < tev->nargs; i++) > + copy_to_probe_trace_arg(&tev->args[i], &pev->args[i]); > + > + return 1; > + > +errout: > + if (*tevs) { > + clear_probe_trace_events(*tevs, 1); > + *tevs = NULL; > + } > + return err; > +} > + > bool __weak arch__prefers_symtab(void) { return false; } > > static int convert_to_probe_trace_events(struct perf_probe_event *pev, > @@ -2620,6 +2751,10 @@ static int convert_to_probe_trace_events(struct > perf_probe_event *pev, > } > } > > + ret = try_to_find_absolute_address(pev, tevs); > + if (ret > 0) > + return ret; > + > if (arch__prefers_symtab() && !perf_probe_event_need_dwarf(pev)) { > ret = find_probe_trace_events_from_map(pev, tevs); > if (ret > 0) > @@ -2787,3 +2922,22 @@ end: > return ret; > } > > +int copy_to_probe_trace_arg(struct probe_trace_arg *tvar, > + struct perf_probe_arg *pvar) > +{ > + tvar->value = strdup(pvar->var); > + if (tvar->value == NULL) > + return -ENOMEM; > + if (pvar->type) { > + tvar->type = strdup(pvar->type); > + if (tvar->type == NULL) > + return -ENOMEM; > + } > + if (pvar->name) { > + tvar->name = strdup(pvar->name); > + if (tvar->name == NULL) > + return -ENOMEM; > + } else > + tvar->name = NULL; > + return 0; > +} > diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h > index 9c7b99e..de0dd13 100644 > --- a/tools/perf/util/probe-event.h > +++ b/tools/perf/util/probe-event.h > @@ -61,6 +61,7 @@ struct perf_probe_point { > bool retprobe; /* Return probe flag */ > char *lazy_line; /* Lazy matching pattern */ > unsigned long offset; /* Offset from function entry */ > + unsigned long abs_address; /* Absolute address of the point */ > }; > > /* Perf probe probing argument field chain */ > @@ -162,4 +163,7 @@ int e_snprintf(char *str, size_t size, const char > *format, ...) > /* Maximum index number of event-name postfix */ > #define MAX_EVENT_INDEX 1024 > > +int copy_to_probe_trace_arg(struct probe_trace_arg *tvar, > + struct perf_probe_arg *pvar); > + > #endif /*_PROBE_EVENT_H */ > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c > index 4b1e074..5ab9cd6 100644 > --- a/tools/perf/util/probe-finder.c > +++ b/tools/perf/util/probe-finder.c > @@ -553,24 +553,9 @@ static int find_variable(Dwarf_Die *sc_die, struct > probe_finder *pf) > char buf[32], *ptr; > int ret = 0; > > - if (!is_c_varname(pf->pvar->var)) { > - /* Copy raw parameters */ > - pf->tvar->value = strdup(pf->pvar->var); > - if (pf->tvar->value == NULL) > - return -ENOMEM; > - if (pf->pvar->type) { > - pf->tvar->type = strdup(pf->pvar->type); > - if (pf->tvar->type == NULL) > - return -ENOMEM; > - } > - if (pf->pvar->name) { > - pf->tvar->name = strdup(pf->pvar->name); > - if (pf->tvar->name == NULL) > - return -ENOMEM; > - } else > - pf->tvar->name = NULL; > - return 0; > - } > + /* Copy raw parameters */ > + if (!is_c_varname(pf->pvar->var)) > + return copy_to_probe_trace_arg(pf->tvar, pf->pvar); > > if (pf->pvar->name) > pf->tvar->name = strdup(pf->pvar->name); > -- > 1.8.3.4
