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Message-ID: <50399556C9727B4D88A595C8584AAB37524EC7CD@GSjpTKYDCembx32.service.hitachi.net>
Date: Wed, 26 Aug 2015 09:49:35 +0000
From: 平松雅巳 / HIRAMATU，MASAMI
<masami.hiramatsu.pt@...achi.com>
To: "'Wang Nan'" <wangnan0@...wei.com>,
"acme@...nel.org" <acme@...nel.org>,
"rostedt@...dmis.org" <rostedt@...dmis.org>
CC: "mingo@...hat.com" <mingo@...hat.com>,
"namhyung@...nel.org" <namhyung@...nel.org>,
"pi3orama@....com" <pi3orama@....com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
sysp-manager <cti.systems-productivity-manager.ts@...achi.com>
Subject: RE: [PATCH v2 3/4] perf probe: Support probing at absolute address
> From: Wang Nan [mailto:wangnan0@...wei.com]
>
> 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 <wangnan0@...wei.com>
> Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> ---
> 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
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