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Commit da15bd9d authored by Wang Nan's avatar Wang Nan Committed by Arnaldo Carvalho de Melo
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perf probe: Support probing at absolute address 



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.

v1 -> v2:
  Drop the leading '+' in cmdline;
  Allow uprobing at offset 0x0;
  Improve 'perf probe -l' result when uprobe at area without debuginfo.

v2 -> v3:
  Split bugfix to a separated patch.

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: default avatarWang Nan <wangnan0@huawei.com>
Acked-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1440586666-235233-7-git-send-email-wangnan0@huawei.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 6c6e024f

tools/perf/util/probe-event.c

+156 −6
Original line number Diff line number Diff line
@@ -1204,9 +1204,27 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev) 


	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;
@@ -1804,14 +1822,29 @@ 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 ? ":" : "",
@@ -2331,7 +2364,9 @@ 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;
@@ -2598,6 +2633,98 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev, 
	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,
@@ -2614,6 +2741,10 @@ 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)
@@ -2784,3 +2915,22 @@ int show_available_funcs(const char *target, struct strfilter *_filter, 
	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;

}

tools/perf/util/probe-event.h

+4 −0
Original line number Diff line number Diff line
@@ -59,6 +59,7 @@ 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 */
@@ -156,4 +157,7 @@ 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 */

tools/perf/util/probe-finder.c

+3 −18
Original line number Diff line number Diff line
@@ -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;

	}

	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);