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Commit b7dcb857 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Arnaldo Carvalho de Melo
Browse files

perf probe: Support static and global variables 



Add static and global variables support to perf probe.
This allows user to trace non-local variables (and
structure members) at probe points.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20100519195749.2885.17451.stgit@localhost6.localdomain6>
Signed-off-by: default avatarMasami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent b2a3c12b

tools/perf/util/probe-event.c

+12 −3
Original line number Diff line number Diff line
@@ -926,6 +926,7 @@ static int __synthesize_kprobe_trace_arg_ref(struct kprobe_trace_arg_ref *ref, 
static int synthesize_kprobe_trace_arg(struct kprobe_trace_arg *arg,

				       char *buf, size_t buflen)

{

	struct kprobe_trace_arg_ref *ref = arg->ref;

	int ret, depth = 0;

	char *tmp = buf;
@@ -939,15 +940,23 @@ static int synthesize_kprobe_trace_arg(struct kprobe_trace_arg *arg, 
	buf += ret;

	buflen -= ret;



	/* Special case: @XXX */

	if (arg->value[0] == '@' && arg->ref)

			ref = ref->next;



	/* Dereferencing arguments */

	if (arg->ref) {

		depth = __synthesize_kprobe_trace_arg_ref(arg->ref, &buf,

	if (ref) {

		depth = __synthesize_kprobe_trace_arg_ref(ref, &buf,

							  &buflen, 1);

		if (depth < 0)

			return depth;

	}



	/* Print argument value */

	if (arg->value[0] == '@' && arg->ref)

		ret = e_snprintf(buf, buflen, "%s%+ld", arg->value,

				 arg->ref->offset);

	else

		ret = e_snprintf(buf, buflen, "%s", arg->value);

	if (ret < 0)

		return ret;

tools/perf/util/probe-finder.c

+61 −24
Original line number Diff line number Diff line
@@ -406,14 +406,50 @@ static Dwarf_Die *die_find_member(Dwarf_Die *st_die, const char *name, 
 * Probe finder related functions

 */



static struct kprobe_trace_arg_ref *alloc_trace_arg_ref(long offs)

{

	struct kprobe_trace_arg_ref *ref;

	ref = zalloc(sizeof(struct kprobe_trace_arg_ref));

	if (ref != NULL)

		ref->offset = offs;

	return ref;

}



/* Show a location */

static int convert_location(Dwarf_Op *op, struct probe_finder *pf)

static int convert_variable_location(Dwarf_Die *vr_die, struct probe_finder *pf)

{

	Dwarf_Attribute attr;

	Dwarf_Op *op;

	size_t nops;

	unsigned int regn;

	Dwarf_Word offs = 0;

	bool ref = false;

	const char *regs;

	struct kprobe_trace_arg *tvar = pf->tvar;

	int ret;



	/* TODO: handle more than 1 exprs */

	if (dwarf_attr(vr_die, DW_AT_location, &attr) == NULL ||

	    dwarf_getlocation_addr(&attr, pf->addr, &op, &nops, 1) <= 0 ||

	    nops == 0) {

		/* TODO: Support const_value */

		pr_err("Failed to find the location of %s at this address.\n"

		       " Perhaps, it has been optimized out.\n", pf->pvar->var);

		return -ENOENT;

	}



	if (op->atom == DW_OP_addr) {

		/* Static variables on memory (not stack), make @varname */

		ret = strlen(dwarf_diename(vr_die));

		tvar->value = zalloc(ret + 2);

		if (tvar->value == NULL)

			return -ENOMEM;

		snprintf(tvar->value, ret + 2, "@%s", dwarf_diename(vr_die));

		tvar->ref = alloc_trace_arg_ref((long)offs);

		if (tvar->ref == NULL)

			return -ENOMEM;

		return 0;

	}



	/* If this is based on frame buffer, set the offset */

	if (op->atom == DW_OP_fbreg) {
@@ -455,10 +491,9 @@ static int convert_location(Dwarf_Op *op, struct probe_finder *pf) 
		return -ENOMEM;



	if (ref) {

		tvar->ref = zalloc(sizeof(struct kprobe_trace_arg_ref));

		tvar->ref = alloc_trace_arg_ref((long)offs);

		if (tvar->ref == NULL)

			return -ENOMEM;

		tvar->ref->offset = (long)offs;

	}

	return 0;

}
@@ -666,20 +701,13 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname, 
/* Show a variables in kprobe event format */

static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)

{

	Dwarf_Attribute attr;

	Dwarf_Die die_mem;

	Dwarf_Op *expr;

	size_t nexpr;

	int ret;



	if (dwarf_attr(vr_die, DW_AT_location, &attr) == NULL)

		goto error;

	/* TODO: handle more than 1 exprs */

	ret = dwarf_getlocation_addr(&attr, pf->addr, &expr, &nexpr, 1);

	if (ret <= 0 || nexpr == 0)

		goto error;

	pr_debug("Converting variable %s into trace event.\n",

		 dwarf_diename(vr_die));



	ret = convert_location(expr, pf);

	ret = convert_variable_location(vr_die, pf);

	if (ret == 0 && pf->pvar->field) {

		ret = convert_variable_fields(vr_die, pf->pvar->var,

					      pf->pvar->field, &pf->tvar->ref,
@@ -690,19 +718,14 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf) 
		ret = convert_variable_type(vr_die, pf->tvar, pf->pvar->type);

	/* *expr will be cached in libdw. Don't free it. */

	return ret;

error:

	/* TODO: Support const_value */

	pr_err("Failed to find the location of %s at this address.\n"

	       " Perhaps, it has been optimized out.\n", pf->pvar->var);

	return -ENOENT;

}



/* Find a variable in a subprogram die */

static int find_variable(Dwarf_Die *sp_die, struct probe_finder *pf)

{

	Dwarf_Die vr_die;

	Dwarf_Die vr_die, *scopes;

	char buf[32], *ptr;

	int ret;

	int ret, nscopes;



	if (pf->pvar->name)

		pf->tvar->name = strdup(pf->pvar->name);
@@ -730,12 +753,26 @@ static int find_variable(Dwarf_Die *sp_die, struct probe_finder *pf) 
	pr_debug("Searching '%s' variable in context.\n",

		 pf->pvar->var);

	/* Search child die for local variables and parameters. */

	if (!die_find_variable(sp_die, pf->pvar->var, &vr_die)) {

	if (die_find_variable(sp_die, pf->pvar->var, &vr_die))

		ret = convert_variable(&vr_die, pf);

	else {

		/* Search upper class */

		nscopes = dwarf_getscopes_die(sp_die, &scopes);

		if (nscopes > 0) {

			ret = dwarf_getscopevar(scopes, nscopes, pf->pvar->var,

						0, NULL, 0, 0, &vr_die);

			if (ret >= 0)

				ret = convert_variable(&vr_die, pf);

			else

				ret = -ENOENT;

			free(scopes);

		} else

			ret = -ENOENT;

	}

	if (ret < 0)

		pr_warning("Failed to find '%s' in this function.\n",

			   pf->pvar->var);

		return -ENOENT;

	}

	return convert_variable(&vr_die, pf);

	return ret;

}



/* Show a probe point to output buffer */