[tip:perf/core] perf probe: Fix to search local variables in appropriate scope

tip-bot for Masami Hiramatsu
2011-08-14T15:46:13Z

Commit-ID: 221d061182b8ff5507d5768aeeecbc74f01c5dfa
Gitweb: http://git.kernel.org/tip/221d061182b8ff5507d5768aeeecbc74f01c5dfa
Author: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
AuthorDate: Thu, 11 Aug 2011 20:02:59 +0900
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Fri, 12 Aug 2011 09:28:45 -0300

perf probe: Fix to search local variables in appropriate scope

Fix perf probe to search local variables in appropriate local inlined
function scope. For example, pre_schedule() has only 2 local variables,
as below;

$ perf probe -L pre_schedule
<pre_schedule@/home/mhiramat/ksrc/linux-2.6/kernel/sched.c:0>
0 static inline void pre_schedule(struct rq *rq, struct task_struct *prev)
{
2 if (prev->sched_class->pre_schedule)
3 prev->sched_class->pre_schedule(rq, prev);
}

However, current perf probe shows 4 local variables on pre_schedule(),
because it searches variables in the caller(schedule()) scope.

$ perf probe -V pre_schedule
Available variables at pre_schedule
@<schedule+445>
int cpu
long unsigned int* switch_count
struct rq* rq
struct task_struct* prev

This patch fixes this issue by searching variables in the local scope of
the instance of inlined function. Here is the result.

$ perf probe -V pre_schedule
Available variables at pre_schedule
@<schedule+445>
struct rq* rq
struct task_struct* prev

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: yrl.pp-manager.tt@hitachi.com
Link: http://lkml.kernel.org/r/20110811110259.19900.85664.stgit@fedora15
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/dwarf-aux.c | 33 ++++++++++
tools/perf/util/dwarf-aux.h | 4 +
tools/perf/util/probe-finder.c | 132 ++++++++++++++++++++++++++++++++--------
tools/perf/util/probe-finder.h | 2 +-
4 files changed, 144 insertions(+), 27 deletions(-)

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index d9b8ad0..425703a 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -96,6 +96,39 @@ int cu_find_lineinfo(Dwarf_Die *cu_die, unsigned long addr,
return *lineno ?: -ENOENT;
}

+static int __die_find_inline_cb(Dwarf_Die *die_mem, void *data);
+
+/**
+ * cu_walk_functions_at - Walk on function DIEs at given address
+ * @cu_die: A CU DIE
+ * @addr: An address
+ * @callback: A callback which called with found DIEs
+ * @data: A user data
+ *
+ * Walk on function DIEs at given @addr in @cu_die. Passed DIEs
+ * should be subprogram or inlined-subroutines.
+ */
+int cu_walk_functions_at(Dwarf_Die *cu_die, Dwarf_Addr addr,
+ int (*callback)(Dwarf_Die *, void *), void *data)
+{
+ Dwarf_Die die_mem;
+ Dwarf_Die *sc_die;
+ int ret = -ENOENT;
+
+ /* Inlined function could be recursive. Trace it until fail */
+ for (sc_die = die_find_realfunc(cu_die, addr, &die_mem);
+ sc_die != NULL;
+ sc_die = die_find_child(sc_die, __die_find_inline_cb, &addr,
+ &die_mem)) {
+ ret = callback(sc_die, data);
+ if (ret)
+ break;
+ }
+
+ return ret;
+
+}
+
/**
* die_compare_name - Compare diename and tname
* @dw_die: a DIE
diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h
index c8e491b..6f46106 100644
--- a/tools/perf/util/dwarf-aux.h
+++ b/tools/perf/util/dwarf-aux.h
@@ -34,6 +34,10 @@ extern const char *cu_get_comp_dir(Dwarf_Die *cu_die);
extern int cu_find_lineinfo(Dwarf_Die *cudie, unsigned long addr,
const char **fname, int *lineno);

+/* Walk on funcitons at given address */
+extern int cu_walk_functions_at(Dwarf_Die *cu_die, Dwarf_Addr addr,
+ int (*callback)(Dwarf_Die *, void *), void *data);
+
/* Compare diename and tname */
extern bool die_compare_name(Dwarf_Die *dw_die, const char *tname);

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index d6d5768..5c83b7d 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -612,8 +612,8 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
return ret;
}

-/* Find a variable in a subprogram die */
-static int find_variable(Dwarf_Die *sp_die, struct probe_finder *pf)
+/* Find a variable in a scope DIE */
+static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf)
{
Dwarf_Die vr_die, *scopes;
char buf[32], *ptr;
@@ -655,11 +655,11 @@ 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_at(sp_die, pf->pvar->var, pf->addr, &vr_die))
+ if (die_find_variable_at(sc_die, pf->pvar->var, pf->addr, &vr_die))
ret = convert_variable(&vr_die, pf);
else {
/* Search upper class */
- nscopes = dwarf_getscopes_die(sp_die, &scopes);
+ nscopes = dwarf_getscopes_die(sc_die, &scopes);
ret = -ENOENT;
while (nscopes-- > 1) {
pr_debug("Searching variables in %s\n",
@@ -717,26 +717,30 @@ static int convert_to_trace_point(Dwarf_Die *sp_die, Dwarf_Addr paddr,
return 0;
}

-/* Call probe_finder callback with real subprogram DIE */
-static int call_probe_finder(Dwarf_Die *sp_die, struct probe_finder *pf)
+/* Call probe_finder callback with scope DIE */
+static int call_probe_finder(Dwarf_Die *sc_die, struct probe_finder *pf)
{
- Dwarf_Die die_mem;
Dwarf_Attribute fb_attr;
size_t nops;
int ret;

- /* If no real subprogram, find a real one */
- if (!sp_die || dwarf_tag(sp_die) != DW_TAG_subprogram) {
- sp_die = die_find_realfunc(&pf->cu_die, pf->addr, &die_mem);
- if (!sp_die) {
+ if (!sc_die) {
+ pr_err("Caller must pass a scope DIE. Program error.\n");
+ return -EINVAL;
+ }
+
+ /* If not a real subprogram, find a real one */
+ if (dwarf_tag(sc_die) != DW_TAG_subprogram) {
+ if (!die_find_realfunc(&pf->cu_die, pf->addr, &pf->sp_die)) {
pr_warning("Failed to find probe point in any "
"functions.\n");
return -ENOENT;
}
- }
+ } else
+ memcpy(&pf->sp_die, sc_die, sizeof(Dwarf_Die));

- /* Get the frame base attribute/ops */
- dwarf_attr(sp_die, DW_AT_frame_base, &fb_attr);
+ /* Get the frame base attribute/ops from subprogram */
+ dwarf_attr(&pf->sp_die, DW_AT_frame_base, &fb_attr);
ret = dwarf_getlocation_addr(&fb_attr, pf->addr, &pf->fb_ops, &nops, 1);
if (ret <= 0 || nops == 0) {
pf->fb_ops = NULL;
@@ -754,7 +758,7 @@ static int call_probe_finder(Dwarf_Die *sp_die, struct probe_finder *pf)
}

/* Call finder's callback handler */
- ret = pf->callback(sp_die, pf);
+ ret = pf->callback(sc_die, pf);

/* *pf->fb_ops will be cached in libdw. Don't free it. */
pf->fb_ops = NULL;
@@ -762,17 +766,82 @@ static int call_probe_finder(Dwarf_Die *sp_die, struct probe_finder *pf)
return ret;
}

+struct find_scope_param {
+ const char *function;
+ const char *file;
+ int line;
+ int diff;
+ Dwarf_Die *die_mem;
+ bool found;
+};
+
+static int find_best_scope_cb(Dwarf_Die *fn_die, void *data)
+{
+ struct find_scope_param *fsp = data;
+ const char *file;
+ int lno;
+
+ /* Skip if declared file name does not match */
+ if (fsp->file) {
+ file = dwarf_decl_file(fn_die);
+ if (!file || strcmp(fsp->file, file) != 0)
+ return 0;
+ }
+ /* If the function name is given, that's what user expects */
+ if (fsp->function) {
+ if (die_compare_name(fn_die, fsp->function)) {
+ memcpy(fsp->die_mem, fn_die, sizeof(Dwarf_Die));
+ fsp->found = true;
+ return 1;
+ }
+ } else {
+ /* With the line number, find the nearest declared DIE */
+ dwarf_decl_line(fn_die, &lno);
+ if (lno < fsp->line && fsp->diff > fsp->line - lno) {
+ /* Keep a candidate and continue */
+ fsp->diff = fsp->line - lno;
+ memcpy(fsp->die_mem, fn_die, sizeof(Dwarf_Die));
+ fsp->found = true;
+ }
+ }
+ return 0;
+}
+
+/* Find an appropriate scope fits to given conditions */
+static Dwarf_Die *find_best_scope(struct probe_finder *pf, Dwarf_Die *die_mem)
+{
+ struct find_scope_param fsp = {
+ .function = pf->pev->point.function,
+ .file = pf->fname,
+ .line = pf->lno,
+ .diff = INT_MAX,
+ .die_mem = die_mem,
+ .found = false,
+ };
+
+ cu_walk_functions_at(&pf->cu_die, pf->addr, find_best_scope_cb, &fsp);
+
+ return fsp.found ? die_mem : NULL;
+}
+
static int probe_point_line_walker(const char *fname, int lineno,
Dwarf_Addr addr, void *data)
{
struct probe_finder *pf = data;
+ Dwarf_Die *sc_die, die_mem;
int ret;

if (lineno != pf->lno || strtailcmp(fname, pf->fname) != 0)
return 0;

pf->addr = addr;
- ret = call_probe_finder(NULL, pf);
+ sc_die = find_best_scope(pf, &die_mem);
+ if (!sc_die) {
+ pr_warning("Failed to find scope of probe point.\n");
+ return -ENOENT;
+ }
+
+ ret = call_probe_finder(sc_die, pf);

/* Continue if no error, because the line will be in inline function */
return ret < 0 ? ret : 0;
@@ -826,6 +895,7 @@ static int probe_point_lazy_walker(const char *fname, int lineno,
Dwarf_Addr addr, void *data)
{
struct probe_finder *pf = data;
+ Dwarf_Die *sc_die, die_mem;
int ret;

if (!line_list__has_line(&pf->lcache, lineno) ||
@@ -835,7 +905,14 @@ static int probe_point_lazy_walker(const char *fname, int lineno,
pr_debug("Probe line found: line:%d addr:0x%llx\n",
lineno, (unsigned long long)addr);
pf->addr = addr;
- ret = call_probe_finder(NULL, pf);
+ pf->lno = lineno;
+ sc_die = find_best_scope(pf, &die_mem);
+ if (!sc_die) {
+ pr_warning("Failed to find scope of probe point.\n");
+ return -ENOENT;
+ }
+
+ ret = call_probe_finder(sc_die, pf);

/*
* Continue if no error, because the lazy pattern will match
@@ -1059,7 +1136,7 @@ found:
}

/* Add a found probe point into trace event list */
-static int add_probe_trace_event(Dwarf_Die *sp_die, struct probe_finder *pf)
+static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf)
{
struct trace_event_finder *tf =
container_of(pf, struct trace_event_finder, pf);
@@ -1074,8 +1151,9 @@ static int add_probe_trace_event(Dwarf_Die *sp_die, struct probe_finder *pf)
}
tev = &tf->tevs[tf->ntevs++];

- ret = convert_to_trace_point(sp_die, pf->addr, pf->pev->point.retprobe,
- &tev->point);
+ /* Trace point should be converted from subprogram DIE */
+ ret = convert_to_trace_point(&pf->sp_die, pf->addr,
+ pf->pev->point.retprobe, &tev->point);
if (ret < 0)
return ret;

@@ -1090,7 +1168,8 @@ static int add_probe_trace_event(Dwarf_Die *sp_die, struct probe_finder *pf)
for (i = 0; i < pf->pev->nargs; i++) {
pf->pvar = &pf->pev->args[i];
pf->tvar = &tev->args[i];
- ret = find_variable(sp_die, pf);
+ /* Variable should be found from scope DIE */
+ ret = find_variable(sc_die, pf);
if (ret != 0)
return ret;
}
@@ -1158,7 +1237,7 @@ static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
}

/* Add a found vars into available variables list */
-static int add_available_vars(Dwarf_Die *sp_die, struct probe_finder *pf)
+static int add_available_vars(Dwarf_Die *sc_die, struct probe_finder *pf)
{
struct available_var_finder *af =
container_of(pf, struct available_var_finder, pf);
@@ -1173,8 +1252,9 @@ static int add_available_vars(Dwarf_Die *sp_die, struct probe_finder *pf)
}
vl = &af->vls[af->nvls++];

- ret = convert_to_trace_point(sp_die, pf->addr, pf->pev->point.retprobe,
- &vl->point);
+ /* Trace point should be converted from subprogram DIE */
+ ret = convert_to_trace_point(&pf->sp_die, pf->addr,
+ pf->pev->point.retprobe, &vl->point);
if (ret < 0)
return ret;

@@ -1186,14 +1266,14 @@ static int add_available_vars(Dwarf_Die *sp_die, struct probe_finder *pf)
if (vl->vars == NULL)
return -ENOMEM;
af->child = true;
- die_find_child(sp_die, collect_variables_cb, (void *)af, &die_mem);
+ die_find_child(sc_die, collect_variables_cb, (void *)af, &die_mem);

/* Find external variables */
if (!af->externs)
goto out;
/* Don't need to search child DIE for externs. */
af->child = false;
- nscopes = dwarf_getscopes_die(sp_die, &scopes);
+ nscopes = dwarf_getscopes_die(sc_die, &scopes);
while (nscopes-- > 1)
die_find_child(&scopes[nscopes], collect_variables_cb,
(void *)af, &die_mem);
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index c478b42..1132c8f 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -57,7 +57,7 @@ struct probe_finder {
struct perf_probe_event *pev; /* Target probe event */

/* Callback when a probe point is found */
- int (*callback)(Dwarf_Die *sp_die, struct probe_finder *pf);
+ int (*callback)(Dwarf_Die *sc_die, struct probe_finder *pf);

/* For function searching */
int lno; /* Line number */