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>

4 files changed, 144 insertions, 27 deletions

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index d9b8ad098498..425703a58638 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 c8e491bc133f..6f46106fd1d5 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 d6d57682473a..5c83b7d3d8ef 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 c478b42a2473..1132c8f0ce89 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 */