perf probe: Fix to search local variables in appropriate scope
Masami Hiramatsu [Thu, 11 Aug 2011 11:02:59 +0000 (20:02 +0900)]
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
tools/perf/util/dwarf-aux.h
tools/perf/util/probe-finder.c
tools/perf/util/probe-finder.h

index d9b8ad0..425703a 100644 (file)
@@ -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
index c8e491b..6f46106 100644 (file)
@@ -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);
 
index d6d5768..5c83b7d 100644 (file)
@@ -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);
index c478b42..1132c8f 100644 (file)
@@ -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 */