perf probe: Support static and global variables
Masami Hiramatsu [Wed, 19 May 2010 19:57:49 +0000 (15:57 -0400)]
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: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/probe-event.c
tools/perf/util/probe-finder.c

index 351baa9..09cf546 100644 (file)
@@ -926,6 +926,7 @@ out:
 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;
 
@@ -939,16 +940,24 @@ 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 */
-       ret = e_snprintf(buf, buflen, "%s", arg->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;
        buf += ret;
index 308664d..3e64e1f 100644 (file)
@@ -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 @@ next:
 /* 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 */