perf probe: Support "string" type

Support string type casting to event argument. If perf-probe finds an argument
casted as string, it ensures the target variable is "(unsigned/signed) char
*(or []). perf-probe also adds dereference if the target is a pointer.

So, both of 'char buf[10];' and 'char *buf;' can be accessed by 'buf:string'

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: <20100519195734.2885.1666.stgit@localhost6.localdomain6>
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 48 insertions, 11 deletions

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index baf66538349..aaea16b1c60 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -464,18 +464,61 @@ static int convert_location(Dwarf_Op *op, struct probe_finder *pf)
 }
 
 static int convert_variable_type(Dwarf_Die *vr_die,
-                                 struct kprobe_trace_arg *targ)
+                                 struct kprobe_trace_arg *tvar,
+                                 const char *cast)
 {
+        struct kprobe_trace_arg_ref **ref_ptr = &tvar->ref;
         Dwarf_Die type;
         char buf[16];
         int ret;
 
+        /* TODO: check all types */
+        if (cast && strcmp(cast, "string") != 0) {
+                /* Non string type is OK */
+                tvar->type = strdup(cast);
+                return (tvar->type == NULL) ? -ENOMEM : 0;
+        }
+
         if (die_get_real_type(vr_die, &type) == NULL) {
                 pr_warning("Failed to get a type information of %s.\n",
                            dwarf_diename(vr_die));
                 return -ENOENT;
         }
 
+        if (cast && strcmp(cast, "string") == 0) {      /* String type */
+                ret = dwarf_tag(&type);
+                if (ret != DW_TAG_pointer_type &&
+                    ret != DW_TAG_array_type) {
+                        pr_warning("Failed to cast into string: "
+                                   "%s(%s) is not a pointer nor array.",
+                                   dwarf_diename(vr_die), dwarf_diename(&type));
+                        return -EINVAL;
+                }
+                if (ret == DW_TAG_pointer_type) {
+                        if (die_get_real_type(&type, &type) == NULL) {
+                                pr_warning("Failed to get a type information.");
+                                return -ENOENT;
+                        }
+                        while (*ref_ptr)
+                                ref_ptr = &(*ref_ptr)->next;
+                        /* Add new reference with offset +0 */
+                        *ref_ptr = zalloc(sizeof(struct kprobe_trace_arg_ref));
+                        if (*ref_ptr == NULL) {
+                                pr_warning("Out of memory error\n");
+                                return -ENOMEM;
+                        }
+                }
+                if (die_compare_name(&type, "char") != 0 &&
+                    die_compare_name(&type, "unsigned char") != 0) {
+                        pr_warning("Failed to cast into string: "
+                                   "%s is not (unsigned) char *.",
+                                   dwarf_diename(vr_die));
+                        return -EINVAL;
+                }
+                tvar->type = strdup(cast);
+                return (tvar->type == NULL) ? -ENOMEM : 0;
+        }
+
         ret = die_get_byte_size(&type) * 8;
         if (ret) {
                 /* Check the bitwidth */
@@ -495,8 +538,8 @@ static int convert_variable_type(Dwarf_Die *vr_die,
                                    strerror(-ret));
                         return ret;
                 }
-                targ->type = strdup(buf);
-                if (targ->type == NULL)
+                tvar->type = strdup(buf);
+                if (tvar->type == NULL)
                         return -ENOMEM;
         }
         return 0;
@@ -606,14 +649,8 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
                                               &die_mem);
                 vr_die = &die_mem;
         }
-        if (ret == 0) {
-                if (pf->pvar->type) {
-                        pf->tvar->type = strdup(pf->pvar->type);
-                        if (pf->tvar->type == NULL)
-                                ret = -ENOMEM;
-                } else
-                        ret = convert_variable_type(vr_die, pf->tvar);
-        }
+        if (ret == 0)
+                ret = convert_variable_type(vr_die, pf->tvar, pf->pvar->type);
         /* *expr will be cached in libdw. Don't free it. */
         return ret;
 error: