perf probe: Query basic types from debuginfo

Query the basic type information (byte-size and signed-flag) from
debuginfo and pass that to kprobe-tracer. This is especially useful
for tracing the members of data structure, because each member has
different byte-size on the memory.

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: <20100412171715.3790.23730.stgit@localhost6.localdomain6>
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 19de8b7..05ca4a9 100644 (file)
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -740,6 +740,13 @@ static int synthesize_kprobe_trace_arg(struct kprobe_trace_arg *arg,
                buf += ret;
                buflen -= ret;
        }
+       /* Print argument type */
+       if (arg->type) {
+               ret = e_snprintf(buf, buflen, ":%s", arg->type);
+               if (ret <= 0)
+                       return ret;
+               buf += ret;
+       }
 
        return buf - tmp;
 }
@@ -848,6 +855,8 @@ void clear_kprobe_trace_event(struct kprobe_trace_event *tev)
                        free(tev->args[i].name);
                if (tev->args[i].value)
                        free(tev->args[i].value);
+               if (tev->args[i].type)
+                       free(tev->args[i].type);
                ref = tev->args[i].ref;
                while (ref) {
                        next = ref->next;

diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index 10411f5..a393a3f 100644 (file)
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -23,6 +23,7 @@ struct kprobe_trace_arg_ref {
 struct kprobe_trace_arg {
        char                            *name;  /* Argument name */
        char                            *value; /* Base value */
+       char                            *type;  /* Type name */
        struct kprobe_trace_arg_ref     *ref;   /* Referencing offset */
 };
 

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 105e95c..ebeb413 100644 (file)
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -84,6 +84,9 @@ const char *x86_64_regs_table[X86_64_MAX_REGS] = {
 #define arch_regs_table x86_32_regs_table
 #endif
 
+/* Kprobe tracer basic type is up to u64 */
+#define MAX_BASIC_TYPE_BITS    64
+
 /* Return architecture dependent register string (for kprobe-tracer) */
 static const char *get_arch_regstr(unsigned int n)
 {
@@ -230,6 +233,31 @@ static Dwarf_Die *die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
        return die_mem;
 }
 
+static bool die_is_signed_type(Dwarf_Die *tp_die)
+{
+       Dwarf_Attribute attr;
+       Dwarf_Word ret;
+
+       if (dwarf_attr(tp_die, DW_AT_encoding, &attr) == NULL ||
+           dwarf_formudata(&attr, &ret) != 0)
+               return false;
+
+       return (ret == DW_ATE_signed_char || ret == DW_ATE_signed ||
+               ret == DW_ATE_signed_fixed);
+}
+
+static int die_get_byte_size(Dwarf_Die *tp_die)
+{
+       Dwarf_Attribute attr;
+       Dwarf_Word ret;
+
+       if (dwarf_attr(tp_die, DW_AT_byte_size, &attr) == NULL ||
+           dwarf_formudata(&attr, &ret) != 0)
+               return 0;
+
+       return (int)ret;
+}
+
 /* Return values for die_find callbacks */
 enum {
        DIE_FIND_CB_FOUND = 0,          /* End of Search */
@@ -406,13 +434,42 @@ static void convert_location(Dwarf_Op *op, struct probe_finder *pf)
        }
 }
 
+static void convert_variable_type(Dwarf_Die *vr_die,
+                                 struct kprobe_trace_arg *targ)
+{
+       Dwarf_Die type;
+       char buf[16];
+       int ret;
+
+       if (die_get_real_type(vr_die, &type) == NULL)
+               die("Failed to get a type information of %s.",
+                   dwarf_diename(vr_die));
+
+       ret = die_get_byte_size(&type) * 8;
+       if (ret) {
+               /* Check the bitwidth */
+               if (ret > MAX_BASIC_TYPE_BITS) {
+                       pr_warning("  Warning: %s exceeds max-bitwidth."
+                                  " Cut down to %d bits.\n",
+                                  dwarf_diename(&type), MAX_BASIC_TYPE_BITS);
+                       ret = MAX_BASIC_TYPE_BITS;
+               }
+
+               ret = snprintf(buf, 16, "%c%d",
+                              die_is_signed_type(&type) ? 's' : 'u', ret);
+               if (ret < 0 || ret >= 16)
+                       die("Failed to convert variable type.");
+               targ->type = xstrdup(buf);
+       }
+}
+
 static void convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
                                    struct perf_probe_arg_field *field,
-                                   struct kprobe_trace_arg_ref **ref_ptr)
+                                   struct kprobe_trace_arg_ref **ref_ptr,
+                                   Dwarf_Die *die_mem)
 {
        struct kprobe_trace_arg_ref *ref = *ref_ptr;
        Dwarf_Attribute attr;
-       Dwarf_Die member;
        Dwarf_Die type;
        Dwarf_Word offs;
 
@@ -450,26 +507,27 @@ static void convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
                        die("Structure on a register is not supported yet.");
        }
 
-       if (die_find_member(&type, field->name, &member) == NULL)
+       if (die_find_member(&type, field->name, die_mem) == NULL)
                die("%s(tyep:%s) has no member %s.", varname,
                    dwarf_diename(&type), field->name);
 
        /* Get the offset of the field */
-       if (dwarf_attr(&member, DW_AT_data_member_location, &attr) == NULL ||
+       if (dwarf_attr(die_mem, DW_AT_data_member_location, &attr) == NULL ||
            dwarf_formudata(&attr, &offs) != 0)
                die("Failed to get the offset of %s.", field->name);
        ref->offset += (long)offs;
 
        /* Converting next field */
        if (field->next)
-               convert_variable_fields(&member, field->name, field->next,
-                                       &ref);
+               convert_variable_fields(die_mem, field->name, field->next,
+                                       &ref, die_mem);
 }
 
 /* Show a variables in kprobe event format */
 static void 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;
@@ -483,9 +541,13 @@ static void convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
 
        convert_location(expr, pf);
 
-       if (pf->pvar->field)
+       if (pf->pvar->field) {
                convert_variable_fields(vr_die, pf->pvar->var,
-                                       pf->pvar->field, &pf->tvar->ref);
+                                       pf->pvar->field, &pf->tvar->ref,
+                                       &die_mem);
+               vr_die = &die_mem;
+       }
+       convert_variable_type(vr_die, pf->tvar);
        /* *expr will be cached in libdw. Don't free it. */
        return ;
 error: