perf probe: Add bitfield member support

Add bitfield member accessing support to probe arguments.

Suggested-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: 2nddept-manager@sdl.hitachi.co.jp
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20110204125211.9507.60265.stgit@ltc236.sdl.hitachi.co.jp>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
[ committer note: Fixed up '%lu' use for return of BYTES_TO_BITS ('%zd') ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 68 insertions, 27 deletions

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 46addfb3183e..fe461f6559f1 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -33,6 +33,7 @@
 #include <ctype.h>
 #include <dwarf-regs.h>
 
+#include <linux/bitops.h>
 #include "event.h"
 #include "debug.h"
 #include "util.h"
@@ -333,13 +334,23 @@ static Dwarf_Die *die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
         return vr_die;
 }
 
-static bool die_is_signed_type(Dwarf_Die *tp_die)
+static int die_get_attr_udata(Dwarf_Die *tp_die, unsigned int attr_name,
+                              Dwarf_Word *result)
 {
         Dwarf_Attribute attr;
+
+        if (dwarf_attr(tp_die, attr_name, &attr) == NULL ||
+            dwarf_formudata(&attr, result) != 0)
+                return -ENOENT;
+
+        return 0;
+}
+
+static bool die_is_signed_type(Dwarf_Die *tp_die)
+{
         Dwarf_Word ret;
 
-        if (dwarf_attr(tp_die, DW_AT_encoding, &attr) == NULL ||
-            dwarf_formudata(&attr, &ret) != 0)
+        if (die_get_attr_udata(tp_die, DW_AT_encoding, &ret))
                 return false;
 
         return (ret == DW_ATE_signed_char || ret == DW_ATE_signed ||
@@ -348,11 +359,29 @@ static bool die_is_signed_type(Dwarf_Die *tp_die)
 
 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)
+        if (die_get_attr_udata(tp_die, DW_AT_byte_size, &ret))
+                return 0;
+
+        return (int)ret;
+}
+
+static int die_get_bit_size(Dwarf_Die *tp_die)
+{
+        Dwarf_Word ret;
+
+        if (die_get_attr_udata(tp_die, DW_AT_bit_size, &ret))
+                return 0;
+
+        return (int)ret;
+}
+
+static int die_get_bit_offset(Dwarf_Die *tp_die)
+{
+        Dwarf_Word ret;
+
+        if (die_get_attr_udata(tp_die, DW_AT_bit_offset, &ret))
                 return 0;
 
         return (int)ret;
@@ -827,6 +856,8 @@ static_var:
         return 0;
 }
 
+#define BYTES_TO_BITS(nb)       ((nb) * BITS_PER_LONG / sizeof(long))
+
 static int convert_variable_type(Dwarf_Die *vr_die,
                                  struct probe_trace_arg *tvar,
                                  const char *cast)
@@ -843,6 +874,14 @@ static int convert_variable_type(Dwarf_Die *vr_die,
                 return (tvar->type == NULL) ? -ENOMEM : 0;
         }
 
+        if (die_get_bit_size(vr_die) != 0) {
+                /* This is a bitfield */
+                ret = snprintf(buf, 16, "b%d@%d/%zd", die_get_bit_size(vr_die),
+                                die_get_bit_offset(vr_die),
+                                BYTES_TO_BITS(die_get_byte_size(vr_die)));
+                goto formatted;
+        }
+
         if (die_get_real_type(vr_die, &type) == NULL) {
                 pr_warning("Failed to get a type information of %s.\n",
                            dwarf_diename(vr_die));
@@ -887,29 +926,31 @@ static int convert_variable_type(Dwarf_Die *vr_die,
                 return (tvar->type == NULL) ? -ENOMEM : 0;
         }
 
-        ret = die_get_byte_size(&type) * 8;
-        if (ret) {
-                /* Check the bitwidth */
-                if (ret > MAX_BASIC_TYPE_BITS) {
-                        pr_info("%s exceeds max-bitwidth."
-                                " Cut down to %d bits.\n",
-                                dwarf_diename(&type), MAX_BASIC_TYPE_BITS);
-                        ret = MAX_BASIC_TYPE_BITS;
-                }
+        ret = BYTES_TO_BITS(die_get_byte_size(&type));
+        if (!ret)
+                /* No size ... try to use default type */
+                return 0;
 
-                ret = snprintf(buf, 16, "%c%d",
-                               die_is_signed_type(&type) ? 's' : 'u', ret);
-                if (ret < 0 || ret >= 16) {
-                        if (ret >= 16)
-                                ret = -E2BIG;
-                        pr_warning("Failed to convert variable type: %s\n",
-                                   strerror(-ret));
-                        return ret;
-                }
-                tvar->type = strdup(buf);
-                if (tvar->type == NULL)
-                        return -ENOMEM;
+        /* Check the bitwidth */
+        if (ret > MAX_BASIC_TYPE_BITS) {
+                pr_info("%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);
+
+formatted:
+        if (ret < 0 || ret >= 16) {
+                if (ret >= 16)
+                        ret = -E2BIG;
+                pr_warning("Failed to convert variable type: %s\n",
+                           strerror(-ret));
+                return ret;
         }
+        tvar->type = strdup(buf);
+        if (tvar->type == NULL)
+                return -ENOMEM;
         return 0;
 }