perf probe: Add data structure member access support
Support accessing members in the data structures. With this,
perf-probe accepts data-structure members(IOW, it now accepts
dot '.' and arrow '->' operators) as probe arguemnts.
e.g.
./perf probe --add 'schedule:44 rq->curr'
./perf probe --add 'vfs_read file->f_op->read file->f_path.dentry'
Note that '>' can be interpreted as redirection in command-line.
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100316220626.32050.57552.stgit@localhost6.localdomain6>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index e02b607..db52ec2 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -206,6 +206,28 @@
return epc;
}
+/* Get type die, but skip qualifiers and typedef */
+static Dwarf_Die *die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
+{
+ Dwarf_Attribute attr;
+ int tag;
+
+ do {
+ if (dwarf_attr(vr_die, DW_AT_type, &attr) == NULL ||
+ dwarf_formref_die(&attr, die_mem) == NULL)
+ return NULL;
+
+ tag = dwarf_tag(die_mem);
+ vr_die = die_mem;
+ } while (tag == DW_TAG_const_type ||
+ tag == DW_TAG_restrict_type ||
+ tag == DW_TAG_volatile_type ||
+ tag == DW_TAG_shared_type ||
+ tag == DW_TAG_typedef);
+
+ return die_mem;
+}
+
/* Return values for die_find callbacks */
enum {
DIE_FIND_CB_FOUND = 0, /* End of Search */
@@ -314,6 +336,25 @@
die_mem);
}
+static int __die_find_member_cb(Dwarf_Die *die_mem, void *data)
+{
+ const char *name = data;
+
+ if ((dwarf_tag(die_mem) == DW_TAG_member) &&
+ (die_compare_name(die_mem, name) == 0))
+ return DIE_FIND_CB_FOUND;
+
+ return DIE_FIND_CB_SIBLING;
+}
+
+/* Find a member called 'name' */
+static Dwarf_Die *die_find_member(Dwarf_Die *st_die, const char *name,
+ Dwarf_Die *die_mem)
+{
+ return die_find_child(st_die, __die_find_member_cb, (void *)name,
+ die_mem);
+}
+
/*
* Probe finder related functions
*/
@@ -363,6 +404,62 @@
}
}
+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 = *ref_ptr;
+ Dwarf_Attribute attr;
+ Dwarf_Die member;
+ Dwarf_Die type;
+ Dwarf_Word offs;
+
+ pr_debug("converting %s in %s\n", field->name, varname);
+ if (die_get_real_type(vr_die, &type) == NULL)
+ die("Failed to get a type information of %s.", varname);
+
+ /* Check the pointer and dereference */
+ if (dwarf_tag(&type) == DW_TAG_pointer_type) {
+ if (!field->ref)
+ die("Semantic error: %s must be referred by '->'",
+ field->name);
+ /* Get the type pointed by this pointer */
+ if (die_get_real_type(&type, &type) == NULL)
+ die("Failed to get a type information of %s.", varname);
+
+ ref = xzalloc(sizeof(struct kprobe_trace_arg_ref));
+ if (*ref_ptr)
+ (*ref_ptr)->next = ref;
+ else
+ *ref_ptr = ref;
+ } else {
+ if (field->ref)
+ die("Semantic error: %s must be referred by '.'",
+ field->name);
+ if (!ref)
+ die("Structure on a register is not supported yet.");
+ }
+
+ /* Verify it is a data structure */
+ if (dwarf_tag(&type) != DW_TAG_structure_type)
+ die("%s is not a data structure.", varname);
+
+ if (die_find_member(&type, field->name, &member) == 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 ||
+ 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);
+}
+
/* Show a variables in kprobe event format */
static void convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
{
@@ -379,6 +476,10 @@
goto error;
convert_location(expr, pf);
+
+ if (pf->pvar->field)
+ convert_variable_fields(vr_die, pf->pvar->name,
+ pf->pvar->field, &pf->tvar->ref);
/* *expr will be cached in libdw. Don't free it. */
return ;
error:
@@ -391,13 +492,15 @@
static void find_variable(Dwarf_Die *sp_die, struct probe_finder *pf)
{
Dwarf_Die vr_die;
+ char buf[128];
/* TODO: Support struct members and arrays */
if (!is_c_varname(pf->pvar->name)) {
/* Copy raw parameters */
pf->tvar->value = xstrdup(pf->pvar->name);
} else {
- pf->tvar->name = xstrdup(pf->pvar->name);
+ synthesize_perf_probe_arg(pf->pvar, buf, 128);
+ pf->tvar->name = xstrdup(buf);
pr_debug("Searching '%s' variable in context.\n",
pf->pvar->name);
/* Search child die for local variables and parameters. */