perf probe: Support tracing an entry of array
Add array-entry tracing support to perf probe. This enables to trace an entry
of array which is indexed by constant value, e.g. array[0].
For example:
$ perf probe -a 'bio_split bi->bi_io_vec[0]'
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20100519195742.2885.5344.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/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt
index 394016d..27d52da 100644
--- a/tools/perf/Documentation/perf-probe.txt
+++ b/tools/perf/Documentation/perf-probe.txt
@@ -94,7 +94,7 @@
[NAME=]LOCALVAR|$retval|%REG|@SYMBOL[:TYPE]
-'NAME' specifies the name of this argument (optional). You can use the name of local variable, local data structure member (e.g. var->field, var.field2), or kprobe-tracer argument format (e.g. $retval, %ax, etc). Note that the name of this argument will be set as the last member name if you specify a local data structure member (e.g. field2 for 'var->field1.field2'.)
+'NAME' specifies the name of this argument (optional). You can use the name of local variable, local data structure member (e.g. var->field, var.field2), local array with fixed index (e.g. array[1], var->array[0], var->pointer[2]), or kprobe-tracer argument format (e.g. $retval, %ax, etc). Note that the name of this argument will be set as the last member name if you specify a local data structure member (e.g. field2 for 'var->field1.field2'.)
'TYPE' casts the type of this argument (optional). If omitted, perf probe automatically set the type based on debuginfo. You can specify 'string' type only for the local variable or structure member which is an array of or a pointer to 'char' or 'unsigned char' type.
LINE SYNTAX
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 914c670..351baa9 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -557,7 +557,7 @@
/* Parse perf-probe event argument */
static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
{
- char *tmp;
+ char *tmp, *goodname;
struct perf_probe_arg_field **fieldp;
pr_debug("parsing arg: %s into ", str);
@@ -580,7 +580,7 @@
pr_debug("type:%s ", arg->type);
}
- tmp = strpbrk(str, "-.");
+ tmp = strpbrk(str, "-.[");
if (!is_c_varname(str) || !tmp) {
/* A variable, register, symbol or special value */
arg->var = strdup(str);
@@ -590,10 +590,11 @@
return 0;
}
- /* Structure fields */
+ /* Structure fields or array element */
arg->var = strndup(str, tmp - str);
if (arg->var == NULL)
return -ENOMEM;
+ goodname = arg->var;
pr_debug("%s, ", arg->var);
fieldp = &arg->field;
@@ -601,22 +602,38 @@
*fieldp = zalloc(sizeof(struct perf_probe_arg_field));
if (*fieldp == NULL)
return -ENOMEM;
- if (*tmp == '.') {
- str = tmp + 1;
- (*fieldp)->ref = false;
- } else if (tmp[1] == '>') {
- str = tmp + 2;
+ if (*tmp == '[') { /* Array */
+ str = tmp;
+ (*fieldp)->index = strtol(str + 1, &tmp, 0);
(*fieldp)->ref = true;
- } else {
- semantic_error("Argument parse error: %s\n", str);
- return -EINVAL;
+ if (*tmp != ']' || tmp == str + 1) {
+ semantic_error("Array index must be a"
+ " number.\n");
+ return -EINVAL;
+ }
+ tmp++;
+ if (*tmp == '\0')
+ tmp = NULL;
+ } else { /* Structure */
+ if (*tmp == '.') {
+ str = tmp + 1;
+ (*fieldp)->ref = false;
+ } else if (tmp[1] == '>') {
+ str = tmp + 2;
+ (*fieldp)->ref = true;
+ } else {
+ semantic_error("Argument parse error: %s\n",
+ str);
+ return -EINVAL;
+ }
+ tmp = strpbrk(str, "-.[");
}
-
- tmp = strpbrk(str, "-.");
if (tmp) {
(*fieldp)->name = strndup(str, tmp - str);
if ((*fieldp)->name == NULL)
return -ENOMEM;
+ if (*str != '[')
+ goodname = (*fieldp)->name;
pr_debug("%s(%d), ", (*fieldp)->name, (*fieldp)->ref);
fieldp = &(*fieldp)->next;
}
@@ -624,11 +641,13 @@
(*fieldp)->name = strdup(str);
if ((*fieldp)->name == NULL)
return -ENOMEM;
+ if (*str != '[')
+ goodname = (*fieldp)->name;
pr_debug("%s(%d)\n", (*fieldp)->name, (*fieldp)->ref);
- /* If no name is specified, set the last field name */
+ /* If no name is specified, set the last field name (not array index)*/
if (!arg->name) {
- arg->name = strdup((*fieldp)->name);
+ arg->name = strdup(goodname);
if (arg->name == NULL)
return -ENOMEM;
}
@@ -776,8 +795,11 @@
len -= ret;
while (field) {
- ret = e_snprintf(tmp, len, "%s%s", field->ref ? "->" : ".",
- field->name);
+ if (field->name[0] == '[')
+ ret = e_snprintf(tmp, len, "%s", field->name);
+ else
+ ret = e_snprintf(tmp, len, "%s%s",
+ field->ref ? "->" : ".", field->name);
if (ret <= 0)
goto error;
tmp += ret;
diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index e9db1a21..bc06d3e 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -50,6 +50,7 @@
struct perf_probe_arg_field {
struct perf_probe_arg_field *next; /* Next field */
char *name; /* Name of the field */
+ long index; /* Array index number */
bool ref; /* Referencing flag */
};
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index aaea16b..308664d 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -485,6 +485,9 @@
return -ENOENT;
}
+ pr_debug("%s type is %s.\n",
+ dwarf_diename(vr_die), dwarf_diename(&type));
+
if (cast && strcmp(cast, "string") == 0) { /* String type */
ret = dwarf_tag(&type);
if (ret != DW_TAG_pointer_type &&
@@ -553,16 +556,44 @@
struct kprobe_trace_arg_ref *ref = *ref_ptr;
Dwarf_Die type;
Dwarf_Word offs;
- int ret;
+ int ret, tag;
pr_debug("converting %s in %s\n", field->name, varname);
if (die_get_real_type(vr_die, &type) == NULL) {
pr_warning("Failed to get the type of %s.\n", varname);
return -ENOENT;
}
+ pr_debug2("Var real type: (%x)\n", (unsigned)dwarf_dieoffset(&type));
+ tag = dwarf_tag(&type);
- /* Check the pointer and dereference */
- if (dwarf_tag(&type) == DW_TAG_pointer_type) {
+ if (field->name[0] == '[' &&
+ (tag == DW_TAG_array_type || tag == DW_TAG_pointer_type)) {
+ if (field->next)
+ /* Save original type for next field */
+ memcpy(die_mem, &type, sizeof(*die_mem));
+ /* Get the type of this array */
+ if (die_get_real_type(&type, &type) == NULL) {
+ pr_warning("Failed to get the type of %s.\n", varname);
+ return -ENOENT;
+ }
+ pr_debug2("Array real type: (%x)\n",
+ (unsigned)dwarf_dieoffset(&type));
+ if (tag == DW_TAG_pointer_type) {
+ ref = zalloc(sizeof(struct kprobe_trace_arg_ref));
+ if (ref == NULL)
+ return -ENOMEM;
+ if (*ref_ptr)
+ (*ref_ptr)->next = ref;
+ else
+ *ref_ptr = ref;
+ }
+ ref->offset += die_get_byte_size(&type) * field->index;
+ if (!field->next)
+ /* Save vr_die for converting types */
+ memcpy(die_mem, vr_die, sizeof(*die_mem));
+ goto next;
+ } else if (tag == DW_TAG_pointer_type) {
+ /* Check the pointer and dereference */
if (!field->ref) {
pr_err("Semantic error: %s must be referred by '->'\n",
field->name);
@@ -588,10 +619,15 @@
*ref_ptr = ref;
} else {
/* Verify it is a data structure */
- if (dwarf_tag(&type) != DW_TAG_structure_type) {
+ if (tag != DW_TAG_structure_type) {
pr_warning("%s is not a data structure.\n", varname);
return -EINVAL;
}
+ if (field->name[0] == '[') {
+ pr_err("Semantic error: %s is not a pointor nor array.",
+ varname);
+ return -EINVAL;
+ }
if (field->ref) {
pr_err("Semantic error: %s must be referred by '.'\n",
field->name);
@@ -618,6 +654,7 @@
}
ref->offset += (long)offs;
+next:
/* Converting next field */
if (field->next)
return convert_variable_fields(die_mem, field->name,
@@ -667,7 +704,6 @@
char buf[32], *ptr;
int ret;
- /* TODO: Support arrays */
if (pf->pvar->name)
pf->tvar->name = strdup(pf->pvar->name);
else {
