Commit cb402730 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Arnaldo Carvalho de Melo

perf probe: Trace a magic number if variable is not found

Trace a magic number as immediate value if the target variable is not
found at some probe points which is based on one probe event.

This feature is good for the case if you trace a source code line with
some local variables, which is compiled into several instructions and
some of the variables are optimized out on some instructions.

Even if so, with this feature, perf probe trace a magic number instead
of such disappeared variables and fold those probes on one event.

E.g. without this patch:

  # perf probe -D "pud_page_vaddr pud"
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  Failed to find 'pud' in this function.
  p:probe/pud_page_vaddr _text+23480787 pud=%ax:x64
  p:probe/pud_page_vaddr _text+23808453 pud=%bp:x64
  p:probe/pud_page_vaddr _text+23558082 pud=%ax:x64
  p:probe/pud_page_vaddr _text+328373 pud=%r8:x64
  p:probe/pud_page_vaddr _text+348448 pud=%bx:x64
  p:probe/pud_page_vaddr _text+23816818 pud=%bx:x64

With this patch:

  # perf probe -D "pud_page_vaddr pud" | head
  spurious_kernel_fault is blacklisted function, skip it.
  vmalloc_fault is blacklisted function, skip it.
  p:probe/pud_page_vaddr _text+23480787 pud=%ax:x64
  p:probe/pud_page_vaddr _text+149051 pud=\deade12d:x64
  p:probe/pud_page_vaddr _text+23808453 pud=%bp:x64
  p:probe/pud_page_vaddr _text+315926 pud=\deade12d:x64
  p:probe/pud_page_vaddr _text+23807209 pud=\deade12d:x64
  p:probe/pud_page_vaddr _text+23557365 pud=%ax:x64
  p:probe/pud_page_vaddr _text+314097 pud=%di:x64
  p:probe/pud_page_vaddr _text+314015 pud=\deade12d:x64
  p:probe/pud_page_vaddr _text+313893 pud=\deade12d:x64
  p:probe/pud_page_vaddr _text+324083 pud=\deade12d:x64
Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Link: http://lore.kernel.org/lkml/157406476931.24476.6261475888681844285.stgit@devnote2Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 66f69b21
...@@ -46,7 +46,7 @@ ...@@ -46,7 +46,7 @@
#define PERFPROBE_GROUP "probe" #define PERFPROBE_GROUP "probe"
bool probe_event_dry_run; /* Dry run flag */ bool probe_event_dry_run; /* Dry run flag */
struct probe_conf probe_conf; struct probe_conf probe_conf = { .magic_num = DEFAULT_PROBE_MAGIC_NUM };
#define semantic_error(msg ...) pr_err("Semantic error :" msg) #define semantic_error(msg ...) pr_err("Semantic error :" msg)
......
...@@ -16,10 +16,13 @@ struct probe_conf { ...@@ -16,10 +16,13 @@ struct probe_conf {
bool no_inlines; bool no_inlines;
bool cache; bool cache;
int max_probes; int max_probes;
unsigned long magic_num;
}; };
extern struct probe_conf probe_conf; extern struct probe_conf probe_conf;
extern bool probe_event_dry_run; extern bool probe_event_dry_run;
#define DEFAULT_PROBE_MAGIC_NUM 0xdeade12d /* u32: 3735937325 */
struct symbol; struct symbol;
/* kprobe-tracer and uprobe-tracer tracing point */ /* kprobe-tracer and uprobe-tracer tracing point */
......
...@@ -536,6 +536,14 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname, ...@@ -536,6 +536,14 @@ static int convert_variable_fields(Dwarf_Die *vr_die, const char *varname,
return 0; return 0;
} }
static void print_var_not_found(const char *varname)
{
pr_err("Failed to find the location of the '%s' variable at this address.\n"
" Perhaps it has been optimized out.\n"
" Use -V with the --range option to show '%s' location range.\n",
varname, varname);
}
/* Show a variables in kprobe event format */ /* Show a variables in kprobe event format */
static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf) static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
{ {
...@@ -547,11 +555,11 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf) ...@@ -547,11 +555,11 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
ret = convert_variable_location(vr_die, pf->addr, pf->fb_ops, ret = convert_variable_location(vr_die, pf->addr, pf->fb_ops,
&pf->sp_die, pf->machine, pf->tvar); &pf->sp_die, pf->machine, pf->tvar);
if (ret == -ENOENT && pf->skip_empty_arg)
/* This can be found in other place. skip it */
return 0;
if (ret == -ENOENT || ret == -EINVAL) { if (ret == -ENOENT || ret == -EINVAL) {
pr_err("Failed to find the location of the '%s' variable at this address.\n" print_var_not_found(pf->pvar->var);
" Perhaps it has been optimized out.\n"
" Use -V with the --range option to show '%s' location range.\n",
pf->pvar->var, pf->pvar->var);
} else if (ret == -ENOTSUP) } else if (ret == -ENOTSUP)
pr_err("Sorry, we don't support this variable location yet.\n"); pr_err("Sorry, we don't support this variable location yet.\n");
else if (ret == 0 && pf->pvar->field) { else if (ret == 0 && pf->pvar->field) {
...@@ -598,6 +606,8 @@ static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf) ...@@ -598,6 +606,8 @@ static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf)
/* Search again in global variables */ /* Search again in global variables */
if (!die_find_variable_at(&pf->cu_die, pf->pvar->var, if (!die_find_variable_at(&pf->cu_die, pf->pvar->var,
0, &vr_die)) { 0, &vr_die)) {
if (pf->skip_empty_arg)
return 0;
pr_warning("Failed to find '%s' in this function.\n", pr_warning("Failed to find '%s' in this function.\n",
pf->pvar->var); pf->pvar->var);
ret = -ENOENT; ret = -ENOENT;
...@@ -1384,6 +1394,44 @@ static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf) ...@@ -1384,6 +1394,44 @@ static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf)
return ret; return ret;
} }
static int fill_empty_trace_arg(struct perf_probe_event *pev,
struct probe_trace_event *tevs, int ntevs)
{
char **valp;
char *type;
int i, j, ret;
for (i = 0; i < pev->nargs; i++) {
type = NULL;
for (j = 0; j < ntevs; j++) {
if (tevs[j].args[i].value) {
type = tevs[j].args[i].type;
break;
}
}
if (j == ntevs) {
print_var_not_found(pev->args[i].var);
return -ENOENT;
}
for (j = 0; j < ntevs; j++) {
valp = &tevs[j].args[i].value;
if (*valp)
continue;
ret = asprintf(valp, "\\%lx", probe_conf.magic_num);
if (ret < 0)
return -ENOMEM;
/* Note that type can be NULL */
if (type) {
tevs[j].args[i].type = strdup(type);
if (!tevs[j].args[i].type)
return -ENOMEM;
}
}
}
return 0;
}
/* Find probe_trace_events specified by perf_probe_event from debuginfo */ /* Find probe_trace_events specified by perf_probe_event from debuginfo */
int debuginfo__find_trace_events(struct debuginfo *dbg, int debuginfo__find_trace_events(struct debuginfo *dbg,
struct perf_probe_event *pev, struct perf_probe_event *pev,
...@@ -1402,7 +1450,13 @@ int debuginfo__find_trace_events(struct debuginfo *dbg, ...@@ -1402,7 +1450,13 @@ int debuginfo__find_trace_events(struct debuginfo *dbg,
tf.tevs = *tevs; tf.tevs = *tevs;
tf.ntevs = 0; tf.ntevs = 0;
if (pev->nargs != 0 && immediate_value_is_supported())
tf.pf.skip_empty_arg = true;
ret = debuginfo__find_probes(dbg, &tf.pf); ret = debuginfo__find_probes(dbg, &tf.pf);
if (ret >= 0 && tf.pf.skip_empty_arg)
ret = fill_empty_trace_arg(pev, tf.tevs, tf.ntevs);
if (ret < 0) { if (ret < 0) {
for (i = 0; i < tf.ntevs; i++) for (i = 0; i < tf.ntevs; i++)
clear_probe_trace_event(&tf.tevs[i]); clear_probe_trace_event(&tf.tevs[i]);
......
...@@ -87,6 +87,7 @@ struct probe_finder { ...@@ -87,6 +87,7 @@ struct probe_finder {
unsigned int machine; /* Target machine arch */ unsigned int machine; /* Target machine arch */
struct perf_probe_arg *pvar; /* Current target variable */ struct perf_probe_arg *pvar; /* Current target variable */
struct probe_trace_arg *tvar; /* Current result variable */ struct probe_trace_arg *tvar; /* Current result variable */
bool skip_empty_arg; /* Skip non-exist args */
}; };
struct trace_event_finder { struct trace_event_finder {
......
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