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authorMasami Hiramatsu <mhiramat@kernel.org>2019-11-18 17:12:49 +0900
committerArnaldo Carvalho de Melo <acme@redhat.com>2019-11-18 19:09:23 -0300
commitcb4027308570841869ec0c6bdafc9658c10f28a3 (patch)
tree5abd815698b9af852371c391ff5f4fb64e3e8e9a /tools/perf/util/probe-finder.c
parentperf probe: Support DW_AT_const_value constant value (diff)
downloadlinux-dev-cb4027308570841869ec0c6bdafc9658c10f28a3.tar.xz
linux-dev-cb4027308570841869ec0c6bdafc9658c10f28a3.zip
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: Masami 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@devnote2 Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/util/probe-finder.c')
-rw-r--r--tools/perf/util/probe-finder.c62
1 files changed, 58 insertions, 4 deletions
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 33e90054ad84..38d6cd22779f 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -536,6 +536,14 @@ next:
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 */
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,
&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) {
- 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",
- pf->pvar->var, pf->pvar->var);
+ print_var_not_found(pf->pvar->var);
} else if (ret == -ENOTSUP)
pr_err("Sorry, we don't support this variable location yet.\n");
else if (ret == 0 && pf->pvar->field) {
@@ -598,6 +606,8 @@ static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf)
/* Search again in global variables */
if (!die_find_variable_at(&pf->cu_die, pf->pvar->var,
0, &vr_die)) {
+ if (pf->skip_empty_arg)
+ return 0;
pr_warning("Failed to find '%s' in this function.\n",
pf->pvar->var);
ret = -ENOENT;
@@ -1384,6 +1394,44 @@ end:
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 */
int debuginfo__find_trace_events(struct debuginfo *dbg,
struct perf_probe_event *pev,
@@ -1402,7 +1450,13 @@ int debuginfo__find_trace_events(struct debuginfo *dbg,
tf.tevs = *tevs;
tf.ntevs = 0;
+ if (pev->nargs != 0 && immediate_value_is_supported())
+ tf.pf.skip_empty_arg = true;
+
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) {
for (i = 0; i < tf.ntevs; i++)
clear_probe_trace_event(&tf.tevs[i]);