[PATCH RFC v1 2/4] perf: Add file name and line number to perf extended error reports

Alexander Shishkin
2015-07-24T11:47:07Z

If kernel debugging is enabled, include additional information to extended
syscall error reports: file name and line number, to make error hunting even
easier.

And in really desperate times, this allows for such things (a variation on
Hugh Dickins' trick [1]):

#undef EINVAL
#define EINVAL perf_err(-22, "")

However, CONFIG_DEBUG_KERNEL might not be the right option for this as I
notice that, for example, debian enables it in its kernels.

[1] http://marc.info/?l=linux-kernel&m=141215166009542

NYet-Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
include/linux/perf_event.h | 11 +++++++++++
kernel/events/core.c | 7 +++++++
2 files changed, 18 insertions(+)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 9e9af962f6..d84a2914f5 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -68,11 +68,21 @@ struct perf_guest_info_callbacks {
struct perf_err_site {
const char *message;
const char *owner;
+#ifdef CONFIG_DEBUG_KERNEL
+ const char *file;
+ const int line;
+#endif
const int code;
};

#ifdef CONFIG_PERF_EVENTS

+#ifdef CONFIG_DEBUG_KERNEL
+#define DEBUG_PERF_ERR .file = __FILE__, .line = __LINE__,
+#else
+#define DEBUG_PERF_ERR
+#endif
+
/*
* Place all occurrences of struct perf_err_site into a special section,
* so that we can find out their offsets, which we'll use to refer back
@@ -88,6 +98,7 @@ extern const struct perf_err_site __start___perf_err[], __stop___perf_err[];
.owner = PERF_MODNAME, \
.code = __builtin_constant_p((__c)) ? \
(__c) : 0, \
+ DEBUG_PERF_ERR \
}; \
(__e) = &__err_site; \
})
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 85bcf3a5f9..4ff09fdc67 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -75,10 +75,17 @@ static void perf_error_report_site(struct perf_event_attr *attr,

buffer = kasprintf(GFP_KERNEL,
"{\n"
+#ifdef CONFIG_DEBUG_KERNEL
+ "\t\"file\": \"%s\",\n"
+ "\t\"line\": %d,\n"
+#endif
"\t\"code\": %d,\n"
"\t\"module\": \"%s\",\n"
"\t\"message\": \"%s\"\n"
"}\n",
+#ifdef CONFIG_DEBUG_KERNEL
+ site->file, site->line,
+#endif
site->code, site->owner, site->message
);
if (!buffer)
--
2.1.4