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Subject[PATCH 28/38] perf tools: Add dso__data_get/put_fd()
Date
Using dso__data_fd() in multi-thread environment is not safe since
returned fd can be closed and/or reused anytime. So convert it to the
dso__data_get/put_fd() pair to protect the access with lock.

The original dso__data_fd() is deprecated and kept only for testing.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/util/dso.c | 44 +++++++++++++++++++++++++++++---------
tools/perf/util/dso.h | 9 ++++++--
tools/perf/util/unwind-libunwind.c | 38 +++++++++++++++++++-------------
3 files changed, 64 insertions(+), 27 deletions(-)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 64aaa45dcdd7..50bb2f93b7e9 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -389,14 +389,15 @@ void dso__data_close(struct dso *dso)
}

/**
- * dso__data_fd - Get dso's data file descriptor
+ * dso__data_get_fd - Get dso's data file descriptor
* @dso: dso object
* @machine: machine object
*
* External interface to find dso's file, open it and
- * returns file descriptor.
+ * returns file descriptor. Should be paired with
+ * dso__data_put_fd().
*/
-int dso__data_fd(struct dso *dso, struct machine *machine)
+int dso__data_get_fd(struct dso *dso, struct machine *machine)
{
enum dso_binary_type binary_type_data[] = {
DSO_BINARY_TYPE__BUILD_ID_CACHE,
@@ -405,11 +406,11 @@ int dso__data_fd(struct dso *dso, struct machine *machine)
};
int i = 0;

+ pthread_mutex_lock(&dso__data_open_lock);
+
if (dso->data.status == DSO_DATA_STATUS_ERROR)
return -1;

- pthread_mutex_lock(&dso__data_open_lock);
-
if (dso->data.fd >= 0)
goto out;

@@ -432,10 +433,31 @@ int dso__data_fd(struct dso *dso, struct machine *machine)
else
dso->data.status = DSO_DATA_STATUS_ERROR;

- pthread_mutex_unlock(&dso__data_open_lock);
return dso->data.fd;
}

+void dso__data_put_fd(struct dso *dso __maybe_unused)
+{
+ pthread_mutex_unlock(&dso__data_open_lock);
+}
+
+/**
+ * dso__data_get_fd - Get dso's data file descriptor
+ * @dso: dso object
+ * @machine: machine object
+ *
+ * Obsolete interface to find dso's file, open it and
+ * returns file descriptor. It's not thread-safe in that
+ * the returned fd may be reused for other file.
+ */
+int dso__data_fd(struct dso *dso, struct machine *machine)
+{
+ int fd = dso__data_get_fd(dso, machine);
+
+ dso__data_put_fd(dso);
+ return fd;
+}
+
bool dso__data_status_seen(struct dso *dso, enum dso_data_status_seen by)
{
u32 flag = 1 << by;
@@ -1144,10 +1166,12 @@ size_t dso__fprintf(struct dso *dso, enum map_type type, FILE *fp)
enum dso_type dso__type(struct dso *dso, struct machine *machine)
{
int fd;
+ enum dso_type type = DSO__TYPE_UNKNOWN;

- fd = dso__data_fd(dso, machine);
- if (fd < 0)
- return DSO__TYPE_UNKNOWN;
+ fd = dso__data_get_fd(dso, machine);
+ if (fd >= 0)
+ type = dso__type_fd(fd);
+ dso__data_put_fd(dso);

- return dso__type_fd(fd);
+ return type;
}
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index da188a73d034..9f1e67da9c01 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -197,7 +197,9 @@ bool dso__needs_decompress(struct dso *dso);

/*
* The dso__data_* external interface provides following functions:
- * dso__data_fd
+ * dso__data_fd (obsolete)
+ * dso__data_get_fd
+ * dso__data_put_fd
* dso__data_close
* dso__data_size
* dso__data_read_offset
@@ -214,8 +216,9 @@ bool dso__needs_decompress(struct dso *dso);
* The current usage of the dso__data_* interface is as follows:
*
* Get DSO's fd:
- * int fd = dso__data_fd(dso, machine);
+ * int fd = dso__data_get_fd(dso, machine);
* USE 'fd' SOMEHOW
+ * dso__data_put_fd(dso)
*
* Read DSO's data:
* n = dso__data_read_offset(dso_0, &machine, 0, buf, BUFSIZE);
@@ -235,6 +238,8 @@ bool dso__needs_decompress(struct dso *dso);
* TODO
*/
int dso__data_fd(struct dso *dso, struct machine *machine);
+int dso__data_get_fd(struct dso *dso, struct machine *machine);
+void dso__data_put_fd(struct dso *dso);
void dso__data_close(struct dso *dso);

off_t dso__data_size(struct dso *dso, struct machine *machine);
diff --git a/tools/perf/util/unwind-libunwind.c b/tools/perf/util/unwind-libunwind.c
index 9d7ecb26fde9..e807ba9d375a 100644
--- a/tools/perf/util/unwind-libunwind.c
+++ b/tools/perf/util/unwind-libunwind.c
@@ -271,13 +271,13 @@ static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
u64 offset = dso->data.frame_offset;

if (offset == 0) {
- fd = dso__data_fd(dso, machine);
- if (fd < 0)
- return -EINVAL;
-
- /* Check the .eh_frame section for unwinding info */
- offset = elf_section_offset(fd, ".eh_frame_hdr");
- dso->data.frame_offset = offset;
+ fd = dso__data_get_fd(dso, machine);
+ if (fd >= 0) {
+ /* Check the .eh_frame section for unwinding info */
+ offset = elf_section_offset(fd, ".eh_frame_hdr");
+ dso->data.frame_offset = offset;
+ }
+ dso__data_put_fd(dso);
}

if (offset)
@@ -296,13 +296,19 @@ static int read_unwind_spec_debug_frame(struct dso *dso,
u64 ofs = dso->data.frame_offset;

if (ofs == 0) {
- fd = dso__data_fd(dso, machine);
- if (fd < 0)
- return -EINVAL;
-
- /* Check the .debug_frame section for unwinding info */
- ofs = elf_section_offset(fd, ".debug_frame");
- dso->data.frame_offset = ofs;
+ int ret = 0;
+
+ fd = dso__data_get_fd(dso, machine);
+ if (fd >= 0) {
+ /* Check the .debug_frame section for unwinding info */
+ ofs = elf_section_offset(fd, ".debug_frame");
+ dso->data.frame_offset = ofs;
+ } else
+ ret = -EINVAL;
+
+ dso__data_put_fd(dso);
+ if (ret)
+ return ret;
}

*offset = ofs;
@@ -355,10 +361,12 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
#ifndef NO_LIBUNWIND_DEBUG_FRAME
/* Check the .debug_frame section for unwinding info */
if (!read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
- int fd = dso__data_fd(map->dso, ui->machine);
+ int fd = dso__data_get_fd(map->dso, ui->machine);
int is_exec = elf_is_exec(fd, map->dso->name);
unw_word_t base = is_exec ? 0 : map->start;

+ dso__data_put_fd(map->dso);
+
memset(&di, 0, sizeof(di));
if (dwarf_find_debug_frame(0, &di, ip, base, map->dso->name,
map->start, map->end))
--
2.2.2


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