perf symbols: Save DSO loading errno to better report errors

Before, when some problem happened while trying to load the kernel
symtab, 'perf top' would show:

      ┌─Warning:───────────────────────────┐
      │The vmlinux file can't be used.     │
      │Kernel samples will not be resolved.│
      │                                    │
      │                                    │
      │Press any key...                    │
      └────────────────────────────────────┘

Now, it reports:

  # perf top --vmlinux /dev/null

      ┌─Warning:───────────────────────────────────────────┐
      │The /tmp/passwd file can't be used: Invalid ELF file│
      │Kernel samples will not be resolved.                │
      │                                                    │
      │                                                    │
      │Press any key...                                    │
      └────────────────────────────────────────────────────┘

This is possible because we now register the reason for not being able
to load the symtab in the dso->load_errno member, and provide a
dso__strerror_load() routine to format this error into a strerror like
string with a short reason for the error while loading.

That can be just forwarding the dso__strerror_load() call to
strerror_r(), or, for a separate errno range providing a custom message.

Reported-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-u5rb5uq63xqhkfb8uv2lxd5u@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index 88f345cc5be2..e0901b4ed8de 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -60,6 +60,31 @@ enum dso_type {
 	DSO__TYPE_X32BIT,
 };
 
+enum dso_load_errno {
+	DSO_LOAD_ERRNO__SUCCESS		= 0,
+
+	/*
+	 * Choose an arbitrary negative big number not to clash with standard
+	 * errno since SUS requires the errno has distinct positive values.
+	 * See 'Issue 6' in the link below.
+	 *
+	 * http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/errno.h.html
+	 */
+	__DSO_LOAD_ERRNO__START		= -10000,
+
+	DSO_LOAD_ERRNO__INTERNAL_ERROR	= __DSO_LOAD_ERRNO__START,
+
+	/* for symsrc__init() */
+	DSO_LOAD_ERRNO__INVALID_ELF,
+	DSO_LOAD_ERRNO__CANNOT_READ_BUILDID,
+	DSO_LOAD_ERRNO__MISMATCHING_BUILDID,
+
+	/* for decompress_kmodule */
+	DSO_LOAD_ERRNO__DECOMPRESSION_FAILURE,
+
+	__DSO_LOAD_ERRNO__END,
+};
+
 #define DSO__SWAP(dso, type, val)			\
 ({							\
 	type ____r = val;				\
@@ -113,6 +138,7 @@ struct dso {
 	enum dso_swap_type	needs_swap;
 	enum dso_binary_type	symtab_type;
 	enum dso_binary_type	binary_type;
+	enum dso_load_errno	load_errno;
 	u8		 adjust_symbols:1;
 	u8		 has_build_id:1;
 	u8		 has_srcline:1;
@@ -294,4 +320,6 @@ void dso__free_a2l(struct dso *dso);
 
 enum dso_type dso__type(struct dso *dso, struct machine *machine);
 
+int dso__strerror_load(struct dso *dso, char *buf, size_t buflen);
+
 #endif /* __PERF_DSO */