perf tools: Add is_compressed callback to compressions array

Add is_compressed callback to the compressions array, that returns 0 if
the file is compressed or != 0 if not.

The new callback is used to recognize the situation when we have a
'compressed' object, like:

  /lib/modules/.../drivers/net/ethernet/intel/igb/igb.ko.xz

but we need to read its debug data from debuginfo files, which might not
be compressed, like:

  /root/.debug/.build-id/d6/...c4b301f/debug

So even for a 'compressed' object we read debug data from a plain
uncompressed object. To keep this transparent, we detect this in
decompress_kmodule() and return the file descriptor to the uncompressed
file.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180817094813.15086-11-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

4 files changed, 33 insertions, 3 deletions

diff --git a/tools/perf/util/compress.h b/tools/perf/util/compress.h
index ecca688a25fb..892e92e7e7fc 100644
--- a/tools/perf/util/compress.h
+++ b/tools/perf/util/compress.h
@@ -4,10 +4,12 @@
 
 #ifdef HAVE_ZLIB_SUPPORT
 int gzip_decompress_to_file(const char *input, int output_fd);
+bool gzip_is_compressed(const char *input);
 #endif
 
 #ifdef HAVE_LZMA_SUPPORT
 int lzma_decompress_to_file(const char *input, int output_fd);
+bool lzma_is_compressed(const char *input);
 #endif
 
 #endif /* PERF_COMPRESS_H */
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index cbeecf683333..8b9243f13b88 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -196,15 +196,16 @@ enum {
 static const struct {
         const char *fmt;
         int (*decompress)(const char *input, int output);
+        bool (*is_compressed)(const char *input);
 } compressions[] = {
         [COMP_ID__NONE] = { .fmt = NULL, },
 #ifdef HAVE_ZLIB_SUPPORT
-        { "gz", gzip_decompress_to_file },
+        { "gz", gzip_decompress_to_file, gzip_is_compressed },
 #endif
 #ifdef HAVE_LZMA_SUPPORT
-        { "xz", lzma_decompress_to_file },
+        { "xz", lzma_decompress_to_file, lzma_is_compressed },
 #endif
-        { NULL, NULL },
+        { NULL, NULL, NULL },
 };
 
 static int is_supported_compression(const char *ext)
@@ -262,6 +263,22 @@ static int decompress_kmodule(struct dso *dso, const char *name,
         if (dso->comp == COMP_ID__NONE)
                 return -1;
 
+        /*
+         * We have proper compression id for DSO and yet the file
+         * behind the 'name' can still be plain uncompressed object.
+         *
+         * The reason is behind the logic we open the DSO object files,
+         * when we try all possible 'debug' objects until we find the
+         * data. So even if the DSO is represented by 'krava.xz' module,
+         * we can end up here opening ~/.debug/....23432432/debug' file
+         * which is not compressed.
+         *
+         * To keep this transparent, we detect this and return the file
+         * descriptor to the uncompressed file.
+         */
+        if (!compressions[dso->comp].is_compressed(name))
+                return open(name, O_RDONLY);
+
         fd = mkstemp(tmpbuf);
         if (fd < 0) {
                 dso->load_errno = errno;
diff --git a/tools/perf/util/lzma.c b/tools/perf/util/lzma.c
index 07498eaddc08..7032caaf75eb 100644
--- a/tools/perf/util/lzma.c
+++ b/tools/perf/util/lzma.c
@@ -99,3 +99,8 @@ err_fclose:
         fclose(infile);
         return err;
 }
+
+bool lzma_is_compressed(const char *input __maybe_unused)
+{
+        return true;
+}
diff --git a/tools/perf/util/zlib.c b/tools/perf/util/zlib.c
index a725b958cf31..e68317214679 100644
--- a/tools/perf/util/zlib.c
+++ b/tools/perf/util/zlib.c
@@ -5,6 +5,7 @@
 #include <sys/stat.h>
 #include <sys/mman.h>
 #include <zlib.h>
+#include <linux/compiler.h>
 
 #include "util/compress.h"
 #include "util/util.h"
@@ -79,3 +80,8 @@ out_close:
 
         return ret == Z_STREAM_END ? 0 : -1;
 }
+
+bool gzip_is_compressed(const char *input __maybe_unused)
+{
+        return true;
+}