[PATCH 4/4] perf: support zstd-compressed kernel modules

[Ivan Shapovalov <intelfx@intelfx.name>]

Support handling loading zstd-compressed DSOs in perf (in addition to
existing support for gzip/xz formats). This allows loading of e.g.
zstd-compressed kernel modules, as shipped by various distros
including Arch.

Signed-off-by: Ivan Shapovalov <intelfx@intelfx.name>
---
 tools/perf/Makefile.config | 2 +-
 tools/perf/util/dso.c      | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 4d5993da9f945..dfdda22becc39 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -982,7 +982,7 @@ ifndef NO_LIBZSTD
     EXTLIBS += -lzstd
     $(call detected,CONFIG_ZSTD)
   else
-    $(warning No libzstd found, disables trace compression, please install libzstd-dev[el] and/or set LIBZSTD_DIR)
+    $(warning No libzstd found, disables zstd kernel module decompression and trace compression, please install libzstd-dev[el] and/or set LIBZSTD_DIR)
     NO_LIBZSTD := 1
   endif
 endif
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 42bfe30a3b518..0e8886172e239 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -277,6 +277,9 @@ static const struct {
 #endif
 #ifdef HAVE_LZMA_SUPPORT
 	{ "xz", lzma_decompress_to_file, lzma_is_compressed },
+#endif
+#ifdef HAVE_ZSTD_SUPPORT
+	{ "zst", zstd_decompress_to_fd, zstd_is_compressed },
 #endif
 	{ NULL, NULL, NULL },
 };
@@ -460,7 +463,7 @@ int __kmod_path__parse(struct kmod_path *m, const char *path,
 
 	m->comp = is_supported_compression(ext + 1);
 	if (m->comp > COMP_ID__NONE)
-		ext -= 3;
+		ext -= strlen(compressions[m->comp].fmt);
 
 	/* Check .ko extension only if there's enough name left. */
 	if (ext > name)

-- 
2.55.0.8.g37e2a0019f