selftests/ring-buffer: Handle meta-page bigger than the system

Handle the case where the meta-page content is bigger than the system
page-size. This prepares the ground for extending features covered by
the meta-page.

Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: linux-kselftest@vger.kernel.org
Link: https://lore.kernel.org/20240910162335.2993310-3-vdonnefort@google.com
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/tools/testing/selftests/ring-buffer/map_test.c b/tools/testing/selftests/ring-buffer/map_test.c
index ba12fd31de87e81fa7ba1a7cac05348d12a45062..d10a847130fbc3949b5a6b9e63ac659988f5db17 100644 (file)
--- a/tools/testing/selftests/ring-buffer/map_test.c
+++ b/tools/testing/selftests/ring-buffer/map_test.c
@@ -92,12 +92,22 @@ int tracefs_cpu_map(struct tracefs_cpu_map_desc *desc, int cpu)
        if (desc->cpu_fd < 0)
                return -ENODEV;
 
+again:
        map = mmap(NULL, page_size, PROT_READ, MAP_SHARED, desc->cpu_fd, 0);
        if (map == MAP_FAILED)
                return -errno;
 
        desc->meta = (struct trace_buffer_meta *)map;
 
+       /* the meta-page is bigger than the original mapping */
+       if (page_size < desc->meta->meta_struct_len) {
+               int meta_page_size = desc->meta->meta_page_size;
+
+               munmap(desc->meta, page_size);
+               page_size = meta_page_size;
+               goto again;
+       }
+
        return 0;
 }