linux-kernel - [PATCH 2/2] ring-buffer/selftest: Handle meta-page bigger than the system

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Message-ID: <20240910144323.2888480-3-vdonnefort@google.com>
Date: Tue, 10 Sep 2024 15:43:23 +0100
From: Vincent Donnefort <vdonnefort@...gle.com>
To: rostedt@...dmis.org
Cc: mhiramat@...nel.org, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org, kernel-team@...roid.com, 
	Vincent Donnefort <vdonnefort@...gle.com>
Subject: [PATCH 2/2] ring-buffer/selftest: 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.

Signed-off-by: Vincent Donnefort <vdonnefort@...gle.com>

diff --git a/tools/testing/selftests/ring-buffer/map_test.c b/tools/testing/selftests/ring-buffer/map_test.c
index ba12fd31de87..d10a847130fb 100644
--- 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;
 }
 
-- 
2.46.0.598.g6f2099f65c-goog