linux-kernel - [PATCH] gcov: support GCC 12.1 and newer compilers

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Date:   Thu, 13 Oct 2022 09:40:59 +0200
From:   Martin Liška <mliska@...e.cz>
To:     linux-kernel@...r.kernel.org
Cc:     oberpar@...ux.ibm.com
Subject: [PATCH] gcov: support GCC 12.1 and newer compilers

Starting with GCC 12.1, there are 2 significant changes to the .gcda
file format that needs to be supported:

a) [gcov: Use system IO buffering] (23eb66d1d46a34cb28c4acbdf8a1deb80a7c5a05) changed
   that all sizes in the format are in bytes and not in words (4B)
b) [gcov: make profile merging smarter] (72e0c742bd01f8e7e6dcca64042b9ad7e75979de)
   add a new checksum to the file header.

Tested with GCC 7.5, 10.4, 12.2 and the current master.

Signed-off-by: Martin Liska <mliska@...e.cz>
---
 kernel/gcov/gcc_4_7.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/kernel/gcov/gcc_4_7.c b/kernel/gcov/gcc_4_7.c
index 460c12b7dfea..7971e989e425 100644
--- a/kernel/gcov/gcc_4_7.c
+++ b/kernel/gcov/gcc_4_7.c
@@ -30,6 +30,13 @@
 
 #define GCOV_TAG_FUNCTION_LENGTH	3
 
+/* Since GCC 12.1 sizes are in BYTES and not in WORDS (4B). */
+#if (__GNUC__ >= 12)
+#define GCOV_UNIT_SIZE				4
+#else
+#define GCOV_UNIT_SIZE				1
+#endif
+
 static struct gcov_info *gcov_info_head;
 
 /**
@@ -383,12 +390,18 @@ size_t convert_to_gcda(char *buffer, struct gcov_info *info)
 	pos += store_gcov_u32(buffer, pos, info->version);
 	pos += store_gcov_u32(buffer, pos, info->stamp);
 
+#if (__GNUC__ >= 12)
+	/* Use zero as checksum of the compilation unit. */
+	pos += store_gcov_u32(buffer, pos, 0);
+#endif
+
 	for (fi_idx = 0; fi_idx < info->n_functions; fi_idx++) {
 		fi_ptr = info->functions[fi_idx];
 
 		/* Function record. */
 		pos += store_gcov_u32(buffer, pos, GCOV_TAG_FUNCTION);
-		pos += store_gcov_u32(buffer, pos, GCOV_TAG_FUNCTION_LENGTH);
+		pos += store_gcov_u32(buffer, pos,
+			GCOV_TAG_FUNCTION_LENGTH * GCOV_UNIT_SIZE);
 		pos += store_gcov_u32(buffer, pos, fi_ptr->ident);
 		pos += store_gcov_u32(buffer, pos, fi_ptr->lineno_checksum);
 		pos += store_gcov_u32(buffer, pos, fi_ptr->cfg_checksum);
@@ -402,7 +415,8 @@ size_t convert_to_gcda(char *buffer, struct gcov_info *info)
 			/* Counter record. */
 			pos += store_gcov_u32(buffer, pos,
 					      GCOV_TAG_FOR_COUNTER(ct_idx));
-			pos += store_gcov_u32(buffer, pos, ci_ptr->num * 2);
+			pos += store_gcov_u32(buffer, pos,
+				ci_ptr->num * 2 * GCOV_UNIT_SIZE);
 
 			for (cv_idx = 0; cv_idx < ci_ptr->num; cv_idx++) {
 				pos += store_gcov_u64(buffer, pos,
-- 
2.37.3