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From: Mike Rapoport <rppt@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Andy Lutomirski <luto@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>,
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	Luis Chamberlain <mcgrof@kernel.org>,
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	Masami Hiramatsu <mhiramat@kernel.org>,
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	Palmer Dabbelt <palmer@dabbelt.com>,
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	Russell King <linux@armlinux.org.uk>,
	Song Liu <song@kernel.org>,
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Subject: [RFC PATCH 4/7] ftrace: Add swap_func to ftrace_process_locs()
Date: Thu, 11 Apr 2024 19:05:23 +0300
Message-ID: <20240411160526.2093408-5-rppt@kernel.org>
In-Reply-To: <20240411160526.2093408-1-rppt@kernel.org>
References: <20240411160526.2093408-1-rppt@kernel.org>
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From: Song Liu <song@kernel.org>

ftrace_process_locs sorts module mcount, which is inside RO memory. Add a
ftrace_swap_func so that archs can use RO-memory-poke function to do the
sorting.

Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
---
 include/linux/ftrace.h |  2 ++
 kernel/trace/ftrace.c  | 13 ++++++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 54d53f345d14..54393ce57f08 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -1172,4 +1172,6 @@ unsigned long arch_syscall_addr(int nr);
 
 #endif /* CONFIG_FTRACE_SYSCALLS */
 
+void ftrace_swap_func(void *a, void *b, int n);
+
 #endif /* _LINUX_FTRACE_H */
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index da1710499698..95f11c8cdc5e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6480,6 +6480,17 @@ static void test_is_sorted(unsigned long *start, unsigned long count)
 }
 #endif
 
+void __weak ftrace_swap_func(void *a, void *b, int n)
+{
+	unsigned long t;
+
+	WARN_ON_ONCE(n != sizeof(t));
+
+	t = *((unsigned long *)a);
+	*(unsigned long *)a = *(unsigned long *)b;
+	*(unsigned long *)b = t;
+}
+
 static int ftrace_process_locs(struct module *mod,
 			       unsigned long *start,
 			       unsigned long *end)
@@ -6507,7 +6518,7 @@ static int ftrace_process_locs(struct module *mod,
 	 */
 	if (!IS_ENABLED(CONFIG_BUILDTIME_MCOUNT_SORT) || mod) {
 		sort(start, count, sizeof(*start),
-		     ftrace_cmp_ips, NULL);
+		     ftrace_cmp_ips, ftrace_swap_func);
 	} else {
 		test_is_sorted(start, count);
 	}
-- 
2.43.0