linux-kernel - [PATCH] tracing: Hide get_vm

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Message-ID: <20250407120111.2ccc9319@gandalf.local.home>
Date: Mon, 7 Apr 2025 12:01:11 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH] tracing: Hide get_vm_area() from MMUless builds

From: Steven Rostedt <rostedt@...dmis.org>

The function get_vm_area() is not defined for non-MMU builds and causes a
build error if it is used. Hide the map_pages() function around a:

 #ifdef CONFIG_MMU

to keep it from being compiled when CONFIG_MMU is not set.

Reported-by: Guenter Roeck <linux@...ck-us.net>
Tested-by: Guenter Roeck <linux@...ck-us.net>
Closes: https://lore.kernel.org/all/4f8ece8b-8862-4f7c-8ede-febd28f8a9fe@roeck-us.net/
Fixes: 394f3f02de531 ("tracing: Use vmap_page_range() to map memmap ring buffer")
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b581e388a9d9..8ddf6b17215c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9806,6 +9806,7 @@ static int instance_mkdir(const char *name)
 	return ret;
 }
 
+#ifdef CONFIG_MMU
 static u64 map_pages(unsigned long start, unsigned long size)
 {
 	unsigned long vmap_start, vmap_end;
@@ -9828,6 +9829,12 @@ static u64 map_pages(unsigned long start, unsigned long size)
 
 	return (u64)vmap_start;
 }
+#else
+static inline u64 map_pages(unsigned long start, unsigned long size)
+{
+	return 0;
+}
+#endif
 
 /**
  * trace_array_get_by_name - Create/Lookup a trace array, given its name.
-- 
2.47.2