From: Huang Shijie <shijie@os.amperecomputing.com>
Date: Tue, 9 Sep 2025 03:32:35 +0000 (+0800)
Subject: arm64: mm: Rework the 'rodata=' options
X-Git-Tag: v6.18-rc1~210^2~6^2~6
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c0f303d7d4723b01c686e949e6f26a93e5cda910;p=thirdparty%2Flinux.git

arm64: mm: Rework the 'rodata=' options

As per admin guide documentation, "rodata=on" should be the default on
platforms. Documentation/admin-guide/kernel-parameters.txt describes
these options as

   rodata=         [KNL,EARLY]
           on      Mark read-only kernel memory as read-only (default).
           off     Leave read-only kernel memory writable for debugging.
           full    Mark read-only kernel memory and aliases as read-only
                   [arm64]

But on arm64 platform, RODATA_FULL_DEFAULT_ENABLED is enabled by default,
so "rodata=full" is the default instead.

For parity with other architectures, namely x86, rework 'rodata=on' to
match the current "full" behaviour and replace 'rodata=full' with a new
'rodata=noalias' option which retains writable aliases in the direct map
for memory regions outside of the kernel image.

Signed-off-by: Huang Shijie <shijie@os.amperecomputing.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
---

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 747a55abf4946..fe99652c584ec 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6405,8 +6405,9 @@
 	rodata=		[KNL,EARLY]
 		on	Mark read-only kernel memory as read-only (default).
 		off	Leave read-only kernel memory writable for debugging.
-		full	Mark read-only kernel memory and aliases as read-only
-		        [arm64]
+		noalias	Mark read-only kernel memory as read-only but retain
+			writable aliases in the direct map for regions outside
+			of the kernel image. [arm64]
 
 	rockchip.usb_uart
 			[EARLY]
diff --git a/arch/arm64/include/asm/setup.h b/arch/arm64/include/asm/setup.h
index ba269a7a32013..3d96dde4d214c 100644
--- a/arch/arm64/include/asm/setup.h
+++ b/arch/arm64/include/asm/setup.h
@@ -21,7 +21,7 @@ static inline bool arch_parse_debug_rodata(char *arg)
 	if (!arg)
 		return false;
 
-	if (!strcmp(arg, "full")) {
+	if (!strcmp(arg, "on")) {
 		rodata_enabled = rodata_full = true;
 		return true;
 	}
@@ -31,7 +31,7 @@ static inline bool arch_parse_debug_rodata(char *arg)
 		return true;
 	}
 
-	if (!strcmp(arg, "on")) {
+	if (!strcmp(arg, "noalias")) {
 		rodata_enabled = true;
 		rodata_full = false;
 		return true;