Commit c0f303d7 authored Sep 09, 2025 by Huang Shijie Committed by Will Deacon Sep 16, 2025

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>

parent b868fff5

Documentation/admin-guide/kernel-parameters.txt

+3 −2

Original line number	Diff line number	Diff line
		@@ -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]

arch/arm64/include/asm/setup.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -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;