@@ -6105,7 +6105,7 @@
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
+ noalias Use more block mappings,may have better performance.
[arm64]
rockchip.usb_uart
@@ -13,6 +13,30 @@
extern phys_addr_t __fdt_pointer __initdata;
extern u64 __cacheline_aligned boot_args[4];
+/*
+ * rodata=on (default)
+ *
+ * This applies read-only attributes to VM areas and to the linear
+ * alias of the backing pages as well. This prevents code or read-
+ * only data from being modified (inadvertently or intentionally),
+ * via another mapping for the same memory page.
+ *
+ * But this might cause linear map region to be mapped down to base
+ * pages, which may adversely affect performance in some cases.
+ *
+ * rodata=off
+ *
+ * This provides more block mappings and contiguous hints for linear
+ * map region which would minimize TLB footprint. This also leaves
+ * read-only kernel memory writable for debugging.
+ *
+ * rodata=noalias
+ *
+ * This provides more block mappings and contiguous hints for linear
+ * map region which would minimize TLB footprint. This leaves the linear
+ * alias of read-only mappings in the vmalloc space writeable, making
+ * them susceptible to inadvertent modification by software.
+ */
static inline bool arch_parse_debug_rodata(char *arg)
{
extern bool rodata_enabled;
@@ -21,7 +45,7 @@ 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 +55,7 @@ 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;
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" is the default instead. This patch implements the following changes. - Make "rodata=on" behaviour same as the original "rodata=full" - Make "rodata=noalias" (new) behaviour same as the original "rodata=on" - Drop the original "rodata=full" - Add comment for arch_parse_debug_rodata() - Update kernel-parameters.txt as required After this patch, the "rodata=on" will be the default on arm64 platform as well. Signed-off-by: Huang Shijie <shijie@os.amperecomputing.com> --- Add more comment for "rodata=noalias" in arch_parse_debug_rodata() from Ard. --- .../admin-guide/kernel-parameters.txt | 2 +- arch/arm64/include/asm/setup.h | 28 +++++++++++++++++-- 2 files changed, 27 insertions(+), 3 deletions(-)