Enable EXECMEM_ROX_CACHE support for ARM64 systems that implement the bbml2_no_abort CPU feature. Using the ROX cache brings a performance boost by reducing linear region fragmentation caused by strict memory permissions (e.g., W^X enforcement). Grouping executable code (which is read-only in the linear region alias) into PMD-sized block mappings reduces TLB pressure and page table size. This is only enabled on systems with bbml2_no_abort, as splitting these large blocks to make pages writable during module loading would otherwise risk triggering TLB Conflict Aborts. Signed-off-by: Adrian Barnaś --- arch/arm64/Kconfig | 1 + arch/arm64/mm/init.c | 22 +++++++++++++++++++++- 2 files changed, 22 insertions(+), 1 deletion(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 38dba5f7e4d2..79c347ab841e 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -285,6 +285,7 @@ config ARM64 select USER_STACKTRACE_SUPPORT select VDSO_GETRANDOM select VMAP_STACK + select ARCH_HAS_EXECMEM_ROX help ARM 64-bit (AArch64) Linux support. diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 71aa745e0bef..8269d7747b84 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -420,6 +420,12 @@ void execmem_fill_trapping_insns(void *ptr, size_t size) flush_icache_range((unsigned long)ptr, (unsigned long)ptr + size); } + +#define MODULE_TEXT_FLAG EXECMEM_ROX_CACHE +#define MODULE_TEXT_PGPROT PAGE_KERNEL_ROX +#else +#define MODULE_TEXT_FLAG (0) +#define MODULE_TEXT_PGPROT PAGE_KERNEL #endif static u64 module_direct_base __ro_after_init = 0; @@ -511,6 +517,8 @@ struct execmem_info __init *execmem_arch_setup(void) { unsigned long fallback_start = 0, fallback_end = 0; unsigned long start = 0, end = 0; + enum execmem_range_flags module_text_flags = 0; + pgprot_t module_text_pgprot = PAGE_KERNEL; module_init_limits(); @@ -531,12 +539,24 @@ struct execmem_info __init *execmem_arch_setup(void) end = module_plt_base + SZ_2G; } + /* + * The ROX Cache requires bbml2_no_abort because it uses large block + * mappings. On systems without this guarantee, splitting these blocks + * to make pages writable for module loading can trigger TLB Conflict + * Aborts. + */ + if (system_supports_bbml2_noabort()) { + module_text_flags = MODULE_TEXT_FLAG; + module_text_pgprot = MODULE_TEXT_PGPROT; + } + execmem_info = (struct execmem_info){ .ranges = { [EXECMEM_MODULE_TEXT] = { .start = start, .end = end, - .pgprot = PAGE_KERNEL, + .flags = module_text_flags, + .pgprot = module_text_pgprot, .alignment = 1, .fallback_start = fallback_start, .fallback_end = fallback_end, -- 2.54.0.1136.gdb2ca164c4-goog