From: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Subject: kasan: clean up feature flags for HW_TAGS mode - Untie kasan_init_hw_tags() code from the default values of kasan_arg_mode and kasan_arg_stacktrace. - Move static_branch_enable(&kasan_flag_enabled) to the end of kasan_init_hw_tags_cpu(). - Remove excessive comments in kasan_arg_mode switch. - Add new comments. Link: https://lkml.kernel.org/r/76ebb340265be57a218564a497e1f52ff36a3879.1643047180.git.andreyknvl@xxxxxxxxxx Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Acked-by: Marco Elver <elver@xxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Evgenii Stepanov <eugenis@xxxxxxxxxx> Cc: Mark Rutland <mark.rutland@xxxxxxx> Cc: Peter Collingbourne <pcc@xxxxxxxxxx> Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/kasan/hw_tags.c | 38 +++++++++++++++++++++----------------- mm/kasan/kasan.h | 2 +- 2 files changed, 22 insertions(+), 18 deletions(-) --- a/mm/kasan/hw_tags.c~kasan-clean-up-feature-flags-for-hw_tags-mode +++ a/mm/kasan/hw_tags.c @@ -42,16 +42,22 @@ static enum kasan_arg kasan_arg __ro_aft static enum kasan_arg_mode kasan_arg_mode __ro_after_init; static enum kasan_arg_stacktrace kasan_arg_stacktrace __initdata; -/* Whether KASAN is enabled at all. */ +/* + * Whether KASAN is enabled at all. + * The value remains false until KASAN is initialized by kasan_init_hw_tags(). + */ DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled); EXPORT_SYMBOL(kasan_flag_enabled); -/* Whether the selected mode is synchronous/asynchronous/asymmetric.*/ +/* + * Whether the selected mode is synchronous, asynchronous, or asymmetric. + * Defaults to KASAN_MODE_SYNC. + */ enum kasan_mode kasan_mode __ro_after_init; EXPORT_SYMBOL_GPL(kasan_mode); /* Whether to collect alloc/free stack traces. */ -DEFINE_STATIC_KEY_FALSE(kasan_flag_stacktrace); +DEFINE_STATIC_KEY_TRUE(kasan_flag_stacktrace); /* kasan=off/on */ static int __init early_kasan_flag(char *arg) @@ -127,7 +133,11 @@ void kasan_init_hw_tags_cpu(void) * as this function is only called for MTE-capable hardware. */ - /* If KASAN is disabled via command line, don't initialize it. */ + /* + * If KASAN is disabled via command line, don't initialize it. + * When this function is called, kasan_flag_enabled is not yet + * set by kasan_init_hw_tags(). Thus, check kasan_arg instead. + */ if (kasan_arg == KASAN_ARG_OFF) return; @@ -154,42 +164,36 @@ void __init kasan_init_hw_tags(void) if (kasan_arg == KASAN_ARG_OFF) return; - /* Enable KASAN. */ - static_branch_enable(&kasan_flag_enabled); - switch (kasan_arg_mode) { case KASAN_ARG_MODE_DEFAULT: - /* - * Default to sync mode. - */ - fallthrough; + /* Default is specified by kasan_mode definition. */ + break; case KASAN_ARG_MODE_SYNC: - /* Sync mode enabled. */ kasan_mode = KASAN_MODE_SYNC; break; case KASAN_ARG_MODE_ASYNC: - /* Async mode enabled. */ kasan_mode = KASAN_MODE_ASYNC; break; case KASAN_ARG_MODE_ASYMM: - /* Asymm mode enabled. */ kasan_mode = KASAN_MODE_ASYMM; break; } switch (kasan_arg_stacktrace) { case KASAN_ARG_STACKTRACE_DEFAULT: - /* Default to enabling stack trace collection. */ - static_branch_enable(&kasan_flag_stacktrace); + /* Default is specified by kasan_flag_stacktrace definition. */ break; case KASAN_ARG_STACKTRACE_OFF: - /* Do nothing, kasan_flag_stacktrace keeps its default value. */ + static_branch_disable(&kasan_flag_stacktrace); break; case KASAN_ARG_STACKTRACE_ON: static_branch_enable(&kasan_flag_stacktrace); break; } + /* KASAN is now initialized, enable it. */ + static_branch_enable(&kasan_flag_enabled); + pr_info("KernelAddressSanitizer initialized (hw-tags, mode=%s, stacktrace=%s)\n", kasan_mode_info(), kasan_stack_collection_enabled() ? "on" : "off"); --- a/mm/kasan/kasan.h~kasan-clean-up-feature-flags-for-hw_tags-mode +++ a/mm/kasan/kasan.h @@ -12,7 +12,7 @@ #include <linux/static_key.h> #include "../slab.h" -DECLARE_STATIC_KEY_FALSE(kasan_flag_stacktrace); +DECLARE_STATIC_KEY_TRUE(kasan_flag_stacktrace); enum kasan_mode { KASAN_MODE_SYNC, _
