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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Sep 2025 20:20:08.3394 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 822ef14f-0e62-47d5-234c-08ddf55e6e6b X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: DB3PEPF0000885A.eurprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM8PR08MB6578 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 25ACA180010 X-Stat-Signature: jj9hhn5pg1hb41bxf1c8xcfzmw3ihfkg X-Rspam-User: X-HE-Tag: 1758054015-595824 X-HE-Meta: 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 ZtSP2xFh pglSK5kJnsUzoIv4FSm9y2aK+kPuiT8LG+ZTBIPmn5ii3wYq4h6sNnvGVH7v5WXmlAkjJStZPnU064kg= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Will, > On Wed, Sep 03, 2025 at 04:00:19PM +0100, Yeoreum Yun wrote: > > Since Armv8.9, FEATURE_MTE_STORE_ONLY feature is introduced to restrict > > raise of tag check fault on store operation only. > > Introcude KASAN write only mode based on this feature. > > Typo ^^ Thanks. > > > > > KASAN write only mode restricts KASAN checks operation for write only and > > omits the checks for fetch/read operations when accessing memory. > > So it might be used not only debugging enviroment but also normal > > enviroment to check memory safty. > > > > This features can be controlled with "kasan.write_only" arguments. > > When "kasan.write_only=on", KASAN checks write operation only otherwise > > KASAN checks all operations. > > > > This changes the MTE_STORE_ONLY feature as BOOT_CPU_FEATURE like > > ARM64_MTE_ASYMM so that makes it initialise in kasan_init_hw_tags() > > with other function together. > > > > Signed-off-by: Yeoreum Yun > > Reviewed-by: Andrey Konovalov > > Reviewed-by: Catalin Marinas > > --- > > Documentation/dev-tools/kasan.rst | 3 ++ > > arch/arm64/include/asm/memory.h | 1 + > > arch/arm64/include/asm/mte-kasan.h | 6 +++ > > arch/arm64/kernel/cpufeature.c | 2 +- > > arch/arm64/kernel/mte.c | 18 ++++++++ > > mm/kasan/hw_tags.c | 70 +++++++++++++++++++++++++++++- > > mm/kasan/kasan.h | 7 +++ > > 7 files changed, 104 insertions(+), 3 deletions(-) > > [...] > > > diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c > > index 9a6927394b54..d5b5fb47d52b 100644 > > --- a/mm/kasan/hw_tags.c > > +++ b/mm/kasan/hw_tags.c > > @@ -41,9 +41,16 @@ enum kasan_arg_vmalloc { > > KASAN_ARG_VMALLOC_ON, > > }; > > > > +enum kasan_arg_write_only { > > + KASAN_ARG_WRITE_ONLY_DEFAULT, > > + KASAN_ARG_WRITE_ONLY_OFF, > > + KASAN_ARG_WRITE_ONLY_ON, > > +}; > > + > > static enum kasan_arg kasan_arg __ro_after_init; > > static enum kasan_arg_mode kasan_arg_mode __ro_after_init; > > static enum kasan_arg_vmalloc kasan_arg_vmalloc __initdata; > > +static enum kasan_arg_write_only kasan_arg_write_only __ro_after_init; > > > > /* > > * Whether KASAN is enabled at all. > > @@ -67,6 +74,9 @@ DEFINE_STATIC_KEY_FALSE(kasan_flag_vmalloc); > > #endif > > EXPORT_SYMBOL_GPL(kasan_flag_vmalloc); > > > > +/* Whether to check write accesses only. */ > > +static bool kasan_flag_write_only = false; > > + > > #define PAGE_ALLOC_SAMPLE_DEFAULT 1 > > #define PAGE_ALLOC_SAMPLE_ORDER_DEFAULT 3 > > > > @@ -141,6 +151,23 @@ static int __init early_kasan_flag_vmalloc(char *arg) > > } > > early_param("kasan.vmalloc", early_kasan_flag_vmalloc); > > > > +/* kasan.write_only=off/on */ > > +static int __init early_kasan_flag_write_only(char *arg) > > +{ > > + if (!arg) > > + return -EINVAL; > > + > > + if (!strcmp(arg, "off")) > > + kasan_arg_write_only = KASAN_ARG_WRITE_ONLY_OFF; > > + else if (!strcmp(arg, "on")) > > + kasan_arg_write_only = KASAN_ARG_WRITE_ONLY_ON; > > + else > > + return -EINVAL; > > + > > + return 0; > > +} > > +early_param("kasan.write_only", early_kasan_flag_write_only); > > + > > static inline const char *kasan_mode_info(void) > > { > > if (kasan_mode == KASAN_MODE_ASYNC) > > @@ -257,15 +284,28 @@ void __init kasan_init_hw_tags(void) > > break; > > } > > > > + switch (kasan_arg_write_only) { > > + case KASAN_ARG_WRITE_ONLY_DEFAULT: > > + /* Default is specified by kasan_flag_write_only definition. */ > > + break; > > + case KASAN_ARG_WRITE_ONLY_OFF: > > + kasan_flag_write_only = false; > > + break; > > + case KASAN_ARG_WRITE_ONLY_ON: > > + kasan_flag_write_only = true; > > + break; > > + } > > + > > kasan_init_tags(); > > I'm probably missing something here, but why have 'enum > kasan_arg_write_only' at all? What stops you from setting > 'kasan_flag_write_only' directly from early_kasan_flag_write_only()? > > This all looks weirdly over-engineered, as though 'kasan_flag_write_only' > is expected to be statically initialised to something other than 'false'. For the conherent pattern for other options. Since other options manage arg value and internal state separately, I just followed former ancestor. > > > /* KASAN is now initialized, enable it. */ > > static_branch_enable(&kasan_flag_enabled); > > > > - pr_info("KernelAddressSanitizer initialized (hw-tags, mode=%s, vmalloc=%s, stacktrace=%s)\n", > > + pr_info("KernelAddressSanitizer initialized (hw-tags, mode=%s, vmalloc=%s, stacktrace=%s, write_only=%s)\n", > > kasan_mode_info(), > > str_on_off(kasan_vmalloc_enabled()), > > - str_on_off(kasan_stack_collection_enabled())); > > + str_on_off(kasan_stack_collection_enabled()), > > + str_on_off(kasan_arg_write_only)); > > It's also confusing, because now you appear to be passing the funny new > 'enum' type to str_on_off(), which expects a bool. Oops. This is my mistake from v3 :( Thanks to point out /// -- Sincerely, Yeoreum Yun