Commit 6f22f85f authored by Vincenzo Frascino's avatar Vincenzo Frascino
Browse files

arm64: mte: Add asymmetric mode support



MTE provides an asymmetric mode for detecting tag exceptions. In
particular, when such a mode is present, the CPU triggers a fault
on a tag mismatch during a load operation and asynchronously updates
a register when a tag mismatch is detected during a store operation.

Add support for MTE asymmetric mode.

Note: If the CPU does not support MTE asymmetric mode the kernel falls
back on synchronous mode which is the default for kasan=on.

Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Vincenzo Frascino's avatarVincenzo Frascino <vincenzo.frascino@arm.com>
parent 2840a839
......@@ -243,6 +243,7 @@ static inline const void *__tag_set(const void *addr, u8 tag)
#ifdef CONFIG_KASAN_HW_TAGS
#define arch_enable_tagging_sync() mte_enable_kernel_sync()
#define arch_enable_tagging_async() mte_enable_kernel_async()
#define arch_enable_tagging_asymm() mte_enable_kernel_asymm()
#define arch_force_async_tag_fault() mte_check_tfsr_exit()
#define arch_get_random_tag() mte_get_random_tag()
#define arch_get_mem_tag(addr) mte_get_mem_tag(addr)
......
......@@ -130,6 +130,7 @@ static inline void mte_set_mem_tag_range(void *addr, size_t size, u8 tag,
void mte_enable_kernel_sync(void);
void mte_enable_kernel_async(void);
void mte_enable_kernel_asymm(void);
#else /* CONFIG_ARM64_MTE */
......@@ -161,6 +162,10 @@ static inline void mte_enable_kernel_async(void)
{
}
static inline void mte_enable_kernel_asymm(void)
{
}
#endif /* CONFIG_ARM64_MTE */
#endif /* __ASSEMBLY__ */
......
......@@ -137,6 +137,32 @@ void mte_enable_kernel_async(void)
if (!system_uses_mte_async_mode())
static_branch_enable(&mte_async_mode);
}
void mte_enable_kernel_asymm(void)
{
if (cpus_have_cap(ARM64_MTE_ASYMM)) {
__mte_enable_kernel("asymmetric", SCTLR_ELx_TCF_ASYMM);
/*
* MTE asymm mode behaves as async mode for store
* operations. The mode is set system wide by the
* first PE that executes this function.
*
* Note: If in future KASAN acquires a runtime switching
* mode in between sync and async, this strategy needs
* to be reviewed.
*/
if (!system_uses_mte_async_mode())
static_branch_enable(&mte_async_mode);
} else {
/*
* If the CPU does not support MTE asymmetric mode the
* kernel falls back on synchronous mode which is the
* default for kasan=on.
*/
mte_enable_kernel_sync();
}
}
#endif
#ifdef CONFIG_KASAN_HW_TAGS
......
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