arm64: kasan: mte: remove redundant mte_report_once logic

We have special logic to suppress MTE tag check fault reporting, based
on a global `mte_report_once` and `reported` variables. These can be
used to suppress calling kasan_report() when taking a tag check fault,
but do not prevent taking the fault in the first place, nor does they
affect the way we disable tag checks upon taking a fault.

The core KASAN code already defaults to reporting a single fault, and
has a `multi_shot` control to permit reporting multiple faults. The only
place we transiently alter `mte_report_once` is in lib/test_kasan.c,
where we also the `multi_shot` state as the same time. Thus
`mte_report_once` and `reported` are redundant, and can be removed.

When a tag check fault is taken, tag checking will be disabled by
`do_tag_recovery` and must be explicitly re-enabled if desired. The test
code does this by calling kasan_enable_tagging_sync().

This patch removes the redundant mte_report_once() logic and associated
variables.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Will Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Tested-by: Andrey Konovalov <andreyknvl@gmail.com>
Link: https://lore.kernel.org/r/20210714143843.56537-4-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

4 files changed, 1 insertions, 39 deletions

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 7f4e6a923aa6..f1745a843414 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -243,7 +243,6 @@ 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_set_tagging_report_once(state)	mte_set_report_once(state)
 #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)
diff --git a/arch/arm64/include/asm/mte-kasan.h b/arch/arm64/include/asm/mte-kasan.h
index 82fa4ac4ad4e..22420e1f8c03 100644
--- a/arch/arm64/include/asm/mte-kasan.h
+++ b/arch/arm64/include/asm/mte-kasan.h
@@ -131,9 +131,6 @@ 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_set_report_once(bool state);
-bool mte_report_once(void);
-
 #else /* CONFIG_ARM64_MTE */
 
 static inline u8 mte_get_ptr_tag(void *ptr)
@@ -164,15 +161,6 @@ static inline void mte_enable_kernel_async(void)
 {
 }
 
-static inline void mte_set_report_once(bool state)
-{
-}
-
-static inline bool mte_report_once(void)
-{
-	return false;
-}
-
 #endif /* CONFIG_ARM64_MTE */
 
 #endif /* __ASSEMBLY__ */
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index b538ff27a912..9d314a3bad3b 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -23,8 +23,6 @@
 #include <asm/ptrace.h>
 #include <asm/sysreg.h>
 
-static bool report_fault_once = true;
-
 static DEFINE_PER_CPU_READ_MOSTLY(u64, mte_tcf_preferred);
 
 #ifdef CONFIG_KASAN_HW_TAGS
@@ -141,16 +139,6 @@ void mte_enable_kernel_async(void)
 }
 #endif
 
-void mte_set_report_once(bool state)
-{
-	WRITE_ONCE(report_fault_once, state);
-}
-
-bool mte_report_once(void)
-{
-	return READ_ONCE(report_fault_once);
-}
-
 #ifdef CONFIG_KASAN_HW_TAGS
 void mte_check_tfsr_el1(void)
 {
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 349c488765ca..9ae24e3b72be 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -309,24 +309,11 @@ static void die_kernel_fault(const char *msg, unsigned long addr,
 static void report_tag_fault(unsigned long addr, unsigned int esr,
 			     struct pt_regs *regs)
 {
-	static bool reported;
-	bool is_write;
-
-	if (READ_ONCE(reported))
-		return;
-
-	/*
-	 * This is used for KASAN tests and assumes that no MTE faults
-	 * happened before running the tests.
-	 */
-	if (mte_report_once())
-		WRITE_ONCE(reported, true);
-
 	/*
 	 * SAS bits aren't set for all faults reported in EL1, so we can't
 	 * find out access size.
 	 */
-	is_write = !!(esr & ESR_ELx_WNR);
+	bool is_write = !!(esr & ESR_ELx_WNR);
 	kasan_report(addr, 0, is_write, regs->pc);
 }
 #else