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authorMark Rutland <mark.rutland@arm.com>2021-07-14 15:38:42 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2021-08-02 18:14:21 +0100
commit82868247897bea2d69a83dca9a6a557e2c96dac4 (patch)
tree6154f97e2b4c00b5a8946d6825b9097d79f76847 /mm/kasan
parentd914b80a8f567d052d621197974ae08f729c963d (diff)
arm64: kasan: mte: use a constant kernel GCR_EL1 value
When KASAN_HW_TAGS is selected, KASAN is enabled at boot time, and the hardware supports MTE, we'll initialize `kernel_gcr_excl` with a value dependent on KASAN_TAG_MAX. While the resulting value is a constant which depends on KASAN_TAG_MAX, we have to perform some runtime work to generate the value, and have to read the value from memory during the exception entry path. It would be better if we could generate this as a constant at compile-time, and use it as such directly. Early in boot within __cpu_setup(), we initialize GCR_EL1 to a safe value, and later override this with the value required by KASAN. If CONFIG_KASAN_HW_TAGS is not selected, or if KASAN is disabeld at boot time, the kernel will not use IRG instructions, and so the initial value of GCR_EL1 is does not matter to the kernel. Thus, we can instead have __cpu_setup() initialize GCR_EL1 to a value consistent with KASAN_TAG_MAX, and avoid the need to re-initialize it during hotplug and resume form suspend. This patch makes arem64 use a compile-time constant KERNEL_GCR_EL1 value, which is compatible with KASAN_HW_TAGS when this is selected. This removes the need to re-initialize GCR_EL1 dynamically, and acts as an optimization to the entry assembly, which no longer needs to load this value from memory. The redundant initialization hooks are removed. In order to do this, KASAN_TAG_MAX needs to be visible outside of the core KASAN code. To do this, I've moved the KASAN_TAG_* values into <linux/kasan-tags.h>. There should be no functional change as a result of this patch. 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: Peter Collingbourne <pcc@google.com> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Will Deacon <will@kernel.org> 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/20210714143843.56537-3-mark.rutland@arm.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'mm/kasan')
-rw-r--r--mm/kasan/hw_tags.c2
-rw-r--r--mm/kasan/kasan.h15
2 files changed, 1 insertions, 16 deletions
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index 4ea8c368b5b8..2c6c6c6ddfa2 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -142,8 +142,6 @@ void kasan_init_hw_tags_cpu(void)
if (kasan_arg == KASAN_ARG_OFF)
return;
- hw_init_tags(KASAN_TAG_MAX);
-
/*
* Enable async mode only when explicitly requested through
* the command line.
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index d739cdd1621a..28a16b80bbef 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -3,6 +3,7 @@
#define __MM_KASAN_KASAN_H
#include <linux/kasan.h>
+#include <linux/kasan-tags.h>
#include <linux/kfence.h>
#include <linux/stackdepot.h>
@@ -51,16 +52,6 @@ extern bool kasan_flag_async __ro_after_init;
#define KASAN_MEMORY_PER_SHADOW_PAGE (KASAN_GRANULE_SIZE << PAGE_SHIFT)
-#define KASAN_TAG_KERNEL 0xFF /* native kernel pointers tag */
-#define KASAN_TAG_INVALID 0xFE /* inaccessible memory tag */
-#define KASAN_TAG_MAX 0xFD /* maximum value for random tags */
-
-#ifdef CONFIG_KASAN_HW_TAGS
-#define KASAN_TAG_MIN 0xF0 /* minimum value for random tags */
-#else
-#define KASAN_TAG_MIN 0x00 /* minimum value for random tags */
-#endif
-
#ifdef CONFIG_KASAN_GENERIC
#define KASAN_FREE_PAGE 0xFF /* page was freed */
#define KASAN_PAGE_REDZONE 0xFE /* redzone for kmalloc_large allocations */
@@ -299,9 +290,6 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
#ifndef arch_enable_tagging_async
#define arch_enable_tagging_async()
#endif
-#ifndef arch_init_tags
-#define arch_init_tags(max_tag)
-#endif
#ifndef arch_set_tagging_report_once
#define arch_set_tagging_report_once(state)
#endif
@@ -320,7 +308,6 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
#define hw_enable_tagging_sync() arch_enable_tagging_sync()
#define hw_enable_tagging_async() arch_enable_tagging_async()
-#define hw_init_tags(max_tag) arch_init_tags(max_tag)
#define hw_set_tagging_report_once(state) arch_set_tagging_report_once(state)
#define hw_force_async_tag_fault() arch_force_async_tag_fault()
#define hw_get_random_tag() arch_get_random_tag()