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From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, andreyknvl@google.com,
	aryabinin@virtuozzo.com, Branislav.Rankov@arm.com,
	catalin.marinas@arm.com, dvyukov@google.com, elver@google.com,
	eugenis@google.com, glider@google.com, gor@linux.ibm.com,
	kevin.brodsky@arm.com, linux-mm@kvack.org,
	mm-commits@vger.kernel.org, torvalds@linux-foundation.org,
	vincenzo.frascino@arm.com, will.deacon@arm.com
Subject: [patch 42/78] arm64: mte: switch GCR_EL1 in kernel entry and exit
Date: Fri, 18 Dec 2020 14:03:43 -0800
Message-ID: <20201218220343.7OU5VdVs1%akpm@linux-foundation.org> (raw)
In-Reply-To: <20201218140046.497484741326828e5b5d46ec@linux-foundation.org>

From: Vincenzo Frascino <vincenzo.frascino@arm.com>
Subject: arm64: mte: switch GCR_EL1 in kernel entry and exit

When MTE is present, the GCR_EL1 register contains the tags mask that
allows to exclude tags from the random generation via the IRG instruction.

With the introduction of the new Tag-Based KASAN API that provides a
mechanism to reserve tags for special reasons, the MTE implementation has
to make sure that the GCR_EL1 setting for the kernel does not affect the
userspace processes and viceversa.

Save and restore the kernel/user mask in GCR_EL1 in kernel entry and exit.

Link: https://lkml.kernel.org/r/578b03294708cc7258fad0dc9c2a2e809e5a8214.1606161801.git.andreyknvl@google.com
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Co-developed-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Marco Elver <elver@google.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/arm64/include/asm/mte-def.h   |    1 
 arch/arm64/include/asm/mte-kasan.h |    5 +++
 arch/arm64/include/asm/mte.h       |    2 +
 arch/arm64/kernel/asm-offsets.c    |    3 +
 arch/arm64/kernel/entry.S          |   41 +++++++++++++++++++++++++++
 arch/arm64/kernel/mte.c            |   31 ++++++++++++++++++--
 6 files changed, 79 insertions(+), 4 deletions(-)

--- a/arch/arm64/include/asm/mte-def.h~arm64-mte-switch-gcr_el1-in-kernel-entry-and-exit
+++ a/arch/arm64/include/asm/mte-def.h
@@ -10,6 +10,5 @@
 #define MTE_TAG_SHIFT		56
 #define MTE_TAG_SIZE		4
 #define MTE_TAG_MASK		GENMASK((MTE_TAG_SHIFT + (MTE_TAG_SIZE - 1)), MTE_TAG_SHIFT)
-#define MTE_TAG_MAX		(MTE_TAG_MASK >> MTE_TAG_SHIFT)
 
 #endif /* __ASM_MTE_DEF_H  */
--- a/arch/arm64/include/asm/mte.h~arm64-mte-switch-gcr_el1-in-kernel-entry-and-exit
+++ a/arch/arm64/include/asm/mte.h
@@ -18,6 +18,8 @@
 
 #include <asm/pgtable-types.h>
 
+extern u64 gcr_kernel_excl;
+
 void mte_clear_page_tags(void *addr);
 unsigned long mte_copy_tags_from_user(void *to, const void __user *from,
 				      unsigned long n);
--- a/arch/arm64/include/asm/mte-kasan.h~arm64-mte-switch-gcr_el1-in-kernel-entry-and-exit
+++ a/arch/arm64/include/asm/mte-kasan.h
@@ -30,6 +30,7 @@ u8 mte_get_random_tag(void);
 void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag);
 
 void mte_enable_kernel(void);
+void mte_init_tags(u64 max_tag);
 
 #else /* CONFIG_ARM64_MTE */
 
@@ -55,6 +56,10 @@ static inline void mte_enable_kernel(voi
 {
 }
 
+static inline void mte_init_tags(u64 max_tag)
+{
+}
+
 #endif /* CONFIG_ARM64_MTE */
 
 #endif /* __ASSEMBLY__ */
--- a/arch/arm64/kernel/asm-offsets.c~arm64-mte-switch-gcr_el1-in-kernel-entry-and-exit
+++ a/arch/arm64/kernel/asm-offsets.c
@@ -47,6 +47,9 @@ int main(void)
   DEFINE(THREAD_KEYS_USER,	offsetof(struct task_struct, thread.keys_user));
   DEFINE(THREAD_KEYS_KERNEL,	offsetof(struct task_struct, thread.keys_kernel));
 #endif
+#ifdef CONFIG_ARM64_MTE
+  DEFINE(THREAD_GCR_EL1_USER,	offsetof(struct task_struct, thread.gcr_user_excl));
+#endif
   BLANK();
   DEFINE(S_X0,			offsetof(struct pt_regs, regs[0]));
   DEFINE(S_X2,			offsetof(struct pt_regs, regs[2]));
--- a/arch/arm64/kernel/entry.S~arm64-mte-switch-gcr_el1-in-kernel-entry-and-exit
+++ a/arch/arm64/kernel/entry.S
@@ -173,6 +173,43 @@ alternative_else_nop_endif
 #endif
 	.endm
 
+	.macro mte_set_gcr, tmp, tmp2
+#ifdef CONFIG_ARM64_MTE
+	/*
+	 * Calculate and set the exclude mask preserving
+	 * the RRND (bit[16]) setting.
+	 */
+	mrs_s	\tmp2, SYS_GCR_EL1
+	bfi	\tmp2, \tmp, #0, #16
+	msr_s	SYS_GCR_EL1, \tmp2
+	isb
+#endif
+	.endm
+
+	.macro mte_set_kernel_gcr, tmp, tmp2
+#ifdef CONFIG_KASAN_HW_TAGS
+alternative_if_not ARM64_MTE
+	b	1f
+alternative_else_nop_endif
+	ldr_l	\tmp, gcr_kernel_excl
+
+	mte_set_gcr \tmp, \tmp2
+1:
+#endif
+	.endm
+
+	.macro mte_set_user_gcr, tsk, tmp, tmp2
+#ifdef CONFIG_ARM64_MTE
+alternative_if_not ARM64_MTE
+	b	1f
+alternative_else_nop_endif
+	ldr	\tmp, [\tsk, #THREAD_GCR_EL1_USER]
+
+	mte_set_gcr \tmp, \tmp2
+1:
+#endif
+	.endm
+
 	.macro	kernel_entry, el, regsize = 64
 	.if	\regsize == 32
 	mov	w0, w0				// zero upper 32 bits of x0
@@ -212,6 +249,8 @@ alternative_else_nop_endif
 
 	ptrauth_keys_install_kernel tsk, x20, x22, x23
 
+	mte_set_kernel_gcr x22, x23
+
 	scs_load tsk, x20
 	.else
 	add	x21, sp, #S_FRAME_SIZE
@@ -315,6 +354,8 @@ alternative_else_nop_endif
 	/* No kernel C function calls after this as user keys are set. */
 	ptrauth_keys_install_user tsk, x0, x1, x2
 
+	mte_set_user_gcr tsk, x0, x1
+
 	apply_ssbd 0, x0, x1
 	.endif
 
--- a/arch/arm64/kernel/mte.c~arm64-mte-switch-gcr_el1-in-kernel-entry-and-exit
+++ a/arch/arm64/kernel/mte.c
@@ -23,6 +23,8 @@
 #include <asm/ptrace.h>
 #include <asm/sysreg.h>
 
+u64 gcr_kernel_excl __ro_after_init;
+
 static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap)
 {
 	pte_t old_pte = READ_ONCE(*ptep);
@@ -129,6 +131,26 @@ void *mte_set_mem_tag_range(void *addr,
 	return ptr;
 }
 
+void mte_init_tags(u64 max_tag)
+{
+	static bool gcr_kernel_excl_initialized;
+
+	if (!gcr_kernel_excl_initialized) {
+		/*
+		 * The format of the tags in KASAN is 0xFF and in MTE is 0xF.
+		 * This conversion extracts an MTE tag from a KASAN tag.
+		 */
+		u64 incl = GENMASK(FIELD_GET(MTE_TAG_MASK >> MTE_TAG_SHIFT,
+					     max_tag), 0);
+
+		gcr_kernel_excl = ~incl & SYS_GCR_EL1_EXCL_MASK;
+		gcr_kernel_excl_initialized = true;
+	}
+
+	/* Enable the kernel exclude mask for random tags generation. */
+	write_sysreg_s(SYS_GCR_EL1_RRND | gcr_kernel_excl, SYS_GCR_EL1);
+}
+
 void mte_enable_kernel(void)
 {
 	/* Enable MTE Sync Mode for EL1. */
@@ -171,7 +193,11 @@ static void update_gcr_el1_excl(u64 excl
 static void set_gcr_el1_excl(u64 excl)
 {
 	current->thread.gcr_user_excl = excl;
-	update_gcr_el1_excl(excl);
+
+	/*
+	 * SYS_GCR_EL1 will be set to current->thread.gcr_user_excl value
+	 * by mte_set_user_gcr() in kernel_exit,
+	 */
 }
 
 void flush_mte_state(void)
@@ -197,7 +223,6 @@ void mte_thread_switch(struct task_struc
 	/* avoid expensive SCTLR_EL1 accesses if no change */
 	if (current->thread.sctlr_tcf0 != next->thread.sctlr_tcf0)
 		update_sctlr_el1_tcf0(next->thread.sctlr_tcf0);
-	update_gcr_el1_excl(next->thread.gcr_user_excl);
 }
 
 void mte_suspend_exit(void)
@@ -205,7 +230,7 @@ void mte_suspend_exit(void)
 	if (!system_supports_mte())
 		return;
 
-	update_gcr_el1_excl(current->thread.gcr_user_excl);
+	update_gcr_el1_excl(gcr_kernel_excl);
 }
 
 long set_mte_ctrl(struct task_struct *task, unsigned long arg)
_

  parent reply index

Thread overview: 89+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-18 22:00 incoming Andrew Morton
2020-12-18 22:01 ` [patch 01/78] mm/memcg: bail early from swap accounting if memcg disabled Andrew Morton
2020-12-18 22:01 ` [patch 02/78] mm/memcg: warning on !memcg after readahead page charged Andrew Morton
2020-12-18 22:01 ` [patch 03/78] mm/memcg: remove unused definitions Andrew Morton
2020-12-18 22:01 ` [patch 04/78] mm, kvm: account kvm_vcpu_mmap to kmemcg Andrew Morton
2020-12-18 22:01 ` [patch 05/78] mm/memcontrol:rewrite mem_cgroup_page_lruvec() Andrew Morton
2020-12-18 22:01 ` [patch 06/78] epoll: check for events when removing a timed out thread from the wait queue Andrew Morton
2020-12-18 22:01 ` [patch 07/78] epoll: simplify signal handling Andrew Morton
2020-12-18 22:01 ` [patch 08/78] epoll: pull fatal signal checks into ep_send_events() Andrew Morton
2020-12-18 22:01 ` [patch 09/78] epoll: move eavail next to the list_empty_careful check Andrew Morton
2020-12-18 22:01 ` [patch 10/78] epoll: simplify and optimize busy loop logic Andrew Morton
2020-12-18 22:02 ` [patch 11/78] epoll: pull all code between fetch_events and send_event into the loop Andrew Morton
2020-12-18 22:02 ` [patch 12/78] epoll: replace gotos with a proper loop Andrew Morton
2020-12-18 22:02 ` [patch 13/78] epoll: eliminate unnecessary lock for zero timeout Andrew Morton
2020-12-18 22:02 ` [patch 14/78] kasan: drop unnecessary GPL text from comment headers Andrew Morton
2020-12-18 22:02 ` [patch 15/78] kasan: KASAN_VMALLOC depends on KASAN_GENERIC Andrew Morton
2020-12-18 22:02 ` [patch 16/78] kasan: group vmalloc code Andrew Morton
2020-12-18 22:02 ` [patch 17/78] kasan: shadow declarations only for software modes Andrew Morton
2020-12-18 22:02 ` [patch 18/78] kasan: rename (un)poison_shadow to (un)poison_range Andrew Morton
2020-12-18 22:02 ` [patch 19/78] kasan: rename KASAN_SHADOW_* to KASAN_GRANULE_* Andrew Morton
2020-12-18 22:02 ` [patch 20/78] kasan: only build init.c for software modes Andrew Morton
2020-12-18 22:02 ` [patch 21/78] kasan: split out shadow.c from common.c Andrew Morton
2020-12-19  0:28   ` Marco Elver
2020-12-19  1:13     ` Andrew Morton
2020-12-19 10:01       ` Marco Elver
2020-12-19 10:11       ` Marco Elver
2020-12-19 18:01       ` Andrey Konovalov
2020-12-19 19:17       ` Linus Torvalds
2020-12-19 19:26         ` Linus Torvalds
2020-12-21  9:46         ` Alexander Potapenko
2020-12-21 17:41           ` Linus Torvalds
2020-12-22 18:38             ` Andrew Morton
2020-12-18 22:02 ` [patch 22/78] kasan: define KASAN_MEMORY_PER_SHADOW_PAGE Andrew Morton
2020-12-18 22:02 ` [patch 23/78] kasan: rename report and tags files Andrew Morton
2020-12-18 22:02 ` [patch 24/78] kasan: don't duplicate config dependencies Andrew Morton
2020-12-18 22:02 ` [patch 25/78] kasan: hide invalid free check implementation Andrew Morton
2020-12-18 22:02 ` [patch 26/78] kasan: decode stack frame only with KASAN_STACK_ENABLE Andrew Morton
2020-12-18 22:02 ` [patch 27/78] kasan, arm64: only init shadow for software modes Andrew Morton
2020-12-18 22:02 ` [patch 28/78] kasan, arm64: only use kasan_depth " Andrew Morton
2020-12-18 22:03 ` [patch 29/78] kasan, arm64: move initialization message Andrew Morton
2020-12-18 22:03 ` [patch 30/78] kasan, arm64: rename kasan_init_tags and mark as __init Andrew Morton
2020-12-18 22:03 ` [patch 31/78] kasan: rename addr_has_shadow to addr_has_metadata Andrew Morton
2020-12-18 22:03 ` [patch 32/78] kasan: rename print_shadow_for_address to print_memory_metadata Andrew Morton
2020-12-18 22:03 ` [patch 33/78] kasan: rename SHADOW layout macros to META Andrew Morton
2020-12-18 22:03 ` [patch 34/78] kasan: separate metadata_fetch_row for each mode Andrew Morton
2020-12-18 22:03 ` [patch 35/78] kasan: introduce CONFIG_KASAN_HW_TAGS Andrew Morton
2020-12-18 22:03 ` [patch 36/78] arm64: enable armv8.5-a asm-arch option Andrew Morton
2020-12-18 22:03 ` [patch 37/78] arm64: mte: add in-kernel MTE helpers Andrew Morton
2020-12-18 22:03 ` [patch 38/78] arm64: mte: reset the page tag in page->flags Andrew Morton
2020-12-18 22:03 ` [patch 39/78] arm64: mte: add in-kernel tag fault handler Andrew Morton
2020-12-18 22:03 ` [patch 40/78] arm64: kasan: allow enabling in-kernel MTE Andrew Morton
2020-12-18 22:03 ` [patch 41/78] arm64: mte: convert gcr_user into an exclude mask Andrew Morton
2020-12-18 22:03 ` Andrew Morton [this message]
2020-12-18 22:03 ` [patch 43/78] kasan, mm: untag page address in free_reserved_area Andrew Morton
2020-12-18 22:03 ` [patch 44/78] arm64: kasan: align allocations for HW_TAGS Andrew Morton
2020-12-18 22:03 ` [patch 45/78] arm64: kasan: add arch layer for memory tagging helpers Andrew Morton
2020-12-18 22:03 ` [patch 46/78] kasan: define KASAN_GRANULE_SIZE for HW_TAGS Andrew Morton
2020-12-18 22:03 ` [patch 47/78] kasan, x86, s390: update undef CONFIG_KASAN Andrew Morton
2020-12-18 22:04 ` [patch 48/78] kasan, arm64: expand CONFIG_KASAN checks Andrew Morton
2020-12-18 22:04 ` [patch 49/78] kasan, arm64: implement HW_TAGS runtime Andrew Morton
2020-12-18 22:04 ` [patch 50/78] kasan, arm64: print report from tag fault handler Andrew Morton
2020-12-18 22:04 ` [patch 51/78] kasan, mm: reset tags when accessing metadata Andrew Morton
2020-12-18 22:04 ` [patch 52/78] kasan, arm64: enable CONFIG_KASAN_HW_TAGS Andrew Morton
2020-12-18 22:04 ` [patch 53/78] kasan: add documentation for hardware tag-based mode Andrew Morton
2020-12-18 22:04 ` [patch 54/78] kselftest/arm64: check GCR_EL1 after context switch Andrew Morton
2020-12-18 22:04 ` [patch 55/78] kasan: simplify quarantine_put call site Andrew Morton
2020-12-18 22:04 ` [patch 56/78] kasan: rename get_alloc/free_info Andrew Morton
2020-12-18 22:04 ` [patch 57/78] kasan: introduce set_alloc_info Andrew Morton
2020-12-18 22:04 ` [patch 58/78] kasan, arm64: unpoison stack only with CONFIG_KASAN_STACK Andrew Morton
2020-12-18 22:04 ` [patch 59/78] kasan: allow VMAP_STACK for HW_TAGS mode Andrew Morton
2020-12-18 22:04 ` [patch 60/78] kasan: remove __kasan_unpoison_stack Andrew Morton
2020-12-18 22:04 ` [patch 61/78] kasan: inline kasan_reset_tag for tag-based modes Andrew Morton
2020-12-18 22:04 ` [patch 62/78] kasan: inline random_tag for HW_TAGS Andrew Morton
2020-12-18 22:04 ` [patch 63/78] kasan: open-code kasan_unpoison_slab Andrew Morton
2020-12-18 22:04 ` [patch 64/78] kasan: inline (un)poison_range and check_invalid_free Andrew Morton
2020-12-18 22:05 ` [patch 65/78] kasan: add and integrate kasan boot parameters Andrew Morton
2020-12-18 22:05 ` [patch 66/78] kasan, mm: check kasan_enabled in annotations Andrew Morton
2020-12-18 22:05 ` [patch 67/78] kasan, mm: rename kasan_poison_kfree Andrew Morton
2020-12-18 22:05 ` [patch 68/78] kasan: don't round_up too much Andrew Morton
2020-12-18 22:05 ` [patch 69/78] kasan: simplify assign_tag and set_tag calls Andrew Morton
2020-12-18 22:05 ` [patch 70/78] kasan: clarify comment in __kasan_kfree_large Andrew Morton
2020-12-18 22:05 ` [patch 71/78] kasan: sanitize objects when metadata doesn't fit Andrew Morton
2020-12-18 22:05 ` [patch 72/78] kasan, mm: allow cache merging with no metadata Andrew Morton
2020-12-18 22:05 ` [patch 73/78] kasan: update documentation Andrew Morton
2020-12-18 22:05 ` [patch 74/78] mm/Kconfig: fix spelling mistake "whats" -> "what's" Andrew Morton
2020-12-18 22:05 ` [patch 75/78] epoll: convert internal api to timespec64 Andrew Morton
2020-12-18 22:05 ` [patch 76/78] epoll: add syscall epoll_pwait2 Andrew Morton
2020-12-18 22:05 ` [patch 77/78] epoll: wire up " Andrew Morton
2020-12-18 22:05 ` [patch 78/78] selftests/filesystems: expand epoll with epoll_pwait2 Andrew Morton

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