8286824789
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>
135 lines
3.2 KiB
C
135 lines
3.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright (C) 2020 ARM Ltd.
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*/
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#ifndef __ASM_MTE_H
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#define __ASM_MTE_H
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#include <asm/compiler.h>
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#include <asm/mte-def.h>
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#ifndef __ASSEMBLY__
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#include <linux/bitfield.h>
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#include <linux/page-flags.h>
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#include <linux/types.h>
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#include <asm/pgtable-types.h>
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void mte_clear_page_tags(void *addr);
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unsigned long mte_copy_tags_from_user(void *to, const void __user *from,
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unsigned long n);
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unsigned long mte_copy_tags_to_user(void __user *to, void *from,
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unsigned long n);
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int mte_save_tags(struct page *page);
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void mte_save_page_tags(const void *page_addr, void *tag_storage);
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bool mte_restore_tags(swp_entry_t entry, struct page *page);
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void mte_restore_page_tags(void *page_addr, const void *tag_storage);
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void mte_invalidate_tags(int type, pgoff_t offset);
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void mte_invalidate_tags_area(int type);
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void *mte_allocate_tag_storage(void);
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void mte_free_tag_storage(char *storage);
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#ifdef CONFIG_ARM64_MTE
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/* track which pages have valid allocation tags */
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#define PG_mte_tagged PG_arch_2
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void mte_zero_clear_page_tags(void *addr);
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void mte_sync_tags(pte_t old_pte, pte_t pte);
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void mte_copy_page_tags(void *kto, const void *kfrom);
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void mte_thread_init_user(void);
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void mte_thread_switch(struct task_struct *next);
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void mte_suspend_enter(void);
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long set_mte_ctrl(struct task_struct *task, unsigned long arg);
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long get_mte_ctrl(struct task_struct *task);
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int mte_ptrace_copy_tags(struct task_struct *child, long request,
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unsigned long addr, unsigned long data);
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#else /* CONFIG_ARM64_MTE */
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/* unused if !CONFIG_ARM64_MTE, silence the compiler */
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#define PG_mte_tagged 0
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static inline void mte_zero_clear_page_tags(void *addr)
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{
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}
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static inline void mte_sync_tags(pte_t old_pte, pte_t pte)
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{
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}
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static inline void mte_copy_page_tags(void *kto, const void *kfrom)
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{
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}
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static inline void mte_thread_init_user(void)
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{
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}
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static inline void mte_thread_switch(struct task_struct *next)
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{
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}
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static inline void mte_suspend_enter(void)
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{
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}
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static inline long set_mte_ctrl(struct task_struct *task, unsigned long arg)
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{
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return 0;
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}
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static inline long get_mte_ctrl(struct task_struct *task)
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{
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return 0;
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}
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static inline int mte_ptrace_copy_tags(struct task_struct *child,
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long request, unsigned long addr,
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unsigned long data)
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{
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return -EIO;
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}
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#endif /* CONFIG_ARM64_MTE */
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#ifdef CONFIG_KASAN_HW_TAGS
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/* Whether the MTE asynchronous mode is enabled. */
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DECLARE_STATIC_KEY_FALSE(mte_async_mode);
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static inline bool system_uses_mte_async_mode(void)
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{
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return static_branch_unlikely(&mte_async_mode);
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}
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void mte_check_tfsr_el1(void);
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static inline void mte_check_tfsr_entry(void)
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{
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mte_check_tfsr_el1();
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}
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static inline void mte_check_tfsr_exit(void)
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{
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/*
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* The asynchronous faults are sync'ed automatically with
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* TFSR_EL1 on kernel entry but for exit an explicit dsb()
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* is required.
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*/
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dsb(nsh);
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isb();
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mte_check_tfsr_el1();
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}
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#else
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static inline bool system_uses_mte_async_mode(void)
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{
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return false;
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}
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static inline void mte_check_tfsr_el1(void)
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{
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}
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static inline void mte_check_tfsr_entry(void)
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{
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}
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static inline void mte_check_tfsr_exit(void)
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{
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}
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#endif /* CONFIG_KASAN_HW_TAGS */
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#endif /* __ASSEMBLY__ */
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#endif /* __ASM_MTE_H */
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