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Diffstat (limited to 'arch/arm64/include/asm/uaccess.h')
| -rw-r--r-- | arch/arm64/include/asm/uaccess.h | 478 |
1 files changed, 478 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h new file mode 100644 index 000000000..5c7b2f9d5 --- /dev/null +++ b/arch/arm64/include/asm/uaccess.h @@ -0,0 +1,478 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Based on arch/arm/include/asm/uaccess.h + * + * Copyright (C) 2012 ARM Ltd. + */ +#ifndef __ASM_UACCESS_H +#define __ASM_UACCESS_H + +#include <asm/alternative.h> +#include <asm/kernel-pgtable.h> +#include <asm/sysreg.h> + +/* + * User space memory access functions + */ +#include <linux/bitops.h> +#include <linux/kasan-checks.h> +#include <linux/string.h> + +#include <asm/asm-extable.h> +#include <asm/cpufeature.h> +#include <asm/mmu.h> +#include <asm/mte.h> +#include <asm/ptrace.h> +#include <asm/memory.h> +#include <asm/extable.h> + +static inline int __access_ok(const void __user *ptr, unsigned long size); + +/* + * Test whether a block of memory is a valid user space address. + * Returns 1 if the range is valid, 0 otherwise. + * + * This is equivalent to the following test: + * (u65)addr + (u65)size <= (u65)TASK_SIZE_MAX + */ +static inline int access_ok(const void __user *addr, unsigned long size) +{ + /* + * Asynchronous I/O running in a kernel thread does not have the + * TIF_TAGGED_ADDR flag of the process owning the mm, so always untag + * the user address before checking. + */ + if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) && + (current->flags & PF_KTHREAD || test_thread_flag(TIF_TAGGED_ADDR))) + addr = untagged_addr(addr); + + return likely(__access_ok(addr, size)); +} +#define access_ok access_ok + +#include <asm-generic/access_ok.h> + +/* + * User access enabling/disabling. + */ +#ifdef CONFIG_ARM64_SW_TTBR0_PAN +static inline void __uaccess_ttbr0_disable(void) +{ + unsigned long flags, ttbr; + + local_irq_save(flags); + ttbr = read_sysreg(ttbr1_el1); + ttbr &= ~TTBR_ASID_MASK; + /* reserved_pg_dir placed before swapper_pg_dir */ + write_sysreg(ttbr - RESERVED_SWAPPER_OFFSET, ttbr0_el1); + isb(); + /* Set reserved ASID */ + write_sysreg(ttbr, ttbr1_el1); + isb(); + local_irq_restore(flags); +} + +static inline void __uaccess_ttbr0_enable(void) +{ + unsigned long flags, ttbr0, ttbr1; + + /* + * Disable interrupts to avoid preemption between reading the 'ttbr0' + * variable and the MSR. A context switch could trigger an ASID + * roll-over and an update of 'ttbr0'. + */ + local_irq_save(flags); + ttbr0 = READ_ONCE(current_thread_info()->ttbr0); + + /* Restore active ASID */ + ttbr1 = read_sysreg(ttbr1_el1); + ttbr1 &= ~TTBR_ASID_MASK; /* safety measure */ + ttbr1 |= ttbr0 & TTBR_ASID_MASK; + write_sysreg(ttbr1, ttbr1_el1); + isb(); + + /* Restore user page table */ + write_sysreg(ttbr0, ttbr0_el1); + isb(); + local_irq_restore(flags); +} + +static inline bool uaccess_ttbr0_disable(void) +{ + if (!system_uses_ttbr0_pan()) + return false; + __uaccess_ttbr0_disable(); + return true; +} + +static inline bool uaccess_ttbr0_enable(void) +{ + if (!system_uses_ttbr0_pan()) + return false; + __uaccess_ttbr0_enable(); + return true; +} +#else +static inline bool uaccess_ttbr0_disable(void) +{ + return false; +} + +static inline bool uaccess_ttbr0_enable(void) +{ + return false; +} +#endif + +static inline void __uaccess_disable_hw_pan(void) +{ + asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, + CONFIG_ARM64_PAN)); +} + +static inline void __uaccess_enable_hw_pan(void) +{ + asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, + CONFIG_ARM64_PAN)); +} + +/* + * The Tag Check Flag (TCF) mode for MTE is per EL, hence TCF0 + * affects EL0 and TCF affects EL1 irrespective of which TTBR is + * used. + * The kernel accesses TTBR0 usually with LDTR/STTR instructions + * when UAO is available, so these would act as EL0 accesses using + * TCF0. + * However futex.h code uses exclusives which would be executed as + * EL1, this can potentially cause a tag check fault even if the + * user disables TCF0. + * + * To address the problem we set the PSTATE.TCO bit in uaccess_enable() + * and reset it in uaccess_disable(). + * + * The Tag check override (TCO) bit disables temporarily the tag checking + * preventing the issue. + */ +static inline void __uaccess_disable_tco(void) +{ + asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(0), + ARM64_MTE, CONFIG_KASAN_HW_TAGS)); +} + +static inline void __uaccess_enable_tco(void) +{ + asm volatile(ALTERNATIVE("nop", SET_PSTATE_TCO(1), + ARM64_MTE, CONFIG_KASAN_HW_TAGS)); +} + +/* + * These functions disable tag checking only if in MTE async mode + * since the sync mode generates exceptions synchronously and the + * nofault or load_unaligned_zeropad can handle them. + */ +static inline void __uaccess_disable_tco_async(void) +{ + if (system_uses_mte_async_or_asymm_mode()) + __uaccess_disable_tco(); +} + +static inline void __uaccess_enable_tco_async(void) +{ + if (system_uses_mte_async_or_asymm_mode()) + __uaccess_enable_tco(); +} + +static inline void uaccess_disable_privileged(void) +{ + __uaccess_disable_tco(); + + if (uaccess_ttbr0_disable()) + return; + + __uaccess_enable_hw_pan(); +} + +static inline void uaccess_enable_privileged(void) +{ + __uaccess_enable_tco(); + + if (uaccess_ttbr0_enable()) + return; + + __uaccess_disable_hw_pan(); +} + +/* + * Sanitize a uaccess pointer such that it cannot reach any kernel address. + * + * Clearing bit 55 ensures the pointer cannot address any portion of the TTBR1 + * address range (i.e. any kernel address), and either the pointer falls within + * the TTBR0 address range or must cause a fault. + */ +#define uaccess_mask_ptr(ptr) (__typeof__(ptr))__uaccess_mask_ptr(ptr) +static inline void __user *__uaccess_mask_ptr(const void __user *ptr) +{ + void __user *safe_ptr; + + asm volatile( + " bic %0, %1, %2\n" + : "=r" (safe_ptr) + : "r" (ptr), + "i" (BIT(55)) + ); + + return safe_ptr; +} + +/* + * The "__xxx" versions of the user access functions do not verify the address + * space - it must have been done previously with a separate "access_ok()" + * call. + * + * The "__xxx_error" versions set the third argument to -EFAULT if an error + * occurs, and leave it unchanged on success. + */ +#define __get_mem_asm(load, reg, x, addr, err, type) \ + asm volatile( \ + "1: " load " " reg "1, [%2]\n" \ + "2:\n" \ + _ASM_EXTABLE_##type##ACCESS_ERR_ZERO(1b, 2b, %w0, %w1) \ + : "+r" (err), "=&r" (x) \ + : "r" (addr)) + +#define __raw_get_mem(ldr, x, ptr, err, type) \ +do { \ + unsigned long __gu_val; \ + switch (sizeof(*(ptr))) { \ + case 1: \ + __get_mem_asm(ldr "b", "%w", __gu_val, (ptr), (err), type); \ + break; \ + case 2: \ + __get_mem_asm(ldr "h", "%w", __gu_val, (ptr), (err), type); \ + break; \ + case 4: \ + __get_mem_asm(ldr, "%w", __gu_val, (ptr), (err), type); \ + break; \ + case 8: \ + __get_mem_asm(ldr, "%x", __gu_val, (ptr), (err), type); \ + break; \ + default: \ + BUILD_BUG(); \ + } \ + (x) = (__force __typeof__(*(ptr)))__gu_val; \ +} while (0) + +/* + * We must not call into the scheduler between uaccess_ttbr0_enable() and + * uaccess_ttbr0_disable(). As `x` and `ptr` could contain blocking functions, + * we must evaluate these outside of the critical section. + */ +#define __raw_get_user(x, ptr, err) \ +do { \ + __typeof__(*(ptr)) __user *__rgu_ptr = (ptr); \ + __typeof__(x) __rgu_val; \ + __chk_user_ptr(ptr); \ + \ + uaccess_ttbr0_enable(); \ + __raw_get_mem("ldtr", __rgu_val, __rgu_ptr, err, U); \ + uaccess_ttbr0_disable(); \ + \ + (x) = __rgu_val; \ +} while (0) + +#define __get_user_error(x, ptr, err) \ +do { \ + __typeof__(*(ptr)) __user *__p = (ptr); \ + might_fault(); \ + if (access_ok(__p, sizeof(*__p))) { \ + __p = uaccess_mask_ptr(__p); \ + __raw_get_user((x), __p, (err)); \ + } else { \ + (x) = (__force __typeof__(x))0; (err) = -EFAULT; \ + } \ +} while (0) + +#define __get_user(x, ptr) \ +({ \ + int __gu_err = 0; \ + __get_user_error((x), (ptr), __gu_err); \ + __gu_err; \ +}) + +#define get_user __get_user + +/* + * We must not call into the scheduler between __uaccess_enable_tco_async() and + * __uaccess_disable_tco_async(). As `dst` and `src` may contain blocking + * functions, we must evaluate these outside of the critical section. + */ +#define __get_kernel_nofault(dst, src, type, err_label) \ +do { \ + __typeof__(dst) __gkn_dst = (dst); \ + __typeof__(src) __gkn_src = (src); \ + int __gkn_err = 0; \ + \ + __uaccess_enable_tco_async(); \ + __raw_get_mem("ldr", *((type *)(__gkn_dst)), \ + (__force type *)(__gkn_src), __gkn_err, K); \ + __uaccess_disable_tco_async(); \ + \ + if (unlikely(__gkn_err)) \ + goto err_label; \ +} while (0) + +#define __put_mem_asm(store, reg, x, addr, err, type) \ + asm volatile( \ + "1: " store " " reg "1, [%2]\n" \ + "2:\n" \ + _ASM_EXTABLE_##type##ACCESS_ERR(1b, 2b, %w0) \ + : "+r" (err) \ + : "r" (x), "r" (addr)) + +#define __raw_put_mem(str, x, ptr, err, type) \ +do { \ + __typeof__(*(ptr)) __pu_val = (x); \ + switch (sizeof(*(ptr))) { \ + case 1: \ + __put_mem_asm(str "b", "%w", __pu_val, (ptr), (err), type); \ + break; \ + case 2: \ + __put_mem_asm(str "h", "%w", __pu_val, (ptr), (err), type); \ + break; \ + case 4: \ + __put_mem_asm(str, "%w", __pu_val, (ptr), (err), type); \ + break; \ + case 8: \ + __put_mem_asm(str, "%x", __pu_val, (ptr), (err), type); \ + break; \ + default: \ + BUILD_BUG(); \ + } \ +} while (0) + +/* + * We must not call into the scheduler between uaccess_ttbr0_enable() and + * uaccess_ttbr0_disable(). As `x` and `ptr` could contain blocking functions, + * we must evaluate these outside of the critical section. + */ +#define __raw_put_user(x, ptr, err) \ +do { \ + __typeof__(*(ptr)) __user *__rpu_ptr = (ptr); \ + __typeof__(*(ptr)) __rpu_val = (x); \ + __chk_user_ptr(__rpu_ptr); \ + \ + uaccess_ttbr0_enable(); \ + __raw_put_mem("sttr", __rpu_val, __rpu_ptr, err, U); \ + uaccess_ttbr0_disable(); \ +} while (0) + +#define __put_user_error(x, ptr, err) \ +do { \ + __typeof__(*(ptr)) __user *__p = (ptr); \ + might_fault(); \ + if (access_ok(__p, sizeof(*__p))) { \ + __p = uaccess_mask_ptr(__p); \ + __raw_put_user((x), __p, (err)); \ + } else { \ + (err) = -EFAULT; \ + } \ +} while (0) + +#define __put_user(x, ptr) \ +({ \ + int __pu_err = 0; \ + __put_user_error((x), (ptr), __pu_err); \ + __pu_err; \ +}) + +#define put_user __put_user + +/* + * We must not call into the scheduler between __uaccess_enable_tco_async() and + * __uaccess_disable_tco_async(). As `dst` and `src` may contain blocking + * functions, we must evaluate these outside of the critical section. + */ +#define __put_kernel_nofault(dst, src, type, err_label) \ +do { \ + __typeof__(dst) __pkn_dst = (dst); \ + __typeof__(src) __pkn_src = (src); \ + int __pkn_err = 0; \ + \ + __uaccess_enable_tco_async(); \ + __raw_put_mem("str", *((type *)(__pkn_src)), \ + (__force type *)(__pkn_dst), __pkn_err, K); \ + __uaccess_disable_tco_async(); \ + \ + if (unlikely(__pkn_err)) \ + goto err_label; \ +} while(0) + +extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n); +#define raw_copy_from_user(to, from, n) \ +({ \ + unsigned long __acfu_ret; \ + uaccess_ttbr0_enable(); \ + __acfu_ret = __arch_copy_from_user((to), \ + __uaccess_mask_ptr(from), (n)); \ + uaccess_ttbr0_disable(); \ + __acfu_ret; \ +}) + +extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n); +#define raw_copy_to_user(to, from, n) \ +({ \ + unsigned long __actu_ret; \ + uaccess_ttbr0_enable(); \ + __actu_ret = __arch_copy_to_user(__uaccess_mask_ptr(to), \ + (from), (n)); \ + uaccess_ttbr0_disable(); \ + __actu_ret; \ +}) + +#define INLINE_COPY_TO_USER +#define INLINE_COPY_FROM_USER + +extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n); +static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n) +{ + if (access_ok(to, n)) { + uaccess_ttbr0_enable(); + n = __arch_clear_user(__uaccess_mask_ptr(to), n); + uaccess_ttbr0_disable(); + } + return n; +} +#define clear_user __clear_user + +extern long strncpy_from_user(char *dest, const char __user *src, long count); + +extern __must_check long strnlen_user(const char __user *str, long n); + +#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE +struct page; +void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len); +extern unsigned long __must_check __copy_user_flushcache(void *to, const void __user *from, unsigned long n); + +static inline int __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size) +{ + kasan_check_write(dst, size); + return __copy_user_flushcache(dst, __uaccess_mask_ptr(src), size); +} +#endif + +#ifdef CONFIG_ARCH_HAS_SUBPAGE_FAULTS + +/* + * Return 0 on success, the number of bytes not probed otherwise. + */ +static inline size_t probe_subpage_writeable(const char __user *uaddr, + size_t size) +{ + if (!system_supports_mte()) + return 0; + return mte_probe_user_range(uaddr, size); +} + +#endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */ + +#endif /* __ASM_UACCESS_H */ |