root/arch/arm/include/asm/uaccess.h
/* SPDX-License-Identifier: GPL-2.0-only */
/*
 *  arch/arm/include/asm/uaccess.h
 */
#ifndef _ASMARM_UACCESS_H
#define _ASMARM_UACCESS_H

/*
 * User space memory access functions
 */
#include <linux/kernel.h>
#include <linux/string.h>
#include <asm/page.h>
#include <asm/domain.h>
#include <linux/unaligned.h>
#include <asm/unified.h>
#include <asm/pgtable.h>
#include <asm/proc-fns.h>
#include <asm/compiler.h>

#include <asm/extable.h>

/*
 * These two functions allow hooking accesses to userspace to increase
 * system integrity by ensuring that the kernel can not inadvertantly
 * perform such accesses (eg, via list poison values) which could then
 * be exploited for priviledge escalation.
 */
#if defined(CONFIG_CPU_SW_DOMAIN_PAN)

static __always_inline unsigned int uaccess_save_and_enable(void)
{
        unsigned int old_domain = get_domain();

        /* Set the current domain access to permit user accesses */
        set_domain((old_domain & ~domain_mask(DOMAIN_USER)) |
                   domain_val(DOMAIN_USER, DOMAIN_CLIENT));

        return old_domain;
}

static __always_inline void uaccess_restore(unsigned int flags)
{
        /* Restore the user access mask */
        set_domain(flags);
}

#elif defined(CONFIG_CPU_TTBR0_PAN)

static __always_inline unsigned int uaccess_save_and_enable(void)
{
        unsigned int old_ttbcr = cpu_get_ttbcr();

        /*
         * Enable TTBR0 page table walks (T0SZ = 0, EDP0 = 0) and ASID from
         * TTBR0 (A1 = 0).
         */
        cpu_set_ttbcr(old_ttbcr & ~(TTBCR_A1 | TTBCR_EPD0 | TTBCR_T0SZ_MASK));
        isb();

        return old_ttbcr;
}

static inline void uaccess_restore(unsigned int flags)
{
        cpu_set_ttbcr(flags);
        isb();
}

#else

static inline unsigned int uaccess_save_and_enable(void)
{
        return 0;
}

static inline void uaccess_restore(unsigned int flags)
{
}

#endif

/*
 * These two are intentionally not defined anywhere - if the kernel
 * code generates any references to them, that's a bug.
 */
extern int __get_user_bad(void);
extern int __put_user_bad(void);

#ifdef CONFIG_MMU

/*
 * This is a type: either unsigned long, if the argument fits into
 * that type, or otherwise unsigned long long.
 */
#define __inttype(x) \
        __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))

/*
 * Sanitise a uaccess pointer such that it becomes NULL if addr+size
 * is above the current addr_limit.
 */
#define uaccess_mask_range_ptr(ptr, size)                       \
        ((__typeof__(ptr))__uaccess_mask_range_ptr(ptr, size))
static inline void __user *__uaccess_mask_range_ptr(const void __user *ptr,
                                                    size_t size)
{
        void __user *safe_ptr = (void __user *)ptr;
        unsigned long tmp;

        asm volatile(
        "       .syntax unified\n"
        "       sub     %1, %3, #1\n"
        "       subs    %1, %1, %0\n"
        "       addhs   %1, %1, #1\n"
        "       subshs  %1, %1, %2\n"
        "       movlo   %0, #0\n"
        : "+r" (safe_ptr), "=&r" (tmp)
        : "r" (size), "r" (TASK_SIZE)
        : "cc");

        csdb();
        return safe_ptr;
}

/*
 * Single-value transfer routines.  They automatically use the right
 * size if we just have the right pointer type.  Note that the functions
 * which read from user space (*get_*) need to take care not to leak
 * kernel data even if the calling code is buggy and fails to check
 * the return value.  This means zeroing out the destination variable
 * or buffer on error.  Normally this is done out of line by the
 * fixup code, but there are a few places where it intrudes on the
 * main code path.  When we only write to user space, there is no
 * problem.
 */
extern int __get_user_1(void *);
extern int __get_user_2(void *);
extern int __get_user_4(void *);
extern int __get_user_32t_8(void *);
extern int __get_user_8(void *);
extern int __get_user_64t_1(void *);
extern int __get_user_64t_2(void *);
extern int __get_user_64t_4(void *);

#define __get_user_x(__r2, __p, __e, __l, __s)                          \
           __asm__ __volatile__ (                                       \
                __asmeq("%0", "r0") __asmeq("%1", "r2")                 \
                __asmeq("%3", "r1")                                     \
                "bl     __get_user_" #__s                               \
                : "=&r" (__e), "=r" (__r2)                              \
                : "0" (__p), "r" (__l)                                  \
                : "ip", "lr", "cc")

/* narrowing a double-word get into a single 32bit word register: */
#ifdef __ARMEB__
#define __get_user_x_32t(__r2, __p, __e, __l, __s)                      \
        __get_user_x(__r2, __p, __e, __l, 32t_8)
#else
#define __get_user_x_32t __get_user_x
#endif

/*
 * storing result into proper least significant word of 64bit target var,
 * different only for big endian case where 64 bit __r2 lsw is r3:
 */
#ifdef __ARMEB__
#define __get_user_x_64t(__r2, __p, __e, __l, __s)                      \
           __asm__ __volatile__ (                                       \
                __asmeq("%0", "r0") __asmeq("%1", "r2")                 \
                __asmeq("%3", "r1")                                     \
                "bl     __get_user_64t_" #__s                           \
                : "=&r" (__e), "=r" (__r2)                              \
                : "0" (__p), "r" (__l)                                  \
                : "ip", "lr", "cc")
#else
#define __get_user_x_64t __get_user_x
#endif


#define __get_user_check(x, p)                                          \
        ({                                                              \
                unsigned long __limit = TASK_SIZE - 1; \
                register typeof(*(p)) __user *__p asm("r0") = (p);      \
                register __inttype(x) __r2 asm("r2");                   \
                register unsigned long __l asm("r1") = __limit;         \
                register int __e asm("r0");                             \
                unsigned int __ua_flags = uaccess_save_and_enable();    \
                int __tmp_e;                                            \
                switch (sizeof(*(__p))) {                               \
                case 1:                                                 \
                        if (sizeof((x)) >= 8)                           \
                                __get_user_x_64t(__r2, __p, __e, __l, 1); \
                        else                                            \
                                __get_user_x(__r2, __p, __e, __l, 1);   \
                        break;                                          \
                case 2:                                                 \
                        if (sizeof((x)) >= 8)                           \
                                __get_user_x_64t(__r2, __p, __e, __l, 2); \
                        else                                            \
                                __get_user_x(__r2, __p, __e, __l, 2);   \
                        break;                                          \
                case 4:                                                 \
                        if (sizeof((x)) >= 8)                           \
                                __get_user_x_64t(__r2, __p, __e, __l, 4); \
                        else                                            \
                                __get_user_x(__r2, __p, __e, __l, 4);   \
                        break;                                          \
                case 8:                                                 \
                        if (sizeof((x)) < 8)                            \
                                __get_user_x_32t(__r2, __p, __e, __l, 4); \
                        else                                            \
                                __get_user_x(__r2, __p, __e, __l, 8);   \
                        break;                                          \
                default: __e = __get_user_bad(); break;                 \
                }                                                       \
                __tmp_e = __e;                                          \
                uaccess_restore(__ua_flags);                            \
                x = (typeof(*(p))) __r2;                                \
                __tmp_e;                                                \
        })

#define get_user(x, p)                                                  \
        ({                                                              \
                might_fault();                                          \
                __get_user_check(x, p);                                 \
         })

extern int __put_user_1(void *, unsigned int);
extern int __put_user_2(void *, unsigned int);
extern int __put_user_4(void *, unsigned int);
extern int __put_user_8(void *, unsigned long long);

#define __put_user_check(__pu_val, __ptr, __err, __s)                   \
        ({                                                              \
                unsigned long __limit = TASK_SIZE - 1; \
                register typeof(__pu_val) __r2 asm("r2") = __pu_val;    \
                register const void __user *__p asm("r0") = __ptr;      \
                register unsigned long __l asm("r1") = __limit;         \
                register int __e asm("r0");                             \
                __asm__ __volatile__ (                                  \
                        __asmeq("%0", "r0") __asmeq("%2", "r2")         \
                        __asmeq("%3", "r1")                             \
                        "bl     __put_user_" #__s                       \
                        : "=&r" (__e)                                   \
                        : "0" (__p), "r" (__r2), "r" (__l)              \
                        : "ip", "lr", "cc");                            \
                __err = __e;                                            \
        })

#else /* CONFIG_MMU */

#define get_user(x, p)  __get_user(x, p)
#define __put_user_check __put_user_nocheck

#endif /* CONFIG_MMU */

#include <asm-generic/access_ok.h>

#ifdef CONFIG_CPU_SPECTRE
/*
 * When mitigating Spectre variant 1, it is not worth fixing the non-
 * verifying accessors, because we need to add verification of the
 * address space there.  Force these to use the standard get_user()
 * version instead.
 */
#define __get_user(x, ptr) get_user(x, ptr)
#else

/*
 * 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.  Note that these
 * versions are void (ie, don't return a value as such).
 */
#define __get_user(x, ptr)                                              \
({                                                                      \
        long __gu_err = 0;                                              \
        __get_user_err((x), (ptr), __gu_err, TUSER());                  \
        __gu_err;                                                       \
})

/*
 * This is a type: either unsigned long, if the argument fits into
 * that type, or otherwise unsigned long long.
 */
#define __long_type(x) \
        __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))

#define __get_user_err(x, ptr, err, __t)                                \
do {                                                                    \
        unsigned long __gu_addr = (unsigned long)(ptr);                 \
        __long_type(x) __gu_val;                                        \
        unsigned int __ua_flags;                                        \
        __chk_user_ptr(ptr);                                            \
        might_fault();                                                  \
        __ua_flags = uaccess_save_and_enable();                         \
        switch (sizeof(*(ptr))) {                                       \
        case 1: __get_user_asm_byte(__gu_val, __gu_addr, err, __t); break;      \
        case 2: __get_user_asm_half(__gu_val, __gu_addr, err, __t); break;      \
        case 4: __get_user_asm_word(__gu_val, __gu_addr, err, __t); break;      \
        case 8: __get_user_asm_dword(__gu_val, __gu_addr, err, __t); break;     \
        default: (__gu_val) = __get_user_bad();                         \
        }                                                               \
        uaccess_restore(__ua_flags);                                    \
        (x) = (__typeof__(*(ptr)))__gu_val;                             \
} while (0)
#endif

#define __get_user_asm(x, addr, err, instr)                     \
        __asm__ __volatile__(                                   \
        "1:     " instr " %1, [%2], #0\n"                       \
        "2:\n"                                                  \
        "       .pushsection .text.fixup,\"ax\"\n"              \
        "       .align  2\n"                                    \
        "3:     mov     %0, %3\n"                               \
        "       mov     %1, #0\n"                               \
        "       b       2b\n"                                   \
        "       .popsection\n"                                  \
        "       .pushsection __ex_table,\"a\"\n"                \
        "       .align  3\n"                                    \
        "       .long   1b, 3b\n"                               \
        "       .popsection"                                    \
        : "+r" (err), "=&r" (x)                                 \
        : "r" (addr), "i" (-EFAULT)                             \
        : "cc")

#define __get_user_asm_byte(x, addr, err, __t)                  \
        __get_user_asm(x, addr, err, "ldrb" __t)

#if __LINUX_ARM_ARCH__ >= 6

#define __get_user_asm_half(x, addr, err, __t)                  \
        __get_user_asm(x, addr, err, "ldrh" __t)

#else

#ifndef __ARMEB__
#define __get_user_asm_half(x, __gu_addr, err, __t)             \
({                                                              \
        unsigned long __b1, __b2;                               \
        __get_user_asm_byte(__b1, __gu_addr, err, __t);         \
        __get_user_asm_byte(__b2, __gu_addr + 1, err, __t);     \
        (x) = __b1 | (__b2 << 8);                               \
})
#else
#define __get_user_asm_half(x, __gu_addr, err, __t)             \
({                                                              \
        unsigned long __b1, __b2;                               \
        __get_user_asm_byte(__b1, __gu_addr, err, __t);         \
        __get_user_asm_byte(__b2, __gu_addr + 1, err, __t);     \
        (x) = (__b1 << 8) | __b2;                               \
})
#endif

#endif /* __LINUX_ARM_ARCH__ >= 6 */

#define __get_user_asm_word(x, addr, err, __t)                  \
        __get_user_asm(x, addr, err, "ldr" __t)

#ifdef __ARMEB__
#define __WORD0_OFFS    4
#define __WORD1_OFFS    0
#else
#define __WORD0_OFFS    0
#define __WORD1_OFFS    4
#endif

#define __get_user_asm_dword(x, addr, err, __t)                         \
        ({                                                              \
        unsigned long __w0, __w1;                                       \
        __get_user_asm(__w0, addr + __WORD0_OFFS, err, "ldr" __t);      \
        __get_user_asm(__w1, addr + __WORD1_OFFS, err, "ldr" __t);      \
        (x) = ((u64)__w1 << 32) | (u64) __w0;                           \
})

#define __put_user_switch(x, ptr, __err, __fn)                          \
        do {                                                            \
                const __typeof__(*(ptr)) __user *__pu_ptr = (ptr);      \
                __typeof__(*(ptr)) __pu_val = (x);                      \
                unsigned int __ua_flags;                                \
                might_fault();                                          \
                __ua_flags = uaccess_save_and_enable();                 \
                switch (sizeof(*(ptr))) {                               \
                case 1: __fn(__pu_val, __pu_ptr, __err, 1); break;      \
                case 2: __fn(__pu_val, __pu_ptr, __err, 2); break;      \
                case 4: __fn(__pu_val, __pu_ptr, __err, 4); break;      \
                case 8: __fn(__pu_val, __pu_ptr, __err, 8); break;      \
                default: __err = __put_user_bad(); break;               \
                }                                                       \
                uaccess_restore(__ua_flags);                            \
        } while (0)

#define put_user(x, ptr)                                                \
({                                                                      \
        int __pu_err = 0;                                               \
        __put_user_switch((x), (ptr), __pu_err, __put_user_check);      \
        __pu_err;                                                       \
})

#ifdef CONFIG_CPU_SPECTRE
/*
 * When mitigating Spectre variant 1.1, all accessors need to include
 * verification of the address space.
 */
#define __put_user(x, ptr) put_user(x, ptr)

#else
#define __put_user(x, ptr)                                              \
({                                                                      \
        long __pu_err = 0;                                              \
        __put_user_switch((x), (ptr), __pu_err, __put_user_nocheck);    \
        __pu_err;                                                       \
})

#define __put_user_nocheck(x, __pu_ptr, __err, __size)                  \
        do {                                                            \
                unsigned long __pu_addr = (unsigned long)__pu_ptr;      \
                __put_user_nocheck_##__size(x, __pu_addr, __err, TUSER());\
        } while (0)

#define __put_user_nocheck_1 __put_user_asm_byte
#define __put_user_nocheck_2 __put_user_asm_half
#define __put_user_nocheck_4 __put_user_asm_word
#define __put_user_nocheck_8 __put_user_asm_dword

#endif /* !CONFIG_CPU_SPECTRE */

#define __put_user_asm(x, __pu_addr, err, instr)                \
        __asm__ __volatile__(                                   \
        "1:     " instr " %1, [%2], #0\n"               \
        "2:\n"                                                  \
        "       .pushsection .text.fixup,\"ax\"\n"              \
        "       .align  2\n"                                    \
        "3:     mov     %0, %3\n"                               \
        "       b       2b\n"                                   \
        "       .popsection\n"                                  \
        "       .pushsection __ex_table,\"a\"\n"                \
        "       .align  3\n"                                    \
        "       .long   1b, 3b\n"                               \
        "       .popsection"                                    \
        : "+r" (err)                                            \
        : "r" (x), "r" (__pu_addr), "i" (-EFAULT)               \
        : "cc")

#define __put_user_asm_byte(x, __pu_addr, err, __t)             \
        __put_user_asm(x, __pu_addr, err, "strb" __t)

#if __LINUX_ARM_ARCH__ >= 6

#define __put_user_asm_half(x, __pu_addr, err, __t)             \
        __put_user_asm(x, __pu_addr, err, "strh" __t)

#else

#ifndef __ARMEB__
#define __put_user_asm_half(x, __pu_addr, err, __t)             \
({                                                              \
        unsigned long __temp = (__force unsigned long)(x);      \
        __put_user_asm_byte(__temp, __pu_addr, err, __t);       \
        __put_user_asm_byte(__temp >> 8, __pu_addr + 1, err, __t);\
})
#else
#define __put_user_asm_half(x, __pu_addr, err, __t)             \
({                                                              \
        unsigned long __temp = (__force unsigned long)(x);      \
        __put_user_asm_byte(__temp >> 8, __pu_addr, err, __t);  \
        __put_user_asm_byte(__temp, __pu_addr + 1, err, __t);   \
})
#endif

#endif /* __LINUX_ARM_ARCH__ >= 6 */

#define __put_user_asm_word(x, __pu_addr, err, __t)             \
        __put_user_asm(x, __pu_addr, err, "str" __t)

#ifndef __ARMEB__
#define __reg_oper0     "%R2"
#define __reg_oper1     "%Q2"
#else
#define __reg_oper0     "%Q2"
#define __reg_oper1     "%R2"
#endif

#define __put_user_asm_dword(x, __pu_addr, err, __t)            \
        __asm__ __volatile__(                                   \
 ARM(   "1:     str" __t "      " __reg_oper1 ", [%1], #4\n"  ) \
 ARM(   "2:     str" __t "      " __reg_oper0 ", [%1]\n"      ) \
 THUMB( "1:     str" __t "      " __reg_oper1 ", [%1]\n"      ) \
 THUMB( "2:     str" __t "      " __reg_oper0 ", [%1, #4]\n"  ) \
        "3:\n"                                                  \
        "       .pushsection .text.fixup,\"ax\"\n"              \
        "       .align  2\n"                                    \
        "4:     mov     %0, %3\n"                               \
        "       b       3b\n"                                   \
        "       .popsection\n"                                  \
        "       .pushsection __ex_table,\"a\"\n"                \
        "       .align  3\n"                                    \
        "       .long   1b, 4b\n"                               \
        "       .long   2b, 4b\n"                               \
        "       .popsection"                                    \
        : "+r" (err), "+r" (__pu_addr)                          \
        : "r" (x), "i" (-EFAULT)                                \
        : "cc")

#define __get_kernel_nofault(dst, src, type, err_label)                 \
do {                                                                    \
        const type *__pk_ptr = (src);                                   \
        unsigned long __src = (unsigned long)(__pk_ptr);                \
        type __val;                                                     \
        int __err = 0;                                                  \
        switch (sizeof(type)) {                                         \
        case 1: __get_user_asm_byte(__val, __src, __err, ""); break;    \
        case 2: __get_user_asm_half(__val, __src, __err, ""); break;    \
        case 4: __get_user_asm_word(__val, __src, __err, ""); break;    \
        case 8: {                                                       \
                u32 *__v32 = (u32*)&__val;                              \
                __get_user_asm_word(__v32[0], __src, __err, "");        \
                if (__err)                                              \
                        break;                                          \
                __get_user_asm_word(__v32[1], __src+4, __err, "");      \
                break;                                                  \
        }                                                               \
        default: __err = __get_user_bad(); break;                       \
        }                                                               \
        if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))         \
                put_unaligned(__val, (type *)(dst));                    \
        else                                                            \
                *(type *)(dst) = __val; /* aligned by caller */         \
        if (__err)                                                      \
                goto err_label;                                         \
} while (0)

#define __put_kernel_nofault(dst, src, type, err_label)                 \
do {                                                                    \
        const type *__pk_ptr = (dst);                                   \
        unsigned long __dst = (unsigned long)__pk_ptr;                  \
        int __err = 0;                                                  \
        type __val = IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) \
                     ? get_unaligned((type *)(src))                     \
                     : *(type *)(src);  /* aligned by caller */         \
        switch (sizeof(type)) {                                         \
        case 1: __put_user_asm_byte(__val, __dst, __err, ""); break;    \
        case 2: __put_user_asm_half(__val, __dst, __err, ""); break;    \
        case 4: __put_user_asm_word(__val, __dst, __err, ""); break;    \
        case 8: __put_user_asm_dword(__val, __dst, __err, ""); break;   \
        default: __err = __put_user_bad(); break;                       \
        }                                                               \
        if (__err)                                                      \
                goto err_label;                                         \
} while (0)

#ifdef CONFIG_MMU
extern unsigned long __must_check
arm_copy_from_user(void *to, const void __user *from, unsigned long n);

static inline unsigned long __must_check
raw_copy_from_user(void *to, const void __user *from, unsigned long n)
{
        unsigned int __ua_flags;

        __ua_flags = uaccess_save_and_enable();
        n = arm_copy_from_user(to, from, n);
        uaccess_restore(__ua_flags);
        return n;
}

extern unsigned long __must_check
arm_copy_to_user(void __user *to, const void *from, unsigned long n);
extern unsigned long __must_check
__copy_to_user_std(void __user *to, const void *from, unsigned long n);

static inline unsigned long __must_check
raw_copy_to_user(void __user *to, const void *from, unsigned long n)
{
#ifndef CONFIG_UACCESS_WITH_MEMCPY
        unsigned int __ua_flags;
        __ua_flags = uaccess_save_and_enable();
        n = arm_copy_to_user(to, from, n);
        uaccess_restore(__ua_flags);
        return n;
#else
        return arm_copy_to_user(to, from, n);
#endif
}

extern unsigned long __must_check
arm_clear_user(void __user *addr, unsigned long n);
extern unsigned long __must_check
__clear_user_std(void __user *addr, unsigned long n);

static inline unsigned long __must_check
__clear_user(void __user *addr, unsigned long n)
{
        unsigned int __ua_flags = uaccess_save_and_enable();
        n = arm_clear_user(addr, n);
        uaccess_restore(__ua_flags);
        return n;
}

#else
static inline unsigned long
raw_copy_from_user(void *to, const void __user *from, unsigned long n)
{
        memcpy(to, (const void __force *)from, n);
        return 0;
}
static inline unsigned long
raw_copy_to_user(void __user *to, const void *from, unsigned long n)
{
        memcpy((void __force *)to, from, n);
        return 0;
}
#define __clear_user(addr, n)           (memset((void __force *)addr, 0, n), 0)
#endif
#define INLINE_COPY_TO_USER
#define INLINE_COPY_FROM_USER

static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
{
        if (access_ok(to, n))
                n = __clear_user(to, n);
        return n;
}

/* These are from lib/ code, and use __get_user() and friends */
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);

#endif /* _ASMARM_UACCESS_H */