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/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Copyright (C) 2026 Richard Qin */
#include <arch/extable.h>
/*
* extern "C" int __uaccess_memcpy(void* dst, const void* src, uint64 len);
*
* a0: dst
* a1: src
* a2: len
* Returns: 0 on success, -EFAULT (-14) on page fault.
*/
.global __uaccess_memcpy
.type __uaccess_memcpy, @function
__uaccess_memcpy:
/* If len == 0, return 0 */
beqz a2, .Lmemcpy_done
/* Enable SUM (Supervisor User Memory) bit: sstatus.SUM is bit 18 */
li t0, (1 << 18)
csrs sstatus, t0
.Lmemcpy_loop:
/* Load byte from src */
1: lb t1, 0(a1)
/* Store byte to dst */
2: sb t1, 0(a0)
addi a0, a0, 1
addi a1, a1, 1
addi a2, a2, -1
bnez a2, .Lmemcpy_loop
.Lmemcpy_done:
/* Disable SUM */
li t0, (1 << 18)
csrc sstatus, t0
li a0, 0
ret
.Lmemcpy_fault:
/* Fixup routine on fault */
/* Disable SUM */
li t0, (1 << 18)
csrc sstatus, t0
li a0, -14 /* -EFAULT */
ret
/* Exception table entries */
EXTABLE(1b, .Lmemcpy_fault)
EXTABLE(2b, .Lmemcpy_fault)
/*
* extern "C" int64 __uaccess_strncpy(char* dst, const char* src, uint64 max_len);
*
* a0: dst
* a1: src
* a2: max_len
* Returns: number of bytes copied (excluding null), or -EFAULT (-14) on page fault.
*/
.global __uaccess_strncpy
.type __uaccess_strncpy, @function
__uaccess_strncpy:
/* If max_len == 0, return 0 */
beqz a2, .Lstrncpy_done_zero
/* Enable SUM */
li t0, (1 << 18)
csrs sstatus, t0
/* t2 will store the length copied */
li t2, 0
.Lstrncpy_loop:
/* Load byte from src */
3: lb t1, 0(a1)
/* Store byte to dst */
4: sb t1, 0(a0)
/* If it was the null terminator, we're done */
beqz t1, .Lstrncpy_done
addi a0, a0, 1
addi a1, a1, 1
addi t2, t2, 1
addi a2, a2, -1
bnez a2, .Lstrncpy_loop
/* Reached max_len without finding null */
/* We must null-terminate at max_len - 1 as per typical strncpy_from_user semantics */
addi a0, a0, -1
sb zero, 0(a0)
addi t2, t2, -1 /* length of string without the forced null terminator */
.Lstrncpy_done:
/* Disable SUM */
li t0, (1 << 18)
csrc sstatus, t0
mv a0, t2
ret
.Lstrncpy_done_zero:
li a0, 0
ret
.Lstrncpy_fault:
/* Fixup routine on fault */
li t0, (1 << 18)
csrc sstatus, t0
li a0, -14 /* -EFAULT */
ret
/* Exception table entries */
EXTABLE(3b, .Lstrncpy_fault)
EXTABLE(4b, .Lstrncpy_fault)
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