1 files changed, 117 insertions, 0 deletions
diff --git a/na/arch/riscv/uaccess/uaccess_memcpy.S b/na/arch/riscv/uaccess/uaccess_memcpy.S
new file mode 100644
index 0000000..615680d
--- /dev/null
+++ b/na/arch/riscv/uaccess/uaccess_memcpy.S
@@ -0,0 +1,117 @@
+/* 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)