/* SPDX-License-Identifier: MPL-2.0 */
.text
.code64
// Copies `size` bytes from `src` to `dst`. This function works with exception handling
// and can recover from a page fault. The source range must not overlap with the destination range
// (In virtual address level. Their corresponding physical addresses can be overlapped).
//
// Returns number of bytes that failed to copy.
//
// Ref: [https://github.com/torvalds/linux/blob/2ab79514109578fc4b6df90633d500cf281eb689/arch/x86/lib/copy_user_64.S]
.global __memcpy_fallible
.type __memcpy_fallible, @function
__memcpy_fallible: # (dst: *mut u8, src: *const u8, size: usize) -> usize
mov rcx, rdx # Move the size to rcx for counting
.move:
rep movsb # Copy the bytes repeatedly
.memcpy_exit:
mov rax, rcx # Return the size remaining
ret
.size __memcpy_fallible, .-__memcpy_fallible
.pushsection .ex_table, "a", @progbits
.align 8
.quad [.move]
.quad [.memcpy_exit]
.popsection