/* SPDX-License-Identifier: GPL-2.0-only */
/* Copyright(c) 2016-2020 Intel Corporation. All rights reserved. */

#include <linux/linkage.h>
#include <asm/asm.h>

#ifndef CONFIG_UML

#ifdef CONFIG_X86_MCE

/*
 * copy_mc_fragile - copy memory with indication if an exception / fault happened
 *
 * The 'fragile' version is opted into by platform quirks and takes
 * pains to avoid unrecoverable corner cases like 'fast-string'
 * instruction sequences, and consuming poison across a cacheline
 * boundary. The non-fragile version is equivalent to memcpy()
 * regardless of CPU machine-check-recovery capability.
 */
SYM_FUNC_START(copy_mc_fragile)
        cmpl $8, %edx
        /* Less than 8 bytes? Go to byte copy loop */
        jb .L_no_whole_words

        /* Check for bad alignment of source */
        testl $7, %esi
        /* Already aligned */
        jz .L_8byte_aligned

        /* Copy one byte at a time until source is 8-byte aligned */
        movl %esi, %ecx
        andl $7, %ecx
        subl $8, %ecx
        negl %ecx
        subl %ecx, %edx
.L_read_leading_bytes:
        movb (%rsi), %al
.L_write_leading_bytes:
        movb %al, (%rdi)
        incq %rsi
        incq %rdi
        decl %ecx
        jnz .L_read_leading_bytes

.L_8byte_aligned:
        movl %edx, %ecx
        andl $7, %edx
        shrl $3, %ecx
        jz .L_no_whole_words

.L_read_words:
        movq (%rsi), %r8
.L_write_words:
        movq %r8, (%rdi)
        addq $8, %rsi
        addq $8, %rdi
        decl %ecx
        jnz .L_read_words

        /* Any trailing bytes? */
.L_no_whole_words:
        andl %edx, %edx
        jz .L_done_memcpy_trap

        /* Copy trailing bytes */
        movl %edx, %ecx
.L_read_trailing_bytes:
        movb (%rsi), %al
.L_write_trailing_bytes:
        movb %al, (%rdi)
        incq %rsi
        incq %rdi
        decl %ecx
        jnz .L_read_trailing_bytes

        /* Copy successful. Return zero */
.L_done_memcpy_trap:
        xorl %eax, %eax
.L_done:
        RET

        /*
         * Return number of bytes not copied for any failure. Note that
         * there is no "tail" handling since the source buffer is 8-byte
         * aligned and poison is cacheline aligned.
         */
.E_read_words:
        shll    $3, %ecx
.E_leading_bytes:
        addl    %edx, %ecx
.E_trailing_bytes:
        mov     %ecx, %eax
        jmp     .L_done

        /*
         * For write fault handling, given the destination is unaligned,
         * we handle faults on multi-byte writes with a byte-by-byte
         * copy up to the write-protected page.
         */
.E_write_words:
        shll    $3, %ecx
        addl    %edx, %ecx
        movl    %ecx, %edx
        jmp copy_mc_fragile_handle_tail

        _ASM_EXTABLE_TYPE(.L_read_leading_bytes, .E_leading_bytes, EX_TYPE_DEFAULT_MCE_SAFE)
        _ASM_EXTABLE_TYPE(.L_read_words, .E_read_words, EX_TYPE_DEFAULT_MCE_SAFE)
        _ASM_EXTABLE_TYPE(.L_read_trailing_bytes, .E_trailing_bytes, EX_TYPE_DEFAULT_MCE_SAFE)
        _ASM_EXTABLE(.L_write_leading_bytes, .E_leading_bytes)
        _ASM_EXTABLE(.L_write_words, .E_write_words)
        _ASM_EXTABLE(.L_write_trailing_bytes, .E_trailing_bytes)

SYM_FUNC_END(copy_mc_fragile)
#endif /* CONFIG_X86_MCE */

/*
 * copy_mc_enhanced_fast_string - memory copy with exception handling
 *
 * Fast string copy + fault / exception handling. If the CPU does
 * support machine check exception recovery, but does not support
 * recovering from fast-string exceptions then this CPU needs to be
 * added to the copy_mc_fragile_key set of quirks. Otherwise, absent any
 * machine check recovery support this version should be no slower than
 * standard memcpy.
 */
SYM_FUNC_START(copy_mc_enhanced_fast_string)
        movq %rdi, %rax
        movq %rdx, %rcx
.L_copy:
        rep movsb
        /* Copy successful. Return zero */
        xorl %eax, %eax
        RET

.E_copy:
        /*
         * On fault %rcx is updated such that the copy instruction could
         * optionally be restarted at the fault position, i.e. it
         * contains 'bytes remaining'. A non-zero return indicates error
         * to copy_mc_generic() users, or indicate short transfers to
         * user-copy routines.
         */
        movq %rcx, %rax
        RET

        _ASM_EXTABLE_TYPE(.L_copy, .E_copy, EX_TYPE_DEFAULT_MCE_SAFE)

SYM_FUNC_END(copy_mc_enhanced_fast_string)
#endif /* !CONFIG_UML */