linux/arch/x86/lib/copy_mc.c

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

#include <linux/jump_label.h>
#include <linux/uaccess.h>
#include <linux/export.h>
#include <linux/instrumented.h>
#include <linux/string.h>
#include <linux/types.h>

#include <asm/mce.h>

#ifdef CONFIG_X86_MCE
static DEFINE_STATIC_KEY_FALSE(copy_mc_fragile_key);

void enable_copy_mc_fragile(void)
{ … }
#define copy_mc_fragile_enabled …

/*
 * Similar to copy_user_handle_tail, probe for the write fault point, or
 * source exception point.
 */
__visible notrace unsigned long
copy_mc_fragile_handle_tail(char *to, char *from, unsigned len)
{ … }
#else
/*
 * No point in doing careful copying, or consulting a static key when
 * there is no #MC handler in the CONFIG_X86_MCE=n case.
 */
void enable_copy_mc_fragile(void)
{
}
#define copy_mc_fragile_enabled …
#endif

unsigned long copy_mc_enhanced_fast_string(void *dst, const void *src, unsigned len);

/**
 * copy_mc_to_kernel - memory copy that handles source exceptions
 *
 * @dst:	destination address
 * @src:	source address
 * @len:	number of bytes to copy
 *
 * Call into the 'fragile' version on systems that benefit from avoiding
 * corner case poison consumption scenarios, For example, accessing
 * poison across 2 cachelines with a single instruction. Almost all
 * other uses case can use copy_mc_enhanced_fast_string() for a fast
 * recoverable copy, or fallback to plain memcpy.
 *
 * Return 0 for success, or number of bytes not copied if there was an
 * exception.
 */
unsigned long __must_check copy_mc_to_kernel(void *dst, const void *src, unsigned len)
{ … }
EXPORT_SYMBOL_GPL(…);

unsigned long __must_check copy_mc_to_user(void __user *dst, const void *src, unsigned len)
{ … }