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// 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/string.h>
#include <linux/types.h>
#include <asm/mce.h>
#ifdef CONFIG_X86_MCE
/*
* See COPY_MC_TEST for self-test of the copy_mc_fragile()
* implementation.
*/
static DEFINE_STATIC_KEY_FALSE(copy_mc_fragile_key);
void enable_copy_mc_fragile(void)
{
static_branch_inc(©_mc_fragile_key);
}
#define copy_mc_fragile_enabled (static_branch_unlikely(©_mc_fragile_key))
/*
* 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)
{
for (; len; --len, to++, from++)
if (copy_mc_fragile(to, from, 1))
break;
return 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 (0)
#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)
{
if (copy_mc_fragile_enabled)
return copy_mc_fragile(dst, src, len);
if (static_cpu_has(X86_FEATURE_ERMS))
return copy_mc_enhanced_fast_string(dst, src, len);
memcpy(dst, src, len);
return 0;
}
EXPORT_SYMBOL_GPL(copy_mc_to_kernel);
unsigned long __must_check copy_mc_to_user(void __user *dst, const void *src, unsigned len)
{
unsigned long ret;
if (copy_mc_fragile_enabled) {
__uaccess_begin();
ret = copy_mc_fragile((__force void *)dst, src, len);
__uaccess_end();
return ret;
}
if (static_cpu_has(X86_FEATURE_ERMS)) {
__uaccess_begin();
ret = copy_mc_enhanced_fast_string((__force void *)dst, src, len);
__uaccess_end();
return ret;
}
return copy_user_generic((__force void *)dst, src, len);
}
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