1 // SPDX-License-Identifier: GPL-2.0 2 /* Copyright(c) 2016-2020 Intel Corporation. All rights reserved. */ 3 4 #include <linux/jump_label.h> 5 #include <linux/uaccess.h> 6 #include <linux/export.h> 7 #include <linux/string.h> 8 #include <linux/types.h> 9 10 #include <asm/mce.h> 11 12 #ifdef CONFIG_X86_MCE 13 /* 14 * See COPY_MC_TEST for self-test of the copy_mc_fragile() 15 * implementation. 16 */ 17 static DEFINE_STATIC_KEY_FALSE(copy_mc_fragile_key); 18 19 void enable_copy_mc_fragile(void) 20 { 21 static_branch_inc(©_mc_fragile_key); 22 } 23 #define copy_mc_fragile_enabled (static_branch_unlikely(©_mc_fragile_key)) 24 25 /* 26 * Similar to copy_user_handle_tail, probe for the write fault point, or 27 * source exception point. 28 */ 29 __visible notrace unsigned long 30 copy_mc_fragile_handle_tail(char *to, char *from, unsigned len) 31 { 32 for (; len; --len, to++, from++) 33 if (copy_mc_fragile(to, from, 1)) 34 break; 35 return len; 36 } 37 #else 38 /* 39 * No point in doing careful copying, or consulting a static key when 40 * there is no #MC handler in the CONFIG_X86_MCE=n case. 41 */ 42 void enable_copy_mc_fragile(void) 43 { 44 } 45 #define copy_mc_fragile_enabled (0) 46 #endif 47 48 /** 49 * copy_mc_to_kernel - memory copy that handles source exceptions 50 * 51 * @dst: destination address 52 * @src: source address 53 * @len: number of bytes to copy 54 * 55 * Call into the 'fragile' version on systems that have trouble 56 * actually do machine check recovery. Everyone else can just 57 * use memcpy(). 58 * 59 * Return 0 for success, or number of bytes not copied if there was an 60 * exception. 61 */ 62 unsigned long __must_check copy_mc_to_kernel(void *dst, const void *src, unsigned len) 63 { 64 if (copy_mc_fragile_enabled) 65 return copy_mc_fragile(dst, src, len); 66 memcpy(dst, src, len); 67 return 0; 68 } 69 EXPORT_SYMBOL_GPL(copy_mc_to_kernel); 70 71 unsigned long __must_check copy_mc_to_user(void *dst, const void *src, unsigned len) 72 { 73 unsigned long ret; 74 75 if (!copy_mc_fragile_enabled) 76 return copy_user_generic(dst, src, len); 77 78 __uaccess_begin(); 79 ret = copy_mc_fragile(dst, src, len); 80 __uaccess_end(); 81 return ret; 82 } 83