1ec6347bbSDan Williams // SPDX-License-Identifier: GPL-2.0 2ec6347bbSDan Williams /* Copyright(c) 2016-2020 Intel Corporation. All rights reserved. */ 3ec6347bbSDan Williams 4ec6347bbSDan Williams #include <linux/jump_label.h> 5ec6347bbSDan Williams #include <linux/uaccess.h> 6ec6347bbSDan Williams #include <linux/export.h> 7ec6347bbSDan Williams #include <linux/string.h> 8ec6347bbSDan Williams #include <linux/types.h> 9ec6347bbSDan Williams 10ec6347bbSDan Williams #include <asm/mce.h> 11ec6347bbSDan Williams 12ec6347bbSDan Williams #ifdef CONFIG_X86_MCE 13ec6347bbSDan Williams /* 14ec6347bbSDan Williams * See COPY_MC_TEST for self-test of the copy_mc_fragile() 15ec6347bbSDan Williams * implementation. 16ec6347bbSDan Williams */ 17ec6347bbSDan Williams static DEFINE_STATIC_KEY_FALSE(copy_mc_fragile_key); 18ec6347bbSDan Williams 19ec6347bbSDan Williams void enable_copy_mc_fragile(void) 20ec6347bbSDan Williams { 21ec6347bbSDan Williams static_branch_inc(©_mc_fragile_key); 22ec6347bbSDan Williams } 23ec6347bbSDan Williams #define copy_mc_fragile_enabled (static_branch_unlikely(©_mc_fragile_key)) 24ec6347bbSDan Williams 25ec6347bbSDan Williams /* 26ec6347bbSDan Williams * Similar to copy_user_handle_tail, probe for the write fault point, or 27ec6347bbSDan Williams * source exception point. 28ec6347bbSDan Williams */ 29ec6347bbSDan Williams __visible notrace unsigned long 30ec6347bbSDan Williams copy_mc_fragile_handle_tail(char *to, char *from, unsigned len) 31ec6347bbSDan Williams { 32ec6347bbSDan Williams for (; len; --len, to++, from++) 33ec6347bbSDan Williams if (copy_mc_fragile(to, from, 1)) 34ec6347bbSDan Williams break; 35ec6347bbSDan Williams return len; 36ec6347bbSDan Williams } 37ec6347bbSDan Williams #else 38ec6347bbSDan Williams /* 39ec6347bbSDan Williams * No point in doing careful copying, or consulting a static key when 40ec6347bbSDan Williams * there is no #MC handler in the CONFIG_X86_MCE=n case. 41ec6347bbSDan Williams */ 42ec6347bbSDan Williams void enable_copy_mc_fragile(void) 43ec6347bbSDan Williams { 44ec6347bbSDan Williams } 45ec6347bbSDan Williams #define copy_mc_fragile_enabled (0) 46ec6347bbSDan Williams #endif 47ec6347bbSDan Williams 485da8e4a6SDan Williams unsigned long copy_mc_enhanced_fast_string(void *dst, const void *src, unsigned len); 495da8e4a6SDan Williams 50ec6347bbSDan Williams /** 51ec6347bbSDan Williams * copy_mc_to_kernel - memory copy that handles source exceptions 52ec6347bbSDan Williams * 53ec6347bbSDan Williams * @dst: destination address 54ec6347bbSDan Williams * @src: source address 55ec6347bbSDan Williams * @len: number of bytes to copy 56ec6347bbSDan Williams * 575da8e4a6SDan Williams * Call into the 'fragile' version on systems that benefit from avoiding 585da8e4a6SDan Williams * corner case poison consumption scenarios, For example, accessing 595da8e4a6SDan Williams * poison across 2 cachelines with a single instruction. Almost all 605da8e4a6SDan Williams * other uses case can use copy_mc_enhanced_fast_string() for a fast 615da8e4a6SDan Williams * recoverable copy, or fallback to plain memcpy. 62ec6347bbSDan Williams * 63ec6347bbSDan Williams * Return 0 for success, or number of bytes not copied if there was an 64ec6347bbSDan Williams * exception. 65ec6347bbSDan Williams */ 66ec6347bbSDan Williams unsigned long __must_check copy_mc_to_kernel(void *dst, const void *src, unsigned len) 67ec6347bbSDan Williams { 68ec6347bbSDan Williams if (copy_mc_fragile_enabled) 69ec6347bbSDan Williams return copy_mc_fragile(dst, src, len); 705da8e4a6SDan Williams if (static_cpu_has(X86_FEATURE_ERMS)) 715da8e4a6SDan Williams return copy_mc_enhanced_fast_string(dst, src, len); 72ec6347bbSDan Williams memcpy(dst, src, len); 73ec6347bbSDan Williams return 0; 74ec6347bbSDan Williams } 75ec6347bbSDan Williams EXPORT_SYMBOL_GPL(copy_mc_to_kernel); 76ec6347bbSDan Williams 77ec6347bbSDan Williams unsigned long __must_check copy_mc_to_user(void *dst, const void *src, unsigned len) 78ec6347bbSDan Williams { 79ec6347bbSDan Williams unsigned long ret; 80ec6347bbSDan Williams 815da8e4a6SDan Williams if (copy_mc_fragile_enabled) { 82ec6347bbSDan Williams __uaccess_begin(); 83ec6347bbSDan Williams ret = copy_mc_fragile(dst, src, len); 84ec6347bbSDan Williams __uaccess_end(); 85ec6347bbSDan Williams return ret; 86ec6347bbSDan Williams } 875da8e4a6SDan Williams 885da8e4a6SDan Williams if (static_cpu_has(X86_FEATURE_ERMS)) { 895da8e4a6SDan Williams __uaccess_begin(); 905da8e4a6SDan Williams ret = copy_mc_enhanced_fast_string(dst, src, len); 915da8e4a6SDan Williams __uaccess_end(); 925da8e4a6SDan Williams return ret; 935da8e4a6SDan Williams } 945da8e4a6SDan Williams 955da8e4a6SDan Williams return copy_user_generic(dst, src, len); 965da8e4a6SDan Williams } 97