1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  * x86 KMSAN support.
4  *
5  * Copyright (C) 2022, Google LLC
6  * Author: Alexander Potapenko <glider@google.com>
7  */
8 
9 #ifndef _ASM_X86_KMSAN_H
10 #define _ASM_X86_KMSAN_H
11 
12 #ifndef MODULE
13 
14 #include <asm/cpu_entry_area.h>
15 #include <asm/processor.h>
16 #include <linux/mmzone.h>
17 
18 DECLARE_PER_CPU(char[CPU_ENTRY_AREA_SIZE], cpu_entry_area_shadow);
19 DECLARE_PER_CPU(char[CPU_ENTRY_AREA_SIZE], cpu_entry_area_origin);
20 
21 /*
22  * Functions below are declared in the header to make sure they are inlined.
23  * They all are called from kmsan_get_metadata() for every memory access in
24  * the kernel, so speed is important here.
25  */
26 
27 /*
28  * Compute metadata addresses for the CPU entry area on x86.
29  */
arch_kmsan_get_meta_or_null(void * addr,bool is_origin)30 static inline void *arch_kmsan_get_meta_or_null(void *addr, bool is_origin)
31 {
32 	unsigned long addr64 = (unsigned long)addr;
33 	char *metadata_array;
34 	unsigned long off;
35 	int cpu;
36 
37 	if ((addr64 < CPU_ENTRY_AREA_BASE) ||
38 	    (addr64 >= (CPU_ENTRY_AREA_BASE + CPU_ENTRY_AREA_MAP_SIZE)))
39 		return NULL;
40 	cpu = (addr64 - CPU_ENTRY_AREA_BASE) / CPU_ENTRY_AREA_SIZE;
41 	off = addr64 - (unsigned long)get_cpu_entry_area(cpu);
42 	if ((off < 0) || (off >= CPU_ENTRY_AREA_SIZE))
43 		return NULL;
44 	metadata_array = is_origin ? cpu_entry_area_origin :
45 				     cpu_entry_area_shadow;
46 	return &per_cpu(metadata_array[off], cpu);
47 }
48 
49 /*
50  * Taken from arch/x86/mm/physaddr.h to avoid using an instrumented version.
51  */
kmsan_phys_addr_valid(unsigned long addr)52 static inline bool kmsan_phys_addr_valid(unsigned long addr)
53 {
54 	if (IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT))
55 		return !(addr >> boot_cpu_data.x86_phys_bits);
56 	else
57 		return true;
58 }
59 
60 /*
61  * Taken from arch/x86/mm/physaddr.c to avoid using an instrumented version.
62  */
kmsan_virt_addr_valid(void * addr)63 static inline bool kmsan_virt_addr_valid(void *addr)
64 {
65 	unsigned long x = (unsigned long)addr;
66 	unsigned long y = x - __START_KERNEL_map;
67 
68 	/* use the carry flag to determine if x was < __START_KERNEL_map */
69 	if (unlikely(x > y)) {
70 		x = y + phys_base;
71 
72 		if (y >= KERNEL_IMAGE_SIZE)
73 			return false;
74 	} else {
75 		x = y + (__START_KERNEL_map - PAGE_OFFSET);
76 
77 		/* carry flag will be set if starting x was >= PAGE_OFFSET */
78 		if ((x > y) || !kmsan_phys_addr_valid(x))
79 			return false;
80 	}
81 
82 	return pfn_valid(x >> PAGE_SHIFT);
83 }
84 
85 #endif /* !MODULE */
86 
87 #endif /* _ASM_X86_KMSAN_H */
88