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
18DECLARE_PER_CPU(char[CPU_ENTRY_AREA_SIZE], cpu_entry_area_shadow);
19DECLARE_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 */
30static 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 */
52static 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 */
63static 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 */