1/* SPDX-License-Identifier: GPL-2.0 */
  2/*
  3 * Functions used by the KMSAN runtime.
  4 *
  5 * Copyright (C) 2017-2022 Google LLC
  6 * Author: Alexander Potapenko <glider@google.com>
  7 *
  8 */
  9
 10#ifndef __MM_KMSAN_KMSAN_H
 11#define __MM_KMSAN_KMSAN_H
 12
 13#include <linux/irqflags.h>
 14#include <linux/kmsan.h>
 15#include <linux/mm.h>
 16#include <linux/nmi.h>
 17#include <linux/pgtable.h>
 18#include <linux/printk.h>
 19#include <linux/sched.h>
 20#include <linux/stackdepot.h>
 21#include <linux/stacktrace.h>
 22
 23#define KMSAN_ALLOCA_MAGIC_ORIGIN 0xabcd0100
 24#define KMSAN_CHAIN_MAGIC_ORIGIN 0xabcd0200
 25
 26#define KMSAN_POISON_NOCHECK 0x0
 27#define KMSAN_POISON_CHECK 0x1
 28#define KMSAN_POISON_FREE 0x2
 29
 30#define KMSAN_ORIGIN_SIZE 4
 31#define KMSAN_MAX_ORIGIN_DEPTH 7
 32
 33#define KMSAN_STACK_DEPTH 64
 34
 35#define KMSAN_META_SHADOW (false)
 36#define KMSAN_META_ORIGIN (true)
 37
 38/*
 39 * A pair of metadata pointers to be returned by the instrumentation functions.
 40 */
 41struct shadow_origin_ptr {
 42	void *shadow, *origin;
 43};
 44
 45struct shadow_origin_ptr kmsan_get_shadow_origin_ptr(void *addr, u64 size,
 46						     bool store);
 47void __init kmsan_init_alloc_meta_for_range(void *start, void *end);
 48
 49enum kmsan_bug_reason {
 50	REASON_ANY,
 51	REASON_COPY_TO_USER,
 52	REASON_SUBMIT_URB,
 53};
 54
 55void kmsan_print_origin(depot_stack_handle_t origin);
 56
 57/**
 58 * kmsan_report() - Report a use of uninitialized value.
 59 * @origin:    Stack ID of the uninitialized value.
 60 * @address:   Address at which the memory access happens.
 61 * @size:      Memory access size.
 62 * @off_first: Offset (from @address) of the first byte to be reported.
 63 * @off_last:  Offset (from @address) of the last byte to be reported.
 64 * @user_addr: When non-NULL, denotes the userspace address to which the kernel
 65 *             is leaking data.
 66 * @reason:    Error type from enum kmsan_bug_reason.
 67 *
 68 * kmsan_report() prints an error message for a consequent group of bytes
 69 * sharing the same origin. If an uninitialized value is used in a comparison,
 70 * this function is called once without specifying the addresses. When checking
 71 * a memory range, KMSAN may call kmsan_report() multiple times with the same
 72 * @address, @size, @user_addr and @reason, but different @off_first and
 73 * @off_last corresponding to different @origin values.
 74 */
 75void kmsan_report(depot_stack_handle_t origin, void *address, int size,
 76		  int off_first, int off_last, const void __user *user_addr,
 77		  enum kmsan_bug_reason reason);
 78
 79DECLARE_PER_CPU(struct kmsan_ctx, kmsan_percpu_ctx);
 80
 81static __always_inline struct kmsan_ctx *kmsan_get_context(void)
 82{
 83	return in_task() ? &current->kmsan_ctx : raw_cpu_ptr(&kmsan_percpu_ctx);
 84}
 85
 86/*
 87 * When a compiler hook or KMSAN runtime function is invoked, it may make a
 88 * call to instrumented code and eventually call itself recursively. To avoid
 89 * that, we guard the runtime entry regions with
 90 * kmsan_enter_runtime()/kmsan_leave_runtime() and exit the hook if
 91 * kmsan_in_runtime() is true.
 92 *
 93 * Non-runtime code may occasionally get executed in nested IRQs from the
 94 * runtime code (e.g. when called via smp_call_function_single()). Because some
 95 * KMSAN routines may take locks (e.g. for memory allocation), we conservatively
 96 * bail out instead of calling them. To minimize the effect of this (potentially
 97 * missing initialization events) kmsan_in_runtime() is not checked in
 98 * non-blocking runtime functions.
 99 */
100static __always_inline bool kmsan_in_runtime(void)
101{
102	if ((hardirq_count() >> HARDIRQ_SHIFT) > 1)
103		return true;
104	if (in_nmi())
105		return true;
106	return kmsan_get_context()->kmsan_in_runtime;
107}
108
109static __always_inline void kmsan_enter_runtime(void)
110{
111	struct kmsan_ctx *ctx;
112
113	ctx = kmsan_get_context();
114	KMSAN_WARN_ON(ctx->kmsan_in_runtime++);
115}
116
117static __always_inline void kmsan_leave_runtime(void)
118{
119	struct kmsan_ctx *ctx = kmsan_get_context();
120
121	KMSAN_WARN_ON(--ctx->kmsan_in_runtime);
122}
123
124depot_stack_handle_t kmsan_save_stack(void);
125depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags,
126						 unsigned int extra_bits);
127
128/*
129 * Pack and unpack the origin chain depth and UAF flag to/from the extra bits
130 * provided by the stack depot.
131 * The UAF flag is stored in the lowest bit, followed by the depth in the upper
132 * bits.
133 * set_dsh_extra_bits() is responsible for clamping the value.
134 */
135static __always_inline unsigned int kmsan_extra_bits(unsigned int depth,
136						     bool uaf)
137{
138	return (depth << 1) | uaf;
139}
140
141static __always_inline bool kmsan_uaf_from_eb(unsigned int extra_bits)
142{
143	return extra_bits & 1;
144}
145
146static __always_inline unsigned int kmsan_depth_from_eb(unsigned int extra_bits)
147{
148	return extra_bits >> 1;
149}
150
151/*
152 * kmsan_internal_ functions are supposed to be very simple and not require the
153 * kmsan_in_runtime() checks.
154 */
155void kmsan_internal_memmove_metadata(void *dst, void *src, size_t n);
156void kmsan_internal_poison_memory(void *address, size_t size, gfp_t flags,
157				  unsigned int poison_flags);
158void kmsan_internal_unpoison_memory(void *address, size_t size, bool checked);
159void kmsan_internal_set_shadow_origin(void *address, size_t size, int b,
160				      u32 origin, bool checked);
161depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id);
162
163void kmsan_internal_task_create(struct task_struct *task);
164
165bool kmsan_metadata_is_contiguous(void *addr, size_t size);
166void kmsan_internal_check_memory(void *addr, size_t size,
167				 const void __user *user_addr, int reason);
168
169struct page *kmsan_vmalloc_to_page_or_null(void *vaddr);
170void kmsan_setup_meta(struct page *page, struct page *shadow,
171		      struct page *origin, int order);
172
173/*
174 * kmsan_internal_is_module_addr() and kmsan_internal_is_vmalloc_addr() are
175 * non-instrumented versions of is_module_address() and is_vmalloc_addr() that
176 * are safe to call from KMSAN runtime without recursion.
177 */
178static inline bool kmsan_internal_is_module_addr(void *vaddr)
179{
180	return ((u64)vaddr >= MODULES_VADDR) && ((u64)vaddr < MODULES_END);
181}
182
183static inline bool kmsan_internal_is_vmalloc_addr(void *addr)
184{
185	return ((u64)addr >= VMALLOC_START) && ((u64)addr < VMALLOC_END);
186}
187
188#endif /* __MM_KMSAN_KMSAN_H */