execmem.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _LINUX_EXECMEM_ALLOC_H
  3#define _LINUX_EXECMEM_ALLOC_H
  4
  5#include <linux/types.h>
  6#include <linux/moduleloader.h>
  7#include <linux/cleanup.h>
  8
  9#if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) && \
 10		!defined(CONFIG_KASAN_VMALLOC)
 11#include <linux/kasan.h>
 12#define MODULE_ALIGN (PAGE_SIZE << KASAN_SHADOW_SCALE_SHIFT)
 13#else
 14#define MODULE_ALIGN PAGE_SIZE
 15#endif
 16
 17/**
 18 * enum execmem_type - types of executable memory ranges
 19 *
 20 * There are several subsystems that allocate executable memory.
 21 * Architectures define different restrictions on placement,
 22 * permissions, alignment and other parameters for memory that can be used
 23 * by these subsystems.
 24 * Types in this enum identify subsystems that allocate executable memory
 25 * and let architectures define parameters for ranges suitable for
 26 * allocations by each subsystem.
 27 *
 28 * @EXECMEM_DEFAULT: default parameters that would be used for types that
 29 * are not explicitly defined.
 30 * @EXECMEM_MODULE_TEXT: parameters for module text sections
 31 * @EXECMEM_KPROBES: parameters for kprobes
 32 * @EXECMEM_FTRACE: parameters for ftrace
 33 * @EXECMEM_BPF: parameters for BPF
 34 * @EXECMEM_MODULE_DATA: parameters for module data sections
 35 * @EXECMEM_TYPE_MAX:
 36 */
 37enum execmem_type {
 38	EXECMEM_DEFAULT,
 39	EXECMEM_MODULE_TEXT = EXECMEM_DEFAULT,
 40	EXECMEM_KPROBES,
 41	EXECMEM_FTRACE,
 42	EXECMEM_BPF,
 43	EXECMEM_MODULE_DATA,
 44	EXECMEM_TYPE_MAX,
 45};
 46
 47/**
 48 * enum execmem_range_flags - options for executable memory allocations
 49 * @EXECMEM_KASAN_SHADOW:	allocate kasan shadow
 50 * @EXECMEM_ROX_CACHE:		allocations should use ROX cache of huge pages
 51 */
 52enum execmem_range_flags {
 53	EXECMEM_KASAN_SHADOW	= (1 << 0),
 54	EXECMEM_ROX_CACHE	= (1 << 1),
 55};
 56
 57#ifdef CONFIG_ARCH_HAS_EXECMEM_ROX
 58/**
 59 * execmem_fill_trapping_insns - set memory to contain instructions that
 60 *				 will trap
 61 * @ptr:	pointer to memory to fill
 62 * @size:	size of the range to fill
 63 *
 64 * A hook for architecures to fill execmem ranges with invalid instructions.
 65 * Architectures that use EXECMEM_ROX_CACHE must implement this.
 66 */
 67void execmem_fill_trapping_insns(void *ptr, size_t size);
 68
 69/**
 70 * execmem_restore_rox - restore read-only-execute permissions
 71 * @ptr:	address of the region to remap
 72 * @size:	size of the region to remap
 73 *
 74 * Restores read-only-execute permissions on a range [@ptr, @ptr + @size)
 75 * after it was temporarily remapped as writable. Relies on architecture
 76 * implementation of set_memory_rox() to restore mapping using large pages.
 77 *
 78 * Return: 0 on success or negative error code on failure.
 79 */
 80int execmem_restore_rox(void *ptr, size_t size);
 81#else
 82static inline int execmem_restore_rox(void *ptr, size_t size) { return 0; }
 83#endif
 84
 85/**
 86 * struct execmem_range - definition of an address space suitable for code and
 87 *			  related data allocations
 88 * @start:	address space start
 89 * @end:	address space end (inclusive)
 90 * @fallback_start: start of the secondary address space range for fallback
 91 *                  allocations on architectures that require it
 92 * @fallback_end:   start of the secondary address space (inclusive)
 93 * @pgprot:	permissions for memory in this address space
 94 * @alignment:	alignment required for text allocations
 95 * @flags:	options for memory allocations for this range
 96 */
 97struct execmem_range {
 98	unsigned long   start;
 99	unsigned long   end;
100	unsigned long   fallback_start;
101	unsigned long   fallback_end;
102	pgprot_t        pgprot;
103	unsigned int	alignment;
104	enum execmem_range_flags flags;
105};
106
107/**
108 * struct execmem_info - architecture parameters for code allocations
109 * @ranges: array of parameter sets defining architecture specific
110 * parameters for executable memory allocations. The ranges that are not
111 * explicitly initialized by an architecture use parameters defined for
112 * @EXECMEM_DEFAULT.
113 */
114struct execmem_info {
115	struct execmem_range	ranges[EXECMEM_TYPE_MAX];
116};
117
118/**
119 * execmem_arch_setup - define parameters for allocations of executable memory
120 *
121 * A hook for architectures to define parameters for allocations of
122 * executable memory. These parameters should be filled into the
123 * @execmem_info structure.
124 *
125 * For architectures that do not implement this method a default set of
126 * parameters will be used
127 *
128 * Return: a structure defining architecture parameters and restrictions
129 * for allocations of executable memory
130 */
131struct execmem_info *execmem_arch_setup(void);
132
133/**
134 * execmem_alloc - allocate executable memory
135 * @type: type of the allocation
136 * @size: how many bytes of memory are required
137 *
138 * Allocates memory that will contain executable code, either generated or
139 * loaded from kernel modules.
140 *
141 * Allocates memory that will contain data coupled with executable code,
142 * like data sections in kernel modules.
143 *
144 * The memory will have protections defined by architecture for executable
145 * region of the @type.
146 *
147 * Return: a pointer to the allocated memory or %NULL
148 */
149void *execmem_alloc(enum execmem_type type, size_t size);
150
151/**
152 * execmem_alloc_rw - allocate writable executable memory
153 * @type: type of the allocation
154 * @size: how many bytes of memory are required
155 *
156 * Allocates memory that will contain executable code, either generated or
157 * loaded from kernel modules.
158 *
159 * Allocates memory that will contain data coupled with executable code,
160 * like data sections in kernel modules.
161 *
162 * Forces writable permissions on the allocated memory and the caller is
163 * responsible to manage the permissions afterwards.
164 *
165 * For architectures that use ROX cache the permissions will be set to R+W.
166 * For architectures that don't use ROX cache the default permissions for @type
167 * will be used as they must be writable.
168 *
169 * Return: a pointer to the allocated memory or %NULL
170 */
171void *execmem_alloc_rw(enum execmem_type type, size_t size);
172
173/**
174 * execmem_free - free executable memory
175 * @ptr: pointer to the memory that should be freed
176 */
177void execmem_free(void *ptr);
178
179DEFINE_FREE(execmem, void *, if (_T) execmem_free(_T));
180
181#ifdef CONFIG_MMU
182/**
183 * execmem_vmap - create virtual mapping for EXECMEM_MODULE_DATA memory
184 * @size: size of the virtual mapping in bytes
185 *
186 * Maps virtually contiguous area in the range suitable for EXECMEM_MODULE_DATA.
187 *
188 * Return: the area descriptor on success or %NULL on failure.
189 */
190struct vm_struct *execmem_vmap(size_t size);
191#endif
192
193/**
194 * execmem_is_rox - check if execmem is read-only
195 * @type - the execmem type to check
196 *
197 * Return: %true if the @type is read-only, %false if it's writable
198 */
199bool execmem_is_rox(enum execmem_type type);
200
201#if defined(CONFIG_EXECMEM) && !defined(CONFIG_ARCH_WANTS_EXECMEM_LATE)
202void execmem_init(void);
203#else
204static inline void execmem_init(void) {}
205#endif
206
207#endif /* _LINUX_EXECMEM_ALLOC_H */