mman.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _LINUX_MMAN_H
  3#define _LINUX_MMAN_H
  4
  5#include <linux/fs.h>
  6#include <linux/mm.h>
  7#include <linux/percpu_counter.h>
  8
  9#include <linux/atomic.h>
 10#include <uapi/linux/mman.h>
 11
 12/*
 13 * Arrange for legacy / undefined architecture specific flags to be
 14 * ignored by mmap handling code.
 15 */
 16#ifndef MAP_32BIT
 17#define MAP_32BIT 0
 18#endif
 19#ifndef MAP_ABOVE4G
 20#define MAP_ABOVE4G 0
 21#endif
 22#ifndef MAP_HUGE_2MB
 23#define MAP_HUGE_2MB 0
 24#endif
 25#ifndef MAP_HUGE_1GB
 26#define MAP_HUGE_1GB 0
 27#endif
 28#ifndef MAP_UNINITIALIZED
 29#define MAP_UNINITIALIZED 0
 30#endif
 31#ifndef MAP_SYNC
 32#define MAP_SYNC 0
 33#endif
 34
 35/*
 36 * The historical set of flags that all mmap implementations implicitly
 37 * support when a ->mmap_validate() op is not provided in file_operations.
 38 *
 39 * MAP_EXECUTABLE and MAP_DENYWRITE are completely ignored throughout the
 40 * kernel.
 41 */
 42#define LEGACY_MAP_MASK (MAP_SHARED \
 43		| MAP_PRIVATE \
 44		| MAP_FIXED \
 45		| MAP_ANONYMOUS \
 46		| MAP_DENYWRITE \
 47		| MAP_EXECUTABLE \
 48		| MAP_UNINITIALIZED \
 49		| MAP_GROWSDOWN \
 50		| MAP_LOCKED \
 51		| MAP_NORESERVE \
 52		| MAP_POPULATE \
 53		| MAP_NONBLOCK \
 54		| MAP_STACK \
 55		| MAP_HUGETLB \
 56		| MAP_32BIT \
 57		| MAP_ABOVE4G \
 58		| MAP_HUGE_2MB \
 59		| MAP_HUGE_1GB)
 60
 61extern int sysctl_overcommit_memory;
 62extern struct percpu_counter vm_committed_as;
 63
 64#ifdef CONFIG_SMP
 65extern s32 vm_committed_as_batch;
 66extern void mm_compute_batch(int overcommit_policy);
 67#else
 68#define vm_committed_as_batch 0
 69static inline void mm_compute_batch(int overcommit_policy)
 70{
 71}
 72#endif
 73
 74unsigned long vm_memory_committed(void);
 75
 76static inline void vm_acct_memory(long pages)
 77{
 78	percpu_counter_add_batch(&vm_committed_as, pages, vm_committed_as_batch);
 79}
 80
 81static inline void vm_unacct_memory(long pages)
 82{
 83	vm_acct_memory(-pages);
 84}
 85
 86/*
 87 * Allow architectures to handle additional protection and flag bits. The
 88 * overriding macros must be defined in the arch-specific asm/mman.h file.
 89 */
 90
 91#ifndef arch_calc_vm_prot_bits
 92#define arch_calc_vm_prot_bits(prot, pkey) 0
 93#endif
 94
 95#ifndef arch_calc_vm_flag_bits
 96#define arch_calc_vm_flag_bits(file, flags) 0
 97#endif
 98
 99#ifndef arch_validate_prot
100/*
101 * This is called from mprotect().  PROT_GROWSDOWN and PROT_GROWSUP have
102 * already been masked out.
103 *
104 * Returns true if the prot flags are valid
105 */
106static inline bool arch_validate_prot(unsigned long prot, unsigned long addr)
107{
108	return (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM)) == 0;
109}
110#define arch_validate_prot arch_validate_prot
111#endif
112
113#ifndef arch_validate_flags
114/*
115 * This is called from mmap() and mprotect() with the updated vma->vm_flags.
116 *
117 * Returns true if the VM_* flags are valid.
118 */
119static inline bool arch_validate_flags(unsigned long flags)
120{
121	return true;
122}
123#define arch_validate_flags arch_validate_flags
124#endif
125
126/*
127 * Optimisation macro.  It is equivalent to:
128 *      (x & bit1) ? bit2 : 0
129 * but this version is faster.
130 * ("bit1" and "bit2" must be single bits)
131 */
132#define _calc_vm_trans(x, bit1, bit2) \
133  ((!(bit1) || !(bit2)) ? 0 : \
134  ((bit1) <= (bit2) ? ((x) & (bit1)) * ((bit2) / (bit1)) \
135   : ((x) & (bit1)) / ((bit1) / (bit2))))
136
137/*
138 * Combine the mmap "prot" argument into "vm_flags" used internally.
139 */
140static inline vm_flags_t
141calc_vm_prot_bits(unsigned long prot, unsigned long pkey)
142{
143	return _calc_vm_trans(prot, PROT_READ,  VM_READ ) |
144	       _calc_vm_trans(prot, PROT_WRITE, VM_WRITE) |
145	       _calc_vm_trans(prot, PROT_EXEC,  VM_EXEC) |
146	       arch_calc_vm_prot_bits(prot, pkey);
147}
148
149/*
150 * Combine the mmap "flags" argument into "vm_flags" used internally.
151 */
152static inline vm_flags_t
153calc_vm_flag_bits(struct file *file, unsigned long flags)
154{
155	return _calc_vm_trans(flags, MAP_GROWSDOWN,  VM_GROWSDOWN ) |
156	       _calc_vm_trans(flags, MAP_LOCKED,     VM_LOCKED    ) |
157	       _calc_vm_trans(flags, MAP_SYNC,	     VM_SYNC      ) |
158#ifdef CONFIG_TRANSPARENT_HUGEPAGE
159	       _calc_vm_trans(flags, MAP_STACK,	     VM_NOHUGEPAGE) |
160#endif
161	       arch_calc_vm_flag_bits(file, flags);
162}
163
164unsigned long vm_commit_limit(void);
165
166#ifndef arch_memory_deny_write_exec_supported
167static inline bool arch_memory_deny_write_exec_supported(void)
168{
169	return true;
170}
171#define arch_memory_deny_write_exec_supported arch_memory_deny_write_exec_supported
172#endif
173
174/*
175 * Denies creating a writable executable mapping or gaining executable permissions.
176 *
177 * This denies the following:
178 *
179 * 	a)	mmap(PROT_WRITE | PROT_EXEC)
180 *
181 *	b)	mmap(PROT_WRITE)
182 *		mprotect(PROT_EXEC)
183 *
184 *	c)	mmap(PROT_WRITE)
185 *		mprotect(PROT_READ)
186 *		mprotect(PROT_EXEC)
187 *
188 * But allows the following:
189 *
190 *	d)	mmap(PROT_READ | PROT_EXEC)
191 *		mmap(PROT_READ | PROT_EXEC | PROT_BTI)
192 *
193 * This is only applicable if the user has set the Memory-Deny-Write-Execute
194 * (MDWE) protection mask for the current process.
195 *
196 * @old specifies the VMA flags the VMA originally possessed, and @new the ones
197 * we propose to set.
198 *
199 * Return: false if proposed change is OK, true if not ok and should be denied.
200 */
201static inline bool map_deny_write_exec(unsigned long old, unsigned long new)
202{
203	/* If MDWE is disabled, we have nothing to deny. */
204	if (!mm_flags_test(MMF_HAS_MDWE, current->mm))
205		return false;
206
207	/* If the new VMA is not executable, we have nothing to deny. */
208	if (!(new & VM_EXEC))
209		return false;
210
211	/* Under MDWE we do not accept newly writably executable VMAs... */
212	if (new & VM_WRITE)
213		return true;
214
215	/* ...nor previously non-executable VMAs becoming executable. */
216	if (!(old & VM_EXEC))
217		return true;
218
219	return false;
220}
221
222#endif /* _LINUX_MMAN_H */