LLVM 20.0.0git
Memory.inc
Go to the documentation of this file.
1//===- Unix/Memory.cpp - Generic UNIX System Configuration ------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines some functions for various memory management utilities.
10//
11//===----------------------------------------------------------------------===//
12
13#include "Unix.h"
14#include "llvm/Config/config.h"
20
21#ifdef HAVE_SYS_MMAN_H
22#include <sys/mman.h>
23#endif
24
25#ifdef __APPLE__
26#include <mach/mach.h>
27#endif
28
29#ifdef __Fuchsia__
30#include <zircon/syscalls.h>
31#endif
32
33#if defined(__APPLE__)
34extern "C" void sys_icache_invalidate(const void *Addr, size_t len);
35#else
36extern "C" void __clear_cache(void *, void *);
37#endif
38
39static int getPosixProtectionFlags(unsigned Flags) {
40 switch (Flags & llvm::sys::Memory::MF_RWE_MASK) {
42 return PROT_READ;
44 return PROT_WRITE;
46 return PROT_READ | PROT_WRITE;
48 return PROT_READ | PROT_EXEC;
51 return PROT_READ | PROT_WRITE | PROT_EXEC;
53#if defined(__FreeBSD__) || defined(__powerpc__)
54 // On PowerPC, having an executable page that has no read permission
55 // can have unintended consequences. The function InvalidateInstruction-
56 // Cache uses instructions dcbf and icbi, both of which are treated by
57 // the processor as loads. If the page has no read permissions,
58 // executing these instructions will result in a segmentation fault.
59 return PROT_READ | PROT_EXEC;
60#else
61 return PROT_EXEC;
62#endif
63 default:
64 llvm_unreachable("Illegal memory protection flag specified!");
65 }
66 // Provide a default return value as required by some compilers.
67 return PROT_NONE;
68}
69
70namespace llvm {
71namespace sys {
72
73MemoryBlock Memory::allocateMappedMemory(size_t NumBytes,
74 const MemoryBlock *const NearBlock,
75 unsigned PFlags, std::error_code &EC) {
76 EC = std::error_code();
77 if (NumBytes == 0)
78 return MemoryBlock();
79
80 // On platforms that have it, we can use MAP_ANON to get a memory-mapped
81 // page without file backing, but we need a fallback of opening /dev/zero
82 // for strictly POSIX platforms instead.
83 int fd;
84#if defined(MAP_ANON)
85 fd = -1;
86#else
87 fd = open("/dev/zero", O_RDWR);
88 if (fd == -1) {
90 return MemoryBlock();
91 }
92#endif
93
94 int MMFlags = MAP_PRIVATE;
95#if defined(MAP_ANON)
96 MMFlags |= MAP_ANON;
97#endif
98 int Protect = getPosixProtectionFlags(PFlags);
99
100#if defined(__NetBSD__) && defined(PROT_MPROTECT)
101 Protect |= PROT_MPROTECT(PROT_READ | PROT_WRITE | PROT_EXEC);
102#endif
103
104 // Use any near hint and the page size to set a page-aligned starting address
105 uintptr_t Start = NearBlock ? reinterpret_cast<uintptr_t>(NearBlock->base()) +
106 NearBlock->allocatedSize()
107 : 0;
108 static const size_t PageSize = Process::getPageSizeEstimate();
109 const size_t NumPages = (NumBytes + PageSize - 1) / PageSize;
110
111 if (Start && Start % PageSize)
112 Start += PageSize - Start % PageSize;
113
114 // FIXME: Handle huge page requests (MF_HUGE_HINT).
115 void *Addr = ::mmap(reinterpret_cast<void *>(Start), PageSize * NumPages,
116 Protect, MMFlags, fd, 0);
117 if (Addr == MAP_FAILED) {
118 if (NearBlock) { // Try again without a near hint
119#if !defined(MAP_ANON)
120 close(fd);
121#endif
122 return allocateMappedMemory(NumBytes, nullptr, PFlags, EC);
123 }
124
126#if !defined(MAP_ANON)
127 close(fd);
128#endif
129 return MemoryBlock();
130 }
131
132#if !defined(MAP_ANON)
133 close(fd);
134#endif
135
136 MemoryBlock Result;
137 Result.Address = Addr;
138 Result.AllocatedSize = PageSize * NumPages;
139 Result.Flags = PFlags;
140
141 // Rely on protectMappedMemory to invalidate instruction cache.
142 if (PFlags & MF_EXEC) {
143 EC = Memory::protectMappedMemory(Result, PFlags);
144 if (EC != std::error_code())
145 return MemoryBlock();
146 }
147
148 return Result;
149}
150
151std::error_code Memory::releaseMappedMemory(MemoryBlock &M) {
152 if (M.Address == nullptr || M.AllocatedSize == 0)
153 return std::error_code();
154
155 if (0 != ::munmap(M.Address, M.AllocatedSize))
156 return errnoAsErrorCode();
157
158 M.Address = nullptr;
159 M.AllocatedSize = 0;
160
161 return std::error_code();
162}
163
164std::error_code Memory::protectMappedMemory(const MemoryBlock &M,
165 unsigned Flags) {
167 if (M.Address == nullptr || M.AllocatedSize == 0)
168 return std::error_code();
169
170 if (!Flags)
171 return std::error_code(EINVAL, std::generic_category());
172
173 int Protect = getPosixProtectionFlags(Flags);
174 uintptr_t Start =
175 alignAddr((const uint8_t *)M.Address - PageSize.value() + 1, PageSize);
176 uintptr_t End =
177 alignAddr((const uint8_t *)M.Address + M.AllocatedSize, PageSize);
178
179 bool InvalidateCache = (Flags & MF_EXEC);
180
181#if defined(__arm__) || defined(__aarch64__)
182 // Certain ARM implementations treat icache clear instruction as a memory
183 // read, and CPU segfaults on trying to clear cache on !PROT_READ page.
184 // Therefore we need to temporarily add PROT_READ for the sake of flushing the
185 // instruction caches.
186 if (InvalidateCache && !(Protect & PROT_READ)) {
187 int Result = ::mprotect((void *)Start, End - Start, Protect | PROT_READ);
188 if (Result != 0)
189 return errnoAsErrorCode();
190
191 Memory::InvalidateInstructionCache(M.Address, M.AllocatedSize);
192 InvalidateCache = false;
193 }
194#endif
195
196 int Result = ::mprotect((void *)Start, End - Start, Protect);
197
198 if (Result != 0)
199 return errnoAsErrorCode();
200
201 if (InvalidateCache)
202 Memory::InvalidateInstructionCache(M.Address, M.AllocatedSize);
203
204 return std::error_code();
205}
206
207/// InvalidateInstructionCache - Before the JIT can run a block of code
208/// that has been emitted it must invalidate the instruction cache on some
209/// platforms.
210void Memory::InvalidateInstructionCache(const void *Addr, size_t Len) {
211
212// icache invalidation for PPC and ARM.
213#if defined(__APPLE__)
214
215#if (defined(__powerpc__) || defined(__arm__) || defined(__arm64__))
216 sys_icache_invalidate(const_cast<void *>(Addr), Len);
217#endif
218
219#elif defined(__Fuchsia__)
220
221 zx_status_t Status = zx_cache_flush(Addr, Len, ZX_CACHE_FLUSH_INSN);
222 assert(Status == ZX_OK && "cannot invalidate instruction cache");
223
224#else
225
226#if defined(__powerpc__) && defined(__GNUC__)
227 const size_t LineSize = 32;
228
229 const intptr_t Mask = ~(LineSize - 1);
230 const intptr_t StartLine = ((intptr_t)Addr) & Mask;
231 const intptr_t EndLine = ((intptr_t)Addr + Len + LineSize - 1) & Mask;
232
233 for (intptr_t Line = StartLine; Line < EndLine; Line += LineSize)
234 asm volatile("dcbf 0, %0" : : "r"(Line));
235 asm volatile("sync");
236
237 for (intptr_t Line = StartLine; Line < EndLine; Line += LineSize)
238 asm volatile("icbi 0, %0" : : "r"(Line));
239 asm volatile("isync");
240#elif (defined(__arm__) || defined(__aarch64__) || defined(__loongarch__) || \
241 defined(__mips__)) && \
242 defined(__GNUC__)
243 // FIXME: Can we safely always call this for __GNUC__ everywhere?
244 const char *Start = static_cast<const char *>(Addr);
245 const char *End = Start + Len;
246 __clear_cache(const_cast<char *>(Start), const_cast<char *>(End));
247#endif
248
249#endif // end apple
250
252}
253
254} // namespace sys
255} // namespace llvm
uint64_t Addr
bool End
Definition: ELF_riscv.cpp:480
static cl::opt< int > PageSize("imp-null-check-page-size", cl::desc("The page size of the target in bytes"), cl::init(4096), cl::Hidden)
Provides a library for accessing information about this process and other processes on the operating ...
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
static std::error_code releaseMappedMemory(MemoryBlock &Block)
This method releases a block of memory that was allocated with the allocateMappedMemory method.
static MemoryBlock allocateMappedMemory(size_t NumBytes, const MemoryBlock *const NearBlock, unsigned Flags, std::error_code &EC)
This method allocates a block of memory that is suitable for loading dynamically generated code (e....
static void InvalidateInstructionCache(const void *Addr, size_t Len)
InvalidateInstructionCache - Before the JIT can run a block of code that has been emitted it must inv...
static std::error_code protectMappedMemory(const MemoryBlock &Block, unsigned Flags)
This method sets the protection flags for a block of memory to the state specified by /p Flags.
static unsigned getPageSizeEstimate()
Get the process's estimated page size.
Definition: Process.h:61
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
constexpr char Align[]
Key for Kernel::Arg::Metadata::mAlign.
constexpr std::underlying_type_t< E > Mask()
Get a bitmask with 1s in all places up to the high-order bit of E's largest value.
Definition: BitmaskEnum.h:121
void ValgrindDiscardTranslations(const void *Addr, size_t Len)
Definition: Valgrind.cpp:36
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
std::error_code errnoAsErrorCode()
Helper to get errno as an std::error_code.
Definition: Error.h:1221
uintptr_t alignAddr(const void *Addr, Align Alignment)
Aligns Addr to Alignment bytes, rounding up.
Definition: Alignment.h:187