1 //===-- linux.cpp -----------------------------------------------*- 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 #include "platform.h" 10 11 #if SCUDO_LINUX 12 13 #include "common.h" 14 #include "linux.h" 15 #include "mutex.h" 16 #include "string_utils.h" 17 18 #include <errno.h> 19 #include <fcntl.h> 20 #include <linux/futex.h> 21 #include <sched.h> 22 #include <stdlib.h> 23 #include <string.h> 24 #include <sys/mman.h> 25 #include <sys/stat.h> 26 #include <sys/syscall.h> 27 #include <sys/time.h> 28 #include <time.h> 29 #include <unistd.h> 30 31 #if SCUDO_ANDROID 32 #include <sys/prctl.h> 33 // Definitions of prctl arguments to set a vma name in Android kernels. 34 #define ANDROID_PR_SET_VMA 0x53564d41 35 #define ANDROID_PR_SET_VMA_ANON_NAME 0 36 #endif 37 38 #ifdef ANDROID_EXPERIMENTAL_MTE 39 #include <bionic/mte_kernel.h> 40 #endif 41 42 namespace scudo { 43 44 uptr getPageSize() { return static_cast<uptr>(sysconf(_SC_PAGESIZE)); } 45 46 void NORETURN die() { abort(); } 47 48 void *map(void *Addr, uptr Size, UNUSED const char *Name, uptr Flags, 49 UNUSED MapPlatformData *Data) { 50 int MmapFlags = MAP_PRIVATE | MAP_ANONYMOUS; 51 int MmapProt; 52 if (Flags & MAP_NOACCESS) { 53 MmapFlags |= MAP_NORESERVE; 54 MmapProt = PROT_NONE; 55 } else { 56 MmapProt = PROT_READ | PROT_WRITE; 57 #if defined(__aarch64__) && defined(ANDROID_EXPERIMENTAL_MTE) 58 if (Flags & MAP_MEMTAG) 59 MmapProt |= PROT_MTE; 60 #endif 61 } 62 if (Addr) { 63 // Currently no scenario for a noaccess mapping with a fixed address. 64 DCHECK_EQ(Flags & MAP_NOACCESS, 0); 65 MmapFlags |= MAP_FIXED; 66 } 67 void *P = mmap(Addr, Size, MmapProt, MmapFlags, -1, 0); 68 if (P == MAP_FAILED) { 69 if (!(Flags & MAP_ALLOWNOMEM) || errno != ENOMEM) 70 dieOnMapUnmapError(errno == ENOMEM); 71 return nullptr; 72 } 73 #if SCUDO_ANDROID 74 if (!(Flags & MAP_NOACCESS)) 75 prctl(ANDROID_PR_SET_VMA, ANDROID_PR_SET_VMA_ANON_NAME, P, Size, Name); 76 #endif 77 return P; 78 } 79 80 void unmap(void *Addr, uptr Size, UNUSED uptr Flags, 81 UNUSED MapPlatformData *Data) { 82 if (munmap(Addr, Size) != 0) 83 dieOnMapUnmapError(); 84 } 85 86 void releasePagesToOS(uptr BaseAddress, uptr Offset, uptr Size, 87 UNUSED MapPlatformData *Data) { 88 void *Addr = reinterpret_cast<void *>(BaseAddress + Offset); 89 while (madvise(Addr, Size, MADV_DONTNEED) == -1 && errno == EAGAIN) { 90 } 91 } 92 93 // Calling getenv should be fine (c)(tm) at any time. 94 const char *getEnv(const char *Name) { return getenv(Name); } 95 96 namespace { 97 enum State : u32 { Unlocked = 0, Locked = 1, Sleeping = 2 }; 98 } 99 100 bool HybridMutex::tryLock() { 101 return atomic_compare_exchange(&M, Unlocked, Locked) == Unlocked; 102 } 103 104 // The following is based on https://akkadia.org/drepper/futex.pdf. 105 void HybridMutex::lockSlow() { 106 u32 V = atomic_compare_exchange(&M, Unlocked, Locked); 107 if (V == Unlocked) 108 return; 109 if (V != Sleeping) 110 V = atomic_exchange(&M, Sleeping, memory_order_acquire); 111 while (V != Unlocked) { 112 syscall(SYS_futex, reinterpret_cast<uptr>(&M), FUTEX_WAIT_PRIVATE, Sleeping, 113 nullptr, nullptr, 0); 114 V = atomic_exchange(&M, Sleeping, memory_order_acquire); 115 } 116 } 117 118 void HybridMutex::unlock() { 119 if (atomic_fetch_sub(&M, 1U, memory_order_release) != Locked) { 120 atomic_store(&M, Unlocked, memory_order_release); 121 syscall(SYS_futex, reinterpret_cast<uptr>(&M), FUTEX_WAKE_PRIVATE, 1, 122 nullptr, nullptr, 0); 123 } 124 } 125 126 u64 getMonotonicTime() { 127 timespec TS; 128 clock_gettime(CLOCK_MONOTONIC, &TS); 129 return static_cast<u64>(TS.tv_sec) * (1000ULL * 1000 * 1000) + 130 static_cast<u64>(TS.tv_nsec); 131 } 132 133 u32 getNumberOfCPUs() { 134 cpu_set_t CPUs; 135 // sched_getaffinity can fail for a variety of legitimate reasons (lack of 136 // CAP_SYS_NICE, syscall filtering, etc), in which case we shall return 0. 137 if (sched_getaffinity(0, sizeof(cpu_set_t), &CPUs) != 0) 138 return 0; 139 return static_cast<u32>(CPU_COUNT(&CPUs)); 140 } 141 142 // Blocking is possibly unused if the getrandom block is not compiled in. 143 bool getRandom(void *Buffer, uptr Length, UNUSED bool Blocking) { 144 if (!Buffer || !Length || Length > MaxRandomLength) 145 return false; 146 ssize_t ReadBytes; 147 #if defined(SYS_getrandom) 148 #if !defined(GRND_NONBLOCK) 149 #define GRND_NONBLOCK 1 150 #endif 151 // Up to 256 bytes, getrandom will not be interrupted. 152 ReadBytes = 153 syscall(SYS_getrandom, Buffer, Length, Blocking ? 0 : GRND_NONBLOCK); 154 if (ReadBytes == static_cast<ssize_t>(Length)) 155 return true; 156 #endif // defined(SYS_getrandom) 157 // Up to 256 bytes, a read off /dev/urandom will not be interrupted. 158 // Blocking is moot here, O_NONBLOCK has no effect when opening /dev/urandom. 159 const int FileDesc = open("/dev/urandom", O_RDONLY); 160 if (FileDesc == -1) 161 return false; 162 ReadBytes = read(FileDesc, Buffer, Length); 163 close(FileDesc); 164 return (ReadBytes == static_cast<ssize_t>(Length)); 165 } 166 167 // Allocation free syslog-like API. 168 extern "C" WEAK int async_safe_write_log(int pri, const char *tag, 169 const char *msg); 170 171 void outputRaw(const char *Buffer) { 172 if (&async_safe_write_log) { 173 constexpr s32 AndroidLogInfo = 4; 174 async_safe_write_log(AndroidLogInfo, "scudo", Buffer); 175 } else { 176 write(2, Buffer, strlen(Buffer)); 177 } 178 } 179 180 extern "C" WEAK void android_set_abort_message(const char *); 181 182 void setAbortMessage(const char *Message) { 183 if (&android_set_abort_message) 184 android_set_abort_message(Message); 185 } 186 187 } // namespace scudo 188 189 #endif // SCUDO_LINUX 190