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 namespace scudo { 39 40 uptr getPageSize() { return static_cast<uptr>(sysconf(_SC_PAGESIZE)); } 41 42 void NORETURN die() { abort(); } 43 44 void *map(void *Addr, uptr Size, UNUSED const char *Name, uptr Flags, 45 UNUSED MapPlatformData *Data) { 46 int MmapFlags = MAP_PRIVATE | MAP_ANONYMOUS; 47 int MmapProt; 48 if (Flags & MAP_NOACCESS) { 49 MmapFlags |= MAP_NORESERVE; 50 MmapProt = PROT_NONE; 51 } else { 52 MmapProt = PROT_READ | PROT_WRITE; 53 } 54 if (Addr) { 55 // Currently no scenario for a noaccess mapping with a fixed address. 56 DCHECK_EQ(Flags & MAP_NOACCESS, 0); 57 MmapFlags |= MAP_FIXED; 58 } 59 void *P = mmap(Addr, Size, MmapProt, MmapFlags, -1, 0); 60 if (P == MAP_FAILED) { 61 if (!(Flags & MAP_ALLOWNOMEM) || errno != ENOMEM) 62 dieOnMapUnmapError(errno == ENOMEM); 63 return nullptr; 64 } 65 #if SCUDO_ANDROID 66 if (!(Flags & MAP_NOACCESS)) 67 prctl(ANDROID_PR_SET_VMA, ANDROID_PR_SET_VMA_ANON_NAME, P, Size, Name); 68 #endif 69 return P; 70 } 71 72 void unmap(void *Addr, uptr Size, UNUSED uptr Flags, 73 UNUSED MapPlatformData *Data) { 74 if (munmap(Addr, Size) != 0) 75 dieOnMapUnmapError(); 76 } 77 78 void releasePagesToOS(uptr BaseAddress, uptr Offset, uptr Size, 79 UNUSED MapPlatformData *Data) { 80 void *Addr = reinterpret_cast<void *>(BaseAddress + Offset); 81 while (madvise(Addr, Size, MADV_DONTNEED) == -1 && errno == EAGAIN) { 82 } 83 } 84 85 // Calling getenv should be fine (c)(tm) at any time. 86 const char *getEnv(const char *Name) { return getenv(Name); } 87 88 namespace { 89 enum State : u32 { Unlocked = 0, Locked = 1, Sleeping = 2 }; 90 } 91 92 bool HybridMutex::tryLock() { 93 return atomic_compare_exchange(&M, Unlocked, Locked) == Unlocked; 94 } 95 96 // The following is based on https://akkadia.org/drepper/futex.pdf. 97 void HybridMutex::lockSlow() { 98 u32 V = atomic_compare_exchange(&M, Unlocked, Locked); 99 if (V == Unlocked) 100 return; 101 if (V != Sleeping) 102 V = atomic_exchange(&M, Sleeping, memory_order_acquire); 103 while (V != Unlocked) { 104 syscall(SYS_futex, reinterpret_cast<uptr>(&M), FUTEX_WAIT_PRIVATE, Sleeping, 105 nullptr, nullptr, 0); 106 V = atomic_exchange(&M, Sleeping, memory_order_acquire); 107 } 108 } 109 110 void HybridMutex::unlock() { 111 if (atomic_fetch_sub(&M, 1U, memory_order_release) != Locked) { 112 atomic_store(&M, Unlocked, memory_order_release); 113 syscall(SYS_futex, reinterpret_cast<uptr>(&M), FUTEX_WAKE_PRIVATE, 1, 114 nullptr, nullptr, 0); 115 } 116 } 117 118 u64 getMonotonicTime() { 119 timespec TS; 120 clock_gettime(CLOCK_MONOTONIC, &TS); 121 return static_cast<u64>(TS.tv_sec) * (1000ULL * 1000 * 1000) + 122 static_cast<u64>(TS.tv_nsec); 123 } 124 125 u32 getNumberOfCPUs() { 126 cpu_set_t CPUs; 127 CHECK_EQ(sched_getaffinity(0, sizeof(cpu_set_t), &CPUs), 0); 128 return static_cast<u32>(CPU_COUNT(&CPUs)); 129 } 130 131 // Blocking is possibly unused if the getrandom block is not compiled in. 132 bool getRandom(void *Buffer, uptr Length, UNUSED bool Blocking) { 133 if (!Buffer || !Length || Length > MaxRandomLength) 134 return false; 135 ssize_t ReadBytes; 136 #if defined(SYS_getrandom) 137 #if !defined(GRND_NONBLOCK) 138 #define GRND_NONBLOCK 1 139 #endif 140 // Up to 256 bytes, getrandom will not be interrupted. 141 ReadBytes = 142 syscall(SYS_getrandom, Buffer, Length, Blocking ? 0 : GRND_NONBLOCK); 143 if (ReadBytes == static_cast<ssize_t>(Length)) 144 return true; 145 #endif // defined(SYS_getrandom) 146 // Up to 256 bytes, a read off /dev/urandom will not be interrupted. 147 // Blocking is moot here, O_NONBLOCK has no effect when opening /dev/urandom. 148 const int FileDesc = open("/dev/urandom", O_RDONLY); 149 if (FileDesc == -1) 150 return false; 151 ReadBytes = read(FileDesc, Buffer, Length); 152 close(FileDesc); 153 return (ReadBytes == static_cast<ssize_t>(Length)); 154 } 155 156 void outputRaw(const char *Buffer) { 157 static HybridMutex Mutex; 158 ScopedLock L(Mutex); 159 write(2, Buffer, strlen(Buffer)); 160 } 161 162 extern "C" WEAK void android_set_abort_message(const char *); 163 164 void setAbortMessage(const char *Message) { 165 if (&android_set_abort_message) 166 android_set_abort_message(Message); 167 } 168 169 } // namespace scudo 170 171 #endif // SCUDO_LINUX 172