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//===-- linux.cc ------------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "platform.h"
#if SCUDO_LINUX
#include "common.h"
#include "linux.h"
#include "mutex.h"
#include "string_utils.h"
#include <errno.h>
#include <fcntl.h>
#include <linux/futex.h>
#include <sched.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <time.h>
#include <unistd.h>
#if SCUDO_ANDROID
#include <sys/prctl.h>
// Definitions of prctl arguments to set a vma name in Android kernels.
#define ANDROID_PR_SET_VMA 0x53564d41
#define ANDROID_PR_SET_VMA_ANON_NAME 0
#endif
namespace scudo {
uptr getPageSize() { return static_cast<uptr>(sysconf(_SC_PAGESIZE)); }
void NORETURN die() { abort(); }
void *map(void *Addr, uptr Size, UNUSED const char *Name, uptr Flags,
UNUSED MapPlatformData *Data) {
int MmapFlags = MAP_PRIVATE | MAP_ANON;
int MmapProt;
if (Flags & MAP_NOACCESS) {
MmapFlags |= MAP_NORESERVE;
MmapProt = PROT_NONE;
} else {
MmapProt = PROT_READ | PROT_WRITE;
}
if (Addr) {
// Currently no scenario for a noaccess mapping with a fixed address.
DCHECK_EQ(Flags & MAP_NOACCESS, 0);
MmapFlags |= MAP_FIXED;
}
void *P = mmap(Addr, Size, MmapProt, MmapFlags, -1, 0);
if (P == MAP_FAILED) {
if (!(Flags & MAP_ALLOWNOMEM) || errno != ENOMEM)
dieOnMapUnmapError(errno == ENOMEM);
return nullptr;
}
#if SCUDO_ANDROID
if (!(Flags & MAP_NOACCESS))
prctl(ANDROID_PR_SET_VMA, ANDROID_PR_SET_VMA_ANON_NAME, P, Size, Name);
#endif
return P;
}
void unmap(void *Addr, uptr Size, UNUSED uptr Flags,
UNUSED MapPlatformData *Data) {
if (munmap(Addr, Size) != 0)
dieOnMapUnmapError();
}
void releasePagesToOS(uptr BaseAddress, uptr Offset, uptr Size,
UNUSED MapPlatformData *Data) {
void *Addr = reinterpret_cast<void *>(BaseAddress + Offset);
while (madvise(Addr, Size, MADV_DONTNEED) == -1 && errno == EAGAIN) {
}
}
// Calling getenv should be fine (c)(tm) at any time.
const char *getEnv(const char *Name) { return getenv(Name); }
namespace {
enum State : u32 { Unlocked = 0, Locked = 1, Sleeping = 2 };
}
bool HybridMutex::tryLock() {
return atomic_compare_exchange(&M, Unlocked, Locked) == Unlocked;
}
// The following is based on https://akkadia.org/drepper/futex.pdf.
void HybridMutex::lockSlow() {
u32 V = atomic_compare_exchange(&M, Unlocked, Locked);
if (V == Unlocked)
return;
if (V != Sleeping)
V = atomic_exchange(&M, Sleeping, memory_order_acquire);
while (V != Unlocked) {
syscall(SYS_futex, reinterpret_cast<uptr>(&M), FUTEX_WAIT_PRIVATE, Sleeping,
nullptr, nullptr, 0);
V = atomic_exchange(&M, Sleeping, memory_order_acquire);
}
}
void HybridMutex::unlock() {
if (atomic_fetch_sub(&M, 1U, memory_order_release) != Locked) {
atomic_store(&M, Unlocked, memory_order_release);
syscall(SYS_futex, reinterpret_cast<uptr>(&M), FUTEX_WAKE_PRIVATE, 1,
nullptr, nullptr, 0);
}
}
u64 getMonotonicTime() {
timespec TS;
clock_gettime(CLOCK_MONOTONIC, &TS);
return static_cast<u64>(TS.tv_sec) * (1000ULL * 1000 * 1000) +
static_cast<u64>(TS.tv_nsec);
}
u32 getNumberOfCPUs() {
cpu_set_t CPUs;
CHECK_EQ(sched_getaffinity(0, sizeof(cpu_set_t), &CPUs), 0);
return static_cast<u32>(CPU_COUNT(&CPUs));
}
// Blocking is possibly unused if the getrandom block is not compiled in.
bool getRandom(void *Buffer, uptr Length, UNUSED bool Blocking) {
if (!Buffer || !Length || Length > MaxRandomLength)
return false;
ssize_t ReadBytes;
#if defined(SYS_getrandom)
#if !defined(GRND_NONBLOCK)
#define GRND_NONBLOCK 1
#endif
// Up to 256 bytes, getrandom will not be interrupted.
ReadBytes =
syscall(SYS_getrandom, Buffer, Length, Blocking ? 0 : GRND_NONBLOCK);
if (ReadBytes == static_cast<ssize_t>(Length))
return true;
#endif // defined(SYS_getrandom)
// Up to 256 bytes, a read off /dev/urandom will not be interrupted.
// Blocking is moot here, O_NONBLOCK has no effect when opening /dev/urandom.
const int FileDesc = open("/dev/urandom", O_RDONLY);
if (FileDesc == -1)
return false;
ReadBytes = read(FileDesc, Buffer, Length);
close(FileDesc);
return (ReadBytes == static_cast<ssize_t>(Length));
}
void outputRaw(const char *Buffer) {
static HybridMutex Mutex;
ScopedLock L(Mutex);
write(2, Buffer, strlen(Buffer));
}
extern "C" WEAK void android_set_abort_message(const char *);
void setAbortMessage(const char *Message) {
if (&android_set_abort_message)
android_set_abort_message(Message);
}
} // namespace scudo
#endif // SCUDO_LINUX
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