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Diffstat (limited to 'tools/fuzzing/libfuzzer/FuzzerUtilFuchsia.cpp')
| -rw-r--r-- | tools/fuzzing/libfuzzer/FuzzerUtilFuchsia.cpp | 565 |
1 files changed, 565 insertions, 0 deletions
diff --git a/tools/fuzzing/libfuzzer/FuzzerUtilFuchsia.cpp b/tools/fuzzing/libfuzzer/FuzzerUtilFuchsia.cpp new file mode 100644 index 0000000000..190fb78666 --- /dev/null +++ b/tools/fuzzing/libfuzzer/FuzzerUtilFuchsia.cpp @@ -0,0 +1,565 @@ +//===- FuzzerUtilFuchsia.cpp - Misc utils for Fuchsia. --------------------===// +// +// 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 +// +//===----------------------------------------------------------------------===// +// Misc utils implementation using Fuchsia/Zircon APIs. +//===----------------------------------------------------------------------===// +#include "FuzzerPlatform.h" + +#if LIBFUZZER_FUCHSIA + +#include "FuzzerInternal.h" +#include "FuzzerUtil.h" +#include <cassert> +#include <cerrno> +#include <cinttypes> +#include <cstdint> +#include <fcntl.h> +#include <lib/fdio/fdio.h> +#include <lib/fdio/spawn.h> +#include <string> +#include <sys/select.h> +#include <thread> +#include <unistd.h> +#include <zircon/errors.h> +#include <zircon/process.h> +#include <zircon/sanitizer.h> +#include <zircon/status.h> +#include <zircon/syscalls.h> +#include <zircon/syscalls/debug.h> +#include <zircon/syscalls/exception.h> +#include <zircon/syscalls/object.h> +#include <zircon/types.h> + +#include <vector> + +namespace fuzzer { + +// Given that Fuchsia doesn't have the POSIX signals that libFuzzer was written +// around, the general approach is to spin up dedicated threads to watch for +// each requested condition (alarm, interrupt, crash). Of these, the crash +// handler is the most involved, as it requires resuming the crashed thread in +// order to invoke the sanitizers to get the needed state. + +// Forward declaration of assembly trampoline needed to resume crashed threads. +// This appears to have external linkage to C++, which is why it's not in the +// anonymous namespace. The assembly definition inside MakeTrampoline() +// actually defines the symbol with internal linkage only. +void CrashTrampolineAsm() __asm__("CrashTrampolineAsm"); + +namespace { + +// Helper function to handle Zircon syscall failures. +void ExitOnErr(zx_status_t Status, const char *Syscall) { + if (Status != ZX_OK) { + Printf("libFuzzer: %s failed: %s\n", Syscall, + _zx_status_get_string(Status)); + exit(1); + } +} + +void AlarmHandler(int Seconds) { + while (true) { + SleepSeconds(Seconds); + Fuzzer::StaticAlarmCallback(); + } +} + +void InterruptHandler() { + fd_set readfds; + // Ctrl-C sends ETX in Zircon. + do { + FD_ZERO(&readfds); + FD_SET(STDIN_FILENO, &readfds); + select(STDIN_FILENO + 1, &readfds, nullptr, nullptr, nullptr); + } while(!FD_ISSET(STDIN_FILENO, &readfds) || getchar() != 0x03); + Fuzzer::StaticInterruptCallback(); +} + +// CFAOffset is used to reference the stack pointer before entering the +// trampoline (Stack Pointer + CFAOffset = prev Stack Pointer). Before jumping +// to the trampoline we copy all the registers onto the stack. We need to make +// sure that the new stack has enough space to store all the registers. +// +// The trampoline holds CFI information regarding the registers stored in the +// stack, which is then used by the unwinder to restore them. +#if defined(__x86_64__) +// In x86_64 the crashing function might also be using the red zone (128 bytes +// on top of their rsp). +constexpr size_t CFAOffset = 128 + sizeof(zx_thread_state_general_regs_t); +#elif defined(__aarch64__) +// In aarch64 we need to always have the stack pointer aligned to 16 bytes, so we +// make sure that we are keeping that same alignment. +constexpr size_t CFAOffset = (sizeof(zx_thread_state_general_regs_t) + 15) & -(uintptr_t)16; +#endif + +// For the crash handler, we need to call Fuzzer::StaticCrashSignalCallback +// without POSIX signal handlers. To achieve this, we use an assembly function +// to add the necessary CFI unwinding information and a C function to bridge +// from that back into C++. + +// FIXME: This works as a short-term solution, but this code really shouldn't be +// architecture dependent. A better long term solution is to implement remote +// unwinding and expose the necessary APIs through sanitizer_common and/or ASAN +// to allow the exception handling thread to gather the crash state directly. +// +// Alternatively, Fuchsia may in future actually implement basic signal +// handling for the machine trap signals. +#if defined(__x86_64__) +#define FOREACH_REGISTER(OP_REG, OP_NUM) \ + OP_REG(rax) \ + OP_REG(rbx) \ + OP_REG(rcx) \ + OP_REG(rdx) \ + OP_REG(rsi) \ + OP_REG(rdi) \ + OP_REG(rbp) \ + OP_REG(rsp) \ + OP_REG(r8) \ + OP_REG(r9) \ + OP_REG(r10) \ + OP_REG(r11) \ + OP_REG(r12) \ + OP_REG(r13) \ + OP_REG(r14) \ + OP_REG(r15) \ + OP_REG(rip) + +#elif defined(__aarch64__) +#define FOREACH_REGISTER(OP_REG, OP_NUM) \ + OP_NUM(0) \ + OP_NUM(1) \ + OP_NUM(2) \ + OP_NUM(3) \ + OP_NUM(4) \ + OP_NUM(5) \ + OP_NUM(6) \ + OP_NUM(7) \ + OP_NUM(8) \ + OP_NUM(9) \ + OP_NUM(10) \ + OP_NUM(11) \ + OP_NUM(12) \ + OP_NUM(13) \ + OP_NUM(14) \ + OP_NUM(15) \ + OP_NUM(16) \ + OP_NUM(17) \ + OP_NUM(18) \ + OP_NUM(19) \ + OP_NUM(20) \ + OP_NUM(21) \ + OP_NUM(22) \ + OP_NUM(23) \ + OP_NUM(24) \ + OP_NUM(25) \ + OP_NUM(26) \ + OP_NUM(27) \ + OP_NUM(28) \ + OP_NUM(29) \ + OP_REG(sp) + +#else +#error "Unsupported architecture for fuzzing on Fuchsia" +#endif + +// Produces a CFI directive for the named or numbered register. +// The value used refers to an assembler immediate operand with the same name +// as the register (see ASM_OPERAND_REG). +#define CFI_OFFSET_REG(reg) ".cfi_offset " #reg ", %c[" #reg "]\n" +#define CFI_OFFSET_NUM(num) CFI_OFFSET_REG(x##num) + +// Produces an assembler immediate operand for the named or numbered register. +// This operand contains the offset of the register relative to the CFA. +#define ASM_OPERAND_REG(reg) \ + [reg] "i"(offsetof(zx_thread_state_general_regs_t, reg) - CFAOffset), +#define ASM_OPERAND_NUM(num) \ + [x##num] "i"(offsetof(zx_thread_state_general_regs_t, r[num]) - CFAOffset), + +// Trampoline to bridge from the assembly below to the static C++ crash +// callback. +__attribute__((noreturn)) +static void StaticCrashHandler() { + Fuzzer::StaticCrashSignalCallback(); + for (;;) { + _Exit(1); + } +} + +// Creates the trampoline with the necessary CFI information to unwind through +// to the crashing call stack: +// * Defining the CFA so that it points to the stack pointer at the point +// of crash. +// * Storing all registers at the point of crash in the stack and refer to them +// via CFI information (relative to the CFA). +// * Setting the return column so the unwinder knows how to continue unwinding. +// * (x86_64) making sure rsp is aligned before calling StaticCrashHandler. +// * Calling StaticCrashHandler that will trigger the unwinder. +// +// The __attribute__((used)) is necessary because the function +// is never called; it's just a container around the assembly to allow it to +// use operands for compile-time computed constants. +__attribute__((used)) +void MakeTrampoline() { + __asm__(".cfi_endproc\n" + ".pushsection .text.CrashTrampolineAsm\n" + ".type CrashTrampolineAsm,STT_FUNC\n" +"CrashTrampolineAsm:\n" + ".cfi_startproc simple\n" + ".cfi_signal_frame\n" +#if defined(__x86_64__) + ".cfi_return_column rip\n" + ".cfi_def_cfa rsp, %c[CFAOffset]\n" + FOREACH_REGISTER(CFI_OFFSET_REG, CFI_OFFSET_NUM) + "mov %%rsp, %%rbp\n" + ".cfi_def_cfa_register rbp\n" + "andq $-16, %%rsp\n" + "call %c[StaticCrashHandler]\n" + "ud2\n" +#elif defined(__aarch64__) + ".cfi_return_column 33\n" + ".cfi_def_cfa sp, %c[CFAOffset]\n" + FOREACH_REGISTER(CFI_OFFSET_REG, CFI_OFFSET_NUM) + ".cfi_offset 33, %c[pc]\n" + ".cfi_offset 30, %c[lr]\n" + "bl %c[StaticCrashHandler]\n" + "brk 1\n" +#else +#error "Unsupported architecture for fuzzing on Fuchsia" +#endif + ".cfi_endproc\n" + ".size CrashTrampolineAsm, . - CrashTrampolineAsm\n" + ".popsection\n" + ".cfi_startproc\n" + : // No outputs + : FOREACH_REGISTER(ASM_OPERAND_REG, ASM_OPERAND_NUM) +#if defined(__aarch64__) + ASM_OPERAND_REG(pc) + ASM_OPERAND_REG(lr) +#endif + [StaticCrashHandler] "i" (StaticCrashHandler), + [CFAOffset] "i" (CFAOffset)); +} + +void CrashHandler(zx_handle_t *Event) { + // This structure is used to ensure we close handles to objects we create in + // this handler. + struct ScopedHandle { + ~ScopedHandle() { _zx_handle_close(Handle); } + zx_handle_t Handle = ZX_HANDLE_INVALID; + }; + + // Create the exception channel. We need to claim to be a "debugger" so the + // kernel will allow us to modify and resume dying threads (see below). Once + // the channel is set, we can signal the main thread to continue and wait + // for the exception to arrive. + ScopedHandle Channel; + zx_handle_t Self = _zx_process_self(); + ExitOnErr(_zx_task_create_exception_channel( + Self, ZX_EXCEPTION_CHANNEL_DEBUGGER, &Channel.Handle), + "_zx_task_create_exception_channel"); + + ExitOnErr(_zx_object_signal(*Event, 0, ZX_USER_SIGNAL_0), + "_zx_object_signal"); + + // This thread lives as long as the process in order to keep handling + // crashes. In practice, the first crashed thread to reach the end of the + // StaticCrashHandler will end the process. + while (true) { + ExitOnErr(_zx_object_wait_one(Channel.Handle, ZX_CHANNEL_READABLE, + ZX_TIME_INFINITE, nullptr), + "_zx_object_wait_one"); + + zx_exception_info_t ExceptionInfo; + ScopedHandle Exception; + ExitOnErr(_zx_channel_read(Channel.Handle, 0, &ExceptionInfo, + &Exception.Handle, sizeof(ExceptionInfo), 1, + nullptr, nullptr), + "_zx_channel_read"); + + // Ignore informational synthetic exceptions. + if (ZX_EXCP_THREAD_STARTING == ExceptionInfo.type || + ZX_EXCP_THREAD_EXITING == ExceptionInfo.type || + ZX_EXCP_PROCESS_STARTING == ExceptionInfo.type) { + continue; + } + + // At this point, we want to get the state of the crashing thread, but + // libFuzzer and the sanitizers assume this will happen from that same + // thread via a POSIX signal handler. "Resurrecting" the thread in the + // middle of the appropriate callback is as simple as forcibly setting the + // instruction pointer/program counter, provided we NEVER EVER return from + // that function (since otherwise our stack will not be valid). + ScopedHandle Thread; + ExitOnErr(_zx_exception_get_thread(Exception.Handle, &Thread.Handle), + "_zx_exception_get_thread"); + + zx_thread_state_general_regs_t GeneralRegisters; + ExitOnErr(_zx_thread_read_state(Thread.Handle, ZX_THREAD_STATE_GENERAL_REGS, + &GeneralRegisters, + sizeof(GeneralRegisters)), + "_zx_thread_read_state"); + + // To unwind properly, we need to push the crashing thread's register state + // onto the stack and jump into a trampoline with CFI instructions on how + // to restore it. +#if defined(__x86_64__) + uintptr_t StackPtr = GeneralRegisters.rsp - CFAOffset; + __unsanitized_memcpy(reinterpret_cast<void *>(StackPtr), &GeneralRegisters, + sizeof(GeneralRegisters)); + GeneralRegisters.rsp = StackPtr; + GeneralRegisters.rip = reinterpret_cast<zx_vaddr_t>(CrashTrampolineAsm); + +#elif defined(__aarch64__) + uintptr_t StackPtr = GeneralRegisters.sp - CFAOffset; + __unsanitized_memcpy(reinterpret_cast<void *>(StackPtr), &GeneralRegisters, + sizeof(GeneralRegisters)); + GeneralRegisters.sp = StackPtr; + GeneralRegisters.pc = reinterpret_cast<zx_vaddr_t>(CrashTrampolineAsm); + +#else +#error "Unsupported architecture for fuzzing on Fuchsia" +#endif + + // Now force the crashing thread's state. + ExitOnErr( + _zx_thread_write_state(Thread.Handle, ZX_THREAD_STATE_GENERAL_REGS, + &GeneralRegisters, sizeof(GeneralRegisters)), + "_zx_thread_write_state"); + + // Set the exception to HANDLED so it resumes the thread on close. + uint32_t ExceptionState = ZX_EXCEPTION_STATE_HANDLED; + ExitOnErr(_zx_object_set_property(Exception.Handle, ZX_PROP_EXCEPTION_STATE, + &ExceptionState, sizeof(ExceptionState)), + "zx_object_set_property"); + } +} + +} // namespace + +// Platform specific functions. +void SetSignalHandler(const FuzzingOptions &Options) { + // Make sure information from libFuzzer and the sanitizers are easy to + // reassemble. `__sanitizer_log_write` has the added benefit of ensuring the + // DSO map is always available for the symbolizer. + // A uint64_t fits in 20 chars, so 64 is plenty. + char Buf[64]; + memset(Buf, 0, sizeof(Buf)); + snprintf(Buf, sizeof(Buf), "==%lu== INFO: libFuzzer starting.\n", GetPid()); + if (EF->__sanitizer_log_write) + __sanitizer_log_write(Buf, sizeof(Buf)); + Printf("%s", Buf); + + // Set up alarm handler if needed. + if (Options.UnitTimeoutSec > 0) { + std::thread T(AlarmHandler, Options.UnitTimeoutSec / 2 + 1); + T.detach(); + } + + // Set up interrupt handler if needed. + if (Options.HandleInt || Options.HandleTerm) { + std::thread T(InterruptHandler); + T.detach(); + } + + // Early exit if no crash handler needed. + if (!Options.HandleSegv && !Options.HandleBus && !Options.HandleIll && + !Options.HandleFpe && !Options.HandleAbrt) + return; + + // Set up the crash handler and wait until it is ready before proceeding. + zx_handle_t Event; + ExitOnErr(_zx_event_create(0, &Event), "_zx_event_create"); + + std::thread T(CrashHandler, &Event); + zx_status_t Status = + _zx_object_wait_one(Event, ZX_USER_SIGNAL_0, ZX_TIME_INFINITE, nullptr); + _zx_handle_close(Event); + ExitOnErr(Status, "_zx_object_wait_one"); + + T.detach(); +} + +void SleepSeconds(int Seconds) { + _zx_nanosleep(_zx_deadline_after(ZX_SEC(Seconds))); +} + +unsigned long GetPid() { + zx_status_t rc; + zx_info_handle_basic_t Info; + if ((rc = _zx_object_get_info(_zx_process_self(), ZX_INFO_HANDLE_BASIC, &Info, + sizeof(Info), NULL, NULL)) != ZX_OK) { + Printf("libFuzzer: unable to get info about self: %s\n", + _zx_status_get_string(rc)); + exit(1); + } + return Info.koid; +} + +size_t GetPeakRSSMb() { + zx_status_t rc; + zx_info_task_stats_t Info; + if ((rc = _zx_object_get_info(_zx_process_self(), ZX_INFO_TASK_STATS, &Info, + sizeof(Info), NULL, NULL)) != ZX_OK) { + Printf("libFuzzer: unable to get info about self: %s\n", + _zx_status_get_string(rc)); + exit(1); + } + return (Info.mem_private_bytes + Info.mem_shared_bytes) >> 20; +} + +template <typename Fn> +class RunOnDestruction { + public: + explicit RunOnDestruction(Fn fn) : fn_(fn) {} + ~RunOnDestruction() { fn_(); } + + private: + Fn fn_; +}; + +template <typename Fn> +RunOnDestruction<Fn> at_scope_exit(Fn fn) { + return RunOnDestruction<Fn>(fn); +} + +static fdio_spawn_action_t clone_fd_action(int localFd, int targetFd) { + return { + .action = FDIO_SPAWN_ACTION_CLONE_FD, + .fd = + { + .local_fd = localFd, + .target_fd = targetFd, + }, + }; +} + +int ExecuteCommand(const Command &Cmd) { + zx_status_t rc; + + // Convert arguments to C array + auto Args = Cmd.getArguments(); + size_t Argc = Args.size(); + assert(Argc != 0); + std::unique_ptr<const char *[]> Argv(new const char *[Argc + 1]); + for (size_t i = 0; i < Argc; ++i) + Argv[i] = Args[i].c_str(); + Argv[Argc] = nullptr; + + // Determine output. On Fuchsia, the fuzzer is typically run as a component + // that lacks a mutable working directory. Fortunately, when this is the case + // a mutable output directory must be specified using "-artifact_prefix=...", + // so write the log file(s) there. + // However, we don't want to apply this logic for absolute paths. + int FdOut = STDOUT_FILENO; + bool discardStdout = false; + bool discardStderr = false; + + if (Cmd.hasOutputFile()) { + std::string Path = Cmd.getOutputFile(); + if (Path == getDevNull()) { + // On Fuchsia, there's no "/dev/null" like-file, so we + // just don't copy the FDs into the spawned process. + discardStdout = true; + } else { + bool IsAbsolutePath = Path.length() > 1 && Path[0] == '/'; + if (!IsAbsolutePath && Cmd.hasFlag("artifact_prefix")) + Path = Cmd.getFlagValue("artifact_prefix") + "/" + Path; + + FdOut = open(Path.c_str(), O_WRONLY | O_CREAT | O_TRUNC, 0); + if (FdOut == -1) { + Printf("libFuzzer: failed to open %s: %s\n", Path.c_str(), + strerror(errno)); + return ZX_ERR_IO; + } + } + } + auto CloseFdOut = at_scope_exit([FdOut]() { + if (FdOut != STDOUT_FILENO) + close(FdOut); + }); + + // Determine stderr + int FdErr = STDERR_FILENO; + if (Cmd.isOutAndErrCombined()) { + FdErr = FdOut; + if (discardStdout) + discardStderr = true; + } + + // Clone the file descriptors into the new process + std::vector<fdio_spawn_action_t> SpawnActions; + SpawnActions.push_back(clone_fd_action(STDIN_FILENO, STDIN_FILENO)); + + if (!discardStdout) + SpawnActions.push_back(clone_fd_action(FdOut, STDOUT_FILENO)); + if (!discardStderr) + SpawnActions.push_back(clone_fd_action(FdErr, STDERR_FILENO)); + + // Start the process. + char ErrorMsg[FDIO_SPAWN_ERR_MSG_MAX_LENGTH]; + zx_handle_t ProcessHandle = ZX_HANDLE_INVALID; + rc = fdio_spawn_etc(ZX_HANDLE_INVALID, + FDIO_SPAWN_CLONE_ALL & (~FDIO_SPAWN_CLONE_STDIO), Argv[0], + Argv.get(), nullptr, SpawnActions.size(), + SpawnActions.data(), &ProcessHandle, ErrorMsg); + + if (rc != ZX_OK) { + Printf("libFuzzer: failed to launch '%s': %s, %s\n", Argv[0], ErrorMsg, + _zx_status_get_string(rc)); + return rc; + } + auto CloseHandle = at_scope_exit([&]() { _zx_handle_close(ProcessHandle); }); + + // Now join the process and return the exit status. + if ((rc = _zx_object_wait_one(ProcessHandle, ZX_PROCESS_TERMINATED, + ZX_TIME_INFINITE, nullptr)) != ZX_OK) { + Printf("libFuzzer: failed to join '%s': %s\n", Argv[0], + _zx_status_get_string(rc)); + return rc; + } + + zx_info_process_t Info; + if ((rc = _zx_object_get_info(ProcessHandle, ZX_INFO_PROCESS, &Info, + sizeof(Info), nullptr, nullptr)) != ZX_OK) { + Printf("libFuzzer: unable to get return code from '%s': %s\n", Argv[0], + _zx_status_get_string(rc)); + return rc; + } + + return Info.return_code; +} + +bool ExecuteCommand(const Command &BaseCmd, std::string *CmdOutput) { + auto LogFilePath = TempPath("SimPopenOut", ".txt"); + Command Cmd(BaseCmd); + Cmd.setOutputFile(LogFilePath); + int Ret = ExecuteCommand(Cmd); + *CmdOutput = FileToString(LogFilePath); + RemoveFile(LogFilePath); + return Ret == 0; +} + +const void *SearchMemory(const void *Data, size_t DataLen, const void *Patt, + size_t PattLen) { + return memmem(Data, DataLen, Patt, PattLen); +} + +// In fuchsia, accessing /dev/null is not supported. There's nothing +// similar to a file that discards everything that is written to it. +// The way of doing something similar in fuchsia is by using +// fdio_null_create and binding that to a file descriptor. +void DiscardOutput(int Fd) { + fdio_t *fdio_null = fdio_null_create(); + if (fdio_null == nullptr) return; + int nullfd = fdio_bind_to_fd(fdio_null, -1, 0); + if (nullfd < 0) return; + dup2(nullfd, Fd); +} + +} // namespace fuzzer + +#endif // LIBFUZZER_FUCHSIA |