1 //===- FuzzerUtilFuchsia.cpp - Misc utils for Fuchsia. --------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
9 // Misc utils implementation using Fuchsia/Zircon APIs.
10 //===----------------------------------------------------------------------===//
11 #include "FuzzerDefs.h"
15 #include "FuzzerInternal.h"
16 #include "FuzzerUtil.h"
21 #include <lib/fdio/spawn.h>
23 #include <sys/select.h>
26 #include <zircon/errors.h>
27 #include <zircon/process.h>
28 #include <zircon/sanitizer.h>
29 #include <zircon/status.h>
30 #include <zircon/syscalls.h>
31 #include <zircon/syscalls/debug.h>
32 #include <zircon/syscalls/exception.h>
33 #include <zircon/syscalls/port.h>
34 #include <zircon/types.h>
38 // Given that Fuchsia doesn't have the POSIX signals that libFuzzer was written
39 // around, the general approach is to spin up dedicated threads to watch for
40 // each requested condition (alarm, interrupt, crash). Of these, the crash
41 // handler is the most involved, as it requires resuming the crashed thread in
42 // order to invoke the sanitizers to get the needed state.
44 // Forward declaration of assembly trampoline needed to resume crashed threads.
45 // This appears to have external linkage to C++, which is why it's not in the
46 // anonymous namespace. The assembly definition inside MakeTrampoline()
47 // actually defines the symbol with internal linkage only.
48 void CrashTrampolineAsm() __asm__("CrashTrampolineAsm");
52 // A magic value for the Zircon exception port, chosen to spell 'FUZZING'
53 // when interpreted as a byte sequence on little-endian platforms.
54 const uint64_t kFuzzingCrash = 0x474e495a5a5546;
56 // Helper function to handle Zircon syscall failures.
57 void ExitOnErr(zx_status_t Status, const char *Syscall) {
58 if (Status != ZX_OK) {
59 Printf("libFuzzer: %s failed: %s\n", Syscall,
60 _zx_status_get_string(Status));
65 void AlarmHandler(int Seconds) {
67 SleepSeconds(Seconds);
68 Fuzzer::StaticAlarmCallback();
72 void InterruptHandler() {
74 // Ctrl-C sends ETX in Zircon.
77 FD_SET(STDIN_FILENO, &readfds);
78 select(STDIN_FILENO + 1, &readfds, nullptr, nullptr, nullptr);
79 } while(!FD_ISSET(STDIN_FILENO, &readfds) || getchar() != 0x03);
80 Fuzzer::StaticInterruptCallback();
83 // For the crash handler, we need to call Fuzzer::StaticCrashSignalCallback
84 // without POSIX signal handlers. To achieve this, we use an assembly function
85 // to add the necessary CFI unwinding information and a C function to bridge
86 // from that back into C++.
88 // FIXME: This works as a short-term solution, but this code really shouldn't be
89 // architecture dependent. A better long term solution is to implement remote
90 // unwinding and expose the necessary APIs through sanitizer_common and/or ASAN
91 // to allow the exception handling thread to gather the crash state directly.
93 // Alternatively, Fuchsia may in future actually implement basic signal
94 // handling for the machine trap signals.
95 #if defined(__x86_64__)
96 #define FOREACH_REGISTER(OP_REG, OP_NUM) \
115 #elif defined(__aarch64__)
116 #define FOREACH_REGISTER(OP_REG, OP_NUM) \
151 #error "Unsupported architecture for fuzzing on Fuchsia"
154 // Produces a CFI directive for the named or numbered register.
155 #define CFI_OFFSET_REG(reg) ".cfi_offset " #reg ", %c[" #reg "]\n"
156 #define CFI_OFFSET_NUM(num) CFI_OFFSET_REG(r##num)
158 // Produces an assembler input operand for the named or numbered register.
159 #define ASM_OPERAND_REG(reg) \
160 [reg] "i"(offsetof(zx_thread_state_general_regs_t, reg)),
161 #define ASM_OPERAND_NUM(num) \
162 [r##num] "i"(offsetof(zx_thread_state_general_regs_t, r[num])),
164 // Trampoline to bridge from the assembly below to the static C++ crash
166 __attribute__((noreturn))
167 static void StaticCrashHandler() {
168 Fuzzer::StaticCrashSignalCallback();
174 // Creates the trampoline with the necessary CFI information to unwind through
175 // to the crashing call stack. The attribute is necessary because the function
176 // is never called; it's just a container around the assembly to allow it to
177 // use operands for compile-time computed constants.
178 __attribute__((used))
179 void MakeTrampoline() {
180 __asm__(".cfi_endproc\n"
181 ".pushsection .text.CrashTrampolineAsm\n"
182 ".type CrashTrampolineAsm,STT_FUNC\n"
183 "CrashTrampolineAsm:\n"
184 ".cfi_startproc simple\n"
185 ".cfi_signal_frame\n"
186 #if defined(__x86_64__)
187 ".cfi_return_column rip\n"
188 ".cfi_def_cfa rsp, 0\n"
189 FOREACH_REGISTER(CFI_OFFSET_REG, CFI_OFFSET_NUM)
190 "call %c[StaticCrashHandler]\n"
192 #elif defined(__aarch64__)
193 ".cfi_return_column 33\n"
194 ".cfi_def_cfa sp, 0\n"
195 ".cfi_offset 33, %c[pc]\n"
196 FOREACH_REGISTER(CFI_OFFSET_REG, CFI_OFFSET_NUM)
197 "bl %[StaticCrashHandler]\n"
199 #error "Unsupported architecture for fuzzing on Fuchsia"
202 ".size CrashTrampolineAsm, . - CrashTrampolineAsm\n"
206 : FOREACH_REGISTER(ASM_OPERAND_REG, ASM_OPERAND_NUM)
207 #if defined(__aarch64__)
210 [StaticCrashHandler] "i" (StaticCrashHandler));
213 void CrashHandler(zx_handle_t *Event) {
214 // This structure is used to ensure we close handles to objects we create in
216 struct ScopedHandle {
217 ~ScopedHandle() { _zx_handle_close(Handle); }
218 zx_handle_t Handle = ZX_HANDLE_INVALID;
221 // Create and bind the exception port. We need to claim to be a "debugger" so
222 // the kernel will allow us to modify and resume dying threads (see below).
223 // Once the port is set, we can signal the main thread to continue and wait
224 // for the exception to arrive.
226 ExitOnErr(_zx_port_create(0, &Port.Handle), "_zx_port_create");
227 zx_handle_t Self = _zx_process_self();
229 ExitOnErr(_zx_task_bind_exception_port(Self, Port.Handle, kFuzzingCrash,
230 ZX_EXCEPTION_PORT_DEBUGGER),
231 "_zx_task_bind_exception_port");
233 ExitOnErr(_zx_object_signal(*Event, 0, ZX_USER_SIGNAL_0),
234 "_zx_object_signal");
236 zx_port_packet_t Packet;
237 ExitOnErr(_zx_port_wait(Port.Handle, ZX_TIME_INFINITE, &Packet),
240 // At this point, we want to get the state of the crashing thread, but
241 // libFuzzer and the sanitizers assume this will happen from that same thread
242 // via a POSIX signal handler. "Resurrecting" the thread in the middle of the
243 // appropriate callback is as simple as forcibly setting the instruction
244 // pointer/program counter, provided we NEVER EVER return from that function
245 // (since otherwise our stack will not be valid).
247 ExitOnErr(_zx_object_get_child(Self, Packet.exception.tid,
248 ZX_RIGHT_SAME_RIGHTS, &Thread.Handle),
249 "_zx_object_get_child");
251 zx_thread_state_general_regs_t GeneralRegisters;
252 ExitOnErr(_zx_thread_read_state(Thread.Handle, ZX_THREAD_STATE_GENERAL_REGS,
253 &GeneralRegisters, sizeof(GeneralRegisters)),
254 "_zx_thread_read_state");
256 // To unwind properly, we need to push the crashing thread's register state
257 // onto the stack and jump into a trampoline with CFI instructions on how
259 #if defined(__x86_64__)
261 (GeneralRegisters.rsp - (128 + sizeof(GeneralRegisters))) &
263 __unsanitized_memcpy(reinterpret_cast<void *>(StackPtr), &GeneralRegisters,
264 sizeof(GeneralRegisters));
265 GeneralRegisters.rsp = StackPtr;
266 GeneralRegisters.rip = reinterpret_cast<zx_vaddr_t>(CrashTrampolineAsm);
268 #elif defined(__aarch64__)
270 (GeneralRegisters.sp - sizeof(GeneralRegisters)) & -(uintptr_t)16;
271 __unsanitized_memcpy(reinterpret_cast<void *>(StackPtr), &GeneralRegisters,
272 sizeof(GeneralRegisters));
273 GeneralRegisters.sp = StackPtr;
274 GeneralRegisters.pc = reinterpret_cast<zx_vaddr_t>(CrashTrampolineAsm);
277 #error "Unsupported architecture for fuzzing on Fuchsia"
280 // Now force the crashing thread's state.
281 ExitOnErr(_zx_thread_write_state(Thread.Handle, ZX_THREAD_STATE_GENERAL_REGS,
282 &GeneralRegisters, sizeof(GeneralRegisters)),
283 "_zx_thread_write_state");
285 ExitOnErr(_zx_task_resume_from_exception(Thread.Handle, Port.Handle, 0),
286 "_zx_task_resume_from_exception");
291 // Platform specific functions.
292 void SetSignalHandler(const FuzzingOptions &Options) {
293 // Set up alarm handler if needed.
294 if (Options.UnitTimeoutSec > 0) {
295 std::thread T(AlarmHandler, Options.UnitTimeoutSec / 2 + 1);
299 // Set up interrupt handler if needed.
300 if (Options.HandleInt || Options.HandleTerm) {
301 std::thread T(InterruptHandler);
305 // Early exit if no crash handler needed.
306 if (!Options.HandleSegv && !Options.HandleBus && !Options.HandleIll &&
307 !Options.HandleFpe && !Options.HandleAbrt)
310 // Set up the crash handler and wait until it is ready before proceeding.
312 ExitOnErr(_zx_event_create(0, &Event), "_zx_event_create");
314 std::thread T(CrashHandler, &Event);
316 _zx_object_wait_one(Event, ZX_USER_SIGNAL_0, ZX_TIME_INFINITE, nullptr);
317 _zx_handle_close(Event);
318 ExitOnErr(Status, "_zx_object_wait_one");
323 void SleepSeconds(int Seconds) {
324 _zx_nanosleep(_zx_deadline_after(ZX_SEC(Seconds)));
327 unsigned long GetPid() {
329 zx_info_handle_basic_t Info;
330 if ((rc = _zx_object_get_info(_zx_process_self(), ZX_INFO_HANDLE_BASIC, &Info,
331 sizeof(Info), NULL, NULL)) != ZX_OK) {
332 Printf("libFuzzer: unable to get info about self: %s\n",
333 _zx_status_get_string(rc));
339 size_t GetPeakRSSMb() {
341 zx_info_task_stats_t Info;
342 if ((rc = _zx_object_get_info(_zx_process_self(), ZX_INFO_TASK_STATS, &Info,
343 sizeof(Info), NULL, NULL)) != ZX_OK) {
344 Printf("libFuzzer: unable to get info about self: %s\n",
345 _zx_status_get_string(rc));
348 return (Info.mem_private_bytes + Info.mem_shared_bytes) >> 20;
351 template <typename Fn>
352 class RunOnDestruction {
354 explicit RunOnDestruction(Fn fn) : fn_(fn) {}
355 ~RunOnDestruction() { fn_(); }
361 template <typename Fn>
362 RunOnDestruction<Fn> at_scope_exit(Fn fn) {
363 return RunOnDestruction<Fn>(fn);
366 int ExecuteCommand(const Command &Cmd) {
369 // Convert arguments to C array
370 auto Args = Cmd.getArguments();
371 size_t Argc = Args.size();
373 std::unique_ptr<const char *[]> Argv(new const char *[Argc + 1]);
374 for (size_t i = 0; i < Argc; ++i)
375 Argv[i] = Args[i].c_str();
376 Argv[Argc] = nullptr;
378 // Determine output. On Fuchsia, the fuzzer is typically run as a component
379 // that lacks a mutable working directory. Fortunately, when this is the case
380 // a mutable output directory must be specified using "-artifact_prefix=...",
381 // so write the log file(s) there.
382 int FdOut = STDOUT_FILENO;
383 if (Cmd.hasOutputFile()) {
385 if (Cmd.hasFlag("artifact_prefix"))
386 Path = Cmd.getFlagValue("artifact_prefix") + "/" + Cmd.getOutputFile();
388 Path = Cmd.getOutputFile();
389 FdOut = open(Path.c_str(), O_WRONLY | O_CREAT | O_TRUNC, 0);
391 Printf("libFuzzer: failed to open %s: %s\n", Path.c_str(),
396 auto CloseFdOut = at_scope_exit([FdOut]() {
397 if (FdOut != STDOUT_FILENO)
402 int FdErr = STDERR_FILENO;
403 if (Cmd.isOutAndErrCombined())
406 // Clone the file descriptors into the new process
407 fdio_spawn_action_t SpawnAction[] = {
409 .action = FDIO_SPAWN_ACTION_CLONE_FD,
412 .local_fd = STDIN_FILENO,
413 .target_fd = STDIN_FILENO,
417 .action = FDIO_SPAWN_ACTION_CLONE_FD,
421 .target_fd = STDOUT_FILENO,
425 .action = FDIO_SPAWN_ACTION_CLONE_FD,
429 .target_fd = STDERR_FILENO,
434 // Start the process.
435 char ErrorMsg[FDIO_SPAWN_ERR_MSG_MAX_LENGTH];
436 zx_handle_t ProcessHandle = ZX_HANDLE_INVALID;
438 ZX_HANDLE_INVALID, FDIO_SPAWN_CLONE_ALL & (~FDIO_SPAWN_CLONE_STDIO),
439 Argv[0], Argv.get(), nullptr, 3, SpawnAction, &ProcessHandle, ErrorMsg);
441 Printf("libFuzzer: failed to launch '%s': %s, %s\n", Argv[0], ErrorMsg,
442 _zx_status_get_string(rc));
445 auto CloseHandle = at_scope_exit([&]() { _zx_handle_close(ProcessHandle); });
447 // Now join the process and return the exit status.
448 if ((rc = _zx_object_wait_one(ProcessHandle, ZX_PROCESS_TERMINATED,
449 ZX_TIME_INFINITE, nullptr)) != ZX_OK) {
450 Printf("libFuzzer: failed to join '%s': %s\n", Argv[0],
451 _zx_status_get_string(rc));
455 zx_info_process_t Info;
456 if ((rc = _zx_object_get_info(ProcessHandle, ZX_INFO_PROCESS, &Info,
457 sizeof(Info), nullptr, nullptr)) != ZX_OK) {
458 Printf("libFuzzer: unable to get return code from '%s': %s\n", Argv[0],
459 _zx_status_get_string(rc));
463 return Info.return_code;
466 const void *SearchMemory(const void *Data, size_t DataLen, const void *Patt,
468 return memmem(Data, DataLen, Patt, PattLen);
471 } // namespace fuzzer
473 #endif // LIBFUZZER_FUCHSIA