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llvm-project/compiler-rt/lib/fuzzer/FuzzerUtilFuchsia.cpp
Petr Hosek a70ece45eb [lib/fuzzer] Fix logging for Fuchsia 
This change fixes two aspects of logging on Fuchsia:

1. When logging to stdout, the output file descriptor should not be
closed in ExecuteCommand, as it prevent fdio_spawn_etc from succeeding
in subsequent calls.
2. When logging to a file in anything other than standalone Zircon, the
log file needs to be created in mutable storage. The best indicator
where this is relative to the Fuchsia component will be given by
'-artifact_prefix=...', so save the log file relative to that path.

Patch by: aarongreen
Differential Revision: https://reviews.llvm.org/D52562

llvm-svn: 343607
2018-10-02 17:21:04 +00:00

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//===- FuzzerUtilFuchsia.cpp - Misc utils for Fuchsia. --------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// Misc utils implementation using Fuchsia/Zircon APIs.
//===----------------------------------------------------------------------===//
#include "FuzzerDefs.h"
#if LIBFUZZER_FUCHSIA
#include "FuzzerInternal.h"
#include "FuzzerUtil.h"
#include <cerrno>
#include <cinttypes>
#include <cstdint>
#include <fcntl.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/port.h>
#include <zircon/types.h>
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 {
// A magic value for the Zircon exception port, chosen to spell 'FUZZING'
// when interpreted as a byte sequence on little-endian platforms.
const uint64_t kFuzzingCrash = 0x474e495a5a5546;
// 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();
}
// 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_NUM(30) \
OP_REG(sp)
#else
#error "Unsupported architecture for fuzzing on Fuchsia"
#endif
// Produces a CFI directive for the named or numbered register.
#define CFI_OFFSET_REG(reg) ".cfi_offset " #reg ", %c[" #reg "]\n"
#define CFI_OFFSET_NUM(num) CFI_OFFSET_REG(r##num)
// Produces an assembler input operand for the named or numbered register.
#define ASM_OPERAND_REG(reg) \
[reg] "i"(offsetof(zx_thread_state_general_regs_t, reg)),
#define ASM_OPERAND_NUM(num) \
[r##num] "i"(offsetof(zx_thread_state_general_regs_t, r[num])),
// 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. The attribute 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, 0\n"
FOREACH_REGISTER(CFI_OFFSET_REG, CFI_OFFSET_NUM)
"call %c[StaticCrashHandler]\n"
"ud2\n"
#elif defined(__aarch64__)
".cfi_return_column 33\n"
".cfi_def_cfa sp, 0\n"
".cfi_offset 33, %c[pc]\n"
FOREACH_REGISTER(CFI_OFFSET_REG, CFI_OFFSET_NUM)
"bl %[StaticCrashHandler]\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)
#endif
[StaticCrashHandler] "i" (StaticCrashHandler));
}
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 and bind the exception port. We need to claim to be a "debugger" so
// the kernel will allow us to modify and resume dying threads (see below).
// Once the port is set, we can signal the main thread to continue and wait
// for the exception to arrive.
ScopedHandle Port;
ExitOnErr(_zx_port_create(0, &Port.Handle), "_zx_port_create");
zx_handle_t Self = _zx_process_self();
ExitOnErr(_zx_task_bind_exception_port(Self, Port.Handle, kFuzzingCrash,
ZX_EXCEPTION_PORT_DEBUGGER),
"_zx_task_bind_exception_port");
ExitOnErr(_zx_object_signal(*Event, 0, ZX_USER_SIGNAL_0),
"_zx_object_signal");
zx_port_packet_t Packet;
ExitOnErr(_zx_port_wait(Port.Handle, ZX_TIME_INFINITE, &Packet),
"_zx_port_wait");
// 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_object_get_child(Self, Packet.exception.tid,
ZX_RIGHT_SAME_RIGHTS, &Thread.Handle),
"_zx_object_get_child");
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 - (128 + sizeof(GeneralRegisters))) &
-(uintptr_t)16;
__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 - sizeof(GeneralRegisters)) & -(uintptr_t)16;
__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");
ExitOnErr(_zx_task_resume_from_exception(Thread.Handle, Port.Handle, 0),
"_zx_task_resume_from_exception");
}
} // namespace
// Platform specific functions.
void SetSignalHandler(const FuzzingOptions &Options) {
// 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);
}
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.
int FdOut = STDOUT_FILENO;
if (Cmd.hasOutputFile()) {
std::string Path;
if (Cmd.hasFlag("artifact_prefix"))
Path = Cmd.getFlagValue("artifact_prefix") + "/" + Cmd.getOutputFile();
else
Path = Cmd.getOutputFile();
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;
// Clone the file descriptors into the new process
fdio_spawn_action_t SpawnAction[] = {
{
.action = FDIO_SPAWN_ACTION_CLONE_FD,
.fd =
{
.local_fd = STDIN_FILENO,
.target_fd = STDIN_FILENO,
},
},
{
.action = FDIO_SPAWN_ACTION_CLONE_FD,
.fd =
{
.local_fd = FdOut,
.target_fd = STDOUT_FILENO,
},
},
{
.action = FDIO_SPAWN_ACTION_CLONE_FD,
.fd =
{
.local_fd = FdErr,
.target_fd = 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, 3, SpawnAction, &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;
}
const void *SearchMemory(const void *Data, size_t DataLen, const void *Patt,
size_t PattLen) {
return memmem(Data, DataLen, Patt, PattLen);
}
} // namespace fuzzer
#endif // LIBFUZZER_FUCHSIA
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