signals-mach.c
// This file is a part of Julia. License is MIT: https://julialang.org/license
#include <mach/clock.h>
#include <mach/clock_types.h>
#include <mach/clock_reply.h>
#include <mach/mach_traps.h>
#include <mach/task.h>
#include <mach/mig_errors.h>
#include <AvailabilityMacros.h>
#ifdef MAC_OS_X_VERSION_10_9
#include <sys/_types/_ucontext64.h>
#else
#define __need_ucontext64_t
#include <sys/_structs.h>
#endif
#include "julia_assert.h"
static void attach_exception_port(thread_port_t thread, int segv_only);
#ifdef JULIA_ENABLE_THREADING
// low 16 bits are the thread id, the next 8 bits are the original gc_state
static arraylist_t suspended_threads;
void jl_mach_gc_end(void)
{
// Requires the safepoint lock to be held
for (size_t i = 0;i < suspended_threads.len;i++) {
uintptr_t item = (uintptr_t)suspended_threads.items[i];
int16_t tid = (int16_t)item;
int8_t gc_state = (int8_t)(item >> 8);
jl_ptls_t ptls2 = jl_all_tls_states[tid];
jl_atomic_store_release(&ptls2->gc_state, gc_state);
thread_resume(pthread_mach_thread_np(ptls2->system_id));
}
suspended_threads.len = 0;
}
// Suspend the thread and return `1` if the GC is running.
// Otherwise return `0`
static int jl_mach_gc_wait(jl_ptls_t ptls2,
mach_port_t thread, int16_t tid)
{
jl_mutex_lock_nogc(&safepoint_lock);
if (!jl_gc_running) {
// GC is done before we get the message or the safepoint is enabled
// for SIGINT.
jl_mutex_unlock_nogc(&safepoint_lock);
return 0;
}
// Otherwise, set the gc state of the thread, suspend and record it
int8_t gc_state = ptls2->gc_state;
jl_atomic_store_release(&ptls2->gc_state, JL_GC_STATE_WAITING);
uintptr_t item = tid | (((uintptr_t)gc_state) << 16);
arraylist_push(&suspended_threads, (void*)item);
thread_suspend(thread);
jl_mutex_unlock_nogc(&safepoint_lock);
return 1;
}
#endif
static mach_port_t segv_port = 0;
extern boolean_t exc_server(mach_msg_header_t *, mach_msg_header_t *);
#define STR(x) #x
#define XSTR(x) STR(x)
#define HANDLE_MACH_ERROR(msg, retval) \
if (retval != KERN_SUCCESS) { mach_error(msg XSTR(: __FILE__:__LINE__:), (retval)); jl_exit(1); }
void *mach_segv_listener(void *arg)
{
(void)arg;
while (1) {
int ret = mach_msg_server(exc_server, 2048, segv_port, MACH_MSG_TIMEOUT_NONE);
jl_safe_printf("mach_msg_server: %s\n", mach_error_string(ret));
jl_exit(128 + SIGSEGV);
}
}
static void allocate_segv_handler()
{
#ifdef JULIA_ENABLE_THREADING
arraylist_new(&suspended_threads, jl_n_threads);
#endif
pthread_t thread;
pthread_attr_t attr;
kern_return_t ret;
mach_port_t self = mach_task_self();
ret = mach_port_allocate(self, MACH_PORT_RIGHT_RECEIVE, &segv_port);
HANDLE_MACH_ERROR("mach_port_allocate",ret);
ret = mach_port_insert_right(self, segv_port, segv_port, MACH_MSG_TYPE_MAKE_SEND);
HANDLE_MACH_ERROR("mach_port_insert_right",ret);
// Alright, create a thread to serve as the listener for exceptions
if (pthread_attr_init(&attr) != 0) {
jl_error("pthread_attr_init failed");
}
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
if (pthread_create(&thread, &attr, mach_segv_listener, NULL) != 0) {
jl_error("pthread_create failed");
}
pthread_attr_destroy(&attr);
for (int16_t tid = 0;tid < jl_n_threads;tid++) {
attach_exception_port(pthread_mach_thread_np(jl_all_tls_states[tid]->system_id), 0);
}
}
#ifdef LIBOSXUNWIND
volatile mach_port_t mach_profiler_thread = 0;
static kern_return_t profiler_segv_handler
(mach_port_t exception_port,
mach_port_t thread,
mach_port_t task,
exception_type_t exception,
exception_data_t code,
mach_msg_type_number_t code_count);
#endif
enum x86_trap_flags {
USER_MODE = 0x4,
WRITE_FAULT = 0x2,
PAGE_PRESENT = 0x1
};
static void jl_call_in_state(jl_ptls_t ptls2, x86_thread_state64_t *state,
void (*fptr)(void))
{
uint64_t rsp = (uint64_t)ptls2->signal_stack + sig_stack_size;
assert(rsp % 16 == 0);
// push (null) $RIP onto the stack
rsp -= sizeof(void*);
*(void**)rsp = NULL;
state->__rsp = rsp; // set stack pointer
state->__rip = (uint64_t)fptr; // "call" the function
}
static void jl_throw_in_thread(int tid, mach_port_t thread, jl_value_t *exception)
{
unsigned int count = MACHINE_THREAD_STATE_COUNT;
x86_thread_state64_t state;
kern_return_t ret = thread_get_state(thread, x86_THREAD_STATE64, (thread_state_t)&state, &count);
HANDLE_MACH_ERROR("thread_get_state", ret);
jl_ptls_t ptls2 = jl_all_tls_states[tid];
if (!ptls2->safe_restore) {
assert(exception);
ptls2->bt_size = rec_backtrace_ctx(ptls2->bt_data, JL_MAX_BT_SIZE,
(bt_context_t*)&state);
ptls2->exception_in_transit = exception;
}
jl_call_in_state(ptls2, &state, &jl_rethrow);
ret = thread_set_state(thread, x86_THREAD_STATE64,
(thread_state_t)&state, count);
HANDLE_MACH_ERROR("thread_set_state",ret);
}
//exc_server uses dlsym to find symbol
JL_DLLEXPORT
kern_return_t catch_exception_raise(mach_port_t exception_port,
mach_port_t thread,
mach_port_t task,
exception_type_t exception,
exception_data_t code,
mach_msg_type_number_t code_count)
{
unsigned int count = MACHINE_THREAD_STATE_COUNT;
unsigned int exc_count = X86_EXCEPTION_STATE64_COUNT;
x86_exception_state64_t exc_state;
x86_thread_state64_t state;
#ifdef LIBOSXUNWIND
if (thread == mach_profiler_thread) {
return profiler_segv_handler(exception_port, thread, task, exception, code, code_count);
}
#endif
int16_t tid;
#ifdef JULIA_ENABLE_THREADING
jl_ptls_t ptls2 = NULL;
for (tid = 0;tid < jl_n_threads;tid++) {
jl_ptls_t _ptls2 = jl_all_tls_states[tid];
if (pthread_mach_thread_np(_ptls2->system_id) == thread) {
ptls2 = _ptls2;
break;
}
}
if (!ptls2) {
// We don't know about this thread, let the kernel try another handler
// instead. This shouldn't actually happen since we only register the
// handler for the threads we know about.
jl_safe_printf("ERROR: Exception handler triggered on unmanaged thread.\n");
return KERN_INVALID_ARGUMENT;
}
#else
jl_ptls_t ptls2 = &jl_tls_states;
tid = 0;
#endif
if (exception == EXC_ARITHMETIC) {
jl_throw_in_thread(tid, thread, jl_diverror_exception);
return KERN_SUCCESS;
}
assert(exception == EXC_BAD_ACCESS);
kern_return_t ret = thread_get_state(thread, x86_EXCEPTION_STATE64, (thread_state_t)&exc_state, &exc_count);
HANDLE_MACH_ERROR("thread_get_state", ret);
uint64_t fault_addr = exc_state.__faultvaddr;
if (jl_addr_is_safepoint(fault_addr)) {
#ifdef JULIA_ENABLE_THREADING
if (jl_mach_gc_wait(ptls2, thread, tid))
return KERN_SUCCESS;
if (ptls2->tid != 0)
return KERN_SUCCESS;
#endif
if (ptls2->defer_signal) {
jl_safepoint_defer_sigint();
}
else if (jl_safepoint_consume_sigint()) {
jl_clear_force_sigint();
jl_throw_in_thread(tid, thread, jl_interrupt_exception);
}
return KERN_SUCCESS;
}
if (ptls2->safe_restore) {
jl_throw_in_thread(tid, thread, jl_stackovf_exception);
return KERN_SUCCESS;
}
#ifdef SEGV_EXCEPTION
if (1) {
#else
if (msync((void*)(fault_addr & ~(jl_page_size - 1)), 1, MS_ASYNC) == 0) { // check if this was a valid address
#endif
jl_value_t *excpt;
if (is_addr_on_stack(ptls2, (void*)fault_addr)) {
excpt = jl_stackovf_exception;
}
#ifdef SEGV_EXCEPTION
else if (msync((void*)(fault_addr & ~(jl_page_size - 1)), 1, MS_ASYNC) != 0) {
// no page mapped at this address
excpt = jl_segv_exception;
}
#endif
else {
if (!(exc_state.__err & WRITE_FAULT))
return KERN_INVALID_ARGUMENT; // rethrow the SEGV since it wasn't an error with writing to read-only memory
excpt = jl_readonlymemory_exception;
}
jl_throw_in_thread(tid, thread, excpt);
return KERN_SUCCESS;
}
else {
kern_return_t ret = thread_get_state(thread, x86_THREAD_STATE64, (thread_state_t)&state, &count);
HANDLE_MACH_ERROR("thread_get_state", ret);
jl_critical_error(SIGSEGV, (unw_context_t*)&state,
ptls2->bt_data, &ptls2->bt_size);
return KERN_INVALID_ARGUMENT;
}
}
static void attach_exception_port(thread_port_t thread, int segv_only)
{
kern_return_t ret;
// http://www.opensource.apple.com/source/xnu/xnu-2782.1.97/osfmk/man/thread_set_exception_ports.html
exception_mask_t mask = EXC_MASK_BAD_ACCESS;
if (!segv_only)
mask |= EXC_MASK_ARITHMETIC;
ret = thread_set_exception_ports(thread, mask, segv_port, EXCEPTION_DEFAULT, MACHINE_THREAD_STATE);
HANDLE_MACH_ERROR("thread_set_exception_ports", ret);
}
static void jl_thread_suspend_and_get_state(int tid, unw_context_t **ctx)
{
jl_ptls_t ptls2 = jl_all_tls_states[tid];
mach_port_t tid_port = pthread_mach_thread_np(ptls2->system_id);
kern_return_t ret = thread_suspend(tid_port);
HANDLE_MACH_ERROR("thread_suspend", ret);
// Do the actual sampling
unsigned int count = MACHINE_THREAD_STATE_COUNT;
static unw_context_t state;
memset(&state, 0, sizeof(unw_context_t));
// Get the state of the suspended thread
ret = thread_get_state(tid_port, x86_THREAD_STATE64, (thread_state_t)&state, &count);
// Initialize the unwind context with the suspend thread's state
*ctx = &state;
}
static void jl_thread_resume(int tid, int sig)
{
jl_ptls_t ptls2 = jl_all_tls_states[tid];
mach_port_t thread = pthread_mach_thread_np(ptls2->system_id);
kern_return_t ret = thread_resume(thread);
HANDLE_MACH_ERROR("thread_resume", ret);
}
// Throw jl_interrupt_exception if the master thread is in a signal async region
// or if SIGINT happens too often.
static void jl_try_deliver_sigint(void)
{
jl_ptls_t ptls2 = jl_all_tls_states[0];
mach_port_t thread = pthread_mach_thread_np(ptls2->system_id);
kern_return_t ret = thread_suspend(thread);
HANDLE_MACH_ERROR("thread_suspend", ret);
// This aborts `sleep` and other syscalls.
ret = thread_abort(thread);
HANDLE_MACH_ERROR("thread_abort", ret);
jl_safepoint_enable_sigint();
int force = jl_check_force_sigint();
if (force || (!ptls2->defer_signal && ptls2->io_wait)) {
jl_safepoint_consume_sigint();
if (force)
jl_safe_printf("WARNING: Force throwing a SIGINT\n");
jl_clear_force_sigint();
jl_throw_in_thread(0, thread, jl_interrupt_exception);
}
else {
jl_wake_libuv();
}
ret = thread_resume(thread);
HANDLE_MACH_ERROR("thread_resume", ret);
}
static void jl_exit_thread0(int exitstate)
{
jl_ptls_t ptls2 = jl_all_tls_states[0];
mach_port_t thread = pthread_mach_thread_np(ptls2->system_id);
kern_return_t ret = thread_suspend(thread);
HANDLE_MACH_ERROR("thread_suspend", ret);
// This aborts `sleep` and other syscalls.
ret = thread_abort(thread);
HANDLE_MACH_ERROR("thread_abort", ret);
unsigned int count = MACHINE_THREAD_STATE_COUNT;
x86_thread_state64_t state;
ret = thread_get_state(thread, x86_THREAD_STATE64,
(thread_state_t)&state, &count);
void (*exit_func)(int) = &_exit;
if (thread0_exit_count <= 1) {
exit_func = &jl_exit;
}
else if (thread0_exit_count == 2) {
exit_func = &exit;
}
// First integer argument. Not portable but good enough =)
state.__rdi = exitstate;
jl_call_in_state(ptls2, &state, (void (*)(void))exit_func);
ret = thread_set_state(thread, x86_THREAD_STATE64,
(thread_state_t)&state, count);
HANDLE_MACH_ERROR("thread_set_state",ret);
ret = thread_resume(thread);
HANDLE_MACH_ERROR("thread_resume", ret);
}
static int profile_started = 0;
mach_timespec_t timerprof;
static pthread_t profiler_thread;
clock_serv_t clk;
static mach_port_t profile_port = 0;
#ifdef LIBOSXUNWIND
volatile static int forceDwarf = -2;
static unw_context_t profiler_uc;
static kern_return_t profiler_segv_handler
(mach_port_t exception_port,
mach_port_t thread,
mach_port_t task,
exception_type_t exception,
exception_data_t code,
mach_msg_type_number_t code_count)
{
assert(thread == mach_profiler_thread);
x86_thread_state64_t state;
// Not currently unwinding. Raise regular segfault
if (forceDwarf == -2)
return KERN_INVALID_ARGUMENT;
if (forceDwarf == 0)
forceDwarf = 1;
else
forceDwarf = -1;
unsigned int count = MACHINE_THREAD_STATE_COUNT;
thread_get_state(thread, x86_THREAD_STATE64, (thread_state_t)&state, &count);
// don't change cs fs gs rflags
uint64_t cs = state.__cs;
uint64_t fs = state.__fs;
uint64_t gs = state.__gs;
uint64_t rflags = state.__rflags;
memcpy(&state, &profiler_uc, sizeof(x86_thread_state64_t));
state.__cs = cs;
state.__fs = fs;
state.__gs = gs;
state.__rflags = rflags;
kern_return_t ret = thread_set_state(thread, x86_THREAD_STATE64, (thread_state_t)&state, count);
HANDLE_MACH_ERROR("thread_set_state", ret);
return KERN_SUCCESS;
}
#endif
void *mach_profile_listener(void *arg)
{
(void)arg;
int i;
const int max_size = 512;
attach_exception_port(mach_thread_self(), 1);
#ifdef LIBOSXUNWIND
mach_profiler_thread = mach_thread_self();
#endif
mig_reply_error_t *bufRequest = (mig_reply_error_t *) malloc(max_size);
while (1) {
kern_return_t ret = mach_msg(&bufRequest->Head, MACH_RCV_MSG,
0, max_size, profile_port,
MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL);
HANDLE_MACH_ERROR("mach_msg", ret);
// sample each thread, round-robin style in reverse order
// (so that thread zero gets notified last)
for (i = jl_n_threads; i-- > 0; ) {
// if there is no space left, break early
if (bt_size_cur >= bt_size_max - 1)
break;
unw_context_t *uc;
jl_thread_suspend_and_get_state(i, &uc);
#ifdef LIBOSXUNWIND
/*
* Unfortunately compact unwind info is incorrectly generated for quite a number of
* libraries by quite a large number of compilers. We can fall back to DWARF unwind info
* in some cases, but in quite a number of cases (especially libraries not compiled in debug
* mode, only the compact unwind info may be available). Even more unfortunately, there is no
* way to detect such bogus compact unwind info (other than noticing the resulting segfault).
* What we do here is ugly, but necessary until the compact unwind info situation improves.
* We try to use the compact unwind info and if that results in a segfault, we retry with DWARF info.
* Note that in a small number of cases this may result in bogus stack traces, but at least the topmost
* entry will always be correct, and the number of cases in which this is an issue is rather small.
* Other than that, this implementation is not incorrect as the other thread is paused while we are profiling
* and during stack unwinding we only ever read memory, but never write it.
*/
forceDwarf = 0;
unw_getcontext(&profiler_uc); // will resume from this point if the next lines segfault at any point
if (forceDwarf == 0) {
// Save the backtrace
bt_size_cur += rec_backtrace_ctx((uintptr_t*)bt_data_prof + bt_size_cur, bt_size_max - bt_size_cur - 1, uc);
}
else if (forceDwarf == 1) {
bt_size_cur += rec_backtrace_ctx_dwarf((uintptr_t*)bt_data_prof + bt_size_cur, bt_size_max - bt_size_cur - 1, uc);
}
else if (forceDwarf == -1) {
jl_safe_printf("WARNING: profiler attempt to access an invalid memory location\n");
}
forceDwarf = -2;
#else
bt_size_cur += rec_backtrace_ctx((uintptr_t*)bt_data_prof + bt_size_cur, bt_size_max - bt_size_cur - 1, uc);
#endif
// Mark the end of this block with 0
bt_data_prof[bt_size_cur++] = 0;
// We're done! Resume the thread.
jl_thread_resume(i, 0);
if (running) {
// Reset the alarm
kern_return_t ret = clock_alarm(clk, TIME_RELATIVE, timerprof, profile_port);
HANDLE_MACH_ERROR("clock_alarm", ret)
}
}
}
}
JL_DLLEXPORT int jl_profile_start_timer(void)
{
kern_return_t ret;
if (!profile_started) {
mach_port_t self = mach_task_self();
ret = host_get_clock_service(mach_host_self(), SYSTEM_CLOCK, (clock_serv_t *)&clk);
HANDLE_MACH_ERROR("host_get_clock_service", ret);
ret = mach_port_allocate(self, MACH_PORT_RIGHT_RECEIVE, &profile_port);
HANDLE_MACH_ERROR("mach_port_allocate", ret);
// Alright, create a thread to serve as the listener for exceptions
pthread_attr_t attr;
if (pthread_attr_init(&attr) != 0) {
jl_error("pthread_attr_init failed");
}
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
if (pthread_create(&profiler_thread, &attr, mach_profile_listener, NULL) != 0) {
jl_error("pthread_create failed");
}
pthread_attr_destroy(&attr);
profile_started = 1;
}
timerprof.tv_sec = nsecprof/GIGA;
timerprof.tv_nsec = nsecprof%GIGA;
running = 1;
ret = clock_alarm(clk, TIME_RELATIVE, timerprof, profile_port);
HANDLE_MACH_ERROR("clock_alarm", ret);
return 0;
}
JL_DLLEXPORT void jl_profile_stop_timer(void)
{
running = 0;
}