signal-handling.c
// This file is a part of Julia. License is MIT: https://julialang.org/license
#include <stdlib.h>
#include <stddef.h>
#include <stdio.h>
#include <inttypes.h>
#include "julia.h"
#include "julia_internal.h"
#ifndef _OS_WINDOWS_
#include <unistd.h>
#include <sys/mman.h>
#endif
#ifdef __cplusplus
extern "C" {
#endif
#include <threading.h>
// Profiler control variables
// Note: these "static" variables are also used in "signals-*.c"
static volatile jl_bt_element_t *bt_data_prof = NULL;
static volatile size_t bt_size_max = 0;
static volatile size_t bt_size_cur = 0;
static volatile uint64_t nsecprof = 0;
static volatile int running = 0;
static const uint64_t GIGA = 1000000000ULL;
static uint64_t profile_cong_rng_seed = 0;
static uint64_t profile_cong_rng_unbias = 0;
static volatile uint64_t *profile_round_robin_thread_order = NULL;
// Timers to take samples at intervals
JL_DLLEXPORT void jl_profile_stop_timer(void);
JL_DLLEXPORT int jl_profile_start_timer(void);
void jl_lock_profile(void);
void jl_unlock_profile(void);
void jl_shuffle_int_array_inplace(volatile uint64_t *carray, size_t size, uint64_t *seed);
JL_DLLEXPORT int jl_profile_is_buffer_full(void)
{
// declare buffer full if there isn't enough room to take samples across all threads
#if defined(_OS_WINDOWS_)
uint64_t nthreads = 1; // windows only profiles the main thread
#else
uint64_t nthreads = jl_n_threads;
#endif
// the `+ 6` is for the two block terminators `0` plus 4 metadata entries
return bt_size_cur + (((JL_BT_MAX_ENTRY_SIZE + 1) + 6) * nthreads) > bt_size_max;
}
static uint64_t jl_last_sigint_trigger = 0;
static uint64_t jl_disable_sigint_time = 0;
static void jl_clear_force_sigint(void)
{
jl_last_sigint_trigger = 0;
}
static int jl_check_force_sigint(void)
{
static double accum_weight = 0;
uint64_t cur_time = uv_hrtime();
uint64_t dt = cur_time - jl_last_sigint_trigger;
uint64_t last_t = jl_last_sigint_trigger;
jl_last_sigint_trigger = cur_time;
if (last_t == 0) {
accum_weight = 0;
return 0;
}
double new_weight = accum_weight * exp(-(dt / 1e9)) + 0.3;
if (!isnormal(new_weight))
new_weight = 0;
accum_weight = new_weight;
if (new_weight > 1) {
jl_disable_sigint_time = cur_time + (uint64_t)0.5e9;
return 1;
}
jl_disable_sigint_time = 0;
return 0;
}
#ifndef _OS_WINDOWS_
// Not thread local, should only be accessed by the signal handler thread.
static volatile int jl_sigint_passed = 0;
static sigset_t jl_sigint_sset;
#endif
static int jl_ignore_sigint(void)
{
// On Unix, we get the SIGINT before the debugger which makes it very
// hard to interrupt a running process in the debugger with `Ctrl-C`.
// Manually raise a `SIGINT` on current thread with the signal temporarily
// unblocked and use it's behavior to decide if we need to handle the signal.
#ifndef _OS_WINDOWS_
jl_sigint_passed = 0;
pthread_sigmask(SIG_UNBLOCK, &jl_sigint_sset, NULL);
// This can swallow an external `SIGINT` but it's not an issue
// since we don't deliver the same number of signals anyway.
pthread_kill(pthread_self(), SIGINT);
pthread_sigmask(SIG_BLOCK, &jl_sigint_sset, NULL);
if (!jl_sigint_passed)
return 1;
#endif
// Force sigint requires pressing `Ctrl-C` repeatedly.
// Ignore sigint for a short time after that to avoid rethrowing sigint too
// quickly again. (Code that has this issue is inherently racy but this is
// an interactive feature anyway.)
return jl_disable_sigint_time && jl_disable_sigint_time > uv_hrtime();
}
static int exit_on_sigint = 0;
JL_DLLEXPORT void jl_exit_on_sigint(int on)
{
exit_on_sigint = on;
}
static uintptr_t jl_get_pc_from_ctx(const void *_ctx);
void jl_show_sigill(void *_ctx);
static size_t jl_safe_read_mem(const volatile char *ptr, char *out, size_t len)
{
jl_jmp_buf *old_buf = jl_get_safe_restore();
jl_jmp_buf buf;
jl_set_safe_restore(&buf);
volatile size_t i = 0;
if (!jl_setjmp(buf, 0)) {
for (; i < len; i++) {
out[i] = ptr[i];
}
}
jl_set_safe_restore(old_buf);
return i;
}
#if defined(_WIN32)
#include "signals-win.c"
#else
#include "signals-unix.c"
#endif
static uintptr_t jl_get_pc_from_ctx(const void *_ctx)
{
#if defined(_OS_LINUX_) && defined(_CPU_X86_64_)
return ((ucontext_t*)_ctx)->uc_mcontext.gregs[REG_RIP];
#elif defined(_OS_FREEBSD_) && defined(_CPU_X86_64_)
return ((ucontext_t*)_ctx)->uc_mcontext.mc_rip;
#elif defined(_OS_LINUX_) && defined(_CPU_X86_)
return ((ucontext_t*)_ctx)->uc_mcontext.gregs[REG_EIP];
#elif defined(_OS_FREEBSD_) && defined(_CPU_X86_)
return ((ucontext_t*)_ctx)->uc_mcontext.mc_eip;
#elif defined(_OS_DARWIN_) && defined(_CPU_x86_64_)
return ((ucontext64_t*)_ctx)->uc_mcontext64->__ss.__rip;
#elif defined(_OS_DARWIN_) && defined(_CPU_AARCH64_)
return ((ucontext64_t*)_ctx)->uc_mcontext64->__ss.__pc;
#elif defined(_OS_WINDOWS_) && defined(_CPU_X86_)
return ((CONTEXT*)_ctx)->Eip;
#elif defined(_OS_WINDOWS_) && defined(_CPU_X86_64_)
return ((CONTEXT*)_ctx)->Rip;
#elif defined(_OS_LINUX_) && defined(_CPU_AARCH64_)
return ((ucontext_t*)_ctx)->uc_mcontext.pc;
#elif defined(_OS_LINUX_) && defined(_CPU_ARM_)
return ((ucontext_t*)_ctx)->uc_mcontext.arm_pc;
#else
// TODO for PPC
return 0;
#endif
}
void jl_show_sigill(void *_ctx)
{
char *pc = (char*)jl_get_pc_from_ctx(_ctx);
// unsupported platform
if (!pc)
return;
#if defined(_CPU_X86_64_) || defined(_CPU_X86_)
uint8_t inst[15]; // max length of x86 instruction
size_t len = jl_safe_read_mem(pc, (char*)inst, sizeof(inst));
// ud2
if (len >= 2 && inst[0] == 0x0f && inst[1] == 0x0b) {
jl_safe_printf("Unreachable reached at %p\n", (void*)pc);
}
else {
jl_safe_printf("Invalid instruction at %p: ", (void*)pc);
for (int i = 0;i < len;i++) {
if (i == 0) {
jl_safe_printf("0x%02" PRIx8, inst[i]);
}
else {
jl_safe_printf(", 0x%02" PRIx8, inst[i]);
}
}
jl_safe_printf("\n");
}
#elif defined(_OS_LINUX_) && defined(_CPU_AARCH64_)
uint32_t inst = 0;
size_t len = jl_safe_read_mem(pc, (char*)&inst, 4);
if (len < 4)
jl_safe_printf("Fault when reading instruction: %d bytes read\n", (int)len);
if (inst == 0xd4200020) { // brk #0x1
// The signal might actually be SIGTRAP instead, doesn't hurt to handle it here though.
jl_safe_printf("Unreachable reached at %p\n", pc);
}
else {
jl_safe_printf("Invalid instruction at %p: 0x%08" PRIx32 "\n", pc, inst);
}
#elif defined(_OS_LINUX_) && defined(_CPU_ARM_)
ucontext_t *ctx = (ucontext_t*)_ctx;
if (ctx->uc_mcontext.arm_cpsr & (1 << 5)) {
// Thumb
uint16_t inst[2] = {0, 0};
size_t len = jl_safe_read_mem(pc, (char*)&inst, 4);
if (len < 2)
jl_safe_printf("Fault when reading Thumb instruction: %d bytes read\n", (int)len);
// LLVM and GCC uses different code for the trap...
if (inst[0] == 0xdefe || inst[0] == 0xdeff) {
// The signal might actually be SIGTRAP instead, doesn't hurt to handle it here though.
jl_safe_printf("Unreachable reached in Thumb mode at %p: 0x%04" PRIx16 "\n",
(void*)pc, inst[0]);
}
else {
jl_safe_printf("Invalid Thumb instruction at %p: 0x%04" PRIx16 ", 0x%04" PRIx16 "\n",
(void*)pc, inst[0], inst[1]);
}
}
else {
uint32_t inst = 0;
size_t len = jl_safe_read_mem(pc, (char*)&inst, 4);
if (len < 4)
jl_safe_printf("Fault when reading instruction: %d bytes read\n", (int)len);
// LLVM and GCC uses different code for the trap...
if (inst == 0xe7ffdefe || inst == 0xe7f000f0) {
// The signal might actually be SIGTRAP instead, doesn't hurt to handle it here though.
jl_safe_printf("Unreachable reached in ARM mode at %p: 0x%08" PRIx32 "\n",
(void*)pc, inst);
}
else {
jl_safe_printf("Invalid ARM instruction at %p: 0x%08" PRIx32 "\n", (void*)pc, inst);
}
}
#else
// TODO for PPC
(void)_ctx;
#endif
}
// what to do on a critical error on a thread
void jl_critical_error(int sig, bt_context_t *context, jl_task_t *ct)
{
jl_bt_element_t *bt_data = ct ? ct->ptls->bt_data : NULL;
size_t *bt_size = ct ? &ct->ptls->bt_size : NULL;
size_t i, n = ct ? *bt_size : 0;
if (sig) {
// kill this task, so that we cannot get back to it accidentally (via an untimely ^C or jlbacktrace in jl_exit)
jl_set_safe_restore(NULL);
if (ct) {
ct->gcstack = NULL;
ct->eh = NULL;
ct->excstack = NULL;
ct->ptls->locks.len = 0;
ct->ptls->in_pure_callback = 0;
ct->ptls->in_finalizer = 1;
ct->world_age = 1;
}
#ifndef _OS_WINDOWS_
sigset_t sset;
sigemptyset(&sset);
// n.b. In `abort()`, Apple's libSystem "helpfully" blocks all signals
// on all threads but SIGABRT. But we also don't know what the thread
// was doing, so unblock all critical signals so that they will crash
// hard, and not just get stuck.
sigaddset(&sset, SIGSEGV);
sigaddset(&sset, SIGBUS);
sigaddset(&sset, SIGILL);
// also unblock fatal signals now, so we won't get back here twice
sigaddset(&sset, SIGTERM);
sigaddset(&sset, SIGABRT);
sigaddset(&sset, SIGQUIT);
// and the original signal is now fatal too, in case it wasn't
// something already listed (?)
if (sig != SIGINT)
sigaddset(&sset, sig);
pthread_sigmask(SIG_UNBLOCK, &sset, NULL);
#endif
jl_safe_printf("\nsignal (%d): %s\n", sig, strsignal(sig));
}
jl_safe_printf("in expression starting at %s:%d\n", jl_filename, jl_lineno);
if (context && ct) {
// Must avoid extended backtrace frames here unless we're sure bt_data
// is properly rooted.
*bt_size = n = rec_backtrace_ctx(bt_data, JL_MAX_BT_SIZE, context, NULL);
}
for (i = 0; i < n; i += jl_bt_entry_size(bt_data + i)) {
jl_print_bt_entry_codeloc(bt_data + i);
}
jl_gc_debug_print_status();
jl_gc_debug_critical_error();
}
///////////////////////
// Utility functions //
///////////////////////
JL_DLLEXPORT int jl_profile_init(size_t maxsize, uint64_t delay_nsec)
{
bt_size_max = maxsize;
nsecprof = delay_nsec;
if (bt_data_prof != NULL)
free((void*)bt_data_prof);
if (profile_round_robin_thread_order == NULL) {
// NOTE: We currently only allocate this once, since jl_n_threads cannot change
// during execution of a julia process. If/when this invariant changes in the
// future, this will have to be adjusted.
profile_round_robin_thread_order = (uint64_t*) calloc(jl_n_threads, sizeof(uint64_t));
for (int i = 0; i < jl_n_threads; i++) {
profile_round_robin_thread_order[i] = i;
}
}
seed_cong(&profile_cong_rng_seed);
unbias_cong(jl_n_threads, &profile_cong_rng_unbias);
bt_data_prof = (jl_bt_element_t*) calloc(maxsize, sizeof(jl_bt_element_t));
if (bt_data_prof == NULL && maxsize > 0)
return -1;
bt_size_cur = 0;
return 0;
}
void jl_shuffle_int_array_inplace(volatile uint64_t *carray, size_t size, uint64_t *seed) {
// The "modern Fisher–Yates shuffle" - O(n) algorithm
// https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
for (size_t i = size - 1; i >= 1; --i) {
size_t j = cong(i, profile_cong_rng_unbias, seed);
uint64_t tmp = carray[j];
carray[j] = carray[i];
carray[i] = tmp;
}
}
JL_DLLEXPORT uint8_t *jl_profile_get_data(void)
{
return (uint8_t*) bt_data_prof;
}
JL_DLLEXPORT size_t jl_profile_len_data(void)
{
return bt_size_cur;
}
JL_DLLEXPORT size_t jl_profile_maxlen_data(void)
{
return bt_size_max;
}
JL_DLLEXPORT uint64_t jl_profile_delay_nsec(void)
{
return nsecprof;
}
JL_DLLEXPORT void jl_profile_clear_data(void)
{
bt_size_cur = 0;
}
JL_DLLEXPORT int jl_profile_is_running(void)
{
return running;
}
#ifdef __cplusplus
}
#endif