diff options
Diffstat (limited to 'src/runtime/cgo/gcc_signal_ios_arm64.c')
| -rw-r--r-- | src/runtime/cgo/gcc_signal_ios_arm64.c | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/src/runtime/cgo/gcc_signal_ios_arm64.c b/src/runtime/cgo/gcc_signal_ios_arm64.c new file mode 100644 index 0000000..6519edd --- /dev/null +++ b/src/runtime/cgo/gcc_signal_ios_arm64.c @@ -0,0 +1,213 @@ +// Copyright 2015 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Emulation of the Unix signal SIGSEGV. +// +// On iOS, Go tests and apps under development are run by lldb. +// The debugger uses a task-level exception handler to intercept signals. +// Despite having a 'handle' mechanism like gdb, lldb will not allow a +// SIGSEGV to pass to the running program. For Go, this means we cannot +// generate a panic, which cannot be recovered, and so tests fail. +// +// We work around this by registering a thread-level mach exception handler +// and intercepting EXC_BAD_ACCESS. The kernel offers thread handlers a +// chance to resolve exceptions before the task handler, so we can generate +// the panic and avoid lldb's SIGSEGV handler. +// +// The dist tool enables this by build flag when testing. + +// +build lldb + +#include <limits.h> +#include <pthread.h> +#include <stdio.h> +#include <signal.h> +#include <stdlib.h> +#include <unistd.h> + +#include <mach/arm/thread_status.h> +#include <mach/exception_types.h> +#include <mach/mach.h> +#include <mach/mach_init.h> +#include <mach/mach_port.h> +#include <mach/thread_act.h> +#include <mach/thread_status.h> + +#include "libcgo.h" +#include "libcgo_unix.h" + +void xx_cgo_panicmem(void); +uintptr_t x_cgo_panicmem = (uintptr_t)xx_cgo_panicmem; + +static pthread_mutex_t mach_exception_handler_port_set_mu; +static mach_port_t mach_exception_handler_port_set = MACH_PORT_NULL; + +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_vector, + mach_msg_type_number_t code_count) +{ + kern_return_t ret; + arm_unified_thread_state_t thread_state; + mach_msg_type_number_t state_count = ARM_UNIFIED_THREAD_STATE_COUNT; + + // Returning KERN_SUCCESS intercepts the exception. + // + // Returning KERN_FAILURE lets the exception fall through to the + // next handler, which is the standard signal emulation code + // registered on the task port. + + if (exception != EXC_BAD_ACCESS) { + return KERN_FAILURE; + } + + ret = thread_get_state(thread, ARM_UNIFIED_THREAD_STATE, (thread_state_t)&thread_state, &state_count); + if (ret) { + fprintf(stderr, "runtime/cgo: thread_get_state failed: %d\n", ret); + abort(); + } + + // Bounce call to sigpanic through asm that makes it look like + // we call sigpanic directly from the faulting code. +#ifdef __arm64__ + thread_state.ts_64.__x[1] = thread_state.ts_64.__lr; + thread_state.ts_64.__x[2] = thread_state.ts_64.__pc; + thread_state.ts_64.__pc = x_cgo_panicmem; +#else + thread_state.ts_32.__r[1] = thread_state.ts_32.__lr; + thread_state.ts_32.__r[2] = thread_state.ts_32.__pc; + thread_state.ts_32.__pc = x_cgo_panicmem; +#endif + + if (0) { + // Useful debugging logic when panicmem is broken. + // + // Sends the first SIGSEGV and lets lldb catch the + // second one, avoiding a loop that locks up iOS + // devices requiring a hard reboot. + fprintf(stderr, "runtime/cgo: caught exc_bad_access\n"); + fprintf(stderr, "__lr = %llx\n", thread_state.ts_64.__lr); + fprintf(stderr, "__pc = %llx\n", thread_state.ts_64.__pc); + static int pass1 = 0; + if (pass1) { + return KERN_FAILURE; + } + pass1 = 1; + } + + ret = thread_set_state(thread, ARM_UNIFIED_THREAD_STATE, (thread_state_t)&thread_state, state_count); + if (ret) { + fprintf(stderr, "runtime/cgo: thread_set_state failed: %d\n", ret); + abort(); + } + + return KERN_SUCCESS; +} + +void +darwin_arm_init_thread_exception_port() +{ + // Called by each new OS thread to bind its EXC_BAD_ACCESS exception + // to mach_exception_handler_port_set. + int ret; + mach_port_t port = MACH_PORT_NULL; + + ret = mach_port_allocate(mach_task_self(), MACH_PORT_RIGHT_RECEIVE, &port); + if (ret) { + fprintf(stderr, "runtime/cgo: mach_port_allocate failed: %d\n", ret); + abort(); + } + ret = mach_port_insert_right( + mach_task_self(), + port, + port, + MACH_MSG_TYPE_MAKE_SEND); + if (ret) { + fprintf(stderr, "runtime/cgo: mach_port_insert_right failed: %d\n", ret); + abort(); + } + + ret = thread_set_exception_ports( + mach_thread_self(), + EXC_MASK_BAD_ACCESS, + port, + EXCEPTION_DEFAULT, + THREAD_STATE_NONE); + if (ret) { + fprintf(stderr, "runtime/cgo: thread_set_exception_ports failed: %d\n", ret); + abort(); + } + + ret = pthread_mutex_lock(&mach_exception_handler_port_set_mu); + if (ret) { + fprintf(stderr, "runtime/cgo: pthread_mutex_lock failed: %d\n", ret); + abort(); + } + ret = mach_port_move_member( + mach_task_self(), + port, + mach_exception_handler_port_set); + if (ret) { + fprintf(stderr, "runtime/cgo: mach_port_move_member failed: %d\n", ret); + abort(); + } + ret = pthread_mutex_unlock(&mach_exception_handler_port_set_mu); + if (ret) { + fprintf(stderr, "runtime/cgo: pthread_mutex_unlock failed: %d\n", ret); + abort(); + } +} + +static void* +mach_exception_handler(void *port) +{ + // Calls catch_exception_raise. + extern boolean_t exc_server(); + mach_msg_server(exc_server, 2048, (mach_port_t)port, 0); + abort(); // never returns +} + +void +darwin_arm_init_mach_exception_handler() +{ + pthread_mutex_init(&mach_exception_handler_port_set_mu, NULL); + + // Called once per process to initialize a mach port server, listening + // for EXC_BAD_ACCESS thread exceptions. + int ret; + pthread_t thr = NULL; + pthread_attr_t attr; + sigset_t ign, oset; + + ret = mach_port_allocate( + mach_task_self(), + MACH_PORT_RIGHT_PORT_SET, + &mach_exception_handler_port_set); + if (ret) { + fprintf(stderr, "runtime/cgo: mach_port_allocate failed for port_set: %d\n", ret); + abort(); + } + + // Block all signals to the exception handler thread + sigfillset(&ign); + pthread_sigmask(SIG_SETMASK, &ign, &oset); + + // Start a thread to handle exceptions. + uintptr_t port_set = (uintptr_t)mach_exception_handler_port_set; + pthread_attr_init(&attr); + pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED); + ret = _cgo_try_pthread_create(&thr, &attr, mach_exception_handler, (void*)port_set); + + pthread_sigmask(SIG_SETMASK, &oset, nil); + + if (ret) { + fprintf(stderr, "runtime/cgo: pthread_create failed: %d\n", ret); + abort(); + } + pthread_attr_destroy(&attr); +} |