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#include "thread_api/tx_init_thread.h"
#if TX_HAVE_THREAD_API
#include "tx_pthread.h"
#include "tx_call.h"
#include "tx_log.h"
#include "tx_prototypes.h"
#include "tx_pthread.h"
#include "tx_utils.h"
#include "thread_api/tx_stage0_mach_ports.h"
#include "thread_api/tx_stage1_shared_memory.h"
#include <assert.h>
#include <stdlib.h>
#include <unistd.h>
// Perform straightforward initialization using a supplied thread port.
static bool
init_with_thread(threadexec_t threadexec) {
DEBUG_TRACE(1, "Using thread 0x%x", threadexec->thread);
assert(threadexec->thread != MACH_PORT_NULL);
// Perform pthread setup if this is a bare thread.
bool ok;
if (threadexec->flags & TX_BARE_THREAD) {
// We assume the thread already has an initialized stack.
ok = tx_pthread_init_bare_thread(threadexec);
if (!ok) {
goto fail;
}
}
// Set up Mach ports to send messages between this task and the remote thread.
ok = tx_stage0_init_mach_ports(threadexec);
if (!ok) {
goto fail;
}
// Set up the shared memory region.
ok = tx_stage1_init_shared_memory(threadexec);
if (!ok) {
goto fail;
}
// Return success.
return true;
fail:
tx_deinit_with_thread_api(threadexec);
return false;
}
// Pick a thread in the task to hijack.
static thread_t pick_hijack_thread(task_t task) {
thread_t hijack = MACH_PORT_NULL;
// Get all the threads in the task.
thread_act_array_t threads;
mach_msg_type_number_t thread_count;
kern_return_t kr = task_threads(task, &threads, &thread_count);
if (kr != KERN_SUCCESS) {
ERROR_CALL(task_threads, "%u", kr);
goto fail_0;
}
if (thread_count == 0) {
ERROR("No threads in task 0x%x", task);
goto fail_1;
}
// Find a candidate thread.
thread_t thread = MACH_PORT_NULL;
for (long i = thread_count - 1; thread == MACH_PORT_NULL && i >= 0; i--) {
int suspend_count = thread_get_suspend_count(threads[i]);
if (suspend_count == 0) {
thread = threads[i];
break;
}
}
if (thread == MACH_PORT_NULL) {
ERROR("No available candidate threads to hijack");
goto fail_1;
}
// Success!
hijack = thread;
// Deallocate the thread ports and array.
fail_1:
for (size_t i = 0; i < thread_count; i++) {
DEBUG_TRACE(2, "Task 0x%x: thread 0x%x", task, threads[i]);
if (threads[i] != hijack) {
mach_port_deallocate(mach_task_self(), threads[i]);
}
}
mach_vm_deallocate(mach_task_self(), (mach_vm_address_t) threads,
thread_count * sizeof(*threads));
fail_0:
return hijack;
}
// Hijack and use an existing thread. This is only safe if we'll kill the task anyway, since the
// thread will be totally consumed.
static bool
init_by_hijacking_thread(threadexec_t threadexec) {
DEBUG_TRACE(1, "Performing thread hijacking");
assert(threadexec->flags & TX_KILL_TASK);
assert(threadexec->thread == MACH_PORT_NULL);
assert((threadexec->flags & (TX_SUSPEND | TX_PRESERVE | TX_RESUME | TX_KILL_THREAD)) == 0);
// First pick a thread to hijack. The thread is not suspended.
thread_t hijack = pick_hijack_thread(threadexec->task);
if (hijack == MACH_PORT_NULL) {
ERROR("Could not hijack a thread in task 0x%x", threadexec->task);
return false;
}
// Now initialize with that.
threadexec->flags |= TX_SUSPEND;
threadexec->thread = hijack;
return tx_init_internal(threadexec);
}
// When we don't have a thread, we will perform thread hijacking to create one. First, we will
// choose a preexisting thread in the task to hijack, and create a threadexec with that using
// TX_PRESERVE semantics. Then we will use that thread to create a new thread. Once we have the new
// thread, we will replace the original thread in the threadexec struct with the new thread.
static bool
init_without_thread(threadexec_t threadexec) {
DEBUG_TRACE(1, "Performing temporary thread hijacking");
ERROR("NOT IMPLEMENTED"); // TODO: There used to be a partial implementation here.
// TODO: The issue appears to be that the suspend/abort/get_state/set_state/resume sequence
// doesn't actually perfectly preserve the state of the original thread. Thus, even after
// setting the state to identically match the original state, the thread will sometimes
// crash on resume. Unfortunately I don't know any way around this.
return false;
}
bool
tx_init_with_thread_api(threadexec_t threadexec) {
DEBUG_TRACE(1, "Using thread API");
// We use different initialization strategies for when we do and don't have a thread port.
if (threadexec->thread != MACH_PORT_NULL) {
return init_with_thread(threadexec);
} else if (threadexec->flags & TX_KILL_TASK) {
// The above condition isn't exactly correct: it should really be: "hijack a thread
// permanently if the user doesn't care about maintaining the integrity of the
// process", which is even more strict than TX_KILL_TASK.
return init_by_hijacking_thread(threadexec);
} else {
return init_without_thread(threadexec);
}
}
void
tx_deinit_with_thread_api(threadexec_t threadexec) {
DEBUG_TRACE(2, "%s", __func__);
if (threadexec->shmem_size) {
// Don't bother deallocating the remote memory if we're killing the task.
if (threadexec->shmem_remote != 0 && (threadexec->flags & TX_KILL_TASK) == 0) {
DEBUG_TRACE(2, "Deallocating remote shared memory");
WARNING("NOT IMPLEMENTED"); // TODO: There used to be an incorrect version.
// Go back to the initial commit to retrieve it.
// TODO: The problem is we can't deallocate the memory that is our
// stack or we'll crash! Therefore we need to save the old SP before we set
// it (implicitly) with a call to thread_call_stack().
}
if (threadexec->shmem != NULL) {
DEBUG_TRACE(2, "Deallocating local shared memory");
mach_vm_deallocate(mach_task_self(), (mach_vm_address_t) threadexec->shmem,
threadexec->shmem_size);
threadexec->shmem = NULL;
}
threadexec->shmem_size = 0;
}
// TODO: Destroy these ports on the remote end.
DEBUG_TRACE(2, "Destroying local Mach ports");
if (threadexec->local_port != MACH_PORT_NULL) {
mach_port_destroy(mach_task_self(), threadexec->local_port);
threadexec->local_port = MACH_PORT_NULL;
}
if (threadexec->remote_port != MACH_PORT_NULL) {
mach_port_deallocate(mach_task_self(), threadexec->remote_port);
threadexec->remote_port = MACH_PORT_NULL;
}
}
#endif // TX_HAVE_THREAD_API
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