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- /* Copyright (C) 2014 Stony Brook University
- This file is part of Graphene Library OS.
- Graphene Library OS is free software: you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public License
- as published by the Free Software Foundation, either version 3 of the
- License, or (at your option) any later version.
- Graphene Library OS is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU Lesser General Public License for more details.
- You should have received a copy of the GNU Lesser General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>. */
- /*
- * db_threading.c
- *
- * This file contain APIs to create, exit and yield a thread.
- */
- #include "api.h"
- #include "pal.h"
- #include "pal_debug.h"
- #include "pal_defs.h"
- #include "pal_error.h"
- #include "pal_internal.h"
- #include "pal_linux.h"
- #include "pal_linux_defs.h"
- #include "spinlock.h"
- #include <errno.h>
- #include <linux/mman.h>
- #include <linux/sched.h>
- #include <linux/signal.h>
- #include <linux/types.h>
- #include <linux/wait.h>
- #if defined(__i386__)
- #include <asm/ldt.h>
- #else
- #include <asm/prctl.h>
- #endif
- /* Linux PAL cannot use mmap/unmap to manage thread stacks because this may overlap with
- * pal_control.user_address. Linux PAL also cannot just use malloc/free because DkThreadExit
- * needs to use raw system calls and inline asm. Thus, we resort to recycling thread stacks
- * allocated by previous threads and not used anymore. This still leaks memory but at least
- * it is bounded by the maximum number of simultaneously executing threads. Note that main
- * thread is not a part of this mechanism (it only allocates a tiny altstack). */
- struct thread_stack_map_t {
- void* stack;
- bool used;
- };
- static struct thread_stack_map_t* g_thread_stack_map = NULL;
- static size_t g_thread_stack_num = 0;
- static size_t g_thread_stack_size = 0;
- static spinlock_t g_thread_stack_lock = INIT_SPINLOCK_UNLOCKED;
- static void* get_thread_stack(void) {
- void* ret = NULL;
- spinlock_lock(&g_thread_stack_lock);
- for (size_t i = 0; i < g_thread_stack_num; i++) {
- if (!g_thread_stack_map[i].used) {
- /* found allocated and unused stack -- use it */
- g_thread_stack_map[i].used = true;
- ret = g_thread_stack_map[i].stack;
- goto out;
- }
- }
- if (g_thread_stack_num == g_thread_stack_size) {
- /* realloc g_thread_stack_map to accommodate more objects (includes the very first time) */
- g_thread_stack_size += 8;
- struct thread_stack_map_t* tmp = malloc(g_thread_stack_size * sizeof(*tmp));
- if (!tmp)
- goto out;
- memcpy(tmp, g_thread_stack_map, g_thread_stack_num * sizeof(*tmp));
- free(g_thread_stack_map);
- g_thread_stack_map = tmp;
- }
- ret = malloc(THREAD_STACK_SIZE + ALT_STACK_SIZE);
- if (!ret)
- goto out;
- g_thread_stack_map[g_thread_stack_num].stack = ret;
- g_thread_stack_map[g_thread_stack_num].used = true;
- g_thread_stack_num++;
- out:
- spinlock_unlock(&g_thread_stack_lock);
- return ret;
- }
- /*
- * pal_thread_init(): An initialization wrapper of a newly-created thread (including
- * the first thread). This function accepts a TCB pointer to be set to the GS register
- * of the thread. The rest of the TCB is used as the alternative stack for signal
- * handling.
- */
- int pal_thread_init (void * tcbptr)
- {
- PAL_TCB_LINUX * tcb = tcbptr;
- int ret;
- ret = INLINE_SYSCALL(arch_prctl, 2, ARCH_SET_GS, tcb);
- if (IS_ERR(ret))
- return -ERRNO(ret);
- if (tcb->alt_stack) {
- // Align stack to 16 bytes
- void* alt_stack_top = ALIGN_DOWN_PTR(tcb, 16);
- assert(alt_stack_top > tcb->alt_stack);
- stack_t ss;
- ss.ss_sp = alt_stack_top;
- ss.ss_flags = 0;
- ss.ss_size = alt_stack_top - tcb->alt_stack;
- ret = INLINE_SYSCALL(sigaltstack, 2, &ss, NULL);
- if (IS_ERR(ret))
- return -ERRNO(ret);
- }
- if (tcb->callback)
- return (*tcb->callback) (tcb->param);
- return 0;
- }
- /* _DkThreadCreate for internal use. Create an internal thread
- inside the current process. The arguments callback and param
- specify the starting function and parameters */
- int _DkThreadCreate (PAL_HANDLE * handle, int (*callback) (void *),
- const void * param)
- {
- int ret = 0;
- PAL_HANDLE hdl = NULL;
- void* stack = get_thread_stack();
- if (!stack) {
- ret = -ENOMEM;
- goto err;
- }
- /* Stack layout for the new thread looks like this (recall that stacks grow towards lower
- * addresses on Linux on x86-64):
- *
- * stack +--> +-------------------+
- * | child stack | THREAD_STACK_SIZE
- * child_stack +--> +-------------------+
- * | alternate stack | ALT_STACK_SIZE - sizeof(PAL_TCB_LINUX)
- * tcb +--> +-------------------+
- * | PAL TCB | sizeof(PAL_TCB_LINUX)
- * +-------------------+
- *
- * We zero out only the first page of the main stack (to comply with the requirement of
- * gcc ABI, in particular that the initial stack frame's return address must be NULL).
- * We zero out the whole altstack (since it is small anyway) and also the PAL TCB. */
- memset(stack + THREAD_STACK_SIZE - PRESET_PAGESIZE, 0, PRESET_PAGESIZE);
- memset(stack + THREAD_STACK_SIZE, 0, ALT_STACK_SIZE);
- void * child_stack = stack + THREAD_STACK_SIZE;
- hdl = malloc(HANDLE_SIZE(thread));
- if (!hdl) {
- ret = -ENOMEM;
- goto err;
- }
- SET_HANDLE_TYPE(hdl, thread);
- // Initialize TCB at the top of the alternative stack.
- PAL_TCB_LINUX * tcb = child_stack + ALT_STACK_SIZE - sizeof(PAL_TCB_LINUX);
- tcb->common.self = &tcb->common;
- tcb->handle = hdl;
- tcb->alt_stack = child_stack; // Stack bottom
- tcb->callback = callback;
- tcb->param = (void *) param;
- /* align child_stack to 16 */
- child_stack = ALIGN_DOWN_PTR(child_stack, 16);
- ret = clone(pal_thread_init, child_stack,
- CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SYSVSEM | CLONE_THREAD |
- CLONE_SIGHAND | CLONE_PARENT_SETTID,
- (void*)tcb, &hdl->thread.tid, NULL);
- if (IS_ERR(ret)) {
- ret = -PAL_ERROR_DENIED;
- goto err;
- }
- hdl->thread.stack = stack;
- *handle = hdl;
- return 0;
- err:
- free(stack);
- free(hdl);
- return ret;
- }
- int _DkThreadDelayExecution (unsigned long * duration)
- {
- struct timespec sleeptime;
- struct timespec remainingtime;
- const unsigned long VERY_LONG_TIME_IN_US = 1000000L * 60 * 60 * 24 * 365 * 128;
- if (*duration > VERY_LONG_TIME_IN_US) {
- /* avoid overflow with time_t */
- sleeptime.tv_sec = VERY_LONG_TIME_IN_US / 1000000;
- sleeptime.tv_nsec = 0;
- } else {
- sleeptime.tv_sec = *duration / 1000000;
- sleeptime.tv_nsec = (*duration - sleeptime.tv_sec * 1000000) * 1000;
- }
- int ret = INLINE_SYSCALL(nanosleep, 2, &sleeptime, &remainingtime);
- if (IS_ERR(ret)) {
- PAL_NUM remaining = remainingtime.tv_sec * 1000000 +
- remainingtime.tv_nsec / 1000;
- *duration -= remaining;
- return -PAL_ERROR_INTERRUPTED;
- }
- return 0;
- }
- /* PAL call DkThreadYieldExecution. Yield the execution
- of the current thread. */
- void _DkThreadYieldExecution (void)
- {
- INLINE_SYSCALL(sched_yield, 0);
- }
- /* _DkThreadExit for internal use: Thread exiting */
- noreturn void _DkThreadExit(int* clear_child_tid) {
- PAL_TCB_LINUX* tcb = get_tcb_linux();
- PAL_HANDLE handle = tcb->handle;
- assert(handle);
- block_async_signals(true);
- if (tcb->alt_stack) {
- stack_t ss;
- ss.ss_sp = NULL;
- ss.ss_flags = SS_DISABLE;
- ss.ss_size = 0;
- // Take precautions to unset the TCB and alternative stack first.
- INLINE_SYSCALL(arch_prctl, 2, ARCH_SET_GS, 0);
- INLINE_SYSCALL(sigaltstack, 2, &ss, NULL);
- }
- /* we do not free thread stack but instead mark it as recycled, see get_thread_stack() */
- spinlock_lock(&g_thread_stack_lock);
- for (size_t i = 0; i < g_thread_stack_num; i++) {
- if (g_thread_stack_map[i].stack == handle->thread.stack) {
- g_thread_stack_map[i].used = false;
- break;
- }
- }
- /* we might still be using the stack we just marked as unused until we enter the asm mode,
- * so we do not unlock now but rather in asm below */
- /* To make sure the compiler doesn't touch the stack after it was freed, need inline asm:
- * 1. Unlock g_thread_stack_lock (so that other threads can start re-using this stack)
- * 2. Set *clear_child_tid = 0 if clear_child_tid != NULL
- * (we thus inform LibOS, where async helper thread is waiting on this to wake up parent)
- * 3. Exit thread */
- static_assert(sizeof(g_thread_stack_lock.lock) == 4, "unexpected g_thread_stack_lock.lock size");
- static_assert(offsetof(__typeof__(g_thread_stack_lock), lock) == 0, "unexpected offset of lock in g_thread_stack_lock");
- static_assert(sizeof(*clear_child_tid) == 4, "unexpected clear_child_tid size");
- __asm__ volatile("movl $0, (%%rdx) \n\t" /* spinlock_unlock(&g_thread_stack_lock) */
- "cmpq $0, %%rbx \n\t" /* check if clear_child_tid != NULL */
- "je 1f \n\t"
- "movl $0, (%%rbx) \n\t" /* set *clear_child_tid = 0 */
- "1: \n\t"
- "syscall \n\t" /* rdi arg is already prepared, call exit */
- : /* no output regs since we don't return from exit */
- : "a"(__NR_exit), "D"(0), /* rdi = exit status == 0 */
- "d"(&g_thread_stack_lock.lock), "b"(clear_child_tid)
- : "cc", "rcx", "r11", "memory" /* syscall instr clobbers cc, rcx, and r11 */
- );
- while (true) {
- /* nothing */
- }
- }
- int _DkThreadResume (PAL_HANDLE threadHandle)
- {
- int ret = INLINE_SYSCALL(tgkill, 3,
- linux_state.pid,
- threadHandle->thread.tid,
- SIGCONT);
- if (IS_ERR(ret))
- return -PAL_ERROR_DENIED;
- return 0;
- }
- struct handle_ops thread_ops = {
- /* nothing */
- };
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