/* 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 . */
/*
* 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
#include
#include
#include
#include
#include
#if defined(__i386__)
#include
#else
#include
#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 */
};