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LibPthread: implicitly call pthread_exit on return from start routine.

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Previously, when returning from a pthread's start_routine, we would
segfault. Now we instead implicitly call pthread_exit as specified in
the standard.

pthread_create now creates a thread running the new
pthread_create_helper, which properly manages the calling and exiting
of the start_routine supplied to pthread_create. To accomplish this,
the thread's stack initialization has been moved out of
sys$create_thread and into the userspace function create_thread.
This commit is contained in:
Drew Stratford 2020-04-25 22:20:44 +12:00 committed by Andreas Kling
parent 4cb765e520
commit 4a37362249
Notes: sideshowbarker 2024-07-19 07:18:19 +09:00 
Author: https://github.com/DrewStratford
Commit: https://github.com/SerenityOS/serenity/commit/4a373622498
Pull-request: https://github.com/SerenityOS/serenity/pull/1949
3 changed files with 32 additions and 8 deletions
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6
Kernel/Process.cpp
View file

@ -3754,7 +3754,7 @@ void Process::send_signal(u8 signal, Process* sender)
thread->send_signal(signal, sender);
}
int Process::sys$create_thread(void* (*entry)(void*), void* argument, const Syscall::SC_create_thread_params* user_params)
int Process::sys$create_thread(void* (*entry)(void*), const Syscall::SC_create_thread_params* user_params)
{
REQUIRE_PROMISE(thread);
if (!validate_read((const void*)entry, sizeof(void*)))
@ -3806,10 +3806,6 @@ int Process::sys$create_thread(void* (*entry)(void*), void* argument, const Sysc
tss.cr3 = page_directory().cr3();
tss.esp = user_stack_address;
// NOTE: The stack needs to be 16-byte aligned.
thread->push_value_on_stack((FlatPtr)argument);
thread->push_value_on_stack(0);
thread->make_thread_specific_region({});
thread->set_state(Thread::State::Runnable);
return thread->tid();

2
Kernel/Process.h
View file

@ -272,7 +272,7 @@ public:
int sys$getpeername(const Syscall::SC_getpeername_params*);
int sys$sched_setparam(pid_t pid, const struct sched_param* param);
int sys$sched_getparam(pid_t pid, struct sched_param* param);
int sys$create_thread(void* (*)(void*), void* argument, const Syscall::SC_create_thread_params*);
int sys$create_thread(void* (*)(void*), const Syscall::SC_create_thread_params*);
void sys$exit_thread(void*);
int sys$join_thread(int tid, void** exit_value);
int sys$detach_thread(int tid);

32
Libraries/LibPthread/pthread.cpp
View file

@ -50,9 +50,37 @@ constexpr size_t highest_reasonable_stack_size = 8 * MB; // That's the default i
extern "C" {
static int create_thread(void* (*entry)(void*), void* argument, void* thread_params)
static void* pthread_create_helper(void* (*routine)(void*), void* argument)
{
return syscall(SC_create_thread, entry, argument, thread_params);
void* ret_val = routine(argument);
pthread_exit(ret_val);
return nullptr;
}
static int create_thread(void* (*entry)(void*), void* argument, PthreadAttrImpl* thread_params)
{
void** stack = (void**)((uintptr_t)thread_params->m_stack_location + thread_params->m_stack_size);
auto push_on_stack = [&](void* data) {
stack--;
*stack = data;
thread_params->m_stack_size -= sizeof(void*);
};
// We set up the stack for pthread_create_helper.
// Note that we need to align the stack to 16B, accounting for
// the fact that we also push 8 bytes.
while (((uintptr_t)stack - 8) % 16 != 0)
push_on_stack(nullptr);
push_on_stack(argument);
push_on_stack((void*)entry);
ASSERT((uintptr_t)stack % 16 == 0);
// Push a fake return address
push_on_stack(nullptr);
return syscall(SC_create_thread, pthread_create_helper, thread_params);
}
static void exit_thread(void* code)