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LibC: Fix uthread deallocation

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Update dtv[0] to the max loadad module when loading dynamic modules

Free uthread if stack allocation or mprotect fails on pthread_create

Don't unmap the currently used stack when detached thread exits
This commit is contained in:
Bananymous
2026-07-20 04:07:23 +03:00
parent f96f2b4cac
commit 390a7674b1
1 changed files with 38 additions and 33 deletions
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userspace/libraries/LibC/pthread.cpp
+38 -33
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@@ -31,6 +31,8 @@ static pthread_attr_t s_default_pthread_attr {
.guardsize = static_cast<size_t>(getpagesize()),
};
static BAN::Atomic<struct uthread*> s_pending_uthread_deletion { nullptr };
static void _pthread_cancel_handler(int)
{
uthread* uthread = _get_uthread();
@@ -122,35 +124,18 @@ extern "C" void _pthread_trampoline_cpp(void* arg)
static void free_uthread(uthread* uthread)
{
const auto lock_dynamic_tls =
[uthread] {
int expected = 0;
while (BAN::atomic_compare_exchange(uthread->dynamic_tls->lock, expected, 1))
{
sched_yield();
expected = 0;
}
};
const auto unlock_dynamic_tls =
[uthread] {
BAN::atomic_store(uthread->dynamic_tls->lock, 0);
};
for (size_t i = uthread->master_tls_module_count; i < uthread->dtv[0]; i++)
for (size_t i = uthread->master_tls_module_count + 1; i <= uthread->dtv[0]; i++)
{
if (uthread->dtv[i] == 0)
continue;
lock_dynamic_tls();
const size_t size = uthread->dynamic_tls->entries[i].master_size;
unlock_dynamic_tls();
munmap(reinterpret_cast<void*>(uthread->dtv[i]), size);
munmap(
reinterpret_cast<void*>(uthread->dtv[i]),
uthread->dynamic_tls->entries[i].master_size
);
}
if (uthread->libc_owns_stack)
munmap(static_cast<uint8_t*>(uthread->attr.stackaddr) - uthread->attr.guardsize, uthread->attr.guardsize + uthread->attr.stacksize);
munmap(static_cast<uint8_t*>(uthread->attr.stackaddr) - uthread->attr.guardsize, uthread->attr.stacksize + uthread->attr.guardsize);
uint8_t* tls_addr = reinterpret_cast<uint8_t*>(uthread) - uthread->master_tls_size;
const size_t tls_size = uthread->master_tls_size + sizeof(struct uthread);
@@ -448,9 +433,6 @@ int pthread_create(pthread_t* __restrict thread, const pthread_attr_t* __restric
if (tls_addr == MAP_FAILED)
goto pthread_create_error;
if (self->master_tls_addr)
memcpy(tls_addr, self->master_tls_addr, self->master_tls_size);
uthread* uthread = reinterpret_cast<struct uthread*>(tls_addr + self->master_tls_size);
*uthread = {
.self = uthread,
@@ -473,12 +455,21 @@ int pthread_create(pthread_t* __restrict thread, const pthread_attr_t* __restric
};
strcpy(uthread->name, self->name);
if (self->master_tls_addr && self->master_tls_size)
memcpy(tls_addr, self->master_tls_addr, self->master_tls_size);
const ptrdiff_t dtv_offset = reinterpret_cast<uint8_t*>(uthread) - reinterpret_cast<uint8_t*>(self);
for (size_t i = 1; i <= self->master_tls_module_count; i++)
uthread->dtv[i] = self->dtv[i] + dtv_offset;
info->uthread = uthread;
if (uthread->attr.stackaddr == nullptr)
{
ASSERT(uthread->attr.stacksize % getpagesize() == 0);
ASSERT(uthread->attr.guardsize % getpagesize() == 0);
void* stack_addr = mmap(nullptr, uthread->attr.guardsize + uthread->attr.stacksize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
void* stack_addr = mmap(nullptr, uthread->attr.stacksize + uthread->attr.guardsize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (stack_addr == nullptr)
goto pthread_create_error;
uthread->attr.stackaddr = static_cast<uint8_t*>(stack_addr) + uthread->attr.guardsize;
@@ -488,12 +479,6 @@ int pthread_create(pthread_t* __restrict thread, const pthread_attr_t* __restric
goto pthread_create_error;
}
const uintptr_t self_addr = reinterpret_cast<uintptr_t>(self);
const uintptr_t uthread_addr = reinterpret_cast<uintptr_t>(uthread);
for (size_t i = 1; i <= self->master_tls_module_count; i++)
uthread->dtv[i] = self->dtv[i] - self_addr + uthread_addr;
info->uthread = uthread;
result = uthread;
}
@@ -558,8 +543,26 @@ void pthread_exit(void* value_ptr)
}
if (uthread->attr.detachstate == PTHREAD_CREATE_DETACHED)
{
if (uthread->libc_owns_stack)
{
if (auto* pending = s_pending_uthread_deletion.exchange(uthread))
{
while (BAN::atomic_load(pending->id) != -1)
sched_yield();
free_uthread(pending);
}
// NOTE: after this store, our stack may get deleted but it should be *fine*
BAN::atomic_store(uthread->id, -1);
_kas_syscall(SYS_THREAD_EXIT, nullptr);
__builtin_trap();
}
free_uthread(uthread);
}
syscall(SYS_THREAD_EXIT, value_ptr);
ASSERT_NOT_REACHED();
}
@@ -1400,6 +1403,8 @@ static void load_dynamic_tls_module(size_t module)
memcpy(dtv_data, entry.master_addr, entry.master_size);
if (module > uthread->dtv[0])
uthread->dtv[0]= module;
uthread->dtv[module] = reinterpret_cast<uintptr_t>(dtv_data);
}