Kernel+LibPthread+LibC: Create secondary thread stacks in userspace

Have pthread_create() allocate a stack and passing it to the kernel
instead of this work happening in the kernel. The more of this we can
do in userspace, the better.

This patch also unexposes the raw create_thread() and exit_thread()
syscalls since they are now only used by LibPthread anyway.

1 files changed, 20 insertions, 3 deletions

diff --git a/Libraries/LibPthread/pthread.cpp b/Libraries/LibPthread/pthread.cpp
index b1e17b1f61..ba844ce400 100644
--- a/Libraries/LibPthread/pthread.cpp
+++ b/Libraries/LibPthread/pthread.cpp
@@ -1,18 +1,36 @@
+#include <AK/Assertions.h>
 #include <AK/Atomic.h>
 #include <AK/StdLibExtras.h>
 #include <Kernel/Syscall.h>
 #include <pthread.h>
-#include <unistd.h>
 #include <stdio.h>
+#include <sys/mman.h>
+#include <unistd.h>
 
 extern "C" {
 
+static int create_thread(void* (*entry)(void*), void* argument, void* stack)
+{
+    int rc = syscall(SC_create_thread, entry, argument, stack);
+    __RETURN_WITH_ERRNO(rc, rc, -1);
+}
+
+static void exit_thread(void* code)
+{
+    syscall(SC_exit_thread, code);
+    ASSERT_NOT_REACHED();
+}
+
 int pthread_create(pthread_t* thread, pthread_attr_t* attributes, void* (*start_routine)(void*), void* argument_to_start_routine)
 {
     if (!thread)
         return -EINVAL;
     UNUSED_PARAM(attributes);
-    int rc = create_thread(start_routine, argument_to_start_routine);
+    const size_t stack_size = 4 * MB;
+    auto* stack = (u8*)mmap_with_name(nullptr, stack_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, 0, 0, "Thread stack");
+    if (!stack)
+        return -1;
+    int rc = create_thread(start_routine, argument_to_start_routine, stack + stack_size);
     if (rc < 0)
         return rc;
     *thread = rc;
@@ -55,5 +73,4 @@ int pthread_mutex_unlock(pthread_mutex_t* mutex)
     atomic->store(false, AK::memory_order_release);
     return 0;
 }
-
 }