From d205814da672985e26db40e9dc3962c6222834a0 Mon Sep 17 00:00:00 2001
From: Daniel Bertalan <dani@danielbertalan.dev>
Date: Sat, 22 Apr 2023 16:29:17 +0200
Subject: [PATCH] Kernel+LibC: Implement `pthread_create` for AArch64

Instead of storing x86_64 register names in `SC_create_thread_params`,
let the Kernel figure out how to pass the parameters to
`pthread_create_helper`.
---
 Kernel/API/Syscall.h                |  8 ++------
 Kernel/Syscalls/thread.cpp          | 19 +++++++++++++++----
 Userland/Libraries/LibC/pthread.cpp | 15 +++------------
 3 files changed, 20 insertions(+), 22 deletions(-)

diff --git a/Kernel/API/Syscall.h b/Kernel/API/Syscall.h
index 19b70741975..b2de4d18087 100644
--- a/Kernel/API/Syscall.h
+++ b/Kernel/API/Syscall.h
@@ -370,12 +370,8 @@ struct SC_create_thread_params {
     unsigned int reported_guard_page_size = 0; // The lie we tell callers
     unsigned int stack_size = 1 * MiB;         // Equal to Thread::default_userspace_stack_size
     void* stack_location;                      // nullptr means any, o.w. process virtual address
-#    if ARCH(X86_64)
-    FlatPtr rdi;
-    FlatPtr rsi;
-    FlatPtr rcx;
-    FlatPtr rdx;
-#    endif
+    void* (*entry)(void*);
+    void* entry_argument;
 };
 
 struct SC_realpath_params {
diff --git a/Kernel/Syscalls/thread.cpp b/Kernel/Syscalls/thread.cpp
index 8e5dfabb38b..1afc29dd787 100644
--- a/Kernel/Syscalls/thread.cpp
+++ b/Kernel/Syscalls/thread.cpp
@@ -63,10 +63,21 @@ ErrorOr<FlatPtr> Process::sys$create_thread(void* (*entry)(void*), Userspace<Sys
     regs.set_flags(0x0202);
     regs.cr3 = address_space().with([](auto& space) { return space->page_directory().cr3(); });
 
-    regs.rdi = params.rdi;
-    regs.rsi = params.rsi;
-    regs.rdx = params.rdx;
-    regs.rcx = params.rcx;
+    // Set up the argument registers expected by pthread_create_helper.
+    regs.rdi = (FlatPtr)params.entry;
+    regs.rsi = (FlatPtr)params.entry_argument;
+    regs.rdx = (FlatPtr)params.stack_location;
+    regs.rcx = (FlatPtr)params.stack_size;
+#elif ARCH(AARCH64)
+    regs.ttbr0_el1 = address_space().with([](auto& space) { return space->page_directory().ttbr0(); });
+
+    // Set up the argument registers expected by pthread_create_helper.
+    regs.x[0] = (FlatPtr)params.entry;
+    regs.x[1] = (FlatPtr)params.entry_argument;
+    regs.x[2] = (FlatPtr)params.stack_location;
+    regs.x[3] = (FlatPtr)params.stack_size;
+#else
+#    error Unknown architecture
 #endif
 
     TRY(thread->make_thread_specific_region({}));
diff --git a/Userland/Libraries/LibC/pthread.cpp b/Userland/Libraries/LibC/pthread.cpp
index ab7c5e25f90..6dbce4a45f7 100644
--- a/Userland/Libraries/LibC/pthread.cpp
+++ b/Userland/Libraries/LibC/pthread.cpp
@@ -90,18 +90,9 @@ static int create_thread(pthread_t* thread, void* (*entry)(void*), void* argumen
     while (((uintptr_t)stack - 16) % 16 != 0)
         push_on_stack(nullptr);
 
-#if ARCH(X86_64)
-    thread_params->rdi = (FlatPtr)entry;
-    thread_params->rsi = (FlatPtr)argument;
-    thread_params->rdx = (FlatPtr)thread_params->stack_location;
-    thread_params->rcx = thread_params->stack_size;
-#elif ARCH(AARCH64)
-    (void)entry;
-    (void)argument;
-    TODO_AARCH64();
-#else
-#    error Unknown architecture
-#endif
+    thread_params->entry = entry;
+    thread_params->entry_argument = argument;
+
     VERIFY((uintptr_t)stack % 16 == 0);
 
     // Push a fake return address