Kernel+LibC+LibELF: Set stack size based on PT_GNU_STACK during execve

Some programs explicitly ask for a different initial stack size than
what the OS provides. This is implemented in ELF by having a
PT_GNU_STACK header which has its p_memsz set to the amount that the
program requires. This commit implements this policy by reading the
p_memsz of the header and setting the main thread stack size to that.
ELF::Image::validate_program_headers ensures that the size attribute is
a reasonable value.

Kernel/API/POSIX/sys/limits.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2022, sin-ack <sin-ack@protonmail.com>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -7,3 +8,5 @@
 #pragma once
 
 #define NGROUPS_MAX 32
+
+#define PTHREAD_STACK_MIN (64 * 1024) // 64KiB

Kernel/API/Syscall.h

@@ -360,7 +360,7 @@ struct SC_create_thread_params {
     // ... ok, if you say so posix. Guess we get to lie to people about guard page size
     unsigned int guard_page_size = 0;          // Rounded up to PAGE_SIZE
     unsigned int reported_guard_page_size = 0; // The lie we tell callers
-    unsigned int stack_size = 1 * MiB;         // Default PTHREAD_STACK_MIN
+    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;

Kernel/API/serenity_limits.h

@@ -0,0 +1,9 @@
+/*
+ * Copyright (c) 2022, sin-ack <sin-ack@protonmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#define PTHREAD_STACK_MAX (8 * 1024 * 1024) // 8MiB