From fc00c656c96528112d05cf0edf8631bd5eaea446 Mon Sep 17 00:00:00 2001
From: Kacper <kacper@mail.openlinux.dev>
Date: Sun, 7 Dec 2025 20:10:31 +0100
Subject: Add build system scaffolding and libc headers

---
 lib/libc/arch/x86_64/crt0.c | 59 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 lib/libc/arch/x86_64/crt0.c

(limited to 'lib/libc/arch/x86_64/crt0.c')

diff --git a/lib/libc/arch/x86_64/crt0.c b/lib/libc/arch/x86_64/crt0.c
new file mode 100644
index 00000000..2c7943ff
--- /dev/null
+++ b/lib/libc/arch/x86_64/crt0.c
@@ -0,0 +1,59 @@
+#include <linux/auxvec.h>
+#include <linux/elf.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sys/time.h>
+#include <thread.h>
+#include <unistd.h>
+
+#define weak_reference(old, new) \
+	extern __typeof(old) new __attribute__((__weak__, __alias__(#old)))
+
+extern int main(int, char *[]);
+char **environ;
+
+static struct __thread_self thread = { .tid = 0, ._errno = 0 };
+
+struct __attribute__((packed)) auxv_t {
+	uintptr_t a_type;
+	uintptr_t a_val;
+} *__auxv;
+
+static void __vdso_setup(Elf64_Ehdr *vdso_addr __attribute__((unused)))
+{
+}
+
+weak_reference(__vdso_setup, vdso_setup);
+
+__attribute__((used)) void __libc_start(uintptr_t *sp)
+{
+	char **argv;
+	int argc;
+
+	argc = (int)(*sp);
+	argv = (char **)(++sp);
+	sp += argc;
+	environ = (char **)(++sp);
+
+	while (*sp)
+		sp++;
+
+	__auxv = (struct auxv_t *)(++sp);
+	while (__auxv->a_type != AT_NULL) {
+		if (__auxv->a_type == AT_SYSINFO_EHDR) {
+			vdso_setup((Elf64_Ehdr *)__auxv->a_val);
+		}
+
+		__auxv++;
+	}
+
+	__asm__ volatile("wrfsbase %0" ::"r"(thread));
+
+	exit(main(argc, argv));
+}
+
+__attribute__((noreturn, naked)) void _start(void)
+{
+	__asm__ __volatile__("mov %rsp, %rdi\n"
+			     "call __libc_start\n");
+}
-- 
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