Day 1

stdlib/src/arena.c

@@ -0,0 +1,22 @@
+#include <common.h>
+#include <arena.h>
+#include <syscall.h>
+
+arena arena_init(usize capacity)
+{
+	void* ptr = mmap(null, capacity, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	return (arena){ .ptr = ptr, .available = 0, .capacity = capacity };
+}
+
+void arena_ensure(arena* arena, usize available)
+{
+	if (arena->available >= available) return;
+
+	available = (available + PAGE_SIZE - 1) & -PAGE_SIZE;
+	if (available > arena->capacity) {
+		available = arena->capacity;
+	}
+
+	mprotect((c8*)arena->ptr + arena->available, available - arena->available, PROT_READ | PROT_WRITE);
+	arena->available = available;
+}

stdlib/src/buffer.c

@@ -0,0 +1,14 @@
+#include <common.h>
+#include <syscall.h>
+
+void* buffer_init(usize size)
+{
+	i32 fd = memfd_create("buffer", 0);
+	ftruncate(fd, size);
+
+	void* ptr = mmap(null, 2 * size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	mmap(            ptr, size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, fd, 0);
+	mmap((c8*)ptr + size, size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, fd, 0);
+
+	return ptr;
+}

stdlib/src/start.s

@@ -0,0 +1,12 @@
+.intel_syntax noprefix
+.text
+	.global _start
+_start:
+	xor rbp, rbp
+	pop rdi
+	mov rsi, rsp
+	and rsp, -16
+	call main
+	mov rdi, rax
+	mov rax, 60
+	syscall

stdlib/src/syscall.c

@@ -0,0 +1,77 @@
+#include <syscall.h>
+
+isize read(i32 fd, void* buf, usize size)
+{
+	isize ret;
+	asm volatile (
+		"syscall"
+		: "=a" (ret)
+		: "a" (0), "D" (fd), "S" (buf), "d" (size)
+		: "rcx", "r11", "memory"
+	);
+	return ret;
+}
+
+isize write(i32 fd, const void* buf, usize size)
+{
+	isize ret;
+	asm volatile (
+		"syscall"
+		: "=a" (ret)
+		: "a" (1), "D" (fd), "S" (buf), "d" (size)
+		: "rcx", "r11", "memory"
+	);
+	return ret;
+}
+
+void* mmap(void* addr, usize length, i32 prot, i32 flags, i32 fd, isize offset)
+{
+	register i32 r10 asm ("r10") = flags;
+	register i32 r8 asm ("r8") = fd;
+	register isize r9 asm ("r9") = offset;
+
+	void* ret;
+	asm volatile (
+		"syscall"
+		: "=a" (ret)
+		: "a" (9), "D" (addr), "S" (length), "d" (prot), "r" (r10), "r" (r8), "r" (r9)
+		: "rcx", "r11", "memory"
+	);
+	return ret;
+}
+
+i32 mprotect(void* addr, usize len, i32 prot)
+{
+	i32 ret;
+	asm volatile (
+		"syscall"
+		: "=a" (ret)
+		: "a" (10), "D" (addr), "S" (len), "d" (prot)
+		: "rcx", "r11", "memory"
+	);
+	return ret;
+}
+
+i32 ftruncate(i32 fd, isize length)
+{
+	i32 ret;
+	asm volatile (
+		"syscall"
+		: "=a" (ret)
+		: "a" (77), "D" (fd), "S" (length)
+		: "rcx", "r11", "memory"
+	);
+	return ret;
+}
+
+i32 memfd_create(const char* name, u32 flags)
+{
+	i32 ret;
+	asm volatile (
+		"syscall"
+		: "=a" (ret)
+		: "a" (319), "D" (name), "S" (flags)
+		: "rcx", "r11", "memory"
+	);
+	return ret;
+}