/*
 * out.c — emit a static ELF64 executable.
 *
 * Layout (file order):
 *   [0..64)       ELF header
 *   [64..120)     program header (one PT_LOAD)
 *   [120..0x1000) zero pad
 *   [0x1000..)    .text bytes
 *
 * The single PT_LOAD covers the whole file, R+X. No interpreter,
 * no dynamic, no .bss yet. Entry point is the address of the
 * symbol named "_start" (or whatever main supplies via -e).
 */
#include "l.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define ET_EXEC		2
#define EM_X86_64	62
#define EV_CURRENT	1
#define ELFCLASS64	2
#define ELFDATA2LSB	1

#define PT_LOAD		1
#define PF_X		1
#define PF_W		2
#define PF_R		4

#pragma pack(push, 1)
typedef struct {
	u8 e_ident[16];
	u16 e_type, e_machine;
	u32 e_version;
	u64 e_entry, e_phoff, e_shoff;
	u32 e_flags;
	u16 e_ehsize, e_phentsize, e_phnum, e_shentsize, e_shnum, e_shstrndx;
} Ehdr;

typedef struct {
	u32 p_type, p_flags;
	u64 p_offset, p_vaddr, p_paddr;
	u64 p_filesz, p_memsz, p_align;
} Phdr;
#pragma pack(pop)

int
l_emit_elf(Lnk *l, FILE *f, u64 base, u64 entry)
{
	/* Dispatch: any loaded shared object plus any dynamic ref means
	 * we owe the loader a real PT_INTERP/PT_DYNAMIC binary. */
	if (l->sos != NULL && l->dyn_n > 0)
		return l_emit_dyn_elf(l, f, base, entry);

	const u64 text_off = 0x1000;
	const u64 text_va  = base + text_off;
	const u64 filesz   = text_off + l->textlen;

	Ehdr eh = {0};
	memcpy(eh.e_ident, "\x7f""ELF", 4);
	eh.e_ident[4] = ELFCLASS64;
	eh.e_ident[5] = ELFDATA2LSB;
	eh.e_ident[6] = EV_CURRENT;
	eh.e_type = ET_EXEC;
	eh.e_machine = EM_X86_64;
	eh.e_version = EV_CURRENT;
	eh.e_entry = entry;
	eh.e_phoff = sizeof(Ehdr);
	eh.e_ehsize = sizeof(Ehdr);
	eh.e_phentsize = sizeof(Phdr);
	eh.e_phnum = 1;
	(void)text_va;

	Phdr ph = {0};
	ph.p_type = PT_LOAD;
	ph.p_flags = PF_R | PF_X;
	ph.p_offset = 0;
	ph.p_vaddr = base;
	ph.p_paddr = base;
	ph.p_filesz = filesz;
	ph.p_memsz = filesz;
	ph.p_align = 0x1000;

	fwrite(&eh, 1, sizeof eh, f);
	fwrite(&ph, 1, sizeof ph, f);

	/* pad to text_off */
	long here = ftell(f);
	for (long i = here; i < (long)text_off; i++) fputc(0, f);

	if (l->textlen) fwrite(l->text, 1, l->textlen, f);

	return 0;
}