From cf0ebd22df2574a2cd361783cff494fdd3922cac Mon Sep 17 00:00:00 2001
From: Sunil Nimmagadda <sunil@nimmagadda.net>
Date: Fri, 16 Oct 2026 10:25:23 +0530
Subject: Pack program header.

---
 mkelf.lua | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)

diff --git a/mkelf.lua b/mkelf.lua
index 3df60f0..6dc985b 100644
--- a/mkelf.lua
+++ b/mkelf.lua
@@ -161,7 +161,79 @@ local header <const> = {
     pack = ElfHeader_pack
 }
 
+---@enum SegmentFlags
+local SegmentFlags <const> = {
+    x = 0x1,
+    w = 0x2,
+    r = 0x3,
+}
+
+---@class ProgramHeader
+---@field type integer
+---@field flags integer
+---@field offset integer
+---@field vaddr integer
+---@field paddr integer
+---@field filesz integer
+---@field memsz integer
+---@field align integer
+
+---@enum SegmentType
+local SegmentType <const> = {
+    null = 0x00000000,
+    load = 0x00000001,
+    dynamic = 0x00000002,
+    interp = 0x00000003,
+    note = 0x00000004,
+    shlib = 0x00000005,
+    phdr = 0x00000006,
+    tls = 0x00000007,
+    loos = 0x60000000,
+    hios = 0x6FFFFFFF,
+    loproc = 0x70000000,
+    hiproc = 0x7FFFFFFF,
+}
+
+---@param hdr ProgramHeader
+---@param endian Endian
+---@param class Class
+---@nodiscard
+local function ElfPHeader_pack(hdr, endian, class)
+    if class == Class.bit32 then
+        return string.pack(efmt(endian) .. string.rep(szfmt(class), 8),
+            hdr.type,
+            hdr.offset,
+            hdr.vaddr,
+            hdr.paddr,
+            hdr.filesz,
+            hdr.memsz,
+            hdr.flags,
+            hdr.align)
+    elseif class == Class.bit64 then
+        return string.pack(efmt(endian) .. "I4I4" .. string.rep(szfmt(class), 6),
+            hdr.type,
+            hdr.flags,
+            hdr.offset,
+            hdr.vaddr,
+            hdr.paddr,
+            hdr.filesz,
+            hdr.memsz,
+            hdr.align)
+    end
+end
+
 local function main()
+    ---@type ProgramHeader
+    local pheader <const> = {
+        type = SegmentType.dynamic,
+        flags = SegmentFlags.x,
+        offset = 0xf,
+        vaddr = 0xff,
+        paddr = 0xfff,
+        filesz = 0xffff,
+        memsz = 0xfffff,
+        align = 1,
+    }
     local output = "a.out"
     for i in ipairs(arg) do
         if arg[i] ~= "-o" then goto continue end
-- 
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