From 9eb604113b9a531331897e14fafe0bef7f62d236 Mon Sep 17 00:00:00 2001
From: Mitja Felicijan <mitja.felicijan@gmail.com>
Date: Thu, 19 Sep 2024 14:13:59 +0200
Subject: Added reading of ELF binaries in Zig

---
 README.md              |   1 +
 zig-elf/.clang-format  |   4 ++++
 zig-elf/Makefile       |   5 +++++
 zig-elf/elf            | Bin 0 -> 16048 bytes
 zig-elf/elf-64-gen.pdf | Bin 0 -> 172444 bytes
 zig-elf/elf.c          |   6 ++++++
 zig-elf/elf.png        | Bin 0 -> 326086 bytes
 zig-elf/main.zig       |  51 +++++++++++++++++++++++++++++++++++++++++++++++++
 8 files changed, 67 insertions(+)
 create mode 100644 zig-elf/.clang-format
 create mode 100644 zig-elf/Makefile
 create mode 100755 zig-elf/elf
 create mode 100644 zig-elf/elf-64-gen.pdf
 create mode 100644 zig-elf/elf.c
 create mode 100644 zig-elf/elf.png
 create mode 100644 zig-elf/main.zig

diff --git a/README.md b/README.md
index 22944a7..b90eafe 100644
--- a/README.md
+++ b/README.md
@@ -35,6 +35,7 @@ running it.
 | [zig-tlv-encoding](./zig-tlv-encoding) | zig-0.13.0 | Naive implementation of TLV encoding in Zig.                   |
 | [zig-embed](./zig-embed)               | zig-0.13.0 | Embedding external resources in compiled binary.               |
 | [zig-struct-bin](./zig-struct-bin)     | zig-0.13.0 | Save a struct into binary file and then reading it back.       |
+| [zig-elf](./zig-elf)                   | zig-0.14.0 | Read execution header of Elf64 format in Zig.                  |
 
 ## License
 
diff --git a/zig-elf/.clang-format b/zig-elf/.clang-format
new file mode 100644
index 0000000..84ac618
--- /dev/null
+++ b/zig-elf/.clang-format
@@ -0,0 +1,4 @@
+BasedOnStyle: LLVM
+ColumnLimit: 120
+IndentWidth: 4
+
diff --git a/zig-elf/Makefile b/zig-elf/Makefile
new file mode 100644
index 0000000..52899e3
--- /dev/null
+++ b/zig-elf/Makefile
@@ -0,0 +1,5 @@
+default:
+	zig run main.zig
+
+elf:
+	clang -o elf elf.c
diff --git a/zig-elf/elf b/zig-elf/elf
new file mode 100755
index 0000000..7178622
Binary files /dev/null and b/zig-elf/elf differ
diff --git a/zig-elf/elf-64-gen.pdf b/zig-elf/elf-64-gen.pdf
new file mode 100644
index 0000000..d80b546
Binary files /dev/null and b/zig-elf/elf-64-gen.pdf differ
diff --git a/zig-elf/elf.c b/zig-elf/elf.c
new file mode 100644
index 0000000..c038330
--- /dev/null
+++ b/zig-elf/elf.c
@@ -0,0 +1,6 @@
+#include <stdio.h>
+
+int main(void) {
+  printf("Oh, hi Mark!\n");
+  return 0;
+}
diff --git a/zig-elf/elf.png b/zig-elf/elf.png
new file mode 100644
index 0000000..22685f5
Binary files /dev/null and b/zig-elf/elf.png differ
diff --git a/zig-elf/main.zig b/zig-elf/main.zig
new file mode 100644
index 0000000..3b4e116
--- /dev/null
+++ b/zig-elf/main.zig
@@ -0,0 +1,51 @@
+// $ readelf -h ./elf
+// https://github.com/bminor/binutils-gdb/blob/master/binutils/readelf.c
+
+// There is still a problem with packed structs and aligment padding
+// better referenced in these two threads (sometime struct is not aligned
+// properly or even has 1 byte more than its C alternative):
+//  - https://ziggit.dev/t/mapping-64-u8-buffer-to-a-struct/6052/19
+//  - https://ziggit.dev/t/wrong-sizes-of-extern-packed-structs/6053/6
+
+const std = @import("std");
+
+const Elf64ExecutionHeader = packed struct {
+    ident: u128,
+    type: u16,
+    machine: u16,
+    version: u32,
+    entry: u64,
+    phoff: u64,
+    shoff: u64,
+    flags: u32,
+    ehsize: u16,
+    phentsize: u16,
+    phnum: u16,
+    shentsize: u16,
+    shnum: u16,
+    shstrndx: u16,
+};
+
+pub fn main() !void {
+    var file = try std.fs.cwd().openFile("./elf", .{});
+    defer file.close();
+
+    var buffer: [64]u8 = undefined;
+    _ = try file.read(buffer[0..]);
+
+    const header: *Elf64ExecutionHeader = @ptrCast(@alignCast(&buffer));
+
+    std.debug.print("Object file type: {}\n", .{header.type});
+    std.debug.print("Architecture: {}\n", .{header.machine});
+    std.debug.print("Object file version: 0x{X:0>2}\n", .{header.version});
+    std.debug.print("Entry point virtual address: 0x{X:0>2}\n", .{header.entry});
+    std.debug.print("Program header table file offset: {}\n", .{header.phoff});
+    std.debug.print("Section header table file offset: {}\n", .{header.shoff});
+    std.debug.print("Processor-specific flags: 0x{X:0>2}\n", .{header.flags});
+    std.debug.print("ELF header size in bytes: {}\n", .{header.ehsize});
+    std.debug.print("Program header table entry size: {}\n", .{header.phentsize});
+    // std.debug.print("Program header table entry count: {}\n", .{header.phnum});
+    // std.debug.print("Section header table entry size: {}\n", .{header.shentsize});
+    // std.debug.print("Section header table entry count: {}\n", .{header.shnum});
+    // std.debug.print("Section header string table index: {}\n", .{header.shstrndx});
+}
-- 
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