First commit

This commit is contained in:
David Gonzalez Martin 2023-07-10 23:56:04 -06:00
commit 736215ffa8
5 changed files with 245 additions and 0 deletions

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.gitattributes vendored Normal file
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# Default behavior, if core.autocrlf is unset.
* text=auto
# Files to be converted to native line endings on checkout.
*.cpp text
*.h text
# Text files to always have LF (unix) line endings on checkout.
*.zig text eol=lf

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.github/workflows/ci.yml vendored Normal file
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name: CI
on:
pull_request:
paths:
- ".github/workflows/ci.yml"
- "**.zig"
push:
paths:
- ".github/workflows/ci.yml"
- "**.zig"
branches:
- main
schedule:
- cron: "0 0 * * *"
concurrency:
# Cancels pending runs when a PR gets updated.
group: ${{ github.head_ref || github.run_id }}-${{ github.actor }}
cancel-in-progress: true
jobs:
build:
strategy:
matrix:
os: [
ubuntu-latest,
]
runs-on: ${{ matrix.os }}
timeout-minutes: 15
steps:
- name: Checkout
uses: actions/checkout@v3
- name: Set up Zig
uses: goto-bus-stop/setup-zig@v2
with:
version: master
- name: Zig environment variables
run: zig env
- name: Test
run: zig build test

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zig-cache
zig-out

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build.zig Normal file
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const std = @import("std");
// Although this function looks imperative, note that its job is to
// declaratively construct a build graph that will be executed by an external
// runner.
pub fn build(b: *std.Build) void {
// Standard target options allows the person running `zig build` to choose
// what target to build for. Here we do not override the defaults, which
// means any target is allowed, and the default is native. Other options
// for restricting supported target set are available.
const target = b.standardTargetOptions(.{});
// Standard optimization options allow the person running `zig build` to select
// between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
// set a preferred release mode, allowing the user to decide how to optimize.
const optimize = b.standardOptimizeOption(.{});
const exe = b.addExecutable(.{
.name = "compiler",
// In this case the main source file is merely a path, however, in more
// complicated build scripts, this could be a generated file.
.root_source_file = .{ .path = "src/main.zig" },
.target = target,
.optimize = optimize,
});
// This declares intent for the executable to be installed into the
// standard location when the user invokes the "install" step (the default
// step when running `zig build`).
b.installArtifact(exe);
// This *creates* a Run step in the build graph, to be executed when another
// step is evaluated that depends on it. The next line below will establish
// such a dependency.
const run_cmd = b.addRunArtifact(exe);
// By making the run step depend on the install step, it will be run from the
// installation directory rather than directly from within the cache directory.
// This is not necessary, however, if the application depends on other installed
// files, this ensures they will be present and in the expected location.
run_cmd.step.dependOn(b.getInstallStep());
// This allows the user to pass arguments to the application in the build
// command itself, like this: `zig build run -- arg1 arg2 etc`
if (b.args) |args| {
run_cmd.addArgs(args);
}
// This creates a build step. It will be visible in the `zig build --help` menu,
// and can be selected like this: `zig build run`
// This will evaluate the `run` step rather than the default, which is "install".
const run_step = b.step("run", "Run the app");
run_step.dependOn(&run_cmd.step);
// Creates a step for unit testing. This only builds the test executable
// but does not run it.
const unit_tests = b.addTest(.{
.root_source_file = .{ .path = "src/main.zig" },
.target = target,
.optimize = optimize,
});
const run_unit_tests = b.addRunArtifact(unit_tests);
// Similar to creating the run step earlier, this exposes a `test` step to
// the `zig build --help` menu, providing a way for the user to request
// running the unit tests.
const test_step = b.step("test", "Run unit tests");
test_step.dependOn(&run_unit_tests.step);
}

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src/main.zig Normal file
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const std = @import("std");
const page_size = std.mem.page_size;
const assert = std.debug.assert;
const expectEqual = std.testing.expectEqual;
const Section = struct {
content: []align(page_size) u8,
index: usize = 0,
};
const Image = struct {
text: Section,
rodata: Section,
data: Section,
entry_point: u32 = 0,
fn create() !Image {
return Image{
.text = .{ .content = try mmap(page_size, .{ .executable = true }) },
.rodata = .{ .content = try mmap(page_size, .{ .executable = false }) },
.data = .{ .content = try mmap(page_size, .{ .executable = false }) },
};
}
inline fn mmap(size: usize, flags: packed struct {
executable: bool,
}) ![]align(page_size) u8 {
const protection_flags = std.os.PROT.READ | std.os.PROT.WRITE | if (flags.executable) std.os.PROT.EXEC else 0;
const mmap_flags = std.os.MAP.ANONYMOUS | std.os.MAP.PRIVATE;
return std.os.mmap(null, size, protection_flags, mmap_flags, -1, 0);
}
fn appendCode(image: *Image, code: []const u8) void {
const destination = image.text.content[image.text.index..][0..code.len];
@memcpy(destination, code);
image.text.index += code.len;
}
fn getEntryPoint(image: *const Image, comptime Function: type) *const Function {
comptime {
assert(@typeInfo(Function) == .Fn);
}
assert(image.text.content.len > 0);
return @as(*const Function, @ptrCast(&image.text.content[image.entry_point]));
}
};
const Rex = enum(u8) {
b = upper_4_bits | (1 << 0),
x = upper_4_bits | (1 << 1),
r = upper_4_bits | (1 << 2),
w = upper_4_bits | (1 << 3),
const upper_4_bits = 0b100_0000;
};
const prefix_rex_w = [1]u8{@intFromEnum(Rex.w)};
const prefix_16_bit_operand = [1]u8{0x66};
const ret = [1]u8{0xc3};
const movabs_to_register_a = [1]u8{0xb8};
inline fn intToArrayOfBytes(integer: anytype) [@sizeOf(@TypeOf(integer))]u8 {
comptime {
assert(@typeInfo(@TypeOf(integer)) == .Int);
}
return @as([@sizeOf(@TypeOf(integer))]u8, @bitCast(integer));
}
inline fn movU16ToA(integer: u16) [4]u8 {
return prefix_16_bit_operand ++ movabs_to_register_a ++ intToArrayOfBytes(integer);
}
inline fn movU32ToA(integer: u32) [5]u8 {
return movabs_to_register_a ++ intToArrayOfBytes(integer);
}
inline fn movU64ToA(integer: u64) [10]u8 {
return prefix_rex_w ++ movabs_to_register_a ++ intToArrayOfBytes(integer);
}
test "ret void" {
var image = try Image.create();
image.appendCode(&ret);
const function_pointer = image.getEntryPoint(fn () callconv(.C) void);
function_pointer();
}
test "ret unsigned integer 16-bit" {
var image = try Image.create();
const expected_number = 0xffff;
image.appendCode(&movU16ToA(expected_number));
image.appendCode(&ret);
const function_pointer = image.getEntryPoint(fn () callconv(.C) u16);
const result = function_pointer();
try expectEqual(result, expected_number);
}
test "ret unsigned integer 32-bit" {
var image = try Image.create();
const expected_number = 0xffff_ffff;
image.appendCode(&movU32ToA(expected_number));
image.appendCode(&ret);
const function_pointer = image.getEntryPoint(fn () callconv(.C) u32);
const result = function_pointer();
try expectEqual(result, expected_number);
}
test "ret unsigned integer 64-bit" {
var image = try Image.create();
const expected_number = 0xffff_ffff_ffff_ffff;
image.appendCode(&movU64ToA(expected_number));
image.appendCode(&ret);
const function_pointer = image.getEntryPoint(fn () callconv(.C) u64);
const result = function_pointer();
try expectEqual(result, expected_number);
}