zig-mtd/update-uboot.zig

const std = @import("std");
const math = std.math;
const mtd_user = @cImport(@cInclude("mtd/mtd-user.h"));

const uboot = @embedFile("uboot-feb2019.bin");
const mtd_rw = @import("mtd-rw.zig");

const Allocator = std.heap.c_allocator;

const c_allocator = std.heap.c_allocator;

fn stripTrailingNulls(buf: []const u8) []const u8 {
    var end: usize = buf.len;
    while (true) {
        if (end > 0) {
            const new_end = end - 1;
            if (buf[new_end] == 0) {
                end = new_end;
                continue;
            }
        }
        break;
    }
    return buf[0..end];
}

test "stripTrailingNulls" {
    const farts0: []const u8 = "farts\x00";
    const farts: []const u8 = "farts";
    var farts0_stripped = stripTrailingNulls(farts0);
    var farts_stripped = stripTrailingNulls(farts);
    std.debug.assert(farts0_stripped.len == 5);
    std.debug.assert(farts_stripped.len == 5);
    std.debug.assert(std.mem.eql(u8, farts0_stripped, farts));
    std.debug.assert(std.mem.eql(u8, farts_stripped, farts));
}

fn mtd_info_get(name: []const u8, out: []u8) !void {
    var path_buf: [64]u8 = undefined;
    const path = try std.fmt.bufPrint(path_buf[0..], "{}/{}", .{"/sys/class/mtd/mtd0/", name});

    //const path = try std.fmt.allocPrint(
    //    c_allocator, "{}/{}", .{"/sys/class/mtd/mtd0", name});
    //defer c_allocator.free(path);

    var f = try std.fs.openFileAbsolute(path, .{.read = true});
    defer f.close();
    const num_read = try f.read(out);
    out = out[0..num_read-1];
}

fn mtd_info_get_usize(name: []const u8) !usize {
    var buf: [64]u8 = undefined;
    var buf_sl = buf[0..];
    try mtd_info_get(name, buf_sl);
    return try std.fmt.parseUnsigned(usize, buf_sl, 10);
}

pub fn main() !u8 {
    try mtd_rw.load();
    defer mtd_rw.unload();

    // Read and hash mtd0

    const mtd0_size = try mtd_info_get_usize("size");

    if (uboot.len > mtd0_size) {
         std.debug.warn("Error: mtd0 isn\'t large enough to hold the new image ({} > {})\n",
                        .{uboot.len, mtd0_size});
         return 1;
    }
    var current_uboot = try Allocator.alloc(u8, mtd0_size);
    var f = try std.fs.openFileAbsolute("/dev/mtd0", .{.read = true});
    defer f.close();
    const num_read = try f.read(current_uboot[0..]);
    if (num_read != mtd0_size) {
        std.debug.warn("Failed to read /dev/mtd0", .{});
        return 2;
    }

    var current_digest: [std.crypto.Md5.digest_length]u8 = undefined;
    std.crypto.Md5.hash(current_uboot, current_digest[0..]);

    var embedded_digest: [std.crypto.Md5.digest_length]u8 = undefined;
    std.crypto.Md5.hash(uboot, embedded_digest[0..]);

    // Compare against payload
    if (std.mem.eql(u8, current_digest[0..], embedded_digest[0..])) {
        std.debug.warn("U-Boot is up to date. Exiting.\n", .{});
        return 0;
    }

    // Erase mtd0
    const mtd0_erasesize = try mtd_info_get_usize("erasesize");
    var erased = 0;
    while (erased < mtd0_size) {
        //erase page
        erased += mtd0_erasesize;
    }
    // Write mtd0

    // Verify mtd0

    std.debug.warn("Done\n", .{});
    return 0;
}