src/startup.zig


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// Copyright (C) 2024 Clyne Sullivan <clyne@bitgloo.com>
//
// Distributed under the GNU GPL v3 or later. You should have received a copy of
// the GNU General Public License along with this program.
// If not, see <https://www.gnu.org/licenses/>.

const main = @import("main.zig");

extern const __data_flash: u32;
extern const __data: u32;
extern const __data_size: u32;
extern const __bss: u32;
extern const __bss_size: u32;

comptime {
    asm (
        \\.extern _start
        \\.extern _tstack
        \\
        \\.section .vector_table
        \\.global init_vector_table
        \\init_vector_table:
        \\    .word _tstack
        \\    .word _start
        \\    .skip 4 * 14
    );
}

inline fn zero_bss() void {
    const bss: [*]volatile u8 = @ptrFromInt(@intFromPtr(&__bss));
    @memset(bss[0..@intFromPtr(&__bss_size)], 0);
}

inline fn copy_data() void {
    const data_flash: [*]volatile u8 = @ptrFromInt(@intFromPtr(&__data_flash));
    const data: [*]volatile u8 = @ptrFromInt(@intFromPtr(&__data));
    const data_size = @intFromPtr(&__data_size);
    @memcpy(data[0..data_size], data_flash[0..data_size]);
}

export fn _start() callconv(.C) noreturn {
    zero_bss();
    copy_data();
    main.main();
    while (true) {}
}