zig-riscv-embedded

 1// Copyright © 2020-2021 Sören Tempel
 2//
 3// This program is free software: you can redistribute it and/or modify
 4// it under the terms of the GNU Affero General Public License as
 5// published by the Free Software Foundation, either version 3 of the
 6// License, or (at your option) any later version.
 7//
 8// This program is distributed in the hope that it will be useful, but
 9// WITHOUT ANY WARRANTY; without even the implied warranty of
10// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11// Affero General Public License for more details.
12//
13// You should have received a copy of the GNU Affero General Public License
14// along with this program. If not, see <https://www.gnu.org/licenses/>.
15
16const console = @import("console.zig");
17const periph = @import("periph.zig");
18const main = @import("main.zig");
19const StackTrace = @import("std").builtin.StackTrace;
20
21// Bitmasks for modifying mcause CSR
22const MCAUSE_EXPCODE = 0x0fff;
23const MCAUSE_INT = 0x80000000;
24
25// Exception codes
26const EXP_BREAKPOINT = 3;
27
28pub fn panic(msg: []const u8, error_return_trace: ?*StackTrace) noreturn {
29    _ = error_return_trace; // unused
30
31    // Copied from the default_panic implementation
32    @setCold(true);
33
34    // Write panic message, unbuffered to standard out
35    console.print("PANIC: {s}\n", .{msg});
36
37    @breakpoint();
38    while (true) {}
39}
40
41export fn level1IRQHandler() void {
42    const mcause = asm ("csrr %[ret], mcause"
43        : [ret] "=r" (-> u32)
44    );
45
46    const expcode: u32 = mcause & MCAUSE_EXPCODE;
47    if ((mcause & MCAUSE_INT) == MCAUSE_INT) {
48        periph.plic0.invokeHandler();
49    } else {
50        if (expcode == EXP_BREAKPOINT) {
51            while (true) {}
52        }
53        @panic("unexpected trap");
54    }
55}
56
57export fn init() void {
58    periph.init();
59    console.print("Booting zig-riscv-embedded...\n", .{});
60
61    main.main() catch |err| {
62        @panic(@errorName(err));
63    };
64}