Daniel Samson
0a8c81b17a
Add lib/ — the shared user-space runtime every user binary links against (init now, servers/drivers later): syscall wrappers, the heap, IPC stub, and the process start shim. - lib/heap.zig: the kernel first-fit free-list ported to user space, grown via the mmap syscall instead of pmm+mapPage. Dual API over one global free list: extern "C" malloc/free/calloc/realloc (C ABI for future C code) and a std.mem.Allocator adapter (with in-place resize) for Zig std containers. - lib/syscall.zig + sys.zig: raw syscall0..5 (arg3 in r10) and typed yield/write/sleep/exit/mmap/munmap over danos.Syscall. - lib/start.zig: naked _start -> rt_start -> root.main() (SysV realign via call), panic -> exit(127). - lib/user.ld: the user link script, moved from sbin/linker.ld (shared by all user binaries). - build.zig: register the `rt` module; add an addUserBinary() helper that is the one recipe for every user binary (freestanding, .large, use_lld, user.ld, image_base), replacing the bespoke init block. - sbin/init.zig: migrated onto rt; drops its hand-rolled syscall2/shims. Now proves the heap (alloc -> write from a heap pointer -> free) before the heartbeat loop. Serial shows "init: heap ok". Suite 28/28.
33 lines
1.2 KiB
Zig
33 lines
1.2 KiB
Zig
//! The user-space process entry shim. Every user binary roots `_start` here (via
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//! `entry = _start` in build.zig) and forces this file to be analysed with
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//! `comptime { _ = &rt.start._start; }`, so the whole runtime is linked in.
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const std = @import("std");
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const sys = @import("sys.zig");
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/// The kernel enters at `_start` with rsp 16-aligned, but a SysV function expects
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/// rsp ≡ 8 (mod 16) on entry (as if reached by `call`). The `call` below pushes
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/// the 8-byte return address, satisfying the ABI before any Zig frame runs; the
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/// `ud2` is a safety net if `rt_start` ever returns.
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pub export fn _start() callconv(.naked) noreturn {
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asm volatile (
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\\call rt_start
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\\ud2
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);
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}
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/// The first Zig frame. The heap is lazy (first alloc grows it), so there is no
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/// runtime init to order here — just hand control to the program's `main`.
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export fn rt_start() callconv(.c) noreturn {
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const root = @import("root"); // the user binary's root source file
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root.main();
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sys.exit(0);
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}
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/// No runtime to unwind into — report a panic as a nonzero exit code.
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pub const panic = std.debug.FullPanic(struct {
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fn panic(_: []const u8, _: ?usize) noreturn {
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sys.exit(127);
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}
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}.panic);
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