Daniel Samson
be81394be3
The `system` module (formerly `danos`) had become a grab-bag: it held the
loader<->kernel handoff *and* the kernel<->user ABI *and* the device wire types, in
one module three different audiences imported. Usage proved the seam — the
bootloader never touched the syscall/device ABI, and user space never touched the
boot handoff — so split it by audience, one module per contract:
system/boot-handoff.zig loader <-> kernel: BootInformation, Framebuffer,
MemoryMap, the VM layout + physicalToVirtual, kernel_abi
system/abi.zig kernel <-> user, core: SystemCall, mmap prot flags,
page_size, notify_badge_bit, ServiceId
system/devices/device-abi.zig kernel <-> user, devices: DeviceDescriptor,
DeviceClass, ResourceDescriptor, ResourceKind, ...
device-abi is the devices sub-project's public interface, exposed as its own module
the way vfs exposes vfs-protocol — importable by user space, unlike the
kernel-internal device model it also feeds. That collapses a real duplication:
DeviceClass and ResourceKind were defined twice (device-model.zig and the contract,
kept "in sync by hand"); device-model now re-exports them from device-abi, so the
enum a driver matches on and the one the kernel classifies with are one type.
Each import now declares which contract it speaks: the bootloader imports only
boot-handoff; a driver only abi + device-abi (via the runtime); the kernel all
three. This also retires the `system` / `runtime.system` name overlap. page_size
lands in abi (it's part of the mmap contract user space aligns to); the bootloader
keeps its own local 4 KiB constant so it depends on nothing but the handoff.
All 21 importers rewired, docs updated to keep /system mapping to source. Build,
host tests, and the QEMU suite (36/36) all green.
95 lines
3.7 KiB
Zig
95 lines
3.7 KiB
Zig
//! User-space IPC helpers over the kernel's synchronous IPC syscalls. A client
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//! `call`s an endpoint (send + block for reply); the VFS server and drivers are
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//! reached this way. The server side (`replyWait`, which returns two values) is
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//! added with the first server binary.
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const abi = @import("abi");
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const sc = @import("system-call.zig");
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/// A small-int handle into the calling process's handle table.
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pub const Handle = usize;
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/// A fixed-size, register-friendly message payload. Server protocols (VFS, driver)
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/// layer their own wire format on top of the bytes a call carries.
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pub const Message = extern struct {
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tag: u64 = 0,
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a: u64 = 0,
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b: u64 = 0,
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c: u64 = 0,
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};
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/// Whether a system_call return value is a wrapped -errno (lands in the top page).
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inline fn failed(r: usize) bool {
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return r > ~@as(usize, 0) - 4095;
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}
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/// Create a new endpoint owned by this process; returns its handle.
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pub fn createEndpoint() ?Handle {
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const r = sc.systemCall0(.create_endpoint);
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return if (failed(r)) null else r;
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}
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/// Publish endpoint `h` under a well-known service id so other processes find it.
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pub fn register(id: abi.ServiceId, h: Handle) bool {
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return !failed(sc.systemCall2(.ipc_register, @intFromEnum(id), h));
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}
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/// Find the endpoint published under `id`, installing a handle to it in this
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/// process.
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pub fn lookup(id: abi.ServiceId) ?Handle {
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const r = sc.systemCall1(.ipc_lookup, @intFromEnum(id));
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return if (failed(r)) null else r;
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}
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pub const CallError = error{Failed};
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/// Send `message` to endpoint `h` and block until the server replies into `reply`.
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/// Returns the reply length.
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pub fn call(h: Handle, message: []const u8, reply: []u8) CallError!usize {
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const r = sc.systemCall5(.ipc_call, h, @intFromPtr(message.ptr), message.len, @intFromPtr(reply.ptr), reply.len);
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return if (failed(r)) error.Failed else r;
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}
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/// Set in `Received.badge` when what arrived is an asynchronous notification — a
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/// bound device interrupt — rather than a client's message. The low bits carry the
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/// GSI. See `isNotification`.
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pub const notify_badge_bit: u64 = abi.notify_badge_bit;
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/// The result of a `replyWait`: the request length and the sender's badge (a
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/// task id, or an IRQ notification if the high bit is set).
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pub const Received = struct {
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len: usize,
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badge: u64,
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/// True if this wake-up was a device interrupt, not a client request. A driver's
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/// event loop branches on this; there is no reply owed on the notification path.
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pub fn isNotification(self: Received) bool {
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return self.badge & notify_badge_bit != 0;
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}
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/// The interrupt source (a GSI), meaningful only when `isNotification`.
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pub fn source(self: Received) u64 {
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return self.badge & ~notify_badge_bit;
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}
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};
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/// Server side of IPC_ReplyWait: deliver `reply` to the client last received (if
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/// any), then block until the next request arrives in `receive`. Returns its length
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/// and the sender badge. This system_call returns two values — the length in rax and
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/// the badge in rdx — so it needs a hand-written stub: rdx is a read-write
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/// operand (input = reply length, arg #3; output = badge).
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pub fn replyWait(h: Handle, reply: []const u8, receive: []u8) Received {
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var rax: usize = undefined;
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var rdx: usize = reply.len; // in: reply_len (arg #3 -> rdx); out: badge
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asm volatile ("syscall"
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: [rax] "={rax}" (rax),
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[rdx] "+{rdx}" (rdx),
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: [n] "{rax}" (@intFromEnum(abi.SystemCall.ipc_reply_wait)),
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[a0] "{rdi}" (h),
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[a1] "{rsi}" (@intFromPtr(reply.ptr)),
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[a3] "{r10}" (@intFromPtr(receive.ptr)),
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[a4] "{r8}" (receive.len),
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: .{ .rcx = true, .r11 = true, .memory = true });
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return .{ .len = rax, .badge = rdx };
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}
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