syscall: Implement opening resources

3 files changed, 60 insertions, 13 deletions

diff --git a/src/lib/process.zig b/src/lib/process.zig
index 0ab11ae..6f8ffce 100644
--- a/src/lib/process.zig
+++ b/src/lib/process.zig
@@ -9,6 +9,7 @@ const instructions = @import("instructions.zig");
 const paging = @import("paging.zig");
 const time = @import("sbi/time.zig");
 const trap = @import("trap.zig");
+const vfs = @import("vfs.zig");
 
 const elf = std.elf;
 
@@ -25,6 +26,10 @@ pub const Error = error{
     NoInit,
 };
 
+pub const ProcessError = error{
+    TooManyResourceDescriptors,
+};
+
 pub const ExeError = error{
     BadEndian,
     BadArch,
@@ -42,23 +47,37 @@ pub const State = enum(u8) {
     terminated,
 };
 
-pub const Info = extern struct {
+pub const Info = struct {
     id: u16,
     trap_frame: trap.Frame,
     stack: *[num_stack_pages * paging.page_size]u8,
     pc: usize,
     page_table: *paging.Table,
     state: State,
+    rds: std.AutoArrayHashMap(usize, vfs.ResourceDescriptor),
 
     pub fn destroy(self: *Info) !void {
         try paging.free(self.stack);
         try self.page_table.unmap();
         try paging.free(self.page_table);
+        self.rds.deinit();
     }
 
     pub fn satp(self: *const Info) paging.Satp {
         return self.page_table.satp(self.id);
     }
+
+    pub fn makeRdHandle(self: *Info, rd: vfs.ResourceDescriptor) !usize {
+        if (self.rds.count() == std.math.maxInt(usize)) {
+            return ProcessError.TooManyResourceDescriptors;
+        }
+
+        var handle = self.rds.count() + 1;
+        while (self.rds.contains(handle)) : (handle +%= 1) {}
+
+        try self.rds.put(handle, rd);
+        return handle;
+    }
 };
 
 pub fn next() ?*Info {
@@ -195,6 +214,7 @@ pub fn create(allocator: std.mem.Allocator, elf_buf: []align(@alignOf(elf.Elf64_
         .pc = hdr.entry,
         .page_table = procmem,
         .state = .waiting,
+        .rds = std.AutoArrayHashMap(usize, vfs.ResourceDescriptor).init(allocator),
     };
     proc.trap_frame.general_purpose_registers[2] = stack_top;
 
diff --git a/src/lib/syscall.zig b/src/lib/syscall.zig
index eece736..c2457c6 100644
--- a/src/lib/syscall.zig
+++ b/src/lib/syscall.zig
@@ -4,6 +4,7 @@
 
 const instructions = @import("instructions.zig");
 const paging = @import("paging.zig");
+const process = @import("process.zig");
 const sysexchange = @import("sysexchange.zig");
 const trap = @import("trap.zig");
 const vfs = @import("vfs.zig");
@@ -12,10 +13,10 @@ pub const Error = error{
     UnknownSyscall,
 };
 
-pub fn handle(trap_frame: *trap.Frame) !void {
+pub fn handle(proc: *process.Info, trap_frame: *trap.Frame) !void {
     switch (trap_frame.general_purpose_registers[17]) {
         100000 => uprint(trap_frame),
-        100001 => open(trap_frame),
+        100001 => open(proc, trap_frame),
         100002 => close(trap_frame),
         100003 => provideStream(trap_frame),
         100004 => provideFile(trap_frame),
@@ -40,12 +41,22 @@ fn uprint(trap_frame: *const trap.Frame) void {
     w.print("User message: {s}\r\n", .{str}) catch unreachable;
 }
 
-// open(path: [*:0]const u8) Result(usize) // fixme: Kernel panic if null pointer
-fn open(trap_frame: *const trap.Frame) void {
+// open(path: [*:0]const u8, data: usize) Result(usize) // fixme: Kernel panic if null pointer
+fn open(proc: *process.Info, trap_frame: *trap.Frame) void {
     const path: [*:0]const u8 = @ptrFromInt(trap_frame.general_purpose_registers[10]);
-
-    _ = path;
-    unreachable;
+    const data = trap_frame.general_purpose_registers[11];
+
+    const user_info = vfs.openZ(path, proc.id, data) catch |err| {
+        sysexchange.frameReturn(usize, trap_frame, err);
+        return;
+    };
+    switch (user_info) {
+        .rd => |resource_descriptor| {
+            const maybe_handle = proc.makeRdHandle(resource_descriptor);
+            sysexchange.frameReturn(null, trap_frame, maybe_handle);
+        },
+        .value => |value| sysexchange.frameReturnResult(usize, trap_frame, value),
+    }
 }
 
 // close(rd: usize) void
@@ -66,7 +77,7 @@ fn provideStream(trap_frame: *trap.Frame) void {
     const readFn: ?vfs.Stream.ReadFn = @ptrFromInt(trap_frame.general_purpose_registers[11]);
     const writeFn: ?vfs.Stream.WriteFn = @ptrFromInt(trap_frame.general_purpose_registers[12]);
 
-    sysexchange.frameReturn(trap_frame, vfs.provideResourceZ(path, .{
+    sysexchange.frameReturn(null, trap_frame, vfs.provideResourceZ(path, .{
         .stream = .{
             .readFn = readFn,
             .writeFn = writeFn,
@@ -88,7 +99,7 @@ fn provideFile(trap_frame: *trap.Frame) void {
     const writeFn: ?vfs.File.WriteFn = @ptrFromInt(trap_frame.general_purpose_registers[13]);
     const closeFn: ?vfs.File.CloseFn = @ptrFromInt(trap_frame.general_purpose_registers[14]);
 
-    sysexchange.frameReturn(trap_frame, vfs.provideResourceZ(path, .{
+    sysexchange.frameReturn(null, trap_frame, vfs.provideResourceZ(path, .{
         .file = .{
             .openFn = openFn,
             .readFn = readFn,
@@ -106,7 +117,7 @@ fn provideHook(trap_frame: *trap.Frame) void {
     const path: [*:0]const u8 = @ptrFromInt(trap_frame.general_purpose_registers[10]);
     const callback: vfs.Hook.Callback = @ptrFromInt(trap_frame.general_purpose_registers[11]);
 
-    sysexchange.frameReturn(trap_frame, vfs.provideResourceZ(path, .{
+    sysexchange.frameReturn(null, trap_frame, vfs.provideResourceZ(path, .{
         .hook = .{
             .callback = callback,
         },
@@ -138,7 +149,7 @@ fn provideDirHook(trap_frame: *trap.Frame) void {
     const findFn: vfs.DirHook.FindFn = @ptrFromInt(trap_frame.general_purpose_registers[12]);
     const removeFn: vfs.DirHook.RemoveFn = @ptrFromInt(trap_frame.general_purpose_registers[13]);
 
-    sysexchange.frameReturn(trap_frame, vfs.provideResourceZ(path, .{
+    sysexchange.frameReturn(null, trap_frame, vfs.provideResourceZ(path, .{
         .dir_hook = .{
             .provideFn = provideFn,
             .findFn = findFn,
diff --git a/src/lib/vfs.zig b/src/lib/vfs.zig
index 0eb57a6..56834d6 100644
--- a/src/lib/vfs.zig
+++ b/src/lib/vfs.zig
@@ -116,7 +116,6 @@ pub const Tree = struct {
 
 pub const ResourceDescriptor = struct {
     inode: *Inode,
-    pos: usize = 0,
 
     pub fn init(inode: *Inode) !ResourceDescriptor {
         inode.refs = std.math.add(usize, inode.refs, 1) catch return Error.TooManyReferences;
@@ -130,6 +129,11 @@ pub const ResourceDescriptor = struct {
     }
 };
 
+pub const UserInfo = union(enum) {
+    rd: ResourceDescriptor,
+    value: sysexchange.Result(usize),
+};
+
 pub fn init(allocator: mem.Allocator) void {
     root = Tree.init(allocator);
 }
@@ -174,3 +178,15 @@ pub fn provideResource(path: []const u8, resource: Resource) !void {
 pub fn provideResourceZ(path_c: [*:0]const u8, resource: Resource) !void {
     return provideResource(mem.sliceTo(path_c, 0), resource);
 }
+
+pub fn open(path: []const u8, pid: u16, data: usize) !UserInfo {
+    const node = find(path) orelse return Error.NotFound;
+    return switch (node.data.resource) {
+        .hook => |hook| .{ .value = hook.callback(pid, data) },
+        else => .{ .rd = try ResourceDescriptor.init(&node.data) },
+    };
+}
+
+pub fn openZ(path_c: [*:0]const u8, pid: u16, data: usize) !UserInfo {
+    return open(mem.sliceTo(path_c, 0), pid, data);
+}