From 270c8f02867bf959fa86a44fcb76bb0680571695 Mon Sep 17 00:00:00 2001
From: Himbeer <himbeer@disroot.org>
Date: Tue, 30 Jul 2024 12:24:01 +0200
Subject: syscall: Provide userinit access (permissions controlled via paging
 in the future)

Fixes #69.
---
 linker.ld            | 7 +++++++
 src/lib/paging.zig   | 3 +++
 src/lib/process.zig  | 4 ++++
 src/lib/syscall.zig  | 9 +++++++++
 src/lib/userinit.zig | 2 +-
 5 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/linker.ld b/linker.ld
index 30c410a..1d16384 100644
--- a/linker.ld
+++ b/linker.ld
@@ -38,6 +38,13 @@ SECTIONS {
 
 		PROVIDE(_rodata_end = .);
 	} > ram AT > ram : lo_r
+	.userinit          : ALIGN(4K) {
+		PROVIDE(_userinit_start = .);
+
+		*(.userinit .userinit.*)
+
+		PROVIDE(_userinit_end = .);
+	} > ram AT > ram : lo_r
 	.data              : ALIGN(4K) {
 		PROVIDE(_data_start = .);
 
diff --git a/src/lib/paging.zig b/src/lib/paging.zig
index dd1feeb..d69a17c 100644
--- a/src/lib/paging.zig
+++ b/src/lib/paging.zig
@@ -14,6 +14,8 @@ pub const text_start = @extern(*anyopaque, .{ .name = "_text_start" });
 pub const text_end = @extern(*anyopaque, .{ .name = "_text_end" });
 pub const rodata_start = @extern(*anyopaque, .{ .name = "_rodata_start" });
 pub const rodata_end = @extern(*anyopaque, .{ .name = "_rodata_end" });
+pub const userinit_start = @extern(*anyopaque, .{ .name = "_userinit_start" });
+pub const userinit_end = @extern(*anyopaque, .{ .name = "_userinit_end" });
 pub const data_start = @extern(*anyopaque, .{ .name = "_data_start" });
 pub const data_end = @extern(*anyopaque, .{ .name = "_data_end" });
 pub const bss_start = @extern(*anyopaque, .{ .name = "_bss_start" });
@@ -458,6 +460,7 @@ pub const Table = struct {
     pub fn mapKernel(root: *Table) !void {
         try root.identityMapRange(@intFromPtr(text_start), @intFromPtr(text_end), EntryFlags.readExec);
         try root.identityMapRange(@intFromPtr(rodata_start), @intFromPtr(rodata_end), EntryFlags.readOnly);
+        try root.identityMapRange(@intFromPtr(userinit_start), @intFromPtr(userinit_end), EntryFlags.readOnly);
         try root.identityMapRange(@intFromPtr(data_start), @intFromPtr(data_end), EntryFlags.readWrite);
         try root.identityMapRange(@intFromPtr(bss_start), @intFromPtr(bss_end), EntryFlags.readWrite);
         try root.identityMapRange(@intFromPtr(stack_start), @intFromPtr(stack_end), EntryFlags.readWrite);
diff --git a/src/lib/process.zig b/src/lib/process.zig
index c8e6d5e..99a89bd 100644
--- a/src/lib/process.zig
+++ b/src/lib/process.zig
@@ -235,6 +235,10 @@ pub fn create(allocator: Allocator, elf_buf: []align(@alignOf(elf.Elf64_Ehdr)) c
 
     try procmem.mapKernel();
 
+    const userinit_start = @intFromPtr(paging.userinit_start);
+    const userinit_end = @intFromPtr(paging.userinit_end);
+    try procmem.identityMapRange(userinit_start, userinit_end, paging.EntryFlags.userReadOnly);
+
     const parse_source = std.io.fixedBufferStream(elf_buf);
 
     var it = hdr.program_header_iterator(parse_source);
diff --git a/src/lib/syscall.zig b/src/lib/syscall.zig
index 03abade..8d42e7a 100644
--- a/src/lib/syscall.zig
+++ b/src/lib/syscall.zig
@@ -9,6 +9,7 @@ const mem = @import("mem.zig");
 const paging = @import("paging.zig");
 const process = @import("process.zig");
 const riscv = @import("riscv.zig");
+const userinit = @import("userinit.zig");
 
 pub const Error = error{
     ZeroAddressSupplied,
@@ -27,6 +28,7 @@ pub fn handler(proc: *process.Info, trap_frame: *TrapFrame) !void {
         100004 => trap_frame.setReturnValue(terminate(proc, trap_frame)),
         100005 => trap_frame.setReturnValue(processId(proc)),
         100006 => trap_frame.setReturnValue(threadId(proc)),
+        100007 => trap_frame.setReturnValue(rawUserinit(trap_frame)),
         else => return HandleError.UnknownSyscall,
     }
 }
@@ -138,3 +140,10 @@ fn processId(proc: *const process.Info) usize {
 fn threadId(proc: *const process.Info) usize {
     return proc.thread_id;
 }
+
+// rawUserinit(ptr: *[*]const u8) usize
+fn rawUserinit(trap_frame: *const TrapFrame) usize {
+    const ptr: *[*]const u8 = @ptrFromInt(trap_frame.general_purpose_registers[10]);
+    ptr.* = userinit.tarball;
+    return userinit.tarball.len;
+}
diff --git a/src/lib/userinit.zig b/src/lib/userinit.zig
index 8c77cdd..7eb0eea 100644
--- a/src/lib/userinit.zig
+++ b/src/lib/userinit.zig
@@ -2,4 +2,4 @@
 //
 // SPDX-License-Identifier: AGPL-3.0-or-later
 
-pub const tarball = @embedFile("cfg/userinit.tar");
+pub export var tarball linksection(".userinit") = @embedFile("cfg/userinit.tar");
-- 
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