syscall: Add errorName syscall to convert error code to string

1 files changed, 34 insertions, 6 deletions

diff --git a/src/lib/syscall.zig b/src/lib/syscall.zig
index db2136f..ab36dc0 100644
--- a/src/lib/syscall.zig
+++ b/src/lib/syscall.zig
@@ -20,16 +20,44 @@ pub const HandleError = error{
 
 pub fn handler(proc: *process.Info, trap_frame: *trap.Frame) !void {
     switch (trap_frame.general_purpose_registers[17]) {
-        100000 => trap_frame.setReturnValue(uprint(trap_frame)),
-        100001 => trap_frame.setReturnValue(launch(trap_frame)),
-        100002 => trap_frame.setReturnValue(end(proc)),
-        100003 => trap_frame.setReturnValue(terminate(proc, trap_frame)),
-        100004 => trap_frame.setReturnValue(processId(proc)),
-        100005 => trap_frame.setReturnValue(threadId(proc)),
+        100000 => trap_frame.setReturnValue(errorName(trap_frame)),
+        100001 => trap_frame.setReturnValue(uprint(trap_frame)),
+        100002 => trap_frame.setReturnValue(launch(trap_frame)),
+        100003 => trap_frame.setReturnValue(end(proc)),
+        100004 => trap_frame.setReturnValue(terminate(proc, trap_frame)),
+        100005 => trap_frame.setReturnValue(processId(proc)),
+        100006 => trap_frame.setReturnValue(threadId(proc)),
         else => return HandleError.UnknownSyscall,
     }
 }
 
+pub const ErrorNameError = error{ErrorOutOfRange};
+
+// errorName(value: usize, buffer: [*]u8, len: usize) !usize
+fn errorName(trap_frame: *const trap.Frame) !usize {
+    const value_wide = trap_frame.general_purpose_registers[10];
+    // fixme: Kernel panic if null pointer
+    const buffer_ptr: [*]u8 = @ptrFromInt(trap_frame.general_purpose_registers[11]);
+    const len = trap_frame.general_purpose_registers[12];
+
+    const value = std.math.cast(u16, value_wide) orelse {
+        return ErrorNameError.ErrorOutOfRange;
+    };
+    const buffer = buffer_ptr[0..len];
+
+    if (value == 0) return 0;
+
+    const error_name = @errorName(@errorFromInt(value));
+
+    const n = @min(buffer.len, error_name.len);
+
+    paging.setUserMemoryAccess(true);
+    defer paging.setUserMemoryAccess(false);
+
+    @memcpy(buffer[0..n], error_name[0..n]);
+    return n;
+}
+
 // uprint(str_addr: usize, len: usize) void
 fn uprint(trap_frame: *const trap.Frame) void {
     const procmem: *paging.Table = @ptrFromInt(instructions.satp.read().ppn << 12);