syscall: Fail on zero address parameter values

Fixes #63.

1 files changed, 5 insertions, 4 deletions

diff --git a/src/lib/syscall.zig b/src/lib/syscall.zig
index 959a8ad..62176db 100644
--- a/src/lib/syscall.zig
+++ b/src/lib/syscall.zig
@@ -12,6 +12,7 @@ const trap = @import("trap.zig");
 
 pub const Error = error{
     Unimplemented,
+    ZeroAddressSupplied,
 };
 
 pub const HandleError = error{
@@ -36,8 +37,8 @@ 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 buffer_opt: ?[*]u8 = @ptrFromInt(trap_frame.general_purpose_registers[11]);
+    const buffer_ptr = buffer_opt orelse return Error.ZeroAddressSupplied;
     const len = trap_frame.general_purpose_registers[12];
 
     const value = std.math.cast(u16, value_wide) orelse {
@@ -75,8 +76,8 @@ fn uprint(trap_frame: *const trap.Frame) void {
 fn launch(trap_frame: *const trap.Frame) !usize {
     const alignment = @alignOf(std.elf.Elf64_Ehdr);
     const bytes_addr = trap_frame.general_purpose_registers[10];
-    // fixme: Kernel panic if null pointer
-    const bytes_ptr: [*]align(alignment) const u8 = @ptrFromInt(bytes_addr);
+    const bytes_opt: ?[*]align(alignment) const u8 = @ptrFromInt(bytes_addr);
+    const bytes_ptr = bytes_opt orelse return Error.ZeroAddressSupplied;
     const len = trap_frame.general_purpose_registers[11];
 
     const bytes = bytes_ptr[0..len];