From 69175ad62f531327e9fd693c13890ca1d472a7a3 Mon Sep 17 00:00:00 2001
From: Stephen Gregoratto <dev@sgregoratto.me>
Date: Tue, 12 Mar 2024 22:21:55 +1100
Subject: [PATCH] Windows: Add wrappers for `GetCurrent(Process|Thread)` via
 NT_TIB

This is how they've been implemented in `kernel32` since NT 3.1.
---
 lib/std/child_process.zig |  2 +-
 lib/std/debug.zig         |  2 +-
 lib/std/os/windows.zig    | 47 ++++++++++++++++++++++++++++++++++++---
 3 files changed, 46 insertions(+), 5 deletions(-)

diff --git a/lib/std/child_process.zig b/lib/std/child_process.zig
index edc97c2c3e..85fa3d294e 100644
--- a/lib/std/child_process.zig
+++ b/lib/std/child_process.zig
@@ -1420,7 +1420,7 @@ fn windowsMakeAsyncPipe(rd: *?windows.HANDLE, wr: *?windows.HANDLE, sattr: *cons
         const pipe_path = std.fmt.bufPrintZ(
             &tmp_buf,
             "\\\\.\\pipe\\zig-childprocess-{d}-{d}",
-            .{ windows.kernel32.GetCurrentProcessId(), pipe_name_counter.fetchAdd(1, .monotonic) },
+            .{ windows.GetCurrentProcessId(), pipe_name_counter.fetchAdd(1, .monotonic) },
         ) catch unreachable;
         const len = std.unicode.wtf8ToWtf16Le(&tmp_bufw, pipe_path) catch unreachable;
         tmp_bufw[len] = 0;
diff --git a/lib/std/debug.zig b/lib/std/debug.zig
index 932fb4a730..13e2d95e2c 100644
--- a/lib/std/debug.zig
+++ b/lib/std/debug.zig
@@ -814,7 +814,7 @@ pub noinline fn walkStackWindows(addresses: []usize, existing_context: ?*const w
         return windows.ntdll.RtlCaptureStackBackTrace(0, addresses.len, @as(**anyopaque, @ptrCast(addresses.ptr)), null);
     }
 
-    const tib = @as(*const windows.NT_TIB, @ptrCast(&windows.teb().Reserved1));
+    const tib = &windows.teb().NtTib;
 
     var context: windows.CONTEXT = undefined;
     if (existing_context) |context_ptr| {
diff --git a/lib/std/os/windows.zig b/lib/std/os/windows.zig
index 24ea53b0a9..147ad7a12b 100644
--- a/lib/std/os/windows.zig
+++ b/lib/std/os/windows.zig
@@ -153,6 +153,24 @@ pub fn OpenFile(sub_path_w: []const u16, options: OpenFileOptions) OpenError!HAN
     }
 }
 
+pub fn GetCurrentProcess() HANDLE {
+    const process_pseudo_handle: usize = @bitCast(@as(isize, -1));
+    return @ptrFromInt(process_pseudo_handle);
+}
+
+pub fn GetCurrentProcessId() DWORD {
+    return @truncate(@intFromPtr(teb().ClientId.UniqueProcess));
+}
+
+pub fn GetCurrentThread() HANDLE {
+    const thread_pseudo_handle: usize = @bitCast(@as(isize, -2));
+    return @ptrFromInt(thread_pseudo_handle);
+}
+
+pub fn GetCurrentThreadId() DWORD {
+    return @truncate(@intFromPtr(teb().ClientId.UniqueThread));
+}
+
 pub const CreatePipeError = error{ Unexpected, SystemResources };
 
 var npfs: ?HANDLE = null;
@@ -259,12 +277,12 @@ pub fn CreatePipe(rd: *HANDLE, wr: *HANDLE, sattr: *const SECURITY_ATTRIBUTES) C
     var write: HANDLE = undefined;
     switch (ntdll.NtCreateFile(
         &write,
-        FILE_GENERIC_WRITE,
+        GENERIC_WRITE | SYNCHRONIZE | FILE_READ_ATTRIBUTES,
         &attrs,
         &iosb,
         null,
         0,
-        FILE_SHARE_READ,
+        FILE_SHARE_READ | FILE_SHARE_WRITE,
         FILE_OPEN,
         FILE_SYNCHRONOUS_IO_NONALERT | FILE_NON_DIRECTORY_FILE,
         null,
@@ -4309,7 +4327,11 @@ pub const THREAD_BASIC_INFORMATION = extern struct {
 };
 
 pub const TEB = extern struct {
-    Reserved1: [12]PVOID,
+    NtTib: NT_TIB,
+    EnvironmentPointer: PVOID,
+    ClientId: CLIENT_ID,
+    ActiveRpcHandle: PVOID,
+    ThreadLocalStoragePointer: PVOID,
     ProcessEnvironmentBlock: *PEB,
     Reserved2: [399]PVOID,
     Reserved3: [1952]u8,
@@ -4321,6 +4343,25 @@ pub const TEB = extern struct {
     TlsExpansionSlots: PVOID,
 };
 
+comptime {
+    // Offsets taken from WinDbg info and Geoff Chappell[1] (RIP)
+    // [1]: https://www.geoffchappell.com/studies/windows/km/ntoskrnl/inc/api/pebteb/teb/index.htm
+    assert(@offsetOf(TEB, "NtTib") == 0x00);
+    if (@sizeOf(usize) == 4) {
+        assert(@offsetOf(TEB, "EnvironmentPointer") == 0x1C);
+        assert(@offsetOf(TEB, "ClientId") == 0x20);
+        assert(@offsetOf(TEB, "ActiveRpcHandle") == 0x28);
+        assert(@offsetOf(TEB, "ThreadLocalStoragePointer") == 0x2C);
+        assert(@offsetOf(TEB, "ProcessEnvironmentBlock") == 0x30);
+    } else if (@sizeOf(usize) == 8) {
+        assert(@offsetOf(TEB, "EnvironmentPointer") == 0x38);
+        assert(@offsetOf(TEB, "ClientId") == 0x40);
+        assert(@offsetOf(TEB, "ActiveRpcHandle") == 0x50);
+        assert(@offsetOf(TEB, "ThreadLocalStoragePointer") == 0x58);
+        assert(@offsetOf(TEB, "ProcessEnvironmentBlock") == 0x60);
+    }
+}
+
 pub const EXCEPTION_REGISTRATION_RECORD = extern struct {
     Next: ?*EXCEPTION_REGISTRATION_RECORD,
     Handler: ?*EXCEPTION_DISPOSITION,