From 2e04b61275062f4a3672cdea2456effbc0cb22a5 Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Fri, 6 Mar 2020 09:17:14 +0100
Subject: [PATCH] std: Work around unexported NtCurrentTeb

Apparently NtCurrentTeb is only exported for i386 and some other
platforms but not for x86_64 nor AArch64. Let's go with the flow and
provide our own NtCurrentTeb like the Windows headers do.

Thank you Microsoft.
---
 lib/std/os/windows.zig       | 20 +++++++++++++++++++-
 lib/std/os/windows/ntdll.zig |  1 -
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/lib/std/os/windows.zig b/lib/std/os/windows.zig
index 14e7b2b04c..ba55845a4f 100644
--- a/lib/std/os/windows.zig
+++ b/lib/std/os/windows.zig
@@ -1083,8 +1083,26 @@ pub fn SetFileTime(
     }
 }
 
+pub fn teb() *TEB {
+    return switch (builtin.arch) {
+        .i386 => asm volatile (
+            \\ movl %%fs:0x18, %[ptr]
+            : [ptr] "=r" (-> *TEB)
+        ),
+        .x86_64 => asm volatile (
+            \\ movq %%gs:0x30, %[ptr]
+            : [ptr] "=r" (-> *TEB)
+        ),
+        .aarch64 => asm volatile (
+            \\ mov %[ptr], x18
+            : [ptr] "=r" (-> *TEB)
+        ),
+        else => @compileError("unsupported arch"),
+    };
+}
+
 pub fn peb() *PEB {
-    return ntdll.NtCurrentTeb().ProcessEnvironmentBlock;
+    return teb().ProcessEnvironmentBlock;
 }
 
 /// A file time is a 64-bit value that represents the number of 100-nanosecond
diff --git a/lib/std/os/windows/ntdll.zig b/lib/std/os/windows/ntdll.zig
index 76a11a19c1..49e60803bc 100644
--- a/lib/std/os/windows/ntdll.zig
+++ b/lib/std/os/windows/ntdll.zig
@@ -16,7 +16,6 @@ pub extern "NtDll" fn NtQueryInformationFile(
     Length: ULONG,
     FileInformationClass: FILE_INFORMATION_CLASS,
 ) callconv(.Stdcall) NTSTATUS;
-pub extern "NtDll" fn NtCurrentTeb() callconv(.Stdcall) *TEB;
 
 pub extern "NtDll" fn NtQueryAttributesFile(
     ObjectAttributes: *OBJECT_ATTRIBUTES,