1 files changed, 41 insertions, 10 deletions

diff --git a/ringlogger/global.go b/ringlogger/global.go
index 60e750a5..5c522a70 100644
--- a/ringlogger/global.go
+++ b/ringlogger/global.go
@@ -1,32 +1,63 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2019-2022 WireGuard LLC. All Rights Reserved.
  */
 
 package ringlogger
 
 import (
 	"log"
-	"path/filepath"
-
-	"golang.zx2c4.com/wireguard/windows/conf"
+	"unsafe"
 )
 
 var Global *Ringlogger
 
-func InitGlobalLogger(tag string) error {
+func InitGlobalLogger(file, tag string) error {
 	if Global != nil {
 		return nil
 	}
-	root, err := conf.RootDirectory()
-	if err != nil {
-		return err
-	}
-	Global, err = NewRinglogger(filepath.Join(root, "log.bin"), tag)
+	var err error
+	Global, err = NewRinglogger(file, tag)
 	if err != nil {
 		return err
 	}
 	log.SetOutput(Global)
 	log.SetFlags(0)
+	overrideWrite = globalWrite
 	return nil
 }
+
+//go:linkname overrideWrite runtime.overrideWrite
+var overrideWrite func(fd uintptr, p unsafe.Pointer, n int32) int32
+
+var (
+	globalBuffer         [maxLogLineLength - 1 - maxTagLength - 3]byte
+	globalBufferLocation int
+)
+
+//go:nosplit
+func globalWrite(fd uintptr, p unsafe.Pointer, n int32) int32 {
+	b := (*[1 << 30]byte)(p)[:n]
+	for len(b) > 0 {
+		amountAvailable := len(globalBuffer) - globalBufferLocation
+		amountToCopy := len(b)
+		if amountToCopy > amountAvailable {
+			amountToCopy = amountAvailable
+		}
+		copy(globalBuffer[globalBufferLocation:], b[:amountToCopy])
+		b = b[amountToCopy:]
+		globalBufferLocation += amountToCopy
+		foundNl := false
+		for i := globalBufferLocation - amountToCopy; i < globalBufferLocation; i++ {
+			if globalBuffer[i] == '\n' {
+				foundNl = true
+				break
+			}
+		}
+		if foundNl || len(b) > 0 {
+			Global.Write(globalBuffer[:globalBufferLocation])
+			globalBufferLocation = 0
+		}
+	}
+	return n
+}