UEFI Target groundwork: runtime: extract Windows PE globals scan helper (#5361)

* runtime: extract Windows PE globals scan helper
* Update src/runtime/os_windows_pe.go
* run goimports

Author: sparques

src/runtime/os_windows.go

@@ -7,44 +7,6 @@ const GOOS = "windows"
 //export GetModuleHandleExA
 func _GetModuleHandleExA(dwFlags uint32, lpModuleName unsafe.Pointer, phModule **exeHeader) bool
 
-// MS-DOS stub with PE header offset:
-// https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#ms-dos-stub-image-only
-type exeHeader struct {
-	signature uint16
-	_         [58]byte // skip DOS header
-	peHeader  uint32   // at offset 0x3C
-}
-
-// COFF file header:
-// https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#file-headers
-type peHeader struct {
-	magic                uint32
-	machine              uint16
-	numberOfSections     uint16
-	timeDateStamp        uint32
-	pointerToSymbolTable uint32
-	numberOfSymbols      uint32
-	sizeOfOptionalHeader uint16
-	characteristics      uint16
-}
-
-// COFF section header:
-// https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#section-table-section-headers
-type peSection struct {
-	name                 [8]byte
-	virtualSize          uint32
-	virtualAddress       uint32
-	sizeOfRawData        uint32
-	pointerToRawData     uint32
-	pointerToRelocations uint32
-	pointerToLinenumbers uint32
-	numberOfRelocations  uint16
-	numberOfLinenumbers  uint16
-	characteristics      uint32
-}
-
-var module *exeHeader
-
 // Mark global variables.
 // Unfortunately, the linker doesn't provide symbols for the start and end of
 // the data/bss sections. Therefore these addresses need to be determined at
@@ -57,9 +19,6 @@ func findGlobals(found func(start, end uintptr)) {
 	const (
 		// https://docs.microsoft.com/en-us/windows/win32/api/libloaderapi/nf-libloaderapi-getmodulehandleexa
 		GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT = 0x00000002
-
-		// https://docs.microsoft.com/en-us/windows/win32/debug/pe-format
-		IMAGE_SCN_MEM_WRITE = 0x80000000
 	)
 
 	if module == nil {
@@ -72,23 +31,7 @@ func findGlobals(found func(start, end uintptr)) {
 		}
 	}
 
-	// Find the PE header at offset 0x3C.
-	pe := (*peHeader)(unsafe.Add(unsafe.Pointer(module), module.peHeader))
-	if gcAsserts && pe.magic != 0x00004550 { // 0x4550 is "PE"
-		runtimePanic("cannot find PE header")
-	}
-
-	// Iterate through sections.
-	section := (*peSection)(unsafe.Pointer(uintptr(unsafe.Pointer(pe)) + uintptr(pe.sizeOfOptionalHeader) + unsafe.Sizeof(peHeader{})))
-	for i := 0; i < int(pe.numberOfSections); i++ {
-		if section.characteristics&IMAGE_SCN_MEM_WRITE != 0 {
-			// Found a writable section. Scan the entire section for roots.
-			start := uintptr(unsafe.Pointer(module)) + uintptr(section.virtualAddress)
-			end := uintptr(unsafe.Pointer(module)) + uintptr(section.virtualAddress) + uintptr(section.virtualSize)
-			found(start, end)
-		}
-		section = (*peSection)(unsafe.Add(unsafe.Pointer(section), unsafe.Sizeof(peSection{})))
-	}
+	findGlobalsForPE(found)
 }
 
 type systeminfo struct {

src/runtime/os_windows_pe.go

@@ -0,0 +1,63 @@
+//go:build windows
+
+package runtime
+
+import "unsafe"
+
+// MS-DOS stub with PE header offset:
+// https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#ms-dos-stub-image-only
+type exeHeader struct {
+	signature uint16
+	_         [58]byte // skip DOS header
+	peHeader  uint32   // at offset 0x3C
+}
+
+// COFF file header:
+// https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#file-headers
+type peHeader struct {
+	magic                uint32
+	machine              uint16
+	numberOfSections     uint16
+	timeDateStamp        uint32
+	pointerToSymbolTable uint32
+	numberOfSymbols      uint32
+	sizeOfOptionalHeader uint16
+	characteristics      uint16
+}
+
+// COFF section header:
+// https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#section-table-section-headers
+type peSection struct {
+	name                 [8]byte
+	virtualSize          uint32
+	virtualAddress       uint32
+	sizeOfRawData        uint32
+	pointerToRawData     uint32
+	pointerToRelocations uint32
+	pointerToLinenumbers uint32
+	numberOfRelocations  uint16
+	numberOfLinenumbers  uint16
+	characteristics      uint32
+}
+
+var module *exeHeader
+
+func findGlobalsForPE(found func(start, end uintptr)) {
+	// https://docs.microsoft.com/en-us/windows/win32/debug/pe-format
+	const imageSCNMemWrite = 0x80000000
+
+	pe := (*peHeader)(unsafe.Add(unsafe.Pointer(module), module.peHeader))
+	if gcAsserts && pe.magic != 0x00004550 { // 0x4550 is "PE"
+		runtimePanic("cannot find PE header")
+	}
+
+	section := (*peSection)(unsafe.Pointer(uintptr(unsafe.Pointer(pe)) + uintptr(pe.sizeOfOptionalHeader) + unsafe.Sizeof(peHeader{})))
+	for i := 0; i < int(pe.numberOfSections); i++ {
+		if section.characteristics&imageSCNMemWrite != 0 {
+			start := uintptr(unsafe.Pointer(module)) + uintptr(section.virtualAddress)
+			end := uintptr(unsafe.Pointer(module)) + uintptr(section.virtualAddress) + uintptr(section.virtualSize)
+			found(start, end)
+		}
+		section = (*peSection)(unsafe.Add(unsafe.Pointer(section), unsafe.Sizeof(peSection{})))
+	}
+}