1 files changed, 97 insertions, 0 deletions
diff --git a/gnu-efi/apps/debughook.c b/gnu-efi/apps/debughook.c
new file mode 100644
index 00000000..78e4a767
--- /dev/null
+++ b/gnu-efi/apps/debughook.c
@@ -0,0 +1,97 @@
+#include <efi.h>
+#include <efilib.h>
+
+EFI_STATUS
+GetVariableAttr(CHAR16 *var, UINT8 **data, UINTN *len, EFI_GUID owner,
+		  UINT32 *attributes)
+{
+	EFI_STATUS efi_status;
+
+	*len = 0;
+
+	efi_status = uefi_call_wrapper(RT->GetVariable, 5, var, &owner,
+				       NULL, len, NULL);
+	if (efi_status != EFI_BUFFER_TOO_SMALL)
+		return efi_status;
+
+	*data = AllocateZeroPool(*len);
+	if (!*data)
+		return EFI_OUT_OF_RESOURCES;
+
+	efi_status = uefi_call_wrapper(RT->GetVariable, 5, var, &owner,
+				       attributes, len, *data);
+
+	if (efi_status != EFI_SUCCESS) {
+		FreePool(*data);
+		*data = NULL;
+	}
+	return efi_status;
+}
+
+EFI_STATUS
+GetVariable(CHAR16 *var, UINT8 **data, UINTN *len, EFI_GUID owner)
+{
+	return GetVariableAttr(var, data, len, owner, NULL);
+}
+
+EFI_GUID DUMMY_GUID =
+{0x55aad538, 0x8f82, 0x4e2a, {0xa4,0xf0,0xbe, 0x59, 0x13, 0xb6, 0x5f, 0x1e}};
+
+#if defined(__clang__)
+# define _OPTNONE __attribute__((optnone))
+#else
+# define _OPTNONE __attribute__((__optimize__("0")))
+#endif
+
+static _OPTNONE void
+DebugHook(void)
+{
+	EFI_GUID guid = DUMMY_GUID;
+	UINT8 *data = NULL;
+	UINTN dataSize = 0;
+	EFI_STATUS efi_status;
+	register volatile unsigned long long x = 0;
+	extern char _text, _data;
+
+	if (x)
+		return;
+
+	efi_status = GetVariable(L"DUMMY_DEBUG", &data, &dataSize, guid);
+	if (EFI_ERROR(efi_status)) {
+		return;
+	}
+
+	Print(L"add-symbol-file /usr/lib/debug/boot/efi/debughook.debug "
+	      L"0x%08x -s .data 0x%08x\n", &_text, &_data);
+
+	Print(L"Pausing for debugger attachment.\n");
+	Print(L"To disable this, remove the EFI variable DUMMY_DEBUG-%g .\n",
+	      &guid);
+	x = 1;
+	while (x++) {
+		/* Make this so it can't /totally/ DoS us. */
+#if defined(__x86_64__) || defined(__i386__) || defined(__i686__)
+		if (x > 4294967294ULL)
+			break;
+		__asm__ __volatile__("pause");
+#elif defined(__aarch64__)
+		if (x > 1000)
+			break;
+		__asm__ __volatile__("wfi");
+#else
+		if (x > 12000)
+			break;
+		uefi_call_wrapper(BS->Stall, 1, 5000);
+#endif
+	}
+	x = 1;
+}
+
+
+EFI_STATUS
+efi_main (EFI_HANDLE image, EFI_SYSTEM_TABLE *systab)
+{
+	InitializeLib(image, systab);
+	DebugHook();
+	return EFI_SUCCESS;
+}