[efi] Allow DEBUG=efi_wrap to be used independently of a loaded image

Allow temporary debugging code to call efi_wrap_systab() to obtain a
pointer to the wrapper EFI system table.  This can then be used to
e.g. forcibly overwrite the boot services table pointer used by an
already loaded and running UEFI driver, in order to trace calls made
by that driver.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 34 insertions, 25 deletions

diff --git a/src/interface/efi/efi_wrap.c b/src/interface/efi/efi_wrap.c
index 66d2d29..5c02a7e 100644
--- a/src/interface/efi/efi_wrap.c
+++ b/src/interface/efi/efi_wrap.c
@@ -37,14 +37,8 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #include <ipxe/efi/Protocol/LoadedImage.h>
 #include <ipxe/efi/efi_wrap.h>
 
-/** EFI system table wrapper */
-static EFI_SYSTEM_TABLE efi_systab_wrapper;
-
-/** EFI boot services table wrapper */
-static EFI_BOOT_SERVICES efi_bs_wrapper;
-
 /** Colour for debug messages */
-#define colour &efi_systab_wrapper
+#define colour &efi_systab
 
 /**
  * Convert EFI status code to text
@@ -1135,28 +1129,17 @@ efi_create_event_ex_wrapper ( UINT32 type, EFI_TPL notify_tpl,
 }
 
 /**
- * Wrap the calls made by a loaded image
+ * Build table wrappers
  *
- * @v handle		Image handle
+ * @ret systab		Wrapped system table
  */
- void efi_wrap ( EFI_HANDLE handle ) {
+EFI_SYSTEM_TABLE * efi_wrap_systab ( void ) {
+	static EFI_SYSTEM_TABLE efi_systab_wrapper;
+	static EFI_BOOT_SERVICES efi_bs_wrapper;
 	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
-	union {
-		EFI_LOADED_IMAGE_PROTOCOL *image;
-		void *intf;
-	} loaded;
-	EFI_STATUS efirc;
-	int rc;
 
-	/* Do nothing unless debugging is enabled */
-	if ( ! DBG_LOG )
-		return;
-
-	/* Populate table wrappers */
-	memcpy ( &efi_systab_wrapper, efi_systab,
-		 sizeof ( efi_systab_wrapper ) );
+	/* Build boot services table wrapper */
 	memcpy ( &efi_bs_wrapper, bs, sizeof ( efi_bs_wrapper ) );
-	efi_systab_wrapper.BootServices	= &efi_bs_wrapper;
 	efi_bs_wrapper.RaiseTPL		= efi_raise_tpl_wrapper;
 	efi_bs_wrapper.RestoreTPL	= efi_restore_tpl_wrapper;
 	efi_bs_wrapper.AllocatePages	= efi_allocate_pages_wrapper;
@@ -1211,6 +1194,32 @@ efi_create_event_ex_wrapper ( UINT32 type, EFI_TPL notify_tpl,
 		= efi_uninstall_multiple_protocol_interfaces_wrapper;
 	efi_bs_wrapper.CreateEventEx	= efi_create_event_ex_wrapper;
 
+	/* Build system table wrapper */
+	memcpy ( &efi_systab_wrapper, efi_systab,
+		 sizeof ( efi_systab_wrapper ) );
+	efi_systab_wrapper.BootServices	= &efi_bs_wrapper;
+
+	return &efi_systab_wrapper;
+}
+
+/**
+ * Wrap the calls made by a loaded image
+ *
+ * @v handle		Image handle
+ */
+void efi_wrap ( EFI_HANDLE handle ) {
+	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
+	union {
+		EFI_LOADED_IMAGE_PROTOCOL *image;
+		void *intf;
+	} loaded;
+	EFI_STATUS efirc;
+	int rc;
+
+	/* Do nothing unless debugging is enabled */
+	if ( ! DBG_LOG )
+		return;
+
 	/* Open loaded image protocol */
 	if ( ( efirc = bs->OpenProtocol ( handle,
 					  &efi_loaded_image_protocol_guid,
@@ -1223,7 +1232,7 @@ efi_create_event_ex_wrapper ( UINT32 type, EFI_TPL notify_tpl,
 	}
 
 	/* Provide system table wrapper to image */
-	loaded.image->SystemTable = &efi_systab_wrapper;
+	loaded.image->SystemTable = efi_wrap_systab();
 	DBGC ( colour, "WRAP %s at base %p has protocols:\n",
 	       efi_handle_name ( handle ), loaded.image->ImageBase );
 	DBGC_EFI_PROTOCOLS ( colour, handle );