[efi] Perform meaningful error code conversions

Exploit the redefinition of iPXE error codes to include a "platform
error code" to allow for meaningful conversion of EFI_STATUS values to
iPXE errors and vice versa.

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

20 files changed, 212 insertions, 200 deletions

diff --git a/src/arch/x86/prefix/efiprefix.c b/src/arch/x86/prefix/efiprefix.c
index bfa94d404..a847045a5 100644
--- a/src/arch/x86/prefix/efiprefix.c
+++ b/src/arch/x86/prefix/efiprefix.c
@@ -20,6 +20,7 @@
 FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <stdlib.h>
+#include <errno.h>
 #include <ipxe/efi/efi.h>
 
 /**
@@ -38,5 +39,5 @@ EFI_STATUS EFIAPI _efi_start ( EFI_HANDLE image_handle,
 		return efirc;
 
 	/* Call to main() */
-	return RC_TO_EFIRC ( main () );
+	return EFIRC ( main () );
 }
diff --git a/src/drivers/net/efi/snpnet.c b/src/drivers/net/efi/snpnet.c
index 977908151..cd9e7e386 100644
--- a/src/drivers/net/efi/snpnet.c
+++ b/src/drivers/net/efi/snpnet.c
@@ -56,20 +56,21 @@ static int snpnet_transmit ( struct net_device *netdev,
 			     struct io_buffer *iobuf ) {
 	struct snpnet_device *snpnetdev = netdev->priv;
 	EFI_SIMPLE_NETWORK_PROTOCOL *snp = snpnetdev->snp;
-	EFI_STATUS efirc;
 	void *txbuf=NULL;
 	size_t len = iob_len ( iobuf );
+	EFI_STATUS efirc;
+	int rc;
 
-	efirc = snp->Transmit ( snp, 0, len, iobuf->data, NULL, NULL, NULL );
-	if (efirc) {
-		return EFIRC_TO_RC ( efirc );
+	if ( ( efirc = snp->Transmit ( snp, 0, len, iobuf->data, NULL, NULL,
+				       NULL ) ) != 0 ) {
+		return -EEFI ( efirc );
 	}
 	/* since GetStatus is so inconsistent, don't try more than one outstanding transmit at a time */
 	while ( txbuf == NULL ) {
-		efirc = snp->GetStatus ( snp, NULL, &txbuf );
-		if ( efirc ) {
+		if ( ( efirc = snp->GetStatus ( snp, NULL, &txbuf ) ) != 0 ) {
+			rc = -EEFI ( efirc );
 			DBGC ( snp, "SNP %p could not get status %s\n", snp,
-			       efi_strerror ( efirc ) );
+			       strerror ( rc ) );
 			break;
 		}
 
@@ -86,9 +87,10 @@ static int snpnet_transmit ( struct net_device *netdev,
 static void snpnet_poll ( struct net_device *netdev ) {
 	struct snpnet_device *snpnetdev = netdev->priv;
 	EFI_SIMPLE_NETWORK_PROTOCOL *snp = snpnetdev->snp;
-	EFI_STATUS efirc;
 	struct io_buffer *iobuf = NULL;
 	UINTN len;
+	EFI_STATUS efirc;
+	int rc;
 
 	/* Process received packets */
 	while ( 1 ) {
@@ -115,12 +117,13 @@ static void snpnet_poll ( struct net_device *netdev ) {
 		}
 
 		/* Other error? */
-		if ( efirc ) {
+		if ( efirc != 0 ) {
+			rc = -EEFI ( efirc );
 			DBGC ( snp, "SNP %p receive packet error: %s "
 				    "(len was %zd, is now %zd)\n",
-			       snp, efi_strerror ( efirc ), iob_len(iobuf),
+			       snp, strerror ( rc ), iob_len(iobuf),
 			       (size_t)len );
-			netdev_rx_err ( netdev, iobuf, efirc );
+			netdev_rx_err ( netdev, iobuf, rc );
 			break;
 		}
 
@@ -139,25 +142,27 @@ static void snpnet_poll ( struct net_device *netdev ) {
 static int snpnet_open ( struct net_device *netdev ) {
 	struct snpnet_device *snpnetdev = netdev->priv;
 	EFI_SIMPLE_NETWORK_PROTOCOL *snp = snpnetdev->snp;
-	EFI_STATUS efirc;
+	EFI_MAC_ADDRESS *mac;
 	UINT32 enableFlags, disableFlags;
+	EFI_STATUS efirc;
+	int rc;
 
 	snpnetdev->close_state = snp->Mode->State;
 	if ( snp->Mode->State != EfiSimpleNetworkInitialized ) {
-		efirc = snp->Initialize ( snp, 0, 0 );
-		if ( efirc ) {
+		if ( ( efirc = snp->Initialize ( snp, 0, 0 ) ) != 0 ) {
+			rc = -EEFI ( efirc );
 			DBGC ( snp, "SNP %p could not initialize: %s\n",
-			       snp, efi_strerror ( efirc ) );
-			return EFIRC_TO_RC ( efirc );
+			       snp, strerror ( rc ) );
+			return rc;
 		}
 	}
 
         /* Use the default MAC address */
-	efirc = snp->StationAddress ( snp, FALSE,
-				      (EFI_MAC_ADDRESS *)netdev->ll_addr );
-	if ( efirc ) {
+	mac = ( ( void * ) netdev->ll_addr );
+	if ( ( efirc = snp->StationAddress ( snp, FALSE, mac ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( snp, "SNP %p could not reset station address: %s\n",
-		       snp, efi_strerror ( efirc ) );
+		       snp, strerror ( rc ) );
 	}
 
 	/* Set up receive filters to receive unicast and broadcast packets
@@ -179,11 +184,11 @@ static int snpnet_open ( struct net_device *netdev ) {
 		enableFlags |= EFI_SIMPLE_NETWORK_RECEIVE_PROMISCUOUS;
 	}
 	disableFlags &= ~enableFlags;
-	efirc = snp->ReceiveFilters ( snp, enableFlags, disableFlags,
-				      FALSE, 0, NULL );
-	if ( efirc ) {
+	if ( ( efirc = snp->ReceiveFilters ( snp, enableFlags, disableFlags,
+					     FALSE, 0, NULL ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( snp, "SNP %p could not set receive filters: %s\n",
-		       snp, efi_strerror ( efirc ) );
+		       snp, strerror ( rc ) );
 	}
 
 	DBGC ( snp, "SNP %p opened\n", snp );
@@ -199,12 +204,13 @@ static void snpnet_close ( struct net_device *netdev ) {
 	struct snpnet_device *snpnetdev = netdev->priv;
 	EFI_SIMPLE_NETWORK_PROTOCOL *snp = snpnetdev->snp;
 	EFI_STATUS efirc;
+	int rc;
 
 	if ( snpnetdev->close_state != EfiSimpleNetworkInitialized ) {
-		efirc = snp->Shutdown ( snp );
-		if ( efirc ) {
+		if ( ( efirc = snp->Shutdown ( snp ) ) != 0 ) {
+			rc = -EEFI ( efirc );
 			DBGC ( snp, "SNP %p could not shut down: %s\n",
-			       snp, efi_strerror ( efirc ) );
+			       snp, strerror ( rc ) );
 		}
 	}
 }
@@ -264,11 +270,10 @@ int snpnet_probe ( struct snp_device *snpdev ) {
 
 	/* Start the interface */
 	if ( snp->Mode->State == EfiSimpleNetworkStopped ) {
-		efirc = snp->Start ( snp );
-		if ( efirc ) {
+		if ( ( efirc = snp->Start ( snp ) ) != 0 ) {
+			rc = -EEFI ( efirc );
 			DBGC ( snp, "SNP %p could not start: %s\n", snp,
-			       efi_strerror ( efirc ) );
-			rc = EFIRC_TO_RC ( efirc );
+			       strerror ( rc ) );
 			goto err_start;
 		}
 	}
@@ -310,25 +315,27 @@ err_start:
  */
 void snpnet_remove ( struct snp_device *snpdev ) {
 	EFI_SIMPLE_NETWORK_PROTOCOL *snp = snpdev->snp;
-	EFI_STATUS efirc;
 	struct net_device *netdev = snpdev->netdev;
+	EFI_STATUS efirc;
+	int rc;
 
 	if ( snp->Mode->State == EfiSimpleNetworkInitialized &&
 	     snpdev->removal_state != EfiSimpleNetworkInitialized ) {
 		DBGC ( snp, "SNP %p shutting down\n", snp );
-		efirc = snp->Shutdown ( snp );
-		if ( efirc ) {
+		if ( ( efirc = snp->Shutdown ( snp ) ) != 0 ) {
+			rc = -EEFI ( efirc );
 			DBGC ( snp, "SNP %p could not shut down: %s\n",
-			       snp, efi_strerror ( efirc ) );
+			       snp, strerror ( rc ) );
 		}
 	}
 
 	if ( snp->Mode->State == EfiSimpleNetworkStarted &&
 	     snpdev->removal_state == EfiSimpleNetworkStopped ) {
 		DBGC ( snp, "SNP %p stopping\n", snp );
-		efirc = snp->Stop ( snp );
-		if ( efirc ) {
-			DBGC ( snp, "SNP %p could not be stopped\n", snp );
+		if ( ( efirc = snp->Stop ( snp ) ) != 0 ) {
+			rc = -EEFI ( efirc );
+			DBGC ( snp, "SNP %p could not be stopped: %s\n",
+			       snp, strerror ( rc ) );
 		}
 	}
 
diff --git a/src/image/efi_image.c b/src/image/efi_image.c
index 0368b82c4..0e90954b2 100644
--- a/src/image/efi_image.c
+++ b/src/image/efi_image.c
@@ -176,9 +176,9 @@ static int efi_image_exec ( struct image *image ) {
 				       user_to_virt ( image->data, 0 ),
 				       image->len, &handle ) ) != 0 ) {
 		/* Not an EFI image */
+		rc = -EEFI ( efirc );
 		DBGC ( image, "EFIIMAGE %p could not load: %s\n",
-		       image, efi_strerror ( efirc ) );
-		rc = -ENOEXEC;
+		       image, strerror ( rc ) );
 		goto err_load_image;
 	}
 
@@ -188,7 +188,7 @@ static int efi_image_exec ( struct image *image ) {
 				   NULL, EFI_OPEN_PROTOCOL_GET_PROTOCOL );
 	if ( efirc ) {
 		/* Should never happen */
-		rc = EFIRC_TO_RC ( efirc );
+		rc = -EEFI ( efirc );
 		goto err_open_protocol;
 	}
 
@@ -205,9 +205,9 @@ static int efi_image_exec ( struct image *image ) {
 
 	/* Start the image */
 	if ( ( efirc = bs->StartImage ( handle, NULL, NULL ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( image, "EFIIMAGE %p returned with status %s\n",
-		       image, efi_strerror ( efirc ) );
-		rc = EFIRC_TO_RC ( efirc );
+		       image, strerror ( rc ) );
 		goto err_start_image;
 	}
 
@@ -220,8 +220,9 @@ static int efi_image_exec ( struct image *image ) {
 	 * have no "unload" operation.
 	 */
 	if ( ( efirc = bs->UnloadImage ( handle ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( image, "EFIIMAGE %p could not unload: %s\n",
-		       image, efi_strerror ( efirc ) );
+		       image, strerror ( rc ) );
 	}
  err_load_image:
 	free ( cmdline );
@@ -246,15 +247,17 @@ static int efi_image_probe ( struct image *image ) {
 	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
 	EFI_HANDLE handle;
 	EFI_STATUS efirc;
+	int rc;
 
 	/* Attempt loading image */
 	if ( ( efirc = bs->LoadImage ( FALSE, efi_image_handle, NULL,
 				       user_to_virt ( image->data, 0 ),
 				       image->len, &handle ) ) != 0 ) {
 		/* Not an EFI image */
+		rc = -EEFI ( efirc );
 		DBGC ( image, "EFIIMAGE %p could not load: %s\n",
-		       image, efi_strerror ( efirc ) );
-		return -ENOEXEC;
+		       image, strerror ( rc ) );
+		return rc;
 	}
 
 	/* Unload the image.  We can't leave it loaded, because we
diff --git a/src/include/ipxe/efi/efi.h b/src/include/ipxe/efi/efi.h
index 3aaac60ee..0a21c6e74 100644
--- a/src/include/ipxe/efi/efi.h
+++ b/src/include/ipxe/efi/efi.h
@@ -108,29 +108,27 @@ struct efi_config_table {
 		.required = (_required),				     \
 	}
 
-/** Convert a iPXE status code to an EFI status code
+/**
+ * Convert an iPXE status code to an EFI status code
  *
- * FIXME: actually perform some kind of conversion.  iPXE error codes
- * will be detected as EFI error codes; both have the top bit set, and
- * the success return code is zero for both.  Anything that just
- * reports a numerical error will be OK, anything attempting to
- * interpret the value or to display a text equivalent will be
- * screwed.
+ * @v rc		iPXE status code
+ * @ret efirc		EFI status code
  */
-#define RC_TO_EFIRC( rc ) (rc)
+#define EFIRC( rc ) ERRNO_TO_PLATFORM ( -(rc) )
 
-/** Convert an EFI status code to a iPXE status code
+/**
+ * Convert an EFI status code to an iPXE status code
  *
- * FIXME: as above
+ * @v efirc		EFI status code
+ * @ret rc		iPXE status code (before negation)
  */
-#define EFIRC_TO_RC( efirc ) (efirc)
+#define EEFI( efirc ) EPLATFORM ( EINFO_EPLATFORM, efirc )
 
 extern EFI_HANDLE efi_image_handle;
 extern EFI_LOADED_IMAGE_PROTOCOL *efi_loaded_image;
 extern EFI_DEVICE_PATH_PROTOCOL *efi_loaded_image_path;
 extern EFI_SYSTEM_TABLE *efi_systab;
 
-extern const char * efi_strerror ( EFI_STATUS efirc );
 extern const char * efi_guid_ntoa ( EFI_GUID *guid );
 
 extern void dbg_efi_protocols ( EFI_HANDLE handle );
diff --git a/src/include/ipxe/efi/efi_driver.h b/src/include/ipxe/efi/efi_driver.h
index e5872ced3..d7eec9649 100644
--- a/src/include/ipxe/efi/efi_driver.h
+++ b/src/include/ipxe/efi/efi_driver.h
@@ -44,6 +44,6 @@ struct efi_driver {
 extern EFI_DEVICE_PATH_PROTOCOL *
 efi_devpath_end ( EFI_DEVICE_PATH_PROTOCOL *path );
 
-extern EFI_STATUS efi_driver_install ( struct efi_driver *efidrv );
+extern int efi_driver_install ( struct efi_driver *efidrv );
 
 #endif /* _IPXE_EFI_DRIVER_H */
diff --git a/src/include/ipxe/efi/efi_pci.h b/src/include/ipxe/efi/efi_pci.h
index 6429f2109..e6b319709 100644
--- a/src/include/ipxe/efi/efi_pci.h
+++ b/src/include/ipxe/efi/efi_pci.h
@@ -38,11 +38,11 @@ struct efi_pci_device {
 
 extern struct efi_pci_device * efipci_create ( struct efi_driver *efidrv,
 					       EFI_HANDLE device );
-extern EFI_STATUS efipci_enable ( struct efi_pci_device *efipci );
+extern int efipci_enable ( struct efi_pci_device *efipci );
 extern struct efi_pci_device * efipci_find_efi ( EFI_HANDLE device );
 extern struct efi_pci_device * efipci_find ( struct device *dev );
-extern EFI_STATUS efipci_child_add ( struct efi_pci_device *efipci,
-				     EFI_HANDLE device );
+extern int efipci_child_add ( struct efi_pci_device *efipci,
+			      EFI_HANDLE device );
 extern void efipci_child_del ( struct efi_pci_device *efipci,
 			       EFI_HANDLE device );
 extern void efipci_destroy ( struct efi_driver *efidrv,
diff --git a/src/include/ipxe/errfile.h b/src/include/ipxe/errfile.h
index f906dbd55..67edcc931 100644
--- a/src/include/ipxe/errfile.h
+++ b/src/include/ipxe/errfile.h
@@ -266,6 +266,15 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #define ERRFILE_nslookup	      ( ERRFILE_OTHER | 0x00300000 )
 #define ERRFILE_efi_snp_hii	      ( ERRFILE_OTHER | 0x00310000 )
 #define ERRFILE_readline	      ( ERRFILE_OTHER | 0x00320000 )
+#define ERRFILE_efi_bofm	      ( ERRFILE_OTHER | 0x00330000 )
+#define ERRFILE_efi_console	      ( ERRFILE_OTHER | 0x00340000 )
+#define ERRFILE_efi_debug	      ( ERRFILE_OTHER | 0x00350000 )
+#define ERRFILE_efi_download	      ( ERRFILE_OTHER | 0x00360000 )
+#define ERRFILE_efi_driver	      ( ERRFILE_OTHER | 0x00370000 )
+#define ERRFILE_efi_file	      ( ERRFILE_OTHER | 0x00380000 )
+#define ERRFILE_efi_init	      ( ERRFILE_OTHER | 0x00390000 )
+#define ERRFILE_efi_timer	      ( ERRFILE_OTHER | 0x003a0000 )
+#define ERRFILE_efi_umalloc	      ( ERRFILE_OTHER | 0x003b0000 )
 
 /** @} */
 
diff --git a/src/interface/efi/efi_bofm.c b/src/interface/efi/efi_bofm.c
index c313d2e97..8a8489bd8 100644
--- a/src/interface/efi/efi_bofm.c
+++ b/src/interface/efi/efi_bofm.c
@@ -181,7 +181,7 @@ efi_bofm_supported ( EFI_DRIVER_BINDING_PROTOCOL *driver,
 	/* Create corresponding PCI device, if any */
 	efipci = efipci_create ( efidrv, device );
 	if ( ! efipci ) {
-		efirc = EFI_UNSUPPORTED;
+		rc = -ENOTSUP;
 		goto err_not_pci;
 	}
 
@@ -189,16 +189,15 @@ efi_bofm_supported ( EFI_DRIVER_BINDING_PROTOCOL *driver,
 	if ( ( rc = bofm_find_driver ( &efipci->pci ) ) != 0 ) {
 		DBGCP ( efidrv, "EFIBOFM " PCI_FMT " has no driver\n",
 			PCI_ARGS ( &efipci->pci ) );
-		efirc = EFI_UNSUPPORTED;
 		goto err_no_driver;
 	}
 
 	/* Locate BOFM protocol */
 	if ( ( efirc = bs->LocateProtocol ( &bofm1_protocol_guid, NULL,
 					    &bofm1.interface ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( efidrv, "EFIBOFM " PCI_FMT " cannot find BOFM "
 		       "protocol\n", PCI_ARGS ( &efipci->pci ) );
-		efirc = EFI_UNSUPPORTED;
 		goto err_not_bofm;
 	}
 
@@ -207,9 +206,10 @@ efi_bofm_supported ( EFI_DRIVER_BINDING_PROTOCOL *driver,
 						      0x04 /* Can change MAC */,
 						      0x00 /* No iSCSI */,
 						      0x02 /* Version */ ))!=0){
+		rc = -EEFI ( efirc );
 		DBGC ( efidrv, "EFIBOFM " PCI_FMT " could not register "
 		       "support: %s\n", PCI_ARGS ( &efipci->pci ),
-		       efi_strerror ( efirc ) );
+		       strerror ( rc ) );
 		goto err_cannot_register;
 	}
 
@@ -226,7 +226,7 @@ efi_bofm_supported ( EFI_DRIVER_BINDING_PROTOCOL *driver,
  err_no_driver:
 	efipci_destroy ( efidrv, efipci );
  err_not_pci:
-	return efirc;
+	return EFIRC ( rc );
 }
 
 /**
@@ -254,25 +254,27 @@ static EFI_STATUS EFIAPI efi_bofm_start ( EFI_DRIVER_BINDING_PROTOCOL *driver,
 	struct efi_pci_device *efipci;
 	IBM_BOFM_TABLE *bofmtab;
 	IBM_BOFM_TABLE *bofmtab2;
-	EFI_STATUS efirc;
 	int bofmrc;
+	EFI_STATUS efirc;
+	int rc;
 
 	DBGCP ( efidrv, "EFIBOFM DRIVER_START %p (%p)\n", device, child );
 
 	/* Create corresponding PCI device */
 	efipci = efipci_create ( efidrv, device );
 	if ( ! efipci ) {
-		efirc = EFI_OUT_OF_RESOURCES;
+		rc = -ENOMEM;
 		goto err_create;
 	}
 
 	/* Enable PCI device */
-	if ( ( efirc = efipci_enable ( efipci ) ) != 0 )
+	if ( ( rc = efipci_enable ( efipci ) ) != 0 )
 		goto err_enable;
 
 	/* Locate BOFM protocol */
 	if ( ( efirc = bs->LocateProtocol ( &bofm1_protocol_guid, NULL,
 					    &bofm1.interface ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( efidrv, "EFIBOFM " PCI_FMT " cannot find BOFM "
 		       "protocol\n", PCI_ARGS ( &efipci->pci ) );
 		goto err_locate_bofm;
@@ -324,17 +326,19 @@ static EFI_STATUS EFIAPI efi_bofm_start ( EFI_DRIVER_BINDING_PROTOCOL *driver,
 	if ( bofmtab2 ) {
 		if ( ( efirc = bofm2.bofm2->SetStatus ( bofm2.bofm2, device,
 							FALSE, bofmrc ) ) != 0){
+			rc = -EEFI ( efirc );
 			DBGC ( efidrv, "EFIBOFM " PCI_FMT " could not set "
 			       "BOFM2 status: %s\n", PCI_ARGS ( &efipci->pci ),
-			       efi_strerror ( efirc ) );
+			       strerror ( rc ) );
 			goto err_set_status;
 		}
 	} else {
 		if ( ( efirc = bofm1.bofm1->SetStatus ( bofm1.bofm1, device,
 							FALSE, bofmrc ) ) != 0){
+			rc = -EEFI ( efirc );
 			DBGC ( efidrv, "EFIBOFM " PCI_FMT " could not set "
 			       "BOFM status: %s\n", PCI_ARGS ( &efipci->pci ),
-			       efi_strerror ( efirc ) );
+			       strerror ( rc ) );
 			goto err_set_status;
 		}
 	}
@@ -350,7 +354,7 @@ static EFI_STATUS EFIAPI efi_bofm_start ( EFI_DRIVER_BINDING_PROTOCOL *driver,
  err_enable:
 	efipci_destroy ( efidrv, efipci );
  err_create:
-	return efirc;
+	return EFIRC ( rc );
 }
 
 /**
@@ -385,12 +389,12 @@ static struct efi_driver efi_bofm_driver =
  */
 static void efi_bofm_driver_init ( void ) {
 	struct efi_driver *efidrv = &efi_bofm_driver;
-	EFI_STATUS efirc;
+	int rc;
 
 	/* Install driver */
-	if ( ( efirc = efi_driver_install ( efidrv ) ) != 0 ) {
+	if ( ( rc = efi_driver_install ( efidrv ) ) != 0 ) {
 		DBGC ( efidrv, "EFIBOFM could not install driver: %s\n",
-		       efi_strerror ( efirc ) );
+		       strerror ( rc ) );
 		return;
 	}
 
diff --git a/src/interface/efi/efi_console.c b/src/interface/efi/efi_console.c
index a30ca301b..d86d30c91 100644
--- a/src/interface/efi/efi_console.c
+++ b/src/interface/efi/efi_console.c
@@ -20,6 +20,8 @@
 FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <stddef.h>
+#include <string.h>
+#include <errno.h>
 #include <assert.h>
 #include <ipxe/efi/efi.h>
 #include <ipxe/ansiesc.h>
@@ -227,6 +229,7 @@ static int efi_getchar ( void ) {
 	const char *ansi_seq;
 	EFI_INPUT_KEY key;
 	EFI_STATUS efirc;
+	int rc;
 
 	/* If we are mid-sequence, pass out the next byte */
 	if ( *ansi_input )
@@ -234,8 +237,8 @@ static int efi_getchar ( void ) {
 
 	/* Read key from real EFI console */
 	if ( ( efirc = conin->ReadKeyStroke ( conin, &key ) ) != 0 ) {
-		DBG ( "EFI could not read keystroke: %s\n",
-		      efi_strerror ( efirc ) );
+		rc = -EEFI ( efirc );
+		DBG ( "EFI could not read keystroke: %s\n", strerror ( rc ) );
 		return 0;
 	}
 	DBG2 ( "EFI read key stroke with unicode %04x scancode %04x\n",
diff --git a/src/interface/efi/efi_debug.c b/src/interface/efi/efi_debug.c
index a7ba7e2ed..4ed666077 100644
--- a/src/interface/efi/efi_debug.c
+++ b/src/interface/efi/efi_debug.c
@@ -28,6 +28,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <stdio.h>
 #include <string.h>
+#include <errno.h>
 #include <ipxe/uuid.h>
 #include <ipxe/efi/efi.h>
 #include <ipxe/efi/efi_driver.h>
@@ -67,12 +68,14 @@ void dbg_efi_protocols ( EFI_HANDLE handle ) {
 	UINTN count;
 	unsigned int i;
 	EFI_STATUS efirc;
+	int rc;
 
 	/* Retrieve list of protocols */
 	if ( ( efirc = bs->ProtocolsPerHandle ( handle, &protocols,
 						&count ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		printf ( "EFI could not retrieve protocols for %p: %s\n",
-			 handle, efi_strerror ( efirc ) );
+			 handle, strerror ( rc ) );
 		return;
 	}
 
diff --git a/src/interface/efi/efi_download.c b/src/interface/efi/efi_download.c
index 7b19ad3a2..80279f7f9 100644
--- a/src/interface/efi/efi_download.c
+++ b/src/interface/efi/efi_download.c
@@ -20,6 +20,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <stdlib.h>
 #include <string.h>
+#include <errno.h>
 #include <ipxe/open.h>
 #include <ipxe/process.h>
 #include <ipxe/iobuf.h>
@@ -59,7 +60,7 @@ struct efi_download_file {
  */
 static void efi_download_close ( struct efi_download_file *file, int rc ) {
 
-	file->finish_callback ( file->context, RC_TO_EFIRC ( rc ) );
+	file->finish_callback ( file->context, EFIRC ( rc ) );
 
 	intf_shutdown ( &file->xfer, rc );
 }
@@ -77,6 +78,7 @@ static int efi_download_deliver_iob ( struct efi_download_file *file,
 				      struct xfer_metadata *meta ) {
 	EFI_STATUS efirc;
 	size_t len = iob_len ( iobuf );
+	int rc;
 
 	/* Calculate new buffer position */
 	if ( meta->flags & XFER_FL_ABS_OFFSET )
@@ -84,14 +86,21 @@ static int efi_download_deliver_iob ( struct efi_download_file *file,
 	file->pos += meta->offset;
 
 	/* Call out to the data handler */
-	efirc = file->data_callback ( file->context, iobuf->data,
-				      len, file->pos );
+	if ( ( efirc = file->data_callback ( file->context, iobuf->data,
+					     len, file->pos ) ) != 0 ) {
+		rc = -EEFI ( efirc );
+		goto err_callback;
+	}
 
 	/* Update current buffer position */
 	file->pos += len;
 
+	/* Success */
+	rc = 0;
+
+ err_callback:
 	free_iob ( iobuf );
-	return EFIRC_TO_RC ( efirc );
+	return rc;
 }
 
 /** Data transfer interface operations */
@@ -135,7 +144,7 @@ efi_download_start ( IPXE_DOWNLOAD_PROTOCOL *This __unused,
 	rc = xfer_open ( &file->xfer, LOCATION_URI_STRING, Url );
 	if ( rc ) {
 		free ( file );
-		return RC_TO_EFIRC ( rc );
+		return EFIRC ( rc );
 	}
 
 	file->pos = 0;
@@ -162,7 +171,7 @@ efi_download_abort ( IPXE_DOWNLOAD_PROTOCOL *This __unused,
 		     EFI_STATUS Status ) {
 	struct efi_download_file *file = File;
 
-	efi_download_close ( file, EFIRC_TO_RC ( Status ) );
+	efi_download_close ( file, -EEFI ( Status ) );
 	return EFI_SUCCESS;
 }
 
@@ -195,6 +204,7 @@ static IPXE_DOWNLOAD_PROTOCOL ipxe_download_protocol_interface = {
 int efi_download_install ( EFI_HANDLE *handle ) {
 	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
 	EFI_STATUS efirc;
+	int rc;
 
 	efirc = bs->InstallMultipleProtocolInterfaces (
 			handle,
@@ -202,9 +212,10 @@ int efi_download_install ( EFI_HANDLE *handle ) {
 			&ipxe_download_protocol_interface,
 			NULL );
 	if ( efirc ) {
+		rc = -EEFI ( efirc );
 		DBG ( "Could not install download protocol: %s\n",
-		      efi_strerror ( efirc ) );
-		return EFIRC_TO_RC ( efirc );
+		      strerror ( rc ) );
+		return rc;
 	}
 
 	return 0;
diff --git a/src/interface/efi/efi_driver.c b/src/interface/efi/efi_driver.c
index deb3cf2cd..13ed1f501 100644
--- a/src/interface/efi/efi_driver.c
+++ b/src/interface/efi/efi_driver.c
@@ -21,6 +21,8 @@ FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <stddef.h>
 #include <stdio.h>
+#include <string.h>
+#include <errno.h>
 #include <ipxe/efi/efi.h>
 #include <ipxe/efi/Protocol/DriverBinding.h>
 #include <ipxe/efi/Protocol/ComponentName2.h>
@@ -122,11 +124,12 @@ efi_driver_get_controller_name ( EFI_COMPONENT_NAME2_PROTOCOL *wtf __unused,
  * @v efidrv		EFI driver
  * @ret efirc		EFI status code
  */
-EFI_STATUS efi_driver_install ( struct efi_driver *efidrv ) {
+int efi_driver_install ( struct efi_driver *efidrv ) {
 	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
 	EFI_DRIVER_BINDING_PROTOCOL *driver = &efidrv->driver;
 	EFI_COMPONENT_NAME2_PROTOCOL *wtf = &efidrv->wtf;
 	EFI_STATUS efirc;
+	int rc;
 
 	/* Configure driver binding protocol */
 	driver->ImageHandle = efi_image_handle;
@@ -148,9 +151,10 @@ EFI_STATUS efi_driver_install ( struct efi_driver *efidrv ) {
 			&efi_driver_binding_protocol_guid, driver,
 			&efi_component_name2_protocol_guid, wtf,
 			NULL ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( efidrv, "EFIDRV %s could not install protocol: %s\n",
-		       efidrv->name, efi_strerror ( efirc ) );
-		return efirc;
+		       efidrv->name, strerror ( rc ) );
+		return rc;
 	}
 
 	DBGC ( efidrv, "EFIDRV %s installed\n", efidrv->name );
diff --git a/src/interface/efi/efi_file.c b/src/interface/efi/efi_file.c
index 6f9d44f83..4c482d2e5 100644
--- a/src/interface/efi/efi_file.c
+++ b/src/interface/efi/efi_file.c
@@ -30,6 +30,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <errno.h>
 #include <wchar.h>
 #include <ipxe/image.h>
 #include <ipxe/efi/efi.h>
@@ -549,6 +550,7 @@ static EFI_BLOCK_IO_PROTOCOL efi_block_io_protocol = {
 int efi_file_install ( EFI_HANDLE *handle ) {
 	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
 	EFI_STATUS efirc;
+	int rc;
 
 	/* Install the simple file system protocol and the block I/O
 	 * protocol.  We don't have a block device, but large parts of
@@ -563,9 +565,10 @@ int efi_file_install ( EFI_HANDLE *handle ) {
 			&efi_block_io_protocol,
 			&efi_simple_file_system_protocol_guid,
 			&efi_simple_file_system_protocol, NULL ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( handle, "Could not install simple file system protocol: "
-		       "%s\n", efi_strerror ( efirc ) );
-		return EFIRC_TO_RC ( efirc );
+		       "%s\n", strerror ( rc ) );
+		return rc;
 	}
 
 	return 0;
diff --git a/src/interface/efi/efi_init.c b/src/interface/efi/efi_init.c
index e40de4dd5..2f6ca89c2 100644
--- a/src/interface/efi/efi_init.c
+++ b/src/interface/efi/efi_init.c
@@ -20,6 +20,7 @@
 FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <string.h>
+#include <errno.h>
 #include <ipxe/efi/efi.h>
 #include <ipxe/efi/Protocol/LoadedImage.h>
 #include <ipxe/efi/Protocol/DevicePath.h>
@@ -94,6 +95,7 @@ EFI_STATUS efi_init ( EFI_HANDLE image_handle,
 	void *loaded_image;
 	void *loaded_image_path;
 	EFI_STATUS efirc;
+	int rc;
 
 	/* Store image handle and system table pointer for future use */
 	efi_image_handle = image_handle;
@@ -149,8 +151,9 @@ EFI_STATUS efi_init ( EFI_HANDLE image_handle,
 				&efi_loaded_image_protocol_guid,
 				&loaded_image, image_handle, NULL,
 				EFI_OPEN_PROTOCOL_GET_PROTOCOL ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( systab, "EFI could not get loaded image protocol: %s",
-		       efi_strerror ( efirc ) );
+		       strerror ( rc ) );
 		return efirc;
 	}
 	efi_loaded_image = loaded_image;
@@ -162,8 +165,9 @@ EFI_STATUS efi_init ( EFI_HANDLE image_handle,
 				&efi_loaded_image_device_path_protocol_guid,
 				&loaded_image_path, image_handle, NULL,
 				EFI_OPEN_PROTOCOL_GET_PROTOCOL ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( systab, "EFI could not get loaded image device path "
-		       "protocol: %s", efi_strerror ( efirc ) );
+		       "protocol: %s", strerror ( rc ) );
 		return efirc;
 	}
 	efi_loaded_image_path = loaded_image_path;
@@ -179,8 +183,9 @@ EFI_STATUS efi_init ( EFI_HANDLE image_handle,
 	if ( ( efirc = bs->CreateEvent ( EVT_SIGNAL_EXIT_BOOT_SERVICES,
 					 TPL_CALLBACK, efi_shutdown_hook,
 					 NULL, &efi_shutdown_event ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( systab, "EFI could not create ExitBootServices event: "
-		       "%s\n", efi_strerror ( efirc ) );
+		       "%s\n", strerror ( rc ) );
 		return efirc;
 	}
 
diff --git a/src/interface/efi/efi_pci.c b/src/interface/efi/efi_pci.c
index 0288cf326..d6095d3e3 100644
--- a/src/interface/efi/efi_pci.c
+++ b/src/interface/efi/efi_pci.c
@@ -57,13 +57,15 @@ static unsigned long efipci_address ( struct pci_device *pci,
 int efipci_read ( struct pci_device *pci, unsigned long location,
 		  void *value ) {
 	EFI_STATUS efirc;
+	int rc;
 
 	if ( ( efirc = efipci->Pci.Read ( efipci, EFIPCI_WIDTH ( location ),
 					  efipci_address ( pci, location ), 1,
 					  value ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBG ( "EFIPCI config read from " PCI_FMT " offset %02lx "
 		      "failed: %s\n", PCI_ARGS ( pci ),
-		      EFIPCI_OFFSET ( location ), efi_strerror ( efirc ) );
+		      EFIPCI_OFFSET ( location ), strerror ( rc ) );
 		return -EIO;
 	}
 
@@ -73,13 +75,15 @@ int efipci_read ( struct pci_device *pci, unsigned long location,
 int efipci_write ( struct pci_device *pci, unsigned long location,
 		   unsigned long value ) {
 	EFI_STATUS efirc;
+	int rc;
 
 	if ( ( efirc = efipci->Pci.Write ( efipci, EFIPCI_WIDTH ( location ),
 					   efipci_address ( pci, location ), 1,
 					   &value ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBG ( "EFIPCI config write to " PCI_FMT " offset %02lx "
 		      "failed: %s\n", PCI_ARGS ( pci ),
-		      EFIPCI_OFFSET ( location ), efi_strerror ( efirc ) );
+		      EFIPCI_OFFSET ( location ), strerror ( rc ) );
 		return -EIO;
 	}
 
@@ -149,6 +153,7 @@ struct efi_pci_device * efipci_create ( struct efi_driver *efidrv,
 					  efidrv->driver.DriverBindingHandle,
 					  device,
 					  EFI_OPEN_PROTOCOL_BY_DRIVER )) !=0 ){
+		rc = -EEFI ( efirc );
 		DBGCP ( efipci, "EFIPCI device %p is not a PCI device\n",
 			device );
 		goto err_open_protocol;
@@ -160,8 +165,9 @@ struct efi_pci_device * efipci_create ( struct efi_driver *efidrv,
 						    &pci_segment,
 						    &pci_bus, &pci_dev,
 						    &pci_fn ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( efipci, "EFIPCI device %p could not get PCI "
-		       "location: %s\n", device, efi_strerror ( efirc ) );
+		       "location: %s\n", device, strerror ( rc ) );
 		goto err_get_location;
 	}
 	DBGC2 ( efipci, "EFIPCI device %p is PCI %04lx:%02lx:%02lx.%lx\n",
@@ -185,6 +191,7 @@ struct efi_pci_device * efipci_create ( struct efi_driver *efidrv,
 					  efidrv->driver.DriverBindingHandle,
 					  device,
 					  EFI_OPEN_PROTOCOL_BY_DRIVER )) !=0 ){
+		rc = -EEFI ( efirc );
 		DBGC ( efipci, "EFIPCI " PCI_FMT " has no device path\n",
 		       PCI_ARGS ( &efipci->pci ) );
 		goto err_no_device_path;
@@ -213,9 +220,9 @@ struct efi_pci_device * efipci_create ( struct efi_driver *efidrv,
  * Enable EFI PCI device
  *
  * @v efipci		EFI PCI device
- * @ret efirc		EFI status code
+ * @ret rc		Return status code
  */
-EFI_STATUS efipci_enable ( struct efi_pci_device *efipci ) {
+int efipci_enable ( struct efi_pci_device *efipci ) {
 	EFI_PCI_IO_PROTOCOL *pci_io = efipci->pci_io;
 
 	/* Try to enable I/O cycles, memory cycles, and bus mastering.
@@ -273,8 +280,7 @@ struct efi_pci_device * efipci_find ( struct device *dev ) {
  * @v device		EFI child device
  * @ret efirc		EFI status code
  */
-EFI_STATUS efipci_child_add ( struct efi_pci_device *efipci,
-			      EFI_HANDLE device ) {
+int efipci_child_add ( struct efi_pci_device *efipci, EFI_HANDLE device ) {
 	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
 	struct efi_driver *efidrv = efipci->efidrv;
 	union {
@@ -282,6 +288,7 @@ EFI_STATUS efipci_child_add ( struct efi_pci_device *efipci,
 		void *interface;
 	} pci_io;
 	EFI_STATUS efirc;
+	int rc;
 
 	/* Re-open the PCI_IO_PROTOCOL */
 	if ( ( efirc = bs->OpenProtocol ( efipci->device,
@@ -291,9 +298,10 @@ EFI_STATUS efipci_child_add ( struct efi_pci_device *efipci,
 					  device,
 					  EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER
 					  ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( efipci, "EFIPCI " PCI_FMT " could not add child: %s\n",
-		       PCI_ARGS ( &efipci->pci ), efi_strerror ( efirc ) );
-		return efirc;
+		       PCI_ARGS ( &efipci->pci ), strerror ( rc ) );
+		return rc;
 	}
 
 	return 0;
@@ -355,7 +363,6 @@ efipci_supported ( EFI_DRIVER_BINDING_PROTOCOL *driver, EFI_HANDLE device,
 	struct efi_driver *efidrv =
 		container_of ( driver, struct efi_driver, driver );
 	struct efi_pci_device *efipci;
-	EFI_STATUS efirc;
 	int rc;
 
 	DBGCP ( efidrv, "EFIPCI DRIVER_SUPPORTED %p (%p)\n", device, child );
@@ -364,7 +371,7 @@ efipci_supported ( EFI_DRIVER_BINDING_PROTOCOL *driver, EFI_HANDLE device,
 	efipci = efipci_create ( efidrv, device );
 	if ( ! efipci ) {
 		/* Non-PCI devices are simply unsupported */
-		efirc = EFI_UNSUPPORTED;
+		rc = -ENOTSUP;
 		goto err_not_pci;
 	}
 
@@ -372,7 +379,6 @@ efipci_supported ( EFI_DRIVER_BINDING_PROTOCOL *driver, EFI_HANDLE device,
 	if ( ( rc = pci_find_driver ( &efipci->pci ) ) != 0 ) {
 		DBGCP ( efipci, "EFIPCI " PCI_FMT " has no driver\n",
 			PCI_ARGS ( &efipci->pci ) );
-		efirc = EFI_UNSUPPORTED;
 		goto err_no_driver;
 	}
 
@@ -387,7 +393,7 @@ efipci_supported ( EFI_DRIVER_BINDING_PROTOCOL *driver, EFI_HANDLE device,
  err_no_driver:
 	efipci_destroy ( efidrv, efipci );
  err_not_pci:
-	return efirc;
+	return EFIRC ( rc );
 }
 
 /**
@@ -404,7 +410,6 @@ efipci_start ( EFI_DRIVER_BINDING_PROTOCOL *driver, EFI_HANDLE device,
 	struct efi_driver *efidrv =
 		container_of ( driver, struct efi_driver, driver );
 	struct efi_pci_device *efipci;
-	EFI_STATUS efirc;
 	int rc;
 
 	DBGC ( efidrv, "EFIPCI DRIVER_START %p (%p)\n", device, child );
@@ -412,7 +417,7 @@ efipci_start ( EFI_DRIVER_BINDING_PROTOCOL *driver, EFI_HANDLE device,
 	/* Create corresponding PCI device */
 	efipci = efipci_create ( efidrv, device );
 	if ( ! efipci ) {
-		efirc = EFI_OUT_OF_RESOURCES;
+		rc = -ENOMEM;
 		goto err_create;
 	}
 
@@ -420,12 +425,11 @@ efipci_start ( EFI_DRIVER_BINDING_PROTOCOL *driver, EFI_HANDLE device,
 	if ( ( rc = pci_find_driver ( &efipci->pci ) ) != 0 ) {
 		DBGC ( efipci, "EFIPCI " PCI_FMT " has no driver\n",
 		       PCI_ARGS ( &efipci->pci ) );
-		efirc = RC_TO_EFIRC ( rc );
 		goto err_find_driver;
 	}
 
 	/* Enable PCI device */
-	if ( ( efirc = efipci_enable ( efipci ) ) != 0 )
+	if ( ( rc = efipci_enable ( efipci ) ) != 0 )
 		goto err_enable;
 
 	/* Probe driver */
@@ -433,7 +437,6 @@ efipci_start ( EFI_DRIVER_BINDING_PROTOCOL *driver, EFI_HANDLE device,
 		DBGC ( efipci, "EFIPCI " PCI_FMT " could not probe driver "
 		       "\"%s\": %s\n", PCI_ARGS ( &efipci->pci ),
 		       efipci->pci.id->name, strerror ( rc ) );
-		efirc = RC_TO_EFIRC ( rc );
 		goto err_probe;
 	}
 
@@ -445,7 +448,7 @@ efipci_start ( EFI_DRIVER_BINDING_PROTOCOL *driver, EFI_HANDLE device,
  err_find_driver:
 	efipci_destroy ( efidrv, efipci );
  err_create:
-	return efirc;
+	return EFIRC ( rc );
 }
 
 /**
@@ -494,12 +497,12 @@ static struct efi_driver efipci_driver =
  */
 static void efipci_driver_startup ( void ) {
 	struct efi_driver *efidrv = &efipci_driver;
-	EFI_STATUS efirc;
+	int rc;
 
 	/* Install driver */
-	if ( ( efirc = efi_driver_install ( efidrv ) ) != 0 ) {
+	if ( ( rc = efi_driver_install ( efidrv ) ) != 0 ) {
 		DBGC ( efidrv, "EFIPCI could not install driver: %s\n",
-		       efi_strerror ( efirc ) );
+		       strerror ( rc ) );
 		return;
 	}
 
diff --git a/src/interface/efi/efi_snp.c b/src/interface/efi/efi_snp.c
index 95e39b7d9..adeb38de3 100644
--- a/src/interface/efi/efi_snp.c
+++ b/src/interface/efi/efi_snp.c
@@ -177,7 +177,7 @@ efi_snp_initialize ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 	if ( ( rc = netdev_open ( snpdev->netdev ) ) != 0 ) {
 		DBGC ( snpdev, "SNPDEV %p could not open %s: %s\n",
 		       snpdev, snpdev->netdev->name, strerror ( rc ) );
-		return RC_TO_EFIRC ( rc );
+		return EFIRC ( rc );
 	}
 
 	snpdev->mode.State = EfiSimpleNetworkInitialized;
@@ -206,7 +206,7 @@ efi_snp_reset ( EFI_SIMPLE_NETWORK_PROTOCOL *snp, BOOLEAN ext_verify ) {
 	if ( ( rc = netdev_open ( snpdev->netdev ) ) != 0 ) {
 		DBGC ( snpdev, "SNPDEV %p could not reopen %s: %s\n",
 		       snpdev, snpdev->netdev->name, strerror ( rc ) );
-		return RC_TO_EFIRC ( rc );
+		return EFIRC ( rc );
 	}
 
 	snpdev->mode.State = EfiSimpleNetworkInitialized;
@@ -366,7 +366,7 @@ efi_snp_mcast_ip_to_mac ( EFI_SIMPLE_NETWORK_PROTOCOL *snp, BOOLEAN ipv6,
 					   ip, mac ) ) != 0 ) {
 		DBGC ( snpdev, "SNPDEV %p could not hash %s: %s\n",
 		       snpdev, ip_str, strerror ( rc ) );
-		return RC_TO_EFIRC ( rc );
+		return EFIRC ( rc );
 	}
 
 	return 0;
@@ -490,7 +490,6 @@ efi_snp_transmit ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 	struct io_buffer *iobuf;
 	size_t payload_len;
 	int rc;
-	EFI_STATUS efirc;
 
 	DBGC2 ( snpdev, "SNPDEV %p TRANSMIT %p+%lx", snpdev, data,
 		( ( unsigned long ) len ) );
@@ -515,25 +514,25 @@ efi_snp_transmit ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 			DBGC ( snpdev, "SNPDEV %p TX invalid header length "
 			       "%ld\n", snpdev,
 			       ( ( unsigned long ) ll_header_len ) );
-			efirc = EFI_INVALID_PARAMETER;
+			rc = -EINVAL;
 			goto err_sanity;
 		}
 		if ( len < ll_header_len ) {
 			DBGC ( snpdev, "SNPDEV %p invalid packet length %ld\n",
 			       snpdev, ( ( unsigned long ) len ) );
-			efirc = EFI_BUFFER_TOO_SMALL;
+			rc = -EINVAL;
 			goto err_sanity;
 		}
 		if ( ! ll_dest ) {
 			DBGC ( snpdev, "SNPDEV %p TX missing destination "
 			       "address\n", snpdev );
-			efirc = EFI_INVALID_PARAMETER;
+			rc = -EINVAL;
 			goto err_sanity;
 		}
 		if ( ! net_proto ) {
 			DBGC ( snpdev, "SNPDEV %p TX missing network "
 			       "protocol\n", snpdev );
-			efirc = EFI_INVALID_PARAMETER;
+			rc = -EINVAL;
 			goto err_sanity;
 		}
 		if ( ! ll_src )
@@ -547,7 +546,7 @@ efi_snp_transmit ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 	if ( ! iobuf ) {
 		DBGC ( snpdev, "SNPDEV %p TX could not allocate %ld-byte "
 		       "buffer\n", snpdev, ( ( unsigned long ) len ) );
-		efirc = EFI_DEVICE_ERROR;
+		rc = -ENOMEM;
 		goto err_alloc_iob;
 	}
 	iob_reserve ( iobuf, ( MAX_LL_HEADER_LEN -
@@ -562,7 +561,6 @@ efi_snp_transmit ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 						htons ( *net_proto ) )) != 0 ){
 			DBGC ( snpdev, "SNPDEV %p TX could not construct "
 			       "header: %s\n", snpdev, strerror ( rc ) );
-			efirc = RC_TO_EFIRC ( rc );
 			goto err_ll_push;
 		}
 	}
@@ -571,7 +569,6 @@ efi_snp_transmit ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 	if ( ( rc = netdev_tx ( snpdev->netdev, iob_disown ( iobuf ) ) ) != 0){
 		DBGC ( snpdev, "SNPDEV %p TX could not transmit: %s\n",
 		       snpdev, strerror ( rc ) );
-		efirc = RC_TO_EFIRC ( rc );
 		goto err_tx;
 	}
 
@@ -586,7 +583,7 @@ efi_snp_transmit ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 	free_iob ( iobuf );
  err_alloc_iob:
  err_sanity:
-	return efirc;
+	return EFIRC ( rc );
 }
 
 /**
@@ -615,7 +612,6 @@ efi_snp_receive ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 	uint16_t iob_net_proto;
 	unsigned int iob_flags;
 	int rc;
-	EFI_STATUS efirc;
 
 	DBGC2 ( snpdev, "SNPDEV %p RECEIVE %p(+%lx)", snpdev, data,
 		( ( unsigned long ) *len ) );
@@ -627,7 +623,7 @@ efi_snp_receive ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 	iobuf = netdev_rx_dequeue ( snpdev->netdev );
 	if ( ! iobuf ) {
 		DBGC2 ( snpdev, "\n" );
-		efirc = EFI_NOT_READY;
+		rc = -EAGAIN;
 		goto out_no_packet;
 	}
 	DBGC2 ( snpdev, "+%zx\n", iob_len ( iobuf ) );
@@ -642,7 +638,6 @@ efi_snp_receive ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 					&iob_flags ) ) != 0 ) {
 		DBGC ( snpdev, "SNPDEV %p could not parse header: %s\n",
 		       snpdev, strerror ( rc ) );
-		efirc = RC_TO_EFIRC ( rc );
 		goto out_bad_ll_header;
 	}
 
@@ -656,12 +651,12 @@ efi_snp_receive ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
 	if ( net_proto )
 		*net_proto = ntohs ( iob_net_proto );
 
-	efirc = 0;
+	rc = 0;
 
  out_bad_ll_header:
 	free_iob ( iobuf );
 out_no_packet:
-	return efirc;
+	return EFIRC ( rc );
 }
 
 /**
@@ -879,9 +874,9 @@ static int efi_snp_probe ( struct net_device *netdev ) {
 	if ( ( efirc = bs->CreateEvent ( EVT_NOTIFY_WAIT, TPL_NOTIFY,
 					 efi_snp_wait_for_packet, snpdev,
 					 &snpdev->snp.WaitForPacket ) ) != 0 ){
+		rc = -EEFI ( efirc );
 		DBGC ( snpdev, "SNPDEV %p could not create event: %s\n",
-		       snpdev, efi_strerror ( efirc ) );
-		rc = EFIRC_TO_RC ( efirc );
+		       snpdev, strerror ( rc ) );
 		goto err_create_event;
 	}
 
@@ -944,18 +939,17 @@ static int efi_snp_probe ( struct net_device *netdev ) {
 			&efi_component_name2_protocol_guid, &snpdev->name2,
 			&efi_load_file_protocol_guid, &snpdev->load_file,
 			NULL ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( snpdev, "SNPDEV %p could not install protocols: "
-		       "%s\n", snpdev, efi_strerror ( efirc ) );
-		rc = EFIRC_TO_RC ( efirc );
+		       "%s\n", snpdev, strerror ( rc ) );
 		goto err_install_protocol_interface;
 	}
 
 	/* Add as child of PCI device */
-	if ( ( efirc = efipci_child_add ( efipci, snpdev->handle ) ) != 0 ) {
+	if ( ( rc = efipci_child_add ( efipci, snpdev->handle ) ) != 0 ) {
 		DBGC ( snpdev, "SNPDEV %p could not become child of " PCI_FMT
 		       ": %s\n", snpdev, PCI_ARGS ( &efipci->pci ),
-		       efi_strerror ( efirc ) );
-		rc = EFIRC_TO_RC ( efirc );
+		       strerror ( rc ) );
 		goto err_efipci_child_add;
 	}
 
diff --git a/src/interface/efi/efi_snp_hii.c b/src/interface/efi/efi_snp_hii.c
index 3a1193a38..9ea15a623 100644
--- a/src/interface/efi/efi_snp_hii.c
+++ b/src/interface/efi/efi_snp_hii.c
@@ -544,7 +544,7 @@ efi_snp_hii_extract_config ( const EFI_HII_CONFIG_ACCESS_PROTOCOL *hii,
 		if ( ( rc = efi_snp_hii_process ( snpdev, pos, progress,
 						  results, &have_setting,
 						  efi_snp_hii_fetch ) ) != 0 ) {
-			return RC_TO_EFIRC ( rc );
+			return EFIRC ( rc );
 		}
 	}
 
@@ -558,7 +558,7 @@ efi_snp_hii_extract_config ( const EFI_HII_CONFIG_ACCESS_PROTOCOL *hii,
 			if ( ( rc = efi_snp_hii_fetch ( snpdev, setting->name,
 							NULL, results,
 							NULL ) ) != 0 ) {
-				return RC_TO_EFIRC ( rc );
+				return EFIRC ( rc );
 			}
 		}
 	}
@@ -592,7 +592,7 @@ efi_snp_hii_route_config ( const EFI_HII_CONFIG_ACCESS_PROTOCOL *hii,
 		if ( ( rc = efi_snp_hii_process ( snpdev, pos, progress,
 						  NULL, NULL,
 						  efi_snp_hii_store ) ) != 0 ) {
-			return RC_TO_EFIRC ( rc );
+			return EFIRC ( rc );
 		}
 	}
 
@@ -657,9 +657,9 @@ int efi_snp_hii_install ( struct efi_snp_device *snpdev ) {
 	if ( ( efirc = efihii->NewPackageList ( efihii, snpdev->package_list,
 						snpdev->handle,
 						&snpdev->hii_handle ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( snpdev, "SNPDEV %p could not add HII packages: %s\n",
-		       snpdev, efi_strerror ( efirc ) );
-		rc = EFIRC_TO_RC ( efirc );
+		       snpdev, strerror ( rc ) );
 		goto err_new_package_list;
 	}
 
@@ -668,9 +668,9 @@ int efi_snp_hii_install ( struct efi_snp_device *snpdev ) {
 			 &snpdev->handle,
 			 &efi_hii_config_access_protocol_guid, &snpdev->hii,
 			 NULL ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBGC ( snpdev, "SNPDEV %p could not install HII protocol: %s\n",
-		       snpdev, efi_strerror ( efirc ) );
-		rc = EFIRC_TO_RC ( efirc );
+		       snpdev, strerror ( rc ) );
 		goto err_install_protocol;
 	}
 
diff --git a/src/interface/efi/efi_strerror.c b/src/interface/efi/efi_strerror.c
deleted file mode 100644
index 46bfbbb5b..000000000
--- a/src/interface/efi/efi_strerror.c
+++ /dev/null
@@ -1,46 +0,0 @@
-/*
- * Copyright (C) 2008 Michael Brown <mbrown@fensystems.co.uk>.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or any later version.
- *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
- * 02110-1301, USA.
- */
-
-FILE_LICENCE ( GPL2_OR_LATER );
-
-#include <stdio.h>
-#include <ipxe/efi/efi.h>
-
-/** @file
- *
- * iPXE error message formatting for EFI
- *
- */
-
-/**
- * Format EFI status code
- *
- * @v efirc		EFI status code
- * @v efi_strerror	EFI status code string
- */
-const char * efi_strerror ( EFI_STATUS efirc ) {
-	static char errbuf[32];
-
-	if ( ! efirc )
-		return "No error";
-
-	snprintf ( errbuf, sizeof ( errbuf ), "Error %lld",
-		   ( unsigned long long ) ( efirc ^ MAX_BIT ) );
-	return errbuf;
-}
diff --git a/src/interface/efi/efi_timer.c b/src/interface/efi/efi_timer.c
index b110cae29..7a1ff7869 100644
--- a/src/interface/efi/efi_timer.c
+++ b/src/interface/efi/efi_timer.c
@@ -19,6 +19,8 @@
 
 FILE_LICENCE ( GPL2_OR_LATER );
 
+#include <string.h>
+#include <errno.h>
 #include <limits.h>
 #include <assert.h>
 #include <unistd.h>
@@ -54,10 +56,12 @@ EFI_REQUIRE_PROTOCOL ( EFI_CPU_ARCH_PROTOCOL, &cpu_arch );
 static void efi_udelay ( unsigned long usecs ) {
 	EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
 	EFI_STATUS efirc;
+	int rc;
 
 	if ( ( efirc = bs->Stall ( usecs ) ) != 0 ) {
+		rc = -EEFI ( efirc );
 		DBG ( "EFI could not delay for %ldus: %s\n",
-		      usecs, efi_strerror ( efirc ) );
+		      usecs, strerror ( rc ) );
 		/* Probably screwed */
 	}
 }
@@ -70,12 +74,13 @@ static void efi_udelay ( unsigned long usecs ) {
 static unsigned long efi_currticks ( void ) {
 	UINT64 time;
 	EFI_STATUS efirc;
+	int rc;
 
 	/* Read CPU timer 0 (TSC) */
 	if ( ( efirc = cpu_arch->GetTimerValue ( cpu_arch, 0, &time,
 						 NULL ) ) != 0 ) {
-		DBG ( "EFI could not read CPU timer: %s\n",
-		      efi_strerror ( efirc ) );
+		rc = -EEFI ( efirc );
+		DBG ( "EFI could not read CPU timer: %s\n", strerror ( rc ) );
 		/* Probably screwed */
 		return -1UL;
 	}
diff --git a/src/interface/efi/efi_umalloc.c b/src/interface/efi/efi_umalloc.c
index b49949327..356efaa6f 100644
--- a/src/interface/efi/efi_umalloc.c
+++ b/src/interface/efi/efi_umalloc.c
@@ -19,6 +19,8 @@
 
 FILE_LICENCE ( GPL2_OR_LATER );
 
+#include <string.h>
+#include <errno.h>
 #include <assert.h>
 #include <ipxe/umalloc.h>
 #include <ipxe/efi/efi.h>
@@ -49,6 +51,7 @@ static userptr_t efi_urealloc ( userptr_t old_ptr, size_t new_size ) {
 	userptr_t new_ptr = UNOWHERE;
 	size_t old_size;
 	EFI_STATUS efirc;
+	int rc;
 
 	/* Allocate new memory if necessary.  If allocation fails,
 	 * return without touching the old block.
@@ -59,8 +62,9 @@ static userptr_t efi_urealloc ( userptr_t old_ptr, size_t new_size ) {
 						   EfiBootServicesData,
 						   new_pages,
 						   &phys_addr ) ) != 0 ) {
+			rc = -EEFI ( efirc );
 			DBG ( "EFI could not allocate %d pages: %s\n",
-			      new_pages, efi_strerror ( efirc ) );
+			      new_pages, strerror ( rc ) );
 			return UNULL;
 		}
 		assert ( phys_addr != 0 );
@@ -84,8 +88,9 @@ static userptr_t efi_urealloc ( userptr_t old_ptr, size_t new_size ) {
 		old_pages = ( EFI_SIZE_TO_PAGES ( old_size ) + 1 );
 		phys_addr = user_to_phys ( old_ptr, -EFI_PAGE_SIZE );
 		if ( ( efirc = bs->FreePages ( phys_addr, old_pages ) ) != 0 ){
+			rc = -EEFI ( efirc );
 			DBG ( "EFI could not free %d pages at %llx: %s\n",
-			      old_pages, phys_addr, efi_strerror ( efirc ) );
+			      old_pages, phys_addr, strerror ( rc ) );
 			/* Not fatal; we have leaked memory but successfully
 			 * allocated (if asked to do so).
 			 */