[PATCH 2/4] MODSIGN: print appropriate status message when getting UEFI certificates list

[Lee, Chun-Yi]

When getting certificates list from UEFI variable, the original error
message shows the state number from UEFI firmware. It's hard to be read
by human. This patch changed the error message to show the appropriate
string.

The message will be showed as:

[    0.788529] MODSIGN: Couldn't get UEFI MokListRT: EFI_NOT_FOUND
[    0.788537] MODSIGN: Couldn't get UEFI MokListXRT: EFI_NOT_FOUND

Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Josh Boyer <jwboyer@xxxxxxxxxxxxxxxxx>
Signed-off-by: "Lee, Chun-Yi" <jlee@xxxxxxxx>
---
 certs/load_uefi.c   | 43 ++++++++++++++++++++++++++++++-------------
 include/linux/efi.h | 25 +++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 13 deletions(-)

diff --git a/certs/load_uefi.c b/certs/load_uefi.c
index d6de4d0..f2f372b 100644
--- a/certs/load_uefi.c
+++ b/certs/load_uefi.c
@@ -4,6 +4,7 @@
 #include <linux/err.h>
 #include <linux/efi.h>
 #include <linux/slab.h>
+#include <linux/ucs2_string.h>
 #include <keys/asymmetric-type.h>
 #include <keys/system_keyring.h>
 #include "internal.h"
@@ -32,6 +33,24 @@ static __init bool uefi_check_ignore_db(void)
 	return status == EFI_SUCCESS;
 }
 
+static __init void print_get_fail(efi_char16_t *char16_str, efi_status_t status)
+{
+	char *utf8_str;
+	unsigned long utf8_size;
+
+	if (!char16_str)
+		return;
+	utf8_size = ucs2_utf8size(char16_str) + 1;
+	utf8_str = kmalloc(utf8_size, GFP_KERNEL);
+	if (!utf8_str)
+		return;
+	ucs2_as_utf8(utf8_str, char16_str, utf8_size);
+
+	pr_info("MODSIGN: Couldn't get UEFI %s: %s\n",
+		utf8_str, efi_status_to_str(status));
+	kfree(utf8_str);
+}
+
 /*
  * Get a certificate list blob from the named EFI variable.
  */
@@ -45,25 +64,29 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid,
 
 	status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb);
 	if (status != EFI_BUFFER_TOO_SMALL) {
-		pr_err("Couldn't get size: 0x%lx\n", status);
-		return NULL;
+		if (status != EFI_NOT_FOUND)
+			pr_err("Couldn't get size: 0x%lx\n", status);
+		goto err;
 	}
 
 	db = kmalloc(lsize, GFP_KERNEL);
 	if (!db) {
 		pr_err("Couldn't allocate memory for uefi cert list\n");
-		return NULL;
+		goto err;
 	}
 
 	status = efi.get_variable(name, guid, NULL, &lsize, db);
 	if (status != EFI_SUCCESS) {
 		kfree(db);
 		pr_err("Error reading db var: 0x%lx\n", status);
-		return NULL;
+		goto err;
 	}
 
 	*size = lsize;
 	return db;
+err:
+	print_get_fail(name, status);
+	return NULL;
 }
 
 /*
@@ -153,9 +176,7 @@ static int __init load_uefi_certs(void)
 	 */
 	if (!uefi_check_ignore_db()) {
 		db = get_cert_list(L"db", &secure_var, &dbsize);
-		if (!db) {
-			pr_err("MODSIGN: Couldn't get UEFI db list\n");
-		} else {
+		if (db) {
 			rc = parse_efi_signature_list("UEFI:db",
 						      db, dbsize, get_handler_for_db);
 			if (rc)
@@ -165,9 +186,7 @@ static int __init load_uefi_certs(void)
 	}
 
 	dbx = get_cert_list(L"dbx", &secure_var, &dbxsize);
-	if (!dbx) {
-		pr_info("MODSIGN: Couldn't get UEFI dbx list\n");
-	} else {
+	if (dbx) {
 		rc = parse_efi_signature_list("UEFI:dbx",
 					      dbx, dbxsize,
 					      get_handler_for_dbx);
@@ -181,9 +200,7 @@ static int __init load_uefi_certs(void)
 		return 0;
 
 	mok = get_cert_list(L"MokListRT", &mok_var, &moksize);
-	if (!mok) {
-		pr_info("MODSIGN: Couldn't get UEFI MokListRT\n");
-	} else {
+	if (mok) {
 		rc = parse_efi_signature_list("UEFI:MokListRT",
 					      mok, moksize, get_handler_for_db);
 		if (rc)
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 2729d6f..c44946c 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1600,4 +1600,29 @@ struct linux_efi_random_seed {
 	u8	bits[];
 };
 
+#define EFI_STATUS_STR(_status)				\
+	case EFI_##_status:				\
+		return "EFI_" __stringify(_status);	\
+
+static inline char *
+efi_status_to_str(efi_status_t status)
+{
+	switch (status) {
+	EFI_STATUS_STR(SUCCESS)
+	EFI_STATUS_STR(LOAD_ERROR)
+	EFI_STATUS_STR(INVALID_PARAMETER)
+	EFI_STATUS_STR(UNSUPPORTED)
+	EFI_STATUS_STR(BAD_BUFFER_SIZE)
+	EFI_STATUS_STR(BUFFER_TOO_SMALL)
+	EFI_STATUS_STR(NOT_READY)
+	EFI_STATUS_STR(DEVICE_ERROR)
+	EFI_STATUS_STR(WRITE_PROTECTED)
+	EFI_STATUS_STR(OUT_OF_RESOURCES)
+	EFI_STATUS_STR(NOT_FOUND)
+	EFI_STATUS_STR(ABORTED)
+	EFI_STATUS_STR(SECURITY_VIOLATION)
+	}
+
+	return "";
+}
 #endif /* _LINUX_EFI_H */
-- 
2.10.2