efi_loader: set CapsuleMax from CONFIG_EFI_CAPSULE_MAX

Adds CONFIG_EFI_CAPSULE_MAX to configure the max index value used in
EFI capsule reports. Prior to this change is the hard coded value was
65535 which would exceed available storage for variables. Now the
default value is 15 which should work fine with most systems.

Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>

3 files changed, 48 insertions, 15 deletions

diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index c05a54df16a..c5835e6ef61 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -226,6 +226,14 @@ config EFI_CAPSULE_AUTHENTICATE
 	  Select this option if you want to enable capsule
 	  authentication
 
+config EFI_CAPSULE_MAX
+	int "Max value for capsule index"
+	default 15
+	range 0 65535
+	help
+	  Select the max capsule index value used for capsule report
+	  variables. This value is used to create CapsuleMax variable.
+
 config EFI_DEVICE_PATH_TO_TEXT
 	bool "Device path to text protocol"
 	default y
diff --git a/lib/efi_loader/efi_capsule.c b/lib/efi_loader/efi_capsule.c
index 0997cd248fe..d5d3ede7ae6 100644
--- a/lib/efi_loader/efi_capsule.c
+++ b/lib/efi_loader/efi_capsule.c
@@ -45,17 +45,7 @@ const efi_guid_t fwu_guid_os_request_fw_accept =
 static struct efi_file_handle *bootdev_root;
 #endif
 
-/**
- * get_last_capsule - get the last capsule index
- *
- * Retrieve the index of the capsule invoked last time from "CapsuleLast"
- * variable.
- *
- * Return:
- * * > 0	- the last capsule index invoked
- * * 0xffff	- on error, or no capsule invoked yet
- */
-static __maybe_unused unsigned int get_last_capsule(void)
+static __maybe_unused unsigned int get_capsule_index(const u16 *variable_name)
 {
 	u16 value16[11]; /* "CapsuleXXXX": non-null-terminated */
 	char value[5];
@@ -65,7 +55,7 @@ static __maybe_unused unsigned int get_last_capsule(void)
 	int i;
 
 	size = sizeof(value16);
-	ret = efi_get_variable_int(u"CapsuleLast", &efi_guid_capsule_report,
+	ret = efi_get_variable_int(variable_name, &efi_guid_capsule_report,
 				   NULL, &size, value16, NULL);
 	if (ret != EFI_SUCCESS || size != 22 ||
 	    u16_strncmp(value16, u"Capsule", 7))
@@ -85,6 +75,35 @@ err:
 }
 
 /**
+ * get_last_capsule - get the last capsule index
+ *
+ * Retrieve the index of the capsule invoked last time from "CapsuleLast"
+ * variable.
+ *
+ * Return:
+ * * > 0	- the last capsule index invoked
+ * * 0xffff	- on error, or no capsule invoked yet
+ */
+static __maybe_unused unsigned int get_last_capsule(void)
+{
+	return get_capsule_index(u"CapsuleLast");
+}
+
+/**
+ * get_max_capsule - get the max capsule index
+ *
+ * Retrieve the max capsule index value from "CapsuleMax" variable.
+ *
+ * Return:
+ * * > 0	- the max capsule index
+ * * 0xffff	- on error, or "CapsuleMax" variable does not exist
+ */
+static __maybe_unused unsigned int get_max_capsule(void)
+{
+	return get_capsule_index(u"CapsuleMax");
+}
+
+/**
  * set_capsule_result - set a result variable
  * @capsule:		Capsule
  * @return_status:	Return status
@@ -1290,7 +1309,7 @@ efi_status_t efi_launch_capsules(void)
 {
 	struct efi_capsule_header *capsule = NULL;
 	u16 **files;
-	unsigned int nfiles, index, i;
+	unsigned int nfiles, index, index_max, i;
 	efi_status_t ret;
 	bool capsule_update = true;
 	bool update_status = true;
@@ -1299,6 +1318,7 @@ efi_status_t efi_launch_capsules(void)
 	if (check_run_capsules() != EFI_SUCCESS)
 		return EFI_SUCCESS;
 
+	index_max = get_max_capsule();
 	index = get_last_capsule();
 
 	/*
@@ -1317,7 +1337,7 @@ efi_status_t efi_launch_capsules(void)
 	/* Launch capsules */
 	for (i = 0, ++index; i < nfiles; i++, index++) {
 		log_debug("Applying %ls\n", files[i]);
-		if (index > 0xffff)
+		if (index > index_max)
 			index = 0;
 		ret = efi_capsule_read_file(files[i], &capsule);
 		if (ret == EFI_SUCCESS) {
diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c
index 69aaefab633..58d4e134023 100644
--- a/lib/efi_loader/efi_setup.c
+++ b/lib/efi_loader/efi_setup.c
@@ -130,12 +130,17 @@ static efi_status_t efi_init_capsule(void)
 	efi_status_t ret = EFI_SUCCESS;
 
 	if (IS_ENABLED(CONFIG_EFI_HAVE_CAPSULE_SUPPORT)) {
+		u16 var_name16[12];
+
+		efi_create_indexed_name(var_name16, sizeof(var_name16),
+					"Capsule", CONFIG_EFI_CAPSULE_MAX);
+
 		ret = efi_set_variable_int(u"CapsuleMax",
 					   &efi_guid_capsule_report,
 					   EFI_VARIABLE_READ_ONLY |
 					   EFI_VARIABLE_BOOTSERVICE_ACCESS |
 					   EFI_VARIABLE_RUNTIME_ACCESS,
-					   22, u"CapsuleFFFF", false);
+					   22, var_name16, false);
 		if (ret != EFI_SUCCESS)
 			printf("EFI: cannot initialize CapsuleMax variable\n");
 	}