discover/platform-powerpc: don't copy IANA from mbox to buffer

This patch adds code that takes into account the size of the IANA
identifier number in the mailbox and doesn't copy it into the data
buffer

Signed-off-by: Maxim Polyakov <m.polyakov@yadro.com>

discover/platform-powerpc.c

@@ -536,6 +536,7 @@ static int get_ipmi_boot_mailbox(struct platform_powerpc *platform,
 	 * on higher numbers.
 	 */
 	for (i = 0; i < UCHAR_MAX; i++) {
+		uint8_t *boot_opt_data;
 		int block_size = get_ipmi_boot_mailbox_block(platform, &mailbox, i);
 		if (block_size < CHASSIS_BOOT_MBOX_IANA_SZ && i == 0) {
 			/*
@@ -552,9 +553,12 @@ static int get_ipmi_boot_mailbox(struct platform_powerpc *platform,
 		if (i == 0) {
 			/*
 			 * The first three bytes of block zero are an IANA
-			 * Enterprise ID number. Check it matches the IBM
-			 * number, '2'.
+			 * Enterprise ID number
 			 */
+			block_size -= CHASSIS_BOOT_MBOX_IANA_SZ;
+			boot_opt_data = &mailbox.b0.data;
+
+			/* Check IANA matches the IBM number, '2' */
 			if (mailbox.b0.iana[0] != 0x02 ||
 				mailbox.b0.iana[1] != 0x00 ||
 				mailbox.b0.iana[2] != 0x00) {
@@ -564,6 +568,8 @@ static int get_ipmi_boot_mailbox(struct platform_powerpc *platform,
 						mailbox.b0.iana[2]);
 				return -1;
 			}
+		} else {
+			boot_opt_data = &mailbox.data;
 		}
 
 		mailbox_buffer = talloc_realloc(platform, mailbox_buffer,
@@ -572,7 +578,7 @@ static int get_ipmi_boot_mailbox(struct platform_powerpc *platform,
 			pb_log_fn("Failed to allocate mailbox buffer\n");
 			return -1;
 		}
-		memcpy(mailbox_buffer + mailbox_size, &mailbox.data, block_size);
+		memcpy(mailbox_buffer + mailbox_size, boot_opt_data, block_size);
 		mailbox_size += block_size;
 	}
 
@@ -583,10 +589,10 @@ static int get_ipmi_boot_mailbox(struct platform_powerpc *platform,
 	else
 		pb_debug_fn("%hu blocks read (%zu bytes)\n", i, mailbox_size);
 
-	if (mailbox_size < 3 + strlen("petitboot,bootdevs="))
+	if (mailbox_size < strlen("petitboot,bootdevs="))
 		return -1;
 
-	prefix = talloc_strndup(mailbox_buffer, mailbox_buffer + 3,
+	prefix = talloc_strndup(mailbox_buffer, mailbox_buffer,
 			strlen("petitboot,bootdevs="));
 	if (!prefix) {
 		pb_log_fn("Couldn't check prefix\n");
@@ -604,9 +610,9 @@ static int get_ipmi_boot_mailbox(struct platform_powerpc *platform,
 	}
 
 	/* Don't include IANA number in buffer */
-	content_size = mailbox_size - 3 - strlen("petitboot,bootdevs=");
+	content_size = mailbox_size - strlen("petitboot,bootdevs=");
 	*buf = talloc_memdup(platform,
-			mailbox_buffer + 3 + strlen("petitboot,bootdevs="),
+			mailbox_buffer + strlen("petitboot,bootdevs="),
 			content_size + 1);
 	(*buf)[content_size] = '\0';