m68k: Rework BI_VIRT_RNG_SEED as BI_RNG_SEED

This is useful on !virt platforms for kexec, so change things from
BI_VIRT_RNG_SEED to be BI_RNG_SEED, and simply remove BI_VIRT_RNG_SEED
because it only ever lasted one release, and nothing is broken by not
having it. At the same time, keep a comment noting that it's been
removed, so that ID isn't reused. In addition, we previously documented
2-byte alignment, but 4-byte alignment is actually necessary, so update
that comment.
Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Fixes: a1ee38ab ("m68k: virt: Use RNG seed from bootinfo block")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20220927130835.1629806-2-Jason@zx2c4.comSigned-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/include/uapi/asm/bootinfo-virt.h

@@ -13,13 +13,8 @@
 #define BI_VIRT_VIRTIO_BASE	0x8004
 #define BI_VIRT_CTRL_BASE	0x8005
 
-/*
- * A random seed used to initialize the RNG. Record format:
- *
- *   - length       [ 2 bytes, 16-bit big endian ]
- *   - seed data    [ `length` bytes, padded to preserve 2-byte alignment ]
- */
-#define BI_VIRT_RNG_SEED	0x8006
+/* No longer used -- replaced with BI_RNG_SEED -- but don't reuse this index:
+ * #define BI_VIRT_RNG_SEED	0x8006 */
 
 #define VIRT_BOOTI_VERSION	MK_BI_VERSION(2, 0)
 

arch/m68k/include/uapi/asm/bootinfo.h

@@ -64,6 +64,13 @@ struct mem_info {
 					/* (struct mem_info) */
 #define BI_COMMAND_LINE		0x0007	/* kernel command line parameters */
 					/* (string) */
+/*
+ * A random seed used to initialize the RNG. Record format:
+ *
+ *   - length       [ 2 bytes, 16-bit big endian ]
+ *   - seed data    [ `length` bytes, padded to preserve 4-byte struct alignment ]
+ */
+#define BI_RNG_SEED		0x0008
 
 
     /*

arch/m68k/kernel/setup_mm.c

@@ -25,6 +25,7 @@
 #include <linux/module.h>
 #include <linux/nvram.h>
 #include <linux/initrd.h>
+#include <linux/random.h>
 
 #include <asm/bootinfo.h>
 #include <asm/byteorder.h>
@@ -151,6 +152,17 @@ static void __init m68k_parse_bootinfo(const struct bi_record *record)
 				sizeof(m68k_command_line));
 			break;
 
+		case BI_RNG_SEED: {
+			u16 len = be16_to_cpup(data);
+			add_bootloader_randomness(data + 2, len);
+			/*
+			 * Zero the data to preserve forward secrecy, and zero the
+			 * length to prevent kexec from using it.
+			 */
+			memzero_explicit((void *)data, len + 2);
+			break;
+		}
+
 		default:
 			if (MACH_IS_AMIGA)
 				unknown = amiga_parse_bootinfo(record);

arch/m68k/virt/config.c

@@ -2,7 +2,6 @@
 
 #include <linux/reboot.h>
 #include <linux/serial_core.h>
-#include <linux/random.h>
 #include <clocksource/timer-goldfish.h>
 
 #include <asm/bootinfo.h>
@@ -93,16 +92,6 @@ int __init virt_parse_bootinfo(const struct bi_record *record)
 		data += 4;
 		virt_bi_data.virtio.irq = be32_to_cpup(data);
 		break;
-	case BI_VIRT_RNG_SEED: {
-		u16 len = be16_to_cpup(data);
-		add_bootloader_randomness(data + 2, len);
-		/*
-		 * Zero the data to preserve forward secrecy, and zero the
-		 * length to prevent kexec from using it.
-		 */
-		memzero_explicit((void *)data, len + 2);
-		break;
-	}
 	default:
 		unknown = 1;
 		break;