Other virt VMs can pass RNG seeds via the "rng-seed" device tree
property or via UEFI, but m68k doesn't have either. Instead it has its
own bootinfo protocol. So this commit adds support for receiving a RNG
seed from it, which will be used at the earliest possible time in boot,
just like device tree.
Reviewed-by: Laurent Vivier <laurent@xxxxxxxxx>
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
---
arch/m68k/include/uapi/asm/bootinfo-virt.h | 7 +++++++
arch/m68k/virt/config.c | 9 +++++++++
2 files changed, 16 insertions(+)
diff --git a/arch/m68k/include/uapi/asm/bootinfo-virt.h b/arch/m68k/include/uapi/asm/bootinfo-virt.h
index e4db7e2213ab..0cb2c2a41610 100644
--- a/arch/m68k/include/uapi/asm/bootinfo-virt.h
+++ b/arch/m68k/include/uapi/asm/bootinfo-virt.h
@@ -13,6 +13,13 @@
#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 ]
+ */
+#define BI_VIRT_RNG_SEED 0x8006
+
#define VIRT_BOOTI_VERSION MK_BI_VERSION(2, 0)
#endif /* _UAPI_ASM_M68K_BOOTINFO_MAC_H */
diff --git a/arch/m68k/virt/config.c b/arch/m68k/virt/config.c
index 632ba200ad42..645acc6918b2 100644
--- a/arch/m68k/virt/config.c
+++ b/arch/m68k/virt/config.c
@@ -2,6 +2,7 @@
#include <linux/reboot.h>
#include <linux/serial_core.h>
+#include <linux/random.h>
#include <clocksource/timer-goldfish.h>
#include <asm/bootinfo.h>
@@ -92,6 +93,14 @@ 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;
--
2.35.1
