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m68k: virt: Use RNG seed from bootinfo block

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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@vivier.eu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20220626111509.330159-1-Jason@zx2c4.com
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
This commit is contained in:
Jason A. Donenfeld 2022-06-26 13:15:09 +02:00 committed by Geert Uytterhoeven
parent 6f08e51cdb
commit a1ee38ab1a
2 changed files with 19 additions and 0 deletions
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8
arch/m68k/include/uapi/asm/bootinfo-virt.h
View file

@ -13,6 +13,14 @@
#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
#define VIRT_BOOTI_VERSION MK_BI_VERSION(2, 0)
#endif /* _UAPI_ASM_M68K_BOOTINFO_MAC_H */

11
arch/m68k/virt/config.c
View file

@ -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 +93,16 @@ 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;