[PATCH v2] m68k: virt: pass RNG seed via bootinfo block

Jason A. Donenfeld
2022-06-26T11:18:27Z

This commit wires up bootinfo's RNG seed attribute so that Linux VMs can
have their RNG seeded from the earliest possible time in boot, just like
the "rng-seed" device tree property on those platforms. The link
contains the corresponding Linux patch.

Link: https://lore.kernel.org/lkml/20220626111509.330159-1-Jason@zx2c4.com/
Based-on: <20220625152318.120849-1-Jason@zx2c4.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
hw/m68k/bootinfo.h | 16 ++++++++++++++++
hw/m68k/virt.c | 7 +++++++
.../standard-headers/asm-m68k/bootinfo-virt.h | 1 +
3 files changed, 24 insertions(+)

diff --git a/hw/m68k/bootinfo.h b/hw/m68k/bootinfo.h
index ff4e155a3c..bd8b212fd3 100644
--- a/hw/m68k/bootinfo.h
+++ b/hw/m68k/bootinfo.h
@@ -56,4 +56,20 @@
stb_phys(as, base++, 0); \
base = (base + 1) & ~1; \
} while (0)
+
+#define BOOTINFODATA(as, base, id, data, len) \
+ do { \
+ int i; \
+ stw_phys(as, base, id); \
+ base += 2; \
+ stw_phys(as, base, \
+ (sizeof(struct bi_record) + len + 3) & ~1); \
+ base += 2; \
+ stw_phys(as, base, len); \
+ base += 2; \
+ for (i = 0; i < len; ++i) { \
+ stb_phys(as, base++, data[i]); \
+ } \
+ base = (base + 1) & ~1; \
+ } while (0)
#endif
diff --git a/hw/m68k/virt.c b/hw/m68k/virt.c
index e215aa3d42..0aa383fa6b 100644
--- a/hw/m68k/virt.c
+++ b/hw/m68k/virt.c
@@ -9,6 +9,7 @@

#include "qemu/osdep.h"
#include "qemu/units.h"
+#include "qemu/guest-random.h"
#include "sysemu/sysemu.h"
#include "cpu.h"
#include "hw/boards.h"
@@ -120,6 +121,7 @@ static void virt_init(MachineState *machine)
hwaddr io_base;
int i;
ResetInfo *reset_info;
+ uint8_t rng_seed[32];

if (ram_size > 3399672 * KiB) {
/*
@@ -245,6 +247,11 @@ static void virt_init(MachineState *machine)
kernel_cmdline);
}

+ /* Pass seed to RNG. */
+ qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed));
+ BOOTINFODATA(cs->as, parameters_base, BI_VIRT_RNG_SEED,
+ rng_seed, sizeof(rng_seed));
+
/* load initrd */
if (initrd_filename) {
initrd_size = get_image_size(initrd_filename);
diff --git a/include/standard-headers/asm-m68k/bootinfo-virt.h b/include/standard-headers/asm-m68k/bootinfo-virt.h
index 81be1e0924..1b1ffd4705 100644
--- a/include/standard-headers/asm-m68k/bootinfo-virt.h
+++ b/include/standard-headers/asm-m68k/bootinfo-virt.h
@@ -12,6 +12,7 @@
#define BI_VIRT_GF_TTY_BASE 0x8003
#define BI_VIRT_VIRTIO_BASE 0x8004
#define BI_VIRT_CTRL_BASE 0x8005
+#define BI_VIRT_RNG_SEED 0x8006

#define VIRT_BOOTI_VERSION MK_BI_VERSION(2, 0)

--
2.35.1