[PATCH qemu] m68k: rework BI_VIRT_RNG_SEED as BI_RNG_SEED

[Jason A. Donenfeld]

Following a change on the kernel side (see link), pass BI_RNG_SEED
instead of BI_VIRT_RNG_SEED. This should have no impact on
compatibility, as there will simply be no effect if it's an old kernel,
which is how things have always been. We then use this as an opportunity
to add this to q800, since now we can, which is a nice improvement.

Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Laurent Vivier <laurent@vivier.eu>
Link: https://lore.kernel.org/lkml/20220923170340.4099226-3-Jason@zx2c4.com/
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 hw/m68k/q800.c                                    | 7 +++++++
 hw/m68k/virt.c                                    | 2 +-
 include/standard-headers/asm-m68k/bootinfo-virt.h | 4 +++-
 include/standard-headers/asm-m68k/bootinfo.h      | 8 +++++++-
 4 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/hw/m68k/q800.c b/hw/m68k/q800.c
index 101ab0f803..9106382066 100644
--- a/hw/m68k/q800.c
+++ b/hw/m68k/q800.c
@@ -23,6 +23,7 @@
 #include "qemu/osdep.h"
 #include "qemu/units.h"
 #include "qemu/datadir.h"
+#include "qemu/guest-random.h"
 #include "sysemu/sysemu.h"
 #include "cpu.h"
 #include "hw/boards.h"
@@ -385,6 +386,7 @@ static void q800_init(MachineState *machine)
     NubusBus *nubus;
     DeviceState *glue;
     DriveInfo *dinfo;
+    uint8_t rng_seed[32];
 
     linux_boot = (kernel_filename != NULL);
 
@@ -634,6 +636,11 @@ static void q800_init(MachineState *machine)
                         kernel_cmdline);
         }
 
+       /* Pass seed to RNG. */
+       qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed));
+       BOOTINFODATA(cs->as, parameters_base, BI_RNG_SEED,
+                    rng_seed, sizeof(rng_seed));
+
         /* load initrd */
         if (initrd_filename) {
             initrd_size = get_image_size(initrd_filename);
diff --git a/hw/m68k/virt.c b/hw/m68k/virt.c
index 2f3ffc0de6..7180325e54 100644
--- a/hw/m68k/virt.c
+++ b/hw/m68k/virt.c
@@ -250,7 +250,7 @@ static void virt_init(MachineState *machine)
 
        /* Pass seed to RNG. */
        qemu_guest_getrandom_nofail(rng_seed, sizeof(rng_seed));
-       BOOTINFODATA(cs->as, parameters_base, BI_VIRT_RNG_SEED,
+       BOOTINFODATA(cs->as, parameters_base, BI_RNG_SEED,
                     rng_seed, sizeof(rng_seed));
 
         /* load initrd */
diff --git a/include/standard-headers/asm-m68k/bootinfo-virt.h 
b/include/standard-headers/asm-m68k/bootinfo-virt.h
index 1b1ffd4705..36697a52b8 100644
--- a/include/standard-headers/asm-m68k/bootinfo-virt.h
+++ b/include/standard-headers/asm-m68k/bootinfo-virt.h
@@ -12,7 +12,9 @@
 #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
+
+/* 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)
 
diff --git a/include/standard-headers/asm-m68k/bootinfo.h 
b/include/standard-headers/asm-m68k/bootinfo.h
index 7b790e8ec8..68a91cdfc5 100644
--- a/include/standard-headers/asm-m68k/bootinfo.h
+++ b/include/standard-headers/asm-m68k/bootinfo.h
@@ -57,7 +57,13 @@ 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 2-byte alignment ]
+ */
+#define BI_RNG_SEED            0x0008
 
     /*
      *  Linux/m68k Architectures (BI_MACHTYPE)
-- 
2.37.3