Messages in this thread | | | Date | Sat, 25 Jun 2022 18:24:16 +0200 | Subject | Re: [PATCH] m68k: virt: pass RNG seed via bootinfo block | From | Laurent Vivier <> |
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Le 25/06/2022 à 18:19, Jason A. Donenfeld a écrit : > On Sat, Jun 25, 2022 at 6:08 PM Laurent Vivier <laurent@vivier.eu> wrote: >> >> Le 25/06/2022 à 17:38, Jason A. Donenfeld a écrit : >>> 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. >>> >>> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> >>> --- >>> arch/m68k/include/uapi/asm/bootinfo-virt.h | 1 + >>> arch/m68k/virt/config.c | 4 ++++ >>> 2 files changed, 5 insertions(+) >>> >>> diff --git a/arch/m68k/include/uapi/asm/bootinfo-virt.h b/arch/m68k/include/uapi/asm/bootinfo-virt.h >>> index e4db7e2213ab..7c3044acdf4a 100644 >>> --- a/arch/m68k/include/uapi/asm/bootinfo-virt.h >>> +++ b/arch/m68k/include/uapi/asm/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) >>> >>> diff --git a/arch/m68k/virt/config.c b/arch/m68k/virt/config.c >>> index 632ba200ad42..ad71af8273ec 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 +93,9 @@ 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: >>> + add_bootloader_randomness(data + 4, be32_to_cpup(data)); >> >> In fact, why don't you use the record->size to get the size of the buffer? >> >> It seems useless to encode twice the length of the buffer, the second time on a 32bit while the >> length cannot exceed a 16bit value. > > Doesn't that make the length ambiguous because of required alignment?
I agree, it's why I understand reviewing the QEMU part of your patch.
> Would rather keep this general. As is, it's also much more like the > others and more uniform to keep it that way. You were able to review > it and see that it was right after glancing for a second. That seems > superior to any imaginary gains we'd get by overloading the record > size.
And what about using a 16bit field rather than a 32bit field as the encoded length cannot be greater than the record length?
Thanks, Laurent
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