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[PATCH v5] hw/i386: pass RNG seed via setup_data entry
From: |
Jason A. Donenfeld |
Subject: |
[PATCH v5] hw/i386: pass RNG seed via setup_data entry |
Date: |
Thu, 21 Jul 2022 12:47:30 +0200 |
Tiny machines optimized for fast boot time generally don't use EFI,
which means a random seed has to be supplied some other way. For this
purpose, Linux (≥5.20) supports passing a seed in the setup_data table
with SETUP_RNG_SEED, specially intended for hypervisors, kexec, and
specialized bootloaders. The linked commit shows the upstream kernel
implementation.
Link: https://git.kernel.org/tip/tip/c/68b8e9713c8
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Eduardo Habkost <eduardo@habkost.net>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
Cc: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
hw/i386/x86.c | 21 +++++++++++++++++---
include/standard-headers/asm-x86/bootparam.h | 1 +
2 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/hw/i386/x86.c b/hw/i386/x86.c
index 6003b4b2df..dd44c72ba3 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -26,6 +26,7 @@
#include "qemu/cutils.h"
#include "qemu/units.h"
#include "qemu/datadir.h"
+#include "qemu/guest-random.h"
#include "qapi/error.h"
#include "qapi/qmp/qerror.h"
#include "qapi/qapi-visit-common.h"
@@ -774,7 +775,7 @@ void x86_load_linux(X86MachineState *x86ms,
int dtb_size, setup_data_offset;
uint32_t initrd_max;
uint8_t header[8192], *setup, *kernel;
- hwaddr real_addr, prot_addr, cmdline_addr, initrd_addr = 0;
+ hwaddr real_addr, prot_addr, cmdline_addr, initrd_addr = 0,
first_setup_data = 0;
FILE *f;
char *vmode;
MachineState *machine = MACHINE(x86ms);
@@ -784,6 +785,7 @@ void x86_load_linux(X86MachineState *x86ms,
const char *dtb_filename = machine->dtb;
const char *kernel_cmdline = machine->kernel_cmdline;
SevKernelLoaderContext sev_load_ctx = {};
+ enum { RNG_SEED_LENGTH = 32 };
/* Align to 16 bytes as a paranoia measure */
cmdline_size = (strlen(kernel_cmdline) + 16) & ~15;
@@ -1063,16 +1065,29 @@ void x86_load_linux(X86MachineState *x86ms,
kernel_size = setup_data_offset + sizeof(struct setup_data) + dtb_size;
kernel = g_realloc(kernel, kernel_size);
- stq_p(header + 0x250, prot_addr + setup_data_offset);
setup_data = (struct setup_data *)(kernel + setup_data_offset);
- setup_data->next = 0;
+ setup_data->next = cpu_to_le64(first_setup_data);
+ first_setup_data = prot_addr + setup_data_offset;
setup_data->type = cpu_to_le32(SETUP_DTB);
setup_data->len = cpu_to_le32(dtb_size);
load_image_size(dtb_filename, setup_data->data, dtb_size);
}
+ setup_data_offset = QEMU_ALIGN_UP(kernel_size, 16);
+ kernel_size = setup_data_offset + sizeof(struct setup_data) +
RNG_SEED_LENGTH;
+ kernel = g_realloc(kernel, kernel_size);
+ setup_data = (struct setup_data *)(kernel + setup_data_offset);
+ setup_data->next = cpu_to_le64(first_setup_data);
+ first_setup_data = prot_addr + setup_data_offset;
+ setup_data->type = cpu_to_le32(SETUP_RNG_SEED);
+ setup_data->len = cpu_to_le32(32);
+ qemu_guest_getrandom_nofail(setup_data->data, RNG_SEED_LENGTH);
+
+ /* Offset 0x250 is a pointer to the first setup_data link. */
+ stq_p(header + 0x250, first_setup_data);
+
/*
* If we're starting an encrypted VM, it will be OVMF based, which uses the
* efi stub for booting and doesn't require any values to be placed in the
diff --git a/include/standard-headers/asm-x86/bootparam.h
b/include/standard-headers/asm-x86/bootparam.h
index 072e2ed546..b2aaad10e5 100644
--- a/include/standard-headers/asm-x86/bootparam.h
+++ b/include/standard-headers/asm-x86/bootparam.h
@@ -10,6 +10,7 @@
#define SETUP_EFI 4
#define SETUP_APPLE_PROPERTIES 5
#define SETUP_JAILHOUSE 6
+#define SETUP_RNG_SEED 9
#define SETUP_INDIRECT (1<<31)
--
2.35.1
- [PATCH v3] hw/i386: pass RNG seed via setup_data entry, Jason A. Donenfeld, 2022/07/11
- [PATCH resend v3] hw/i386: pass RNG seed via setup_data entry, Jason A. Donenfeld, 2022/07/19
- Re: [PATCH resend v3] hw/i386: pass RNG seed via setup_data entry, Jason A. Donenfeld, 2022/07/20
- Re: [PATCH resend v3] hw/i386: pass RNG seed via setup_data entry, Paolo Bonzini, 2022/07/21
- Re: [PATCH resend v3] hw/i386: pass RNG seed via setup_data entry, Jason A. Donenfeld, 2022/07/21
- Re: [PATCH resend v3] hw/i386: pass RNG seed via setup_data entry, Jason A. Donenfeld, 2022/07/21
- [PATCH v4] hw/i386: pass RNG seed via setup_data entry, Jason A. Donenfeld, 2022/07/21
- Re: [PATCH v4] hw/i386: pass RNG seed via setup_data entry, Michael S. Tsirkin, 2022/07/21
- Re: [PATCH v4] hw/i386: pass RNG seed via setup_data entry, Jason A. Donenfeld, 2022/07/21
- [PATCH v5] hw/i386: pass RNG seed via setup_data entry,
Jason A. Donenfeld <=
- [PATCH v6] hw/i386: pass RNG seed via setup_data entry, Jason A. Donenfeld, 2022/07/21
- Re: [PATCH v6] hw/i386: pass RNG seed via setup_data entry, Michael S. Tsirkin, 2022/07/21
- Re: [PATCH v6] hw/i386: pass RNG seed via setup_data entry, Jason A. Donenfeld, 2022/07/21
- Re: [PATCH v6] hw/i386: pass RNG seed via setup_data entry, Paolo Bonzini, 2022/07/21
- Re: [PATCH v6] hw/i386: pass RNG seed via setup_data entry, Jason A. Donenfeld, 2022/07/21
- Re: [PATCH v6] hw/i386: pass RNG seed via setup_data entry, Daniel P . Berrangé, 2022/07/21
- Re: [PATCH v6] hw/i386: pass RNG seed via setup_data entry, Paolo Bonzini, 2022/07/21
- Re: [PATCH v6] hw/i386: pass RNG seed via setup_data entry, Jason A. Donenfeld, 2022/07/21
- [PATCH v7] hw/i386: pass RNG seed via setup_data entry, Jason A. Donenfeld, 2022/07/21
- Re: [PATCH v7] hw/i386: pass RNG seed via setup_data entry, Paolo Bonzini, 2022/07/21