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hw/arm/virt: dt: add rng-seed property

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In 60592cfed2 ("hw/arm/virt: dt: add kaslr-seed property"), the
kaslr-seed property was added, but the equally as important rng-seed
property was forgotten about, which has identical semantics for a
similar purpose. This commit implements it in exactly the same way as
kaslr-seed. It then changes the name of the disabling option to reflect
that this has more to do with randomness vs determinism, rather than
something particular about kaslr.

Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
[PMM: added deprecated.rst section for the deprecation]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Jason A. Donenfeld 2022-07-07 11:36:07 +01:00 committed by Peter Maydell
parent 8e9398e3b1
commit 5242876f37
4 changed files with 47 additions and 24 deletions
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8
docs/about/deprecated.rst
View file

@ -225,6 +225,14 @@ Use the more generic event ``DEVICE_UNPLUG_GUEST_ERROR`` instead.
System emulator machines
------------------------
Arm ``virt`` machine ``dtb-kaslr-seed`` property
''''''''''''''''''''''''''''''''''''''''''''''''
The ``dtb-kaslr-seed`` property on the ``virt`` board has been
deprecated; use the new name ``dtb-randomness`` instead. The new name
better reflects the way this property affects all random data within
the device tree blob, not just the ``kaslr-seed`` node.
PPC 405 ``taihu`` machine (since 7.0)
'''''''''''''''''''''''''''''''''''''

17
docs/system/arm/virt.rst
View file

@ -126,13 +126,18 @@ ras
Set ``on``/``off`` to enable/disable reporting host memory errors to a guest
using ACPI and guest external abort exceptions. The default is off.
dtb-randomness
Set ``on``/``off`` to pass random seeds via the guest DTB
rng-seed and kaslr-seed nodes (in both "/chosen" and
"/secure-chosen") to use for features like the random number
generator and address space randomisation. The default is
``on``. You will want to disable it if your trusted boot chain
will verify the DTB it is passed, since this option causes the
DTB to be non-deterministic. It would be the responsibility of
the firmware to come up with a seed and pass it on if it wants to.
dtb-kaslr-seed
Set ``on``/``off`` to pass a random seed via the guest dtb
kaslr-seed node (in both "/chosen" and /secure-chosen) to use
for features like address space randomisation. The default is
``on``. You will want to disable it if your trusted boot chain will
verify the DTB it is passed. It would be the responsibility of the
firmware to come up with a seed and pass it on if it wants to.
A deprecated synonym for dtb-randomness.
Linux guest kernel configuration
""""""""""""""""""""""""""""""""

44
hw/arm/virt.c
View file

@ -221,14 +221,18 @@ static bool cpu_type_valid(const char *cpu)
return false;
}
static void create_kaslr_seed(MachineState *ms, const char *node)
static void create_randomness(MachineState *ms, const char *node)
{
uint64_t seed;
struct {
uint64_t kaslr;
uint8_t rng[32];
} seed;
if (qemu_guest_getrandom(&seed, sizeof(seed), NULL)) {
return;
}
qemu_fdt_setprop_u64(ms->fdt, node, "kaslr-seed", seed);
qemu_fdt_setprop_u64(ms->fdt, node, "kaslr-seed", seed.kaslr);
qemu_fdt_setprop(ms->fdt, node, "rng-seed", seed.rng, sizeof(seed.rng));
}
static void create_fdt(VirtMachineState *vms)
@ -251,14 +255,14 @@ static void create_fdt(VirtMachineState *vms)
/* /chosen must exist for load_dtb to fill in necessary properties later */
qemu_fdt_add_subnode(fdt, "/chosen");
if (vms->dtb_kaslr_seed) {
create_kaslr_seed(ms, "/chosen");
if (vms->dtb_randomness) {
create_randomness(ms, "/chosen");
}
if (vms->secure) {
qemu_fdt_add_subnode(fdt, "/secure-chosen");
if (vms->dtb_kaslr_seed) {
create_kaslr_seed(ms, "/secure-chosen");
if (vms->dtb_randomness) {
create_randomness(ms, "/secure-chosen");
}
}
@ -2340,18 +2344,18 @@ static void virt_set_its(Object *obj, bool value, Error **errp)
vms->its = value;
}
static bool virt_get_dtb_kaslr_seed(Object *obj, Error **errp)
static bool virt_get_dtb_randomness(Object *obj, Error **errp)
{
VirtMachineState *vms = VIRT_MACHINE(obj);
return vms->dtb_kaslr_seed;
return vms->dtb_randomness;
}
static void virt_set_dtb_kaslr_seed(Object *obj, bool value, Error **errp)
static void virt_set_dtb_randomness(Object *obj, bool value, Error **errp)
{
VirtMachineState *vms = VIRT_MACHINE(obj);
vms->dtb_kaslr_seed = value;
vms->dtb_randomness = value;
}
static char *virt_get_oem_id(Object *obj, Error **errp)
@ -2980,12 +2984,18 @@ static void virt_machine_class_init(ObjectClass *oc, void *data)
"Set on/off to enable/disable "
"ITS instantiation");
object_class_property_add_bool(oc, "dtb-randomness",
virt_get_dtb_randomness,
virt_set_dtb_randomness);
object_class_property_set_description(oc, "dtb-randomness",
"Set off to disable passing random or "
"non-deterministic dtb nodes to guest");
object_class_property_add_bool(oc, "dtb-kaslr-seed",
virt_get_dtb_kaslr_seed,
virt_set_dtb_kaslr_seed);
virt_get_dtb_randomness,
virt_set_dtb_randomness);
object_class_property_set_description(oc, "dtb-kaslr-seed",
"Set off to disable passing of kaslr-seed "
"dtb node to guest");
"Deprecated synonym of dtb-randomness");
object_class_property_add_str(oc, "x-oem-id",
virt_get_oem_id,
@ -3053,8 +3063,8 @@ static void virt_instance_init(Object *obj)
/* MTE is disabled by default. */
vms->mte = false;
/* Supply a kaslr-seed by default */
vms->dtb_kaslr_seed = true;
/* Supply kaslr-seed and rng-seed by default */
vms->dtb_randomness = true;
vms->irqmap = a15irqmap;

2
include/hw/arm/virt.h
View file

@ -152,7 +152,7 @@ struct VirtMachineState {
bool virt;
bool ras;
bool mte;
bool dtb_kaslr_seed;
bool dtb_randomness;
OnOffAuto acpi;
VirtGICType gic_version;
VirtIOMMUType iommu;