| Message ID | 20220630103739.1727346-1-Jason@zx2c4.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] hw/arm/virt: dt: add rng-seed property | expand |
On Thu, 30 Jun 2022 at 11:39, Jason A. Donenfeld <Jason@zx2c4.com> wrote: > > 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> Thanks for this respin; I think this is the right way to go. > --- > docs/system/arm/virt.rst | 17 ++++++++++------ > hw/arm/virt.c | 44 ++++++++++++++++++++++++---------------- > include/hw/arm/virt.h | 2 +- > 3 files changed, 39 insertions(+), 24 deletions(-) > > diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst > index 3d1058a80c..3b6ba69a9a 100644 > --- a/docs/system/arm/virt.rst > +++ b/docs/system/arm/virt.rst > @@ -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. We should also add a section to docs/about/deprecated.rst noting that the old name is deprecated in favour of the new one. I'll fold that in when I add the patch to target-arm.next, to save you doing a respin: --- a/docs/about/deprecated.rst +++ b/docs/about/deprecated.rst @@ -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. + > + 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"); I was going to suggest object_property_add_alias() but that works at the object level, not the class level, so never mind. This will work, and eventually we'll delete the code when it hits the deprecation-to-removal horizon. So Reviewed-by: Peter Maydell <peter.maydell@linaro.org> and applied to target-arm.next. thanks -- PMM
Hi Peter, On Mon, Jul 04, 2022 at 03:42:55PM +0100, Peter Maydell wrote: > We should also add a section to docs/about/deprecated.rst > noting that the old name is deprecated in favour of the new one. > I'll fold that in when I add the patch to target-arm.next, to > save you doing a respin: Thanks for doing that. Your text looks good to me. Jason
diff --git a/docs/system/arm/virt.rst b/docs/system/arm/virt.rst index 3d1058a80c..3b6ba69a9a 100644 --- a/docs/system/arm/virt.rst +++ b/docs/system/arm/virt.rst @@ -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 """""""""""""""""""""""""""""""" diff --git a/hw/arm/virt.c b/hw/arm/virt.c index 097238faa7..924ded7f85 100644 --- a/hw/arm/virt.c +++ b/hw/arm/virt.c @@ -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"); } } @@ -2348,18 +2352,18 @@ 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) @@ -2988,12 +2992,18 @@ 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, @@ -3061,8 +3071,8 @@ 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; diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h index 15feabac63..6ec479ca2b 100644 --- a/include/hw/arm/virt.h +++ b/include/hw/arm/virt.h @@ -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;
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> --- docs/system/arm/virt.rst | 17 ++++++++++------ hw/arm/virt.c | 44 ++++++++++++++++++++++++---------------- include/hw/arm/virt.h | 2 +- 3 files changed, 39 insertions(+), 24 deletions(-)