The hypervisor is expected to create a value for the HASHPKEY SPR for
each partition. Currently it uses zero for all partitions, use a
random number instead, which in theory might make kernel ROP protection
more secure.

Signed-of-by: Nicholas Piggin <npiggin@gmail.com>
---
 include/hw/ppc/spapr.h  | 1 +
 hw/ppc/spapr.c          | 3 +++
 hw/ppc/spapr_cpu_core.c | 2 ++
 3 files changed, 6 insertions(+)

diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index af4aa1cb0fb..db44893689b 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -201,6 +201,7 @@ struct SpaprMachineState {
     uint32_t fdt_initial_size;
     void *fdt_blob;
     uint8_t fdt_rng_seed[32];
+    uint64_t hashpkey_val;
     long kernel_size;
     bool kernel_le;
     uint64_t kernel_addr;
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index fa05e0c5156..34934afd551 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2888,6 +2888,9 @@ static void spapr_machine_init(MachineState *machine)
         spapr_ovec_set(spapr->ov5, OV5_XIVE_EXPLOIT);
     }
 
+    qemu_guest_getrandom_nofail(&spapr->hashpkey_val,
+                                sizeof(spapr->hashpkey_val));
+
     /* init CPUs */
     spapr_init_cpus(spapr);
 
diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
index 88d743a3c3f..bf9f29f4ff3 100644
--- a/hw/ppc/spapr_cpu_core.c
+++ b/hw/ppc/spapr_cpu_core.c
@@ -273,6 +273,8 @@ static bool spapr_realize_vcpu(PowerPCCPU *cpu, SpaprMachineState *spapr,
     env->spr_cb[SPR_PIR].default_value = cs->cpu_index;
     env->spr_cb[SPR_TIR].default_value = thread_index;
 
+    env->spr_cb[SPR_HASHPKEYR].default_value = spapr->hashpkey_val;
+
     cpu_ppc_set_1lpar(cpu);
 
     /* Set time-base frequency to 512 MHz. vhyp must be set first. */
-- 
2.45.2

On 19/12/24 04:40, Nicholas Piggin wrote:
> The hypervisor is expected to create a value for the HASHPKEY SPR for
> each partition. Currently it uses zero for all partitions, use a
> random number instead, which in theory might make kernel ROP protection
> more secure.
> 
> Signed-of-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>   include/hw/ppc/spapr.h  | 1 +
>   hw/ppc/spapr.c          | 3 +++
>   hw/ppc/spapr_cpu_core.c | 2 ++
>   3 files changed, 6 insertions(+)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

On 12/19/24 09:10, Nicholas Piggin wrote:
> The hypervisor is expected to create a value for the HASHPKEY SPR for
> each partition. Currently it uses zero for all partitions, use a
> random number instead, which in theory might make kernel ROP protection
> more secure.
> 
> Signed-of-by: Nicholas Piggin <npiggin@gmail.com>

Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>

> ---
>   include/hw/ppc/spapr.h  | 1 +
>   hw/ppc/spapr.c          | 3 +++
>   hw/ppc/spapr_cpu_core.c | 2 ++
>   3 files changed, 6 insertions(+)
> 
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index af4aa1cb0fb..db44893689b 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -201,6 +201,7 @@ struct SpaprMachineState {
>       uint32_t fdt_initial_size;
>       void *fdt_blob;
>       uint8_t fdt_rng_seed[32];
> +    uint64_t hashpkey_val;
>       long kernel_size;
>       bool kernel_le;
>       uint64_t kernel_addr;
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index fa05e0c5156..34934afd551 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2888,6 +2888,9 @@ static void spapr_machine_init(MachineState *machine)
>           spapr_ovec_set(spapr->ov5, OV5_XIVE_EXPLOIT);
>       }
>   
> +    qemu_guest_getrandom_nofail(&spapr->hashpkey_val,
> +                                sizeof(spapr->hashpkey_val));
> +
>       /* init CPUs */
>       spapr_init_cpus(spapr);
>   
> diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> index 88d743a3c3f..bf9f29f4ff3 100644
> --- a/hw/ppc/spapr_cpu_core.c
> +++ b/hw/ppc/spapr_cpu_core.c
> @@ -273,6 +273,8 @@ static bool spapr_realize_vcpu(PowerPCCPU *cpu, SpaprMachineState *spapr,
>       env->spr_cb[SPR_PIR].default_value = cs->cpu_index;
>       env->spr_cb[SPR_TIR].default_value = thread_index;
>   
> +    env->spr_cb[SPR_HASHPKEYR].default_value = spapr->hashpkey_val;
> +
>       cpu_ppc_set_1lpar(cpu);
>   
>       /* Set time-base frequency to 512 MHz. vhyp must be set first. */