diff mbox series

[v12,01/20] target/riscv: expose *envcfg csr and priv to qemu-user as well

Message ID 20240829233425.1005029-2-debug@rivosinc.com
State New
Headers show
Series riscv support for control flow integrity extensions | expand

Commit Message

Deepak Gupta Aug. 29, 2024, 11:34 p.m. UTC
Execution environment config CSR controlling user env and current
privilege state shouldn't be limited to qemu-system only. *envcfg
CSRs control enabling of features in next lesser mode. In some cases
bits *envcfg CSR can be lit up by kernel as part of kernel policy or
software (user app) can choose to opt-in by issuing a system call
(e.g. prctl). In case of qemu-user, it should be no different because
qemu is providing underlying execution environment facility and thus
either should provide some default value in *envcfg CSRs or react to
system calls (prctls) initiated from application. priv is set to PRV_U
and menvcfg/senvcfg set to 0 for qemu-user on reest.

`henvcfg` has been left for qemu-system only because it is not expected
that someone will use qemu-user where application is expected to have
hypervisor underneath which is controlling its execution environment. If
such a need arises then `henvcfg` could be exposed as well.

Relevant discussion:
https://lore.kernel.org/all/CAKmqyKOTVWPFep2msTQVdUmJErkH+bqCcKEQ4hAnyDFPdWKe0Q@mail.gmail.com/

Signed-off-by: Deepak Gupta <debug@rivosinc.com>
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
---
 target/riscv/cpu.c | 5 +++++
 target/riscv/cpu.h | 9 +++++----
 2 files changed, 10 insertions(+), 4 deletions(-)

Comments

Richard Henderson Aug. 30, 2024, 2:10 a.m. UTC | #1
On 8/30/24 09:34, Deepak Gupta wrote:
> Execution environment config CSR controlling user env and current
> privilege state shouldn't be limited to qemu-system only. *envcfg
> CSRs control enabling of features in next lesser mode. In some cases
> bits *envcfg CSR can be lit up by kernel as part of kernel policy or
> software (user app) can choose to opt-in by issuing a system call
> (e.g. prctl). In case of qemu-user, it should be no different because
> qemu is providing underlying execution environment facility and thus
> either should provide some default value in *envcfg CSRs or react to
> system calls (prctls) initiated from application. priv is set to PRV_U
> and menvcfg/senvcfg set to 0 for qemu-user on reest.
> 
> `henvcfg` has been left for qemu-system only because it is not expected
> that someone will use qemu-user where application is expected to have
> hypervisor underneath which is controlling its execution environment. If
> such a need arises then `henvcfg` could be exposed as well.
> 
> Relevant discussion:
> https://lore.kernel.org/all/ 
> CAKmqyKOTVWPFep2msTQVdUmJErkH+bqCcKEQ4hAnyDFPdWKe0Q@mail.gmail.com/
> 
> Signed-off-by: Deepak Gupta<debug@rivosinc.com>
> Suggested-by: Richard Henderson<richard.henderson@linaro.org>
> Reviewed-by: Alistair Francis<alistair.francis@wdc.com>
> ---
>   target/riscv/cpu.c | 5 +++++
>   target/riscv/cpu.h | 9 +++++----
>   2 files changed, 10 insertions(+), 4 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~
diff mbox series

Patch

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 33ef4eb795..c4ea1d4038 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -1011,7 +1011,12 @@  static void riscv_cpu_reset_hold(Object *obj, ResetType type)
     }
 
     pmp_unlock_entries(env);
+#else
+    env->priv = PRV_U;
+    env->senvcfg = 0;
+    env->menvcfg = 0;
 #endif
+
     env->xl = riscv_cpu_mxl(env);
     riscv_cpu_update_mask(env);
     cs->exception_index = RISCV_EXCP_NONE;
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 87742047ce..270a2a031c 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -226,8 +226,12 @@  struct CPUArchState {
     uint32_t elf_flags;
 #endif
 
-#ifndef CONFIG_USER_ONLY
     target_ulong priv;
+    /* CSRs for execution environment configuration */
+    uint64_t menvcfg;
+    target_ulong senvcfg;
+
+#ifndef CONFIG_USER_ONLY
     /* This contains QEMU specific information about the virt state. */
     bool virt_enabled;
     target_ulong geilen;
@@ -429,12 +433,9 @@  struct CPUArchState {
     target_ulong upmmask;
     target_ulong upmbase;
 
-    /* CSRs for execution environment configuration */
-    uint64_t menvcfg;
     uint64_t mstateen[SMSTATEEN_MAX_COUNT];
     uint64_t hstateen[SMSTATEEN_MAX_COUNT];
     uint64_t sstateen[SMSTATEEN_MAX_COUNT];
-    target_ulong senvcfg;
     uint64_t henvcfg;
 #endif
     target_ulong cur_pmmask;