[PATCH v9 11/11] hvf: arm: Adhere to SMCCC 1.3 section 5.2

[Alexander Graf]

The SMCCC 1.3 spec section 5.2 says

  The Unknown SMC Function Identifier is a sign-extended value of (-1)
  that is returned in the R0, W0 or X0 registers. An implementation must
  return this error code when it receives:

    * An SMC or HVC call with an unknown Function Identifier
    * An SMC or HVC call for a removed Function Identifier
    * An SMC64/HVC64 call from AArch32 state

To comply with these statements, let's always return -1 when we encounter
an unknown HVC or SMC call.

Signed-off-by: Alexander Graf <ag...@csgraf.de>

---

v7 -> v8:

  - fix checkpatch

v8 -> v9:

  - Remove Windows specifics and just comply with SMCCC spec
---
 target/arm/hvf/hvf.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
index b62cfa3976..6a7ccfa91e 100644
--- a/target/arm/hvf/hvf.c
+++ b/target/arm/hvf/hvf.c
@@ -1177,7 +1177,8 @@ int hvf_vcpu_exec(CPUState *cpu)
         cpu_synchronize_state(cpu);
         if (hvf_handle_psci_call(cpu)) {
             trace_hvf_unknown_hvf(env->xregs[0]);
-            hvf_raise_exception(cpu, EXCP_UDEF, syn_uncategorized());
+            /* SMCCC 1.3 section 5.2 says every unknown HVC call returns -1 */
+            env->xregs[0] = -1;
         }
         break;
     case EC_AA64_SMC:
@@ -1186,7 +1187,9 @@ int hvf_vcpu_exec(CPUState *cpu)
             advance_pc = true;
         } else {
             trace_hvf_unknown_smc(env->xregs[0]);
-            hvf_raise_exception(cpu, EXCP_UDEF, syn_uncategorized());
+            /* SMCCC 1.3 section 5.2 says every unknown SMC call returns -1 */
+            env->xregs[0] = -1;
+            advance_pc = true;
         }
         break;
     default:
-- 
2.30.1 (Apple Git-130)