[Qemu-devel] [PATCH v4 03/21] target-arm: Define exception record for AArch64 exceptions

[Peter Maydell <peter.maydell@linaro.org>]

For AArch32 exceptions, the only information provided about
the cause of an exception is the individual exception type (data
abort, undef, etc), which we store in env->exception_index. For
AArch64, the CPU provides much more detail about the cause of
the exception, which can be found in the syndrome register.
Create a set of fields in CPUARMState which must be filled in
whenever an exception is raised, so that exception entry can
correctly fill in the syndrome register for the guest.
This includes the information which in AArch32 appears in
the DFAR and IFAR (fault address registers) and the DFSR
and IFSR (fault status registers) for data aborts and
prefetch aborts, since if we end up taking the MMU fault
to AArch64 rather than AArch32 this will need to end up
in different system registers.

This patch does a refactoring which moves the setting of the
AArch32 DFAR/DFSR/IFAR/IFSR from the point where the exception
is raised to the point where it is taken. (This is no change
for cores with an MMU, retains the existing clearly incorrect
behaviour for ARM946 of trashing the MP access permissions
registers which share the c5_data and c5_insn state fields,
and has no effect for v7M because we don't implement its
MPU fault status or address registers.)

As a side effect of the cleanup we fix a bug in the AArch64
linux-user mode code where we were passing a 64 bit fault
address through the 32 bit c6_data/c6_insn fields: it now
goes via the always-64-bit exception.vaddress.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 linux-user/main.c    | 56 ++++++++++++++++++++++------------------------------
 target-arm/cpu.h     | 15 ++++++++++++++
 target-arm/helper.c  | 23 ++++++++++++---------
 target-arm/machine.c |  3 +++
 4 files changed, 56 insertions(+), 41 deletions(-)

diff --git a/linux-user/main.c b/linux-user/main.c
index 9192977..a17ee47 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -483,17 +483,17 @@ static void arm_kernel_cmpxchg64_helper(CPUARMState *env)
     addr = env->regs[2];
 
     if (get_user_u64(oldval, env->regs[0])) {
-        env->cp15.c6_data = env->regs[0];
+        env->exception.vaddress = env->regs[0];
         goto segv;
     };
 
     if (get_user_u64(newval, env->regs[1])) {
-        env->cp15.c6_data = env->regs[1];
+        env->exception.vaddress = env->regs[1];
         goto segv;
     };
 
     if (get_user_u64(val, addr)) {
-        env->cp15.c6_data = addr;
+        env->exception.vaddress = addr;
         goto segv;
     }
 
@@ -501,7 +501,7 @@ static void arm_kernel_cmpxchg64_helper(CPUARMState *env)
         val = newval;
 
         if (put_user_u64(val, addr)) {
-            env->cp15.c6_data = addr;
+            env->exception.vaddress = addr;
             goto segv;
         };
 
@@ -523,7 +523,7 @@ segv:
     info.si_errno = 0;
     /* XXX: check env->error_code */
     info.si_code = TARGET_SEGV_MAPERR;
-    info._sifields._sigfault._addr = env->cp15.c6_data;
+    info._sifields._sigfault._addr = env->exception.vaddress;
     queue_signal(env, info.si_signo, &info);
 
     end_exclusive();
@@ -620,14 +620,14 @@ static int do_strex(CPUARMState *env)
         abort();
     }
     if (segv) {
-        env->cp15.c6_data = addr;
+        env->exception.vaddress = addr;
         goto done;
     }
     if (size == 3) {
         uint32_t valhi;
         segv = get_user_u32(valhi, addr + 4);
         if (segv) {
-            env->cp15.c6_data = addr + 4;
+            env->exception.vaddress = addr + 4;
             goto done;
         }
         val = deposit64(val, 32, 32, valhi);
@@ -650,14 +650,14 @@ static int do_strex(CPUARMState *env)
         break;
     }
     if (segv) {
-        env->cp15.c6_data = addr;
+        env->exception.vaddress = addr;
         goto done;
     }
     if (size == 3) {
         val = env->regs[(env->exclusive_info >> 12) & 0xf];
         segv = put_user_u32(val, addr + 4);
         if (segv) {
-            env->cp15.c6_data = addr + 4;
+            env->exception.vaddress = addr + 4;
             goto done;
         }
     }
@@ -832,12 +832,14 @@ void cpu_loop(CPUARMState *env)
         case EXCP_INTERRUPT:
             /* just indicate that signals should be handled asap */
             break;
+        case EXCP_STREX:
+            if (!do_strex(env)) {
+                break;
+            }
+            /* fall through for segv */
         case EXCP_PREFETCH_ABORT:
-            addr = env->cp15.c6_insn;
-            goto do_segv;
         case EXCP_DATA_ABORT:
-            addr = env->cp15.c6_data;
-        do_segv:
+            addr = env->exception.vaddress;
             {
                 info.si_signo = SIGSEGV;
                 info.si_errno = 0;
@@ -865,12 +867,6 @@ void cpu_loop(CPUARMState *env)
             if (do_kernel_trap(env))
               goto error;
             break;
-        case EXCP_STREX:
-            if (do_strex(env)) {
-                addr = env->cp15.c6_data;
-                goto do_segv;
-            }
-            break;
         default:
         error:
             fprintf(stderr, "qemu: unhandled CPU exception 0x%x - aborting\n",
@@ -933,7 +929,7 @@ static int do_strex_a64(CPUARMState *env)
         abort();
     }
     if (segv) {
-        env->cp15.c6_data = addr;
+        env->exception.vaddress = addr;
         goto error;
     }
     if (val != env->exclusive_val) {
@@ -946,7 +942,7 @@ static int do_strex_a64(CPUARMState *env)
             segv = get_user_u64(val, addr + 8);
         }
         if (segv) {
-            env->cp15.c6_data = addr + (size == 2 ? 4 : 8);
+            env->exception.vaddress = addr + (size == 2 ? 4 : 8);
             goto error;
         }
         if (val != env->exclusive_high) {
@@ -981,7 +977,7 @@ static int do_strex_a64(CPUARMState *env)
             segv = put_user_u64(val, addr + 8);
         }
         if (segv) {
-            env->cp15.c6_data = addr + (size == 2 ? 4 : 8);
+            env->exception.vaddress = addr + (size == 2 ? 4 : 8);
             goto error;
         }
     }
@@ -1037,12 +1033,14 @@ void cpu_loop(CPUARMState *env)
             info._sifields._sigfault._addr = env->pc;
             queue_signal(env, info.si_signo, &info);
             break;
+        case EXCP_STREX:
+            if (!do_strex_a64(env)) {
+                break;
+            }
+            /* fall through for segv */
         case EXCP_PREFETCH_ABORT:
-            addr = env->cp15.c6_insn;
-            goto do_segv;
         case EXCP_DATA_ABORT:
-            addr = env->cp15.c6_data;
-        do_segv:
+            addr = env->exception.vaddress;
             info.si_signo = SIGSEGV;
             info.si_errno = 0;
             /* XXX: check env->error_code */
@@ -1060,12 +1058,6 @@ void cpu_loop(CPUARMState *env)
                 queue_signal(env, info.si_signo, &info);
             }
             break;
-        case EXCP_STREX:
-            if (do_strex_a64(env)) {
-                addr = env->cp15.c6_data;
-                goto do_segv;
-            }
-            break;
         default:
             fprintf(stderr, "qemu: unhandled CPU exception 0x%x - aborting\n",
                     trapnr);
diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index 45eb6a2..9982e47 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -229,6 +229,21 @@ typedef struct CPUARMState {
         int pending_exception;
     } v7m;
 
+    /* Information associated with an exception about to be taken:
+     * code which raises an exception must set env->exception_index and
+     * the relevant parts of this structure; the cpu_do_interrupt function
+     * will then set the guest-visible registers as part of the exception
+     * entry process.
+     */
+    struct {
+        uint32_t syndrome; /* AArch64 format syndrome register */
+        uint32_t fsr; /* AArch32 format fault status register info */
+        uint64_t vaddress; /* virtual addr associated with exception, if any */
+        /* If we implement EL2 we will also need to store information
+         * about the intermediate physical address for stage 2 faults.
+         */
+    } exception;
+
     /* Thumb-2 EE state.  */
     uint32_t teecr;
     uint32_t teehbr;
diff --git a/target-arm/helper.c b/target-arm/helper.c
index f7168c1..2fa01ae 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -2610,12 +2610,11 @@ void arm_cpu_do_interrupt(CPUState *cs)
 int cpu_arm_handle_mmu_fault (CPUARMState *env, target_ulong address, int rw,
                               int mmu_idx)
 {
+    env->exception.vaddress = address;
     if (rw == 2) {
         env->exception_index = EXCP_PREFETCH_ABORT;
-        env->cp15.c6_insn = address;
     } else {
         env->exception_index = EXCP_DATA_ABORT;
-        env->cp15.c6_data = address;
     }
     return 1;
 }
@@ -2820,6 +2819,9 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
         return;
     case EXCP_PREFETCH_ABORT:
     case EXCP_DATA_ABORT:
+        /* TODO: if we implemented the MPU registers, this is where we
+         * should set the MMFAR, etc from exception.fsr and exception.vaddress.
+         */
         armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_MEM);
         return;
     case EXCP_BKPT:
@@ -2934,9 +2936,11 @@ void arm_cpu_do_interrupt(CPUState *cs)
                 return;
             }
         }
-        env->cp15.c5_insn = 2;
+        env->exception.fsr = 2;
         /* Fall through to prefetch abort.  */
     case EXCP_PREFETCH_ABORT:
+        env->cp15.c5_insn = env->exception.fsr;
+        env->cp15.c6_insn = env->exception.vaddress;
         qemu_log_mask(CPU_LOG_INT, "...with IFSR 0x%x IFAR 0x%x\n",
                       env->cp15.c5_insn, env->cp15.c6_insn);
         new_mode = ARM_CPU_MODE_ABT;
@@ -2945,6 +2949,8 @@ void arm_cpu_do_interrupt(CPUState *cs)
         offset = 4;
         break;
     case EXCP_DATA_ABORT:
+        env->cp15.c5_data = env->exception.fsr;
+        env->cp15.c6_data = env->exception.vaddress;
         qemu_log_mask(CPU_LOG_INT, "...with DFSR 0x%x DFAR 0x%x\n",
                       env->cp15.c5_data, env->cp15.c6_data);
         new_mode = ARM_CPU_MODE_ABT;
@@ -3593,16 +3599,15 @@ int cpu_arm_handle_mmu_fault (CPUARMState *env, target_ulong address,
     }
 
     if (access_type == 2) {
-        env->cp15.c5_insn = ret;
-        env->cp15.c6_insn = address;
         env->exception_index = EXCP_PREFETCH_ABORT;
     } else {
-        env->cp15.c5_data = ret;
-        if (access_type == 1 && arm_feature(env, ARM_FEATURE_V6))
-            env->cp15.c5_data |= (1 << 11);
-        env->cp15.c6_data = address;
+        if (access_type == 1 && arm_feature(env, ARM_FEATURE_V6)) {
+            ret |= (1 << 11);
+        }
         env->exception_index = EXCP_DATA_ABORT;
     }
+    env->exception.vaddress = address;
+    env->exception.fsr = ret;
     return 1;
 }
 
diff --git a/target-arm/machine.c b/target-arm/machine.c
index 8f9e7d4..fc8825e 100644
--- a/target-arm/machine.c
+++ b/target-arm/machine.c
@@ -257,6 +257,9 @@ const VMStateDescription vmstate_arm_cpu = {
         VMSTATE_UINT64(env.exclusive_val, ARMCPU),
         VMSTATE_UINT64(env.exclusive_high, ARMCPU),
         VMSTATE_UINT64(env.features, ARMCPU),
+        VMSTATE_UINT32(env.exception.syndrome, ARMCPU),
+        VMSTATE_UINT32(env.exception.fsr, ARMCPU),
+        VMSTATE_UINT64(env.exception.vaddress, ARMCPU),
         VMSTATE_TIMER(gt_timer[GTIMER_PHYS], ARMCPU),
         VMSTATE_TIMER(gt_timer[GTIMER_VIRT], ARMCPU),
         VMSTATE_END_OF_LIST()
-- 
1.9.0