[Qemu-devel] [PATCH v6 13/37] target-arm: Use dedicated CPU state fields for ARM946 access bit registers

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

The ARM946 model currently uses the c5_data and c5_insn fields in the CPU
state struct to store the contents of its access permission registers.
This is confusing and a good source of bugs because for all the MMU-based
CPUs those fields are fault status and fault address registers, which
behave completely differently; they just happen to use the same cpreg
encoding. Split them out to use their own fields instead.

These registers are only present in PMSAv5 MPU systems (of which the
ARM946 is our only current example); PMSAv6 and PMSAv7 (which we have
no implementations of) handle access permissions differently. We name
the new state fields accordingly.

Note that this change fixes a bug where a data abort or prefetch abort
on the ARM946 would accidentally corrupt the access permission registers
because the interrupt handling code assumed the c5_data and c5_insn
fields were always fault status registers.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
---
 target-arm/cpu.h    |  2 ++
 target-arm/helper.c | 24 ++++++++++++++----------
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index a00ff73..42fa7db 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -179,6 +179,8 @@ typedef struct CPUARMState {
         uint32_t c2_insn; /* MPU instruction cachable bits.  */
         uint32_t c3; /* MMU domain access control register
                         MPU write buffer control.  */
+        uint32_t pmsav5_data_ap; /* PMSAv5 MPU data access permissions */
+        uint32_t pmsav5_insn_ap; /* PMSAv5 MPU insn access permissions */
         uint32_t c5_insn; /* Fault status registers.  */
         uint32_t c5_data;
         uint32_t c6_region[8]; /* MPU base/size registers.  */
diff --git a/target-arm/helper.c b/target-arm/helper.c
index 2ffc588..289a5c0 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -1275,40 +1275,44 @@ static uint32_t extended_mpu_ap_bits(uint32_t val)
 static void pmsav5_data_ap_write(CPUARMState *env, const ARMCPRegInfo *ri,
                                  uint64_t value)
 {
-    env->cp15.c5_data = extended_mpu_ap_bits(value);
+    env->cp15.pmsav5_data_ap = extended_mpu_ap_bits(value);
 }
 
 static uint64_t pmsav5_data_ap_read(CPUARMState *env, const ARMCPRegInfo *ri)
 {
-    return simple_mpu_ap_bits(env->cp15.c5_data);
+    return simple_mpu_ap_bits(env->cp15.pmsav5_data_ap);
 }
 
 static void pmsav5_insn_ap_write(CPUARMState *env, const ARMCPRegInfo *ri,
                                  uint64_t value)
 {
-    env->cp15.c5_insn = extended_mpu_ap_bits(value);
+    env->cp15.pmsav5_insn_ap = extended_mpu_ap_bits(value);
 }
 
 static uint64_t pmsav5_insn_ap_read(CPUARMState *env, const ARMCPRegInfo *ri)
 {
-    return simple_mpu_ap_bits(env->cp15.c5_insn);
+    return simple_mpu_ap_bits(env->cp15.pmsav5_insn_ap);
 }
 
 static const ARMCPRegInfo pmsav5_cp_reginfo[] = {
     { .name = "DATA_AP", .cp = 15, .crn = 5, .crm = 0, .opc1 = 0, .opc2 = 0,
       .access = PL1_RW, .type = ARM_CP_NO_MIGRATE,
-      .fieldoffset = offsetof(CPUARMState, cp15.c5_data), .resetvalue = 0,
+      .fieldoffset = offsetof(CPUARMState, cp15.pmsav5_data_ap),
+      .resetvalue = 0,
       .readfn = pmsav5_data_ap_read, .writefn = pmsav5_data_ap_write, },
     { .name = "INSN_AP", .cp = 15, .crn = 5, .crm = 0, .opc1 = 0, .opc2 = 1,
       .access = PL1_RW, .type = ARM_CP_NO_MIGRATE,
-      .fieldoffset = offsetof(CPUARMState, cp15.c5_insn), .resetvalue = 0,
+      .fieldoffset = offsetof(CPUARMState, cp15.pmsav5_insn_ap),
+      .resetvalue = 0,
       .readfn = pmsav5_insn_ap_read, .writefn = pmsav5_insn_ap_write, },
     { .name = "DATA_EXT_AP", .cp = 15, .crn = 5, .crm = 0, .opc1 = 0, .opc2 = 2,
       .access = PL1_RW,
-      .fieldoffset = offsetof(CPUARMState, cp15.c5_data), .resetvalue = 0, },
+      .fieldoffset = offsetof(CPUARMState, cp15.pmsav5_data_ap),
+      .resetvalue = 0, },
     { .name = "INSN_EXT_AP", .cp = 15, .crn = 5, .crm = 0, .opc1 = 0, .opc2 = 3,
       .access = PL1_RW,
-      .fieldoffset = offsetof(CPUARMState, cp15.c5_insn), .resetvalue = 0, },
+      .fieldoffset = offsetof(CPUARMState, cp15.pmsav5_insn_ap),
+      .resetvalue = 0, },
     { .name = "DCACHE_CFG", .cp = 15, .crn = 2, .crm = 0, .opc1 = 0, .opc2 = 0,
       .access = PL1_RW,
       .fieldoffset = offsetof(CPUARMState, cp15.c2_data), .resetvalue = 0, },
@@ -3676,9 +3680,9 @@ static int get_phys_addr_mpu(CPUARMState *env, uint32_t address,
 	return 2;
 
     if (access_type == 2) {
-	mask = env->cp15.c5_insn;
+        mask = env->cp15.pmsav5_insn_ap;
     } else {
-	mask = env->cp15.c5_data;
+        mask = env->cp15.pmsav5_data_ap;
     }
     mask = (mask >> (n * 4)) & 0xf;
     switch (mask) {
-- 
1.9.1