target-mips: add RI and XI fields to TLB entry

In Revision 3 of the architecture, the RI and XI bits were added to the TLB
to enable more secure access of memory pages. These bits (along with the Dirty
bit) allow the implementation of read-only, write-only, no-execute access
policies for mapped pages.
Signed-off-by: NLeon Alrae <leon.alrae@imgtec.com>
Reviewed-by: NYongbok Kim <yongbok.kim@imgtec.com>

target-mips/cpu.h

@@ -30,6 +30,10 @@ struct r4k_tlb_t {
     uint_fast16_t V1:1;
     uint_fast16_t D0:1;
     uint_fast16_t D1:1;
+    uint_fast16_t XI0:1;
+    uint_fast16_t XI1:1;
+    uint_fast16_t RI0:1;
+    uint_fast16_t RI1:1;
     target_ulong PFN[2];
 };
 
@@ -229,6 +233,13 @@ struct CPUMIPSState {
 #define CP0VPEOpt_DWX0	0
     target_ulong CP0_EntryLo0;
     target_ulong CP0_EntryLo1;
+#if defined(TARGET_MIPS64)
+# define CP0EnLo_RI 63
+# define CP0EnLo_XI 62
+#else
+# define CP0EnLo_RI 31
+# define CP0EnLo_XI 30
+#endif
     target_ulong CP0_Context;
     target_ulong CP0_KScratch[MIPS_KSCRATCH_NUM];
     int32_t CP0_PageMask;

target-mips/helper.c

@@ -27,6 +27,8 @@
 #include "sysemu/kvm.h"
 
 enum {
+    TLBRET_XI = -6,
+    TLBRET_RI = -5,
     TLBRET_DIRTY = -4,
     TLBRET_INVALID = -3,
     TLBRET_NOMATCH = -2,
@@ -85,8 +87,15 @@ int r4k_map_address (CPUMIPSState *env, hwaddr *physical, int *prot,
             /* TLB match */
             int n = !!(address & mask & ~(mask >> 1));
             /* Check access rights */
-            if (!(n ? tlb->V1 : tlb->V0))
+            if (!(n ? tlb->V1 : tlb->V0)) {
                 return TLBRET_INVALID;
+            }
+            if (rw == MMU_INST_FETCH && (n ? tlb->XI1 : tlb->XI0)) {
+                return TLBRET_XI;
+            }
+            if (rw == MMU_DATA_LOAD && (n ? tlb->RI1 : tlb->RI0)) {
+                return TLBRET_RI;
+            }
             if (rw != MMU_DATA_STORE || (n ? tlb->D1 : tlb->D0)) {
                 *physical = tlb->PFN[n] | (address & (mask >> 1));
                 *prot = PAGE_READ;

target-mips/op_helper.c

@@ -1849,10 +1849,14 @@ static void r4k_fill_tlb(CPUMIPSState *env, int idx)
     tlb->V0 = (env->CP0_EntryLo0 & 2) != 0;
     tlb->D0 = (env->CP0_EntryLo0 & 4) != 0;
     tlb->C0 = (env->CP0_EntryLo0 >> 3) & 0x7;
+    tlb->XI0 = (env->CP0_EntryLo0 >> CP0EnLo_XI) & 1;
+    tlb->RI0 = (env->CP0_EntryLo0 >> CP0EnLo_RI) & 1;
     tlb->PFN[0] = (env->CP0_EntryLo0 >> 6) << 12;
     tlb->V1 = (env->CP0_EntryLo1 & 2) != 0;
     tlb->D1 = (env->CP0_EntryLo1 & 4) != 0;
     tlb->C1 = (env->CP0_EntryLo1 >> 3) & 0x7;
+    tlb->XI1 = (env->CP0_EntryLo1 >> CP0EnLo_XI) & 1;
+    tlb->RI1 = (env->CP0_EntryLo1 >> CP0EnLo_RI) & 1;
     tlb->PFN[1] = (env->CP0_EntryLo1 >> 6) << 12;
 }
 
@@ -1964,8 +1968,12 @@ void r4k_helper_tlbr(CPUMIPSState *env)
     env->CP0_EntryHi = tlb->VPN | tlb->ASID;
     env->CP0_PageMask = tlb->PageMask;
     env->CP0_EntryLo0 = tlb->G | (tlb->V0 << 1) | (tlb->D0 << 2) |
+                        ((target_ulong)tlb->RI0 << CP0EnLo_RI) |
+                        ((target_ulong)tlb->XI0 << CP0EnLo_XI) |
                         (tlb->C0 << 3) | (tlb->PFN[0] >> 6);
     env->CP0_EntryLo1 = tlb->G | (tlb->V1 << 1) | (tlb->D1 << 2) |
+                        ((target_ulong)tlb->RI1 << CP0EnLo_RI) |
+                        ((target_ulong)tlb->XI1 << CP0EnLo_XI) |
                         (tlb->C1 << 3) | (tlb->PFN[1] >> 6);
 }