[Qemu-devel] [PATCH 4/7] target/sparc: Correctly handle bus errors in page table walks

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

Currently we use the ldl_phys() function to read page table entries.
With the unassigned_access hook in place, if these hit an unassigned
area of memory then the hook will cause us to wrongly generate
an exception with a fault address matching the address of the
page table entry.

Change to using address_space_ldl() so we can detect and correctly
handle bus errors and give them their correct behaviour of
causing a translation error with a suitable fault status register.

Note that this won't actually take effect until we switch the
over to using the do_translation_failed hook.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/sparc/mmu_helper.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/target/sparc/mmu_helper.c b/target/sparc/mmu_helper.c
index cbd1e911796..351055a09b1 100644
--- a/target/sparc/mmu_helper.c
+++ b/target/sparc/mmu_helper.c
@@ -98,6 +98,7 @@ static int get_physical_address(CPUSPARCState *env, hwaddr *physical,
     int error_code = 0, is_dirty, is_user;
     unsigned long page_offset;
     CPUState *cs = env_cpu(env);
+    MemTxResult result;
 
     is_user = mmu_idx == MMU_USER_IDX;
 
@@ -120,7 +121,10 @@ static int get_physical_address(CPUSPARCState *env, hwaddr *physical,
     /* SPARC reference MMU table walk: Context table->L1->L2->PTE */
     /* Context base + context number */
     pde_ptr = (env->mmuregs[1] << 4) + (env->mmuregs[2] << 2);
-    pde = ldl_phys(cs->as, pde_ptr);
+    pde = address_space_ldl(cs->as, pde_ptr, MEMTXATTRS_UNSPECIFIED, &result);
+    if (result != MEMTX_OK) {
+        return 4 << 2; /* Translation fault, L = 0 */
+    }
 
     /* Ctx pde */
     switch (pde & PTE_ENTRYTYPE_MASK) {
@@ -132,7 +136,11 @@ static int get_physical_address(CPUSPARCState *env, hwaddr *physical,
         return 4 << 2;
     case 1: /* L0 PDE */
         pde_ptr = ((address >> 22) & ~3) + ((pde & ~3) << 4);
-        pde = ldl_phys(cs->as, pde_ptr);
+        pde = address_space_ldl(cs->as, pde_ptr,
+                                MEMTXATTRS_UNSPECIFIED, &result);
+        if (result != MEMTX_OK) {
+            return (1 << 8) | (4 << 2); /* Translation fault, L = 1 */
+        }
 
         switch (pde & PTE_ENTRYTYPE_MASK) {
         default:
@@ -142,7 +150,11 @@ static int get_physical_address(CPUSPARCState *env, hwaddr *physical,
             return (1 << 8) | (4 << 2);
         case 1: /* L1 PDE */
             pde_ptr = ((address & 0xfc0000) >> 16) + ((pde & ~3) << 4);
-            pde = ldl_phys(cs->as, pde_ptr);
+            pde = address_space_ldl(cs->as, pde_ptr,
+                                    MEMTXATTRS_UNSPECIFIED, &result);
+            if (result != MEMTX_OK) {
+                return (2 << 8) | (4 << 2); /* Translation fault, L = 2 */
+            }
 
             switch (pde & PTE_ENTRYTYPE_MASK) {
             default:
@@ -152,7 +164,11 @@ static int get_physical_address(CPUSPARCState *env, hwaddr *physical,
                 return (2 << 8) | (4 << 2);
             case 1: /* L2 PDE */
                 pde_ptr = ((address & 0x3f000) >> 10) + ((pde & ~3) << 4);
-                pde = ldl_phys(cs->as, pde_ptr);
+                pde = address_space_ldl(cs->as, pde_ptr,
+                                        MEMTXATTRS_UNSPECIFIED, &result);
+                if (result != MEMTX_OK) {
+                    return (3 << 8) | (4 << 2); /* Translation fault, L = 3 */
+                }
 
                 switch (pde & PTE_ENTRYTYPE_MASK) {
                 default:
-- 
2.20.1