[PATCH v6 25/25] target/riscv: Reorg sum check in get_physical_address

[Richard Henderson]

Implement this by adjusting prot, which reduces the set of
checks required.  This prevents exec to be set for U pages
in MMUIdx_S_SUM.  While it had been technically incorrect,
it did not manifest as a bug, because we will never attempt
to execute from MMUIdx_S_SUM.

Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
 target/riscv/cpu_helper.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 725ca45106..7336d1273b 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -800,7 +800,7 @@ static int get_physical_address(CPURISCVState *env, hwaddr 
*physical,
     *ret_prot = 0;
 
     hwaddr base;
-    int levels, ptidxbits, ptesize, vm, sum, widened;
+    int levels, ptidxbits, ptesize, vm, widened;
 
     if (first_stage == true) {
         if (use_background) {
@@ -831,7 +831,7 @@ static int get_physical_address(CPURISCVState *env, hwaddr 
*physical,
         }
         widened = 2;
     }
-    sum = mmuidx_sum(mmu_idx);
+
     switch (vm) {
     case VM_1_10_SV32:
       levels = 2; ptidxbits = 10; ptesize = 4; break;
@@ -999,15 +999,15 @@ restart:
         prot |= PAGE_EXEC;
     }
 
-    if ((pte & PTE_U) &&
-        ((mode != PRV_U) && (!sum || access_type == MMU_INST_FETCH))) {
-        /*
-         * User PTE flags when not U mode and mstatus.SUM is not set,
-         * or the access type is an instruction fetch.
-         */
-        return TRANSLATE_FAIL;
-    }
-    if (!(pte & PTE_U) && (mode != PRV_S)) {
+    if (pte & PTE_U) {
+        if (mode != PRV_U) {
+            if (!mmuidx_sum(mmu_idx)) {
+                return TRANSLATE_FAIL;
+            }
+            /* SUM allows only read+write, not execute. */
+            prot &= PAGE_READ | PAGE_WRITE;
+        }
+    } else if (mode != PRV_S) {
         /* Supervisor PTE flags when not S mode */
         return TRANSLATE_FAIL;
     }
-- 
2.34.1