[Qemu-arm] [PATCH v2 18/26] armv7m: update base region policy

[Michael Davidsaver]

Update MPU background policy as per ARM.
Main changes are preventing writes to ROM
and no-exec for device regions.
---
 target-arm/helper.c | 35 +++++++++++++++++++++++++++--------
 1 file changed, 27 insertions(+), 8 deletions(-)

diff --git a/target-arm/helper.c b/target-arm/helper.c
index e73f7a6..e42f6d0 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -7062,16 +7062,35 @@ static inline void 
get_phys_addr_pmsav7_default(CPUARMState *env,
                                                 ARMMMUIdx mmu_idx,
                                                 int32_t address, int *prot)
 {
-    *prot = PAGE_READ | PAGE_WRITE;
-    switch (address) {
-    case 0xF0000000 ... 0xFFFFFFFF:
-        if (regime_sctlr(env, mmu_idx) & SCTLR_V) { /* hivecs execing is ok */
+    if (!IS_M(env)) {
+        *prot = PAGE_READ | PAGE_WRITE;
+        switch (address) {
+        case 0xF0000000 ... 0xFFFFFFFF:
+            if (regime_sctlr(env, mmu_idx) & SCTLR_V) {
+                /* hivecs execing is ok */
+                *prot |= PAGE_EXEC;
+            }
+            break;
+        case 0x00000000 ... 0x7FFFFFFF:
             *prot |= PAGE_EXEC;
+            break;
+        }
+    } else {
+        /* ARM specfies XN (PAGE_EXEC) but leaves R/W to implementation.
+         * Mark ROM as read only since writes would otherwise be ignored.
+         */
+        switch (address) {
+        case 0 ... 0x1fffffff: /* ROM */
+            *prot = PAGE_READ | PAGE_EXEC;
+            break;
+        case 0x20000000 ... 0x3fffffff:  /* SRAM */
+        case 0x60000000 ... 0x7fffffff: /* RAM */
+        case 0x80000000 ... 0x9fffffff: /* RAM */
+            *prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
+            break;
+        default: /* Peripheral, 2x Device, and System */
+            *prot = PAGE_READ | PAGE_WRITE;
         }
-        break;
-    case 0x00000000 ... 0x7FFFFFFF:
-        *prot |= PAGE_EXEC;
-        break;
     }
 
 }
-- 
2.1.4