Verify memory access permissions in PMP regions

Checks if a memory access falls within a configured region by comparing
the requested address and size against the region boundaries. When a
matching region is found, validates that the region's permissions match
the requested operation type.

Author: HeatCrab

arch/riscv/pmp.c

@@ -263,3 +263,41 @@ int32_t pmp_get_region(const pmp_config_t *config, uint8_t region_idx,
 
     return ERR_OK;
 }
+
+int32_t pmp_check_access(const pmp_config_t *config, uint32_t addr,
+                         uint32_t size, uint8_t is_write, uint8_t is_execute)
+{
+    if (!config)
+        return ERR_PMP_INVALID_REGION;
+
+    uint32_t access_end = addr + size;
+
+    /* In TOR mode, check all regions in priority order */
+    for (uint8_t i = 0; i < config->region_count; i++) {
+        const pmp_region_t *region = &config->regions[i];
+
+        /* Skip disabled regions */
+        if (region->addr_start == 0 && region->addr_end == 0)
+            continue;
+
+        /* Check if access falls within this region */
+        if (addr >= region->addr_start && access_end <= region->addr_end) {
+            /* Verify permissions match access type */
+            uint8_t required_perm = 0;
+            if (is_write)
+                required_perm |= PMPCFG_W;
+            if (is_execute)
+                required_perm |= PMPCFG_X;
+            if (!is_write && !is_execute)
+                required_perm = PMPCFG_R;
+
+            if ((region->permissions & required_perm) == required_perm)
+                return 1; /* Access allowed */
+            else
+                return 0; /* Access denied */
+        }
+    }
+
+    /* Access not covered by any region */
+    return 0;
+}