fix pte_create to deal with protection bits correctly

2 files changed, 25 insertions, 6 deletions

diff --git a/pk/vm.c b/pk/vm.c
index 2303ae1..b1ee62c 100644
--- a/pk/vm.c
+++ b/pk/vm.c
@@ -79,12 +79,30 @@ static pte_t ptd_create(uintptr_t ppn)
 static inline pte_t pte_create(uintptr_t ppn, int prot, int user)
 {
   pte_t pte = (ppn << PTE_PPN_SHIFT) | PTE_V;
-  if (prot & PROT_WRITE)
-    pte |= PTE_TYPE_URW_SRW;
-  if (prot & PROT_EXEC)
-    pte |= PTE_TYPE_URX_SRX;
-  if (!user)
-    pte |= PTE_TYPE_SR;
+  prot &= PROT_READ|PROT_WRITE|PROT_EXEC;
+  if (user) {
+    switch (prot) {
+      case PROT_NONE: pte |= PTE_TYPE_SR; break;
+      case PROT_READ: pte |= PTE_TYPE_UR_SR; break;
+      case PROT_WRITE: pte |= PTE_TYPE_URW_SRW; break;
+      case PROT_EXEC: pte |= PTE_TYPE_URX_SRX; break;
+      case PROT_READ|PROT_WRITE: pte |= PTE_TYPE_URW_SRW; break;
+      case PROT_READ|PROT_EXEC: pte |= PTE_TYPE_URX_SRX; break;
+      case PROT_WRITE|PROT_EXEC: pte |= PTE_TYPE_URWX_SRWX; break;
+      case PROT_READ|PROT_WRITE|PROT_EXEC: pte |= PTE_TYPE_URWX_SRWX; break;
+    }
+  } else {
+    switch (prot) {
+      case PROT_NONE: kassert(0); break;
+      case PROT_READ: pte |= PTE_TYPE_SR; break;
+      case PROT_WRITE: pte |= PTE_TYPE_SRW; break;
+      case PROT_EXEC: pte |= PTE_TYPE_SRX; break;
+      case PROT_READ|PROT_WRITE: pte |= PTE_TYPE_SRW; break;
+      case PROT_READ|PROT_EXEC: pte |= PTE_TYPE_SRX; break;
+      case PROT_WRITE|PROT_EXEC: pte |= PTE_TYPE_SRWX; break;
+      case PROT_READ|PROT_WRITE|PROT_EXEC: pte |= PTE_TYPE_SRWX; break;
+    }
+  }
   return pte;
 }
 
diff --git a/pk/vm.h b/pk/vm.h
index 71d9be2..4a24e56 100644
--- a/pk/vm.h
+++ b/pk/vm.h
@@ -17,6 +17,7 @@
 # define VA_BITS 32
 #endif
 
+#define PROT_NONE 0
 #define PROT_READ 1
 #define PROT_WRITE 2
 #define PROT_EXEC 4