env: trap and page fault filter mechanism (#40)

Certain tests (particularly negative) may require a fault to occur.

However in order to pass the tests, page fault and traps must return back
to the tests. This patch add support for page fault and trap filtering
in env.

Signed-off-by: Deepak Gupta <debug@rivosinc.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/v/vm.c b/v/vm.c
index 277b67c..178d90b 100644
--- a/v/vm.c
+++ b/v/vm.c
@@ -136,8 +136,14 @@ static void evict(unsigned long addr)
   }
 }
 
+extern int pf_filter(uintptr_t addr, uintptr_t *pte, int *copy);
+extern int trap_filter(trapframe_t *tf);
+
 void handle_fault(uintptr_t addr, uintptr_t cause)
 {
+  uintptr_t filter_encodings = 0;
+  int copy_page = 1;
+
   assert(addr >= PGSIZE && addr < MAX_TEST_PAGES * PGSIZE);
   addr = addr/PGSIZE*PGSIZE;
 
@@ -159,6 +165,11 @@ void handle_fault(uintptr_t addr, uintptr_t cause)
     freelist_tail = 0;
 
   uintptr_t new_pte = (node->addr >> PGSHIFT << PTE_PPN_SHIFT) | PTE_V | PTE_U | PTE_R | PTE_W | PTE_X;
+
+  if (pf_filter(addr, &filter_encodings, &copy_page)) {
+      new_pte = (node->addr >> PGSHIFT << PTE_PPN_SHIFT) | filter_encodings;
+  }
+
   user_llpt[addr/PGSIZE] = new_pte | PTE_A | PTE_D;
   flush_page(addr);
 
@@ -177,6 +188,10 @@ void handle_fault(uintptr_t addr, uintptr_t cause)
 
 void handle_trap(trapframe_t* tf)
 {
+  if (trap_filter(tf)) {
+    pop_tf(tf);
+  }
+
   if (tf->cause == CAUSE_USER_ECALL)
   {
     int n = tf->gpr[10];