arm: Fix broken page table permissions checks in remote GDB

The remote GDB interface currently doesn't check if translations are
valid before reading memory. This causes a panic when GDB tries to
access unmapped memory (e.g., when getting a stack trace). There are
two reasons for this: 1) The function used to check for valid
translations (virtvalid()) doesn't work and panics on invalid
translations. 2) The method in the GDB interface used to test if a
translation is valid (RemoteGDB::acc) always returns true regardless
of the return from virtvalid().

This changeset fixes both of these issues.

1 files changed, 6 insertions, 9 deletions

diff --git a/src/arch/arm/remote_gdb.cc b/src/arch/arm/remote_gdb.cc
index 1686cab39..d52a9db17 100644
--- a/src/arch/arm/remote_gdb.cc
+++ b/src/arch/arm/remote_gdb.cc
@@ -142,6 +142,7 @@
 #include "arch/arm/system.hh"
 #include "arch/arm/utility.hh"
 #include "arch/arm/vtophys.hh"
+#include "base/chunk_generator.hh"
 #include "base/intmath.hh"
 #include "base/remote_gdb.hh"
 #include "base/socket.hh"
@@ -172,16 +173,12 @@ bool
 RemoteGDB::acc(Addr va, size_t len)
 {
     if (FullSystem) {
-        Addr last_va;
-        va       = truncPage(va);
-        last_va  = roundPage(va + len);
-
-        do  {
-            if (virtvalid(context, va)) {
-                return true;
+        for (ChunkGenerator gen(va, len, PageBytes); !gen.done(); gen.next()) {
+            if (!virtvalid(context, gen.addr())) {
+                DPRINTF(GDBAcc, "acc:   %#x mapping is invalid\n", va);
+                return false;
             }
-            va += PageBytes;
-        } while (va < last_va);
+        }
 
         DPRINTF(GDBAcc, "acc:   %#x mapping is valid\n", va);
         return true;