[Qemu-devel] [PATCH 01/26] tcg: Assert h2g_valid for 32-bit guest on 64-bit host

[Richard Henderson]

For this combination, we can tell whether or not the address
being accessed is within the 4GB range that is accessible by
the guest.  Otherwise the fault must be elsewhere in qemu,
accessing qemu data structures.

Signed-off-by: Richard Henderson <address@hidden>
---
 accel/tcg/user-exec.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c
index 0789984fe6..fa9380a380 100644
--- a/accel/tcg/user-exec.c
+++ b/accel/tcg/user-exec.c
@@ -143,6 +143,15 @@ static inline int handle_cpu_signal(uintptr_t pc, 
siginfo_t *info,
         }
     }
 
+    /*
+     * For a 32-bit guest on a 64-bit host, the set of addresses that we
+     * access on behalf of the guest is constrained.  Anything outside
+     * that range is a bug elsewhere in QEMU.
+     */
+#if TARGET_LONG_BITS == 32 && HOST_LONG_BITS == 64
+    g_assert(h2g_valid(address));
+#endif
+
     /* Convert forcefully to guest address space, invalid addresses
        are still valid segv ones */
     address = h2g_nocheck(address);
-- 
2.17.1