[Qemu-devel] [PATCH] cpu-all.h: Don't accidentally sign extend in g2h()

[Peter Maydell <peter.maydell@linaro.org>]

Cast the argument of the g2h() macro to a target_ulong so that
it isn't accidentally sign-extended if it is a signed 32 bit
type and long is a 64 bit type. In particular, this fixes a
bug where it would return the wrong value for 32 bit guests
on 64 bit hosts when passed in one of the arg* values from
do_syscall() [which are all abi_long and thus signed types].
This could result in spurious failure of mlock(), among others.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
This should be committed before Alex's patch to make mmap allocate
downwards (http://patchwork.ozlabs.org/patch/144476/) because that
hugely increases the chances that g2h will get passed a pointer
that has the high bit set.

 cpu-all.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/cpu-all.h b/cpu-all.h
index 80e6d42..a174532 100644
--- a/cpu-all.h
+++ b/cpu-all.h
@@ -197,7 +197,7 @@ extern unsigned long reserved_va;
 #endif
 
 /* All direct uses of g2h and h2g need to go away for usermode softmmu.  */
-#define g2h(x) ((void *)((unsigned long)(x) + GUEST_BASE))
+#define g2h(x) ((void *)((unsigned long)(target_ulong)(x) + GUEST_BASE))
 
 #if HOST_LONG_BITS <= TARGET_VIRT_ADDR_SPACE_BITS
 #define h2g_valid(x) 1
-- 
1.7.1