[Qemu-devel] [PATCH v2] Support running QEMU on Valgrind

[Qemu-devel] [PATCH v2] Support running QEMU on Valgrind

[Stefan Weil]

Valgrind is a tool which can automatically detect many kinds of bugs.

Running QEMU on Valgrind with x86_64 hosts was not possible because
Valgrind aborts when memalign is called with an alignment larger than
1 MiB. QEMU normally uses 2 MiB on Linux x86_64.

Now the alignment is reduced to the page size when QEMU is running on
Valgrind.

v2:
Instead of using the macro RUNNING_ON_VALGRIND from valgrind.h,
the patch now uses a hack from libvirt which tests for the pre-loaded
vgpreload_*.so shared libraries. This avoids the need for valgrind.h.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
---
 oslib-posix.c |   22 +++++++++++++++++++---
 1 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/oslib-posix.c b/oslib-posix.c
index dbc8ee8..6f29762 100644
--- a/oslib-posix.c
+++ b/oslib-posix.c
@@ -36,8 +36,11 @@ extern int daemon(int, int);
 #endif
 
 #if defined(__linux__) && defined(__x86_64__)
-   /* Use 2MB alignment so transparent hugepages can be used by KVM */
+   /* Use 2 MiB alignment so transparent hugepages can be used by KVM.
+      Valgrind does not support alignments larger than 1 MiB,
+      therefore we need special code which handles running on Valgrind. */
 #  define QEMU_VMALLOC_ALIGN (512 * 4096)
+#  define CONFIG_VALGRIND
 #else
 #  define QEMU_VMALLOC_ALIGN getpagesize()
 #endif
@@ -47,7 +50,11 @@ extern int daemon(int, int);
 #include "trace.h"
 #include "qemu_socket.h"
 
-
+#if defined(CONFIG_VALGRIND)
+static int running_on_valgrind = -1;
+#else
+#  define running_on_valgrind 0
+#endif
 
 int qemu_daemon(int nochdir, int noclose)
 {
@@ -89,7 +96,16 @@ void *qemu_vmalloc(size_t size)
     void *ptr;
     size_t align = QEMU_VMALLOC_ALIGN;
 
-    if (size < align) {
+#if defined(CONFIG_VALGRIND)
+    if (running_on_valgrind < 0) {
+        /* First call, test whether we are running on Valgrind.
+           This is a substitute for RUNNING_ON_VALGRIND from valgrind.h. */
+        const char *ld = getenv("LD_PRELOAD");
+        running_on_valgrind = (ld != NULL && strstr(ld, "vgpreload"));
+    }
+#endif
+
+    if (size < align || running_on_valgrind) {
         align = getpagesize();
     }
     ptr = qemu_memalign(align, size);
-- 
1.7.2.5

Re: [Qemu-devel] [PATCH v2] Support running QEMU on Valgrind

[Anthony Liguori]

On 10/31/2011 03:29 PM, Stefan Weil wrote:
> Valgrind is a tool which can automatically detect many kinds of bugs.
>
> Running QEMU on Valgrind with x86_64 hosts was not possible because
> Valgrind aborts when memalign is called with an alignment larger than
> 1 MiB. QEMU normally uses 2 MiB on Linux x86_64.
>
> Now the alignment is reduced to the page size when QEMU is running on
> Valgrind.
>
> v2:
> Instead of using the macro RUNNING_ON_VALGRIND from valgrind.h,
> the patch now uses a hack from libvirt which tests for the pre-loaded
> vgpreload_*.so shared libraries. This avoids the need for valgrind.h.
>
> Signed-off-by: Stefan Weil<sw@weilnetz.de>

Applied.  Thanks.

Regards,

Anthony Liguori

> ---
>   oslib-posix.c |   22 +++++++++++++++++++---
>   1 files changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/oslib-posix.c b/oslib-posix.c
> index dbc8ee8..6f29762 100644
> --- a/oslib-posix.c
> +++ b/oslib-posix.c
> @@ -36,8 +36,11 @@ extern int daemon(int, int);
>   #endif
>
>   #if defined(__linux__)&&  defined(__x86_64__)
> -   /* Use 2MB alignment so transparent hugepages can be used by KVM */
> +   /* Use 2 MiB alignment so transparent hugepages can be used by KVM.
> +      Valgrind does not support alignments larger than 1 MiB,
> +      therefore we need special code which handles running on Valgrind. */
>   #  define QEMU_VMALLOC_ALIGN (512 * 4096)
> +#  define CONFIG_VALGRIND
>   #else
>   #  define QEMU_VMALLOC_ALIGN getpagesize()
>   #endif
> @@ -47,7 +50,11 @@ extern int daemon(int, int);
>   #include "trace.h"
>   #include "qemu_socket.h"
>
> -
> +#if defined(CONFIG_VALGRIND)
> +static int running_on_valgrind = -1;
> +#else
> +#  define running_on_valgrind 0
> +#endif
>
>   int qemu_daemon(int nochdir, int noclose)
>   {
> @@ -89,7 +96,16 @@ void *qemu_vmalloc(size_t size)
>       void *ptr;
>       size_t align = QEMU_VMALLOC_ALIGN;
>
> -    if (size<  align) {
> +#if defined(CONFIG_VALGRIND)
> +    if (running_on_valgrind<  0) {
> +        /* First call, test whether we are running on Valgrind.
> +           This is a substitute for RUNNING_ON_VALGRIND from valgrind.h. */
> +        const char *ld = getenv("LD_PRELOAD");
> +        running_on_valgrind = (ld != NULL&&  strstr(ld, "vgpreload"));
> +    }
> +#endif
> +
> +    if (size<  align || running_on_valgrind) {
>           align = getpagesize();
>       }
>       ptr = qemu_memalign(align, size);