Re: [PATCH 2/4] coroutine: Add check for SafeStack in sigalstack

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 4/29/20 9:44 PM, Daniele Buono wrote:
> LLVM's SafeStack instrumentation cannot be used inside signal handlers
> that make use of sigaltstack().
> Since coroutine-sigaltstack relies on sigaltstack(), it is not
> compatible with SafeStack. The resulting binary is incorrect, with
> different coroutines sharing the same unsafe stack and producing
> undefined behavior at runtime.
> To avoid this, we add a check in coroutine-sigaltstack that throws a
> preprocessor #error and interrupt the compilation if SafeStack is
> enabled.
> 
> Signed-off-by: Daniele Buono <dbuono@linux.vnet.ibm.com>
> ---
>   util/coroutine-sigaltstack.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/util/coroutine-sigaltstack.c b/util/coroutine-sigaltstack.c
> index f6fc49a0e5..b7cdc959f8 100644
> --- a/util/coroutine-sigaltstack.c
> +++ b/util/coroutine-sigaltstack.c
> @@ -30,6 +30,10 @@
>   #include "qemu-common.h"
>   #include "qemu/coroutine_int.h"
>   
> +#ifdef CONFIG_SAFESTACK
> +#error "SafeStack does not work with sigaltstack's implementation"
> +#endif
> +
>   typedef struct {
>       Coroutine base;
>       void *stack;
> 

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>