From: Andrew Cooper Date: Mon, 17 Sep 2018 15:32:32 +0000 (+0100) Subject: x86/hvm: Adjust hvmemul_rep_stos() to compile with -Wvla X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=e70934f44ad63e5433756f785ab4bcb316f860f2;p=people%2Froyger%2Fxen.git x86/hvm: Adjust hvmemul_rep_stos() to compile with -Wvla When using -Wvla, the typecast of buf triggers a Variable Length Array warning. This is less than ideal, as this typecast doesn't occupy any stack space, but we don't have a finer grain option to use. Alter the asm expression to avoid the typecast, which necessitates the introduction of a memory clobber as the compiler can no longer identify the total quantity of written memory. Despite the memory clobber, there is no change to the generated asm. Signed-off-by: Andrew Cooper Reviewed-by: Paul Durrant Reviewed-by: Wei Liu --- diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c index a577685dc6..eab66eab77 100644 --- a/xen/arch/x86/hvm/emulate.c +++ b/xen/arch/x86/hvm/emulate.c @@ -1859,7 +1859,7 @@ static int hvmemul_rep_stos( switch ( p2mt ) { unsigned long bytes; - void *buf; + char *buf; default: /* Allocate temporary buffer. */ @@ -1882,10 +1882,10 @@ static int hvmemul_rep_stos( #define CASE(bits, suffix) \ case (bits) / 8: \ asm ( "rep stos" #suffix \ - : "=m" (*(char (*)[bytes])buf), \ + : "=m" (*buf), \ "=D" (dummy), "=c" (dummy) \ : "a" (*(const uint##bits##_t *)p_data), \ - "1" (buf), "2" (*reps) ); \ + "1" (buf), "2" (*reps) : "memory" ); \ break CASE(8, b); CASE(16, w);