Hello Please don't post HTML mails.
On Fri, Apr 15, 2016 at 03:49:20PM +0800, Zakirasafi wrote: > Dear All > The following code is for side channel attack on xen hypevisor. In this > code I am having problem in understanding the highlighted red line. In the > line what ".byte 15, byte 49" do??? > I don't have HTML capable mail reader, so I can't see "highlighted red line", but I get you idea. > #include <sys/types.h> > #include <sys/socket.h> > #include <netinet/in.h> > #include <openssl/aes.h> > unsigned int timestamp(void) > { > unsigned int bottom; > unsigned int top; > *asm volatile(".byte 15;.byte 49" : "=a"(bottom),"=d"(top)); return bottom;* > } This is probably some sort of opcode. You can probably find out what they mean in Intel or AMD software developer manual. Other than that, I don't think we can help you much regarding this program. You will have better luck contacting the researchers (?) who wrote this code. And, if you do find it a security issue in real life, we have a process of dealing with that, too. http://www.xenproject.org/security-policy.html Thanks Wei. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel