On 04/27/2017 04:41 AM, Jan Beulich wrote:
> While the hypervisor side of commit cd91ab08ea ("x86emul: correct stub
> invocation constraints") was fine, the tools side triggered a bogus
> error with old gcc (4.3 and 4.4 at least). Use a slightly less
> appropriate variant instead, proven to be good enough to not
> re-introduce the original problem: Which of the addresses is actually
> used doesn't matter much as long as the compiler can't prove that the
> two pointers don't alias one another.
>
> Reported-by: Boris Ostrovsky <boris.ostrov...@oracle.com>
> Signed-off-by: Jan Beulich <jbeul...@suse.com>
>
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -901,7 +901,7 @@ do{ asm volatile (
> # define invoke_stub(pre, post, constraints...) \
> asm volatile ( pre "\n\tcall *%[stub]\n\t" post \
> : constraints, [stub] "rm" (stub.func), \
> - "m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.buf) )
> + "m" (*(typeof(stub.buf) *)stub.addr) )
> #endif
>
> #define emulate_stub(dst, src...) do { \
Tested-by: Boris Ostrovsky <boris.ostrov...@oracle.com>
And to answer your earlier question --- this was tools-specific (but you
already know this now).
-boris
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