| Message ID | 5901CAE30200007800154B17@prv-mh.provo.novell.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 27/04/2017 09:41, 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.ostrovsky@oracle.com> > Signed-off-by: Jan Beulich <jbeulich@suse.com> Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
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.ostrovsky@oracle.com> > Signed-off-by: Jan Beulich <jbeulich@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.ostrovsky@oracle.com> And to answer your earlier question --- this was tools-specific (but you already know this now). -boris
Jan Beulich writes ("[PATCH] x86emul: correct stub invocation constraints again"):
> 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.ostrovsky@oracle.com>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Ian Jackson <ian.jackson@eu.citrix.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 { \
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.ostrovsky@oracle.com> Signed-off-by: Jan Beulich <jbeulich@suse.com> x86emul: correct stub invocation constraints again 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.ostrovsky@oracle.com> Signed-off-by: Jan Beulich <jbeulich@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 { \