[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] x86/entry: Fix passing 6th argument for compat hypercalls
On 16/03/18 19:55, Jason Andryuk wrote: > Commit ec05090403ef4d760fbe701e31afd0f0edc414d5 ("x86/entry: Erase guest > GPR state on entry to Xen") zero-ed %rbp, compat arg 6, but it is not > restored before passing to hypercalls. We need to pass the saved compat > arg 6 to the hypercall in r9, the 6th function argument. > > Signed-off-by: Jason Andryuk <jandryuk@xxxxxxxxx> > --- Jan: for reference, this is precisely the reason why I recommended that you backport the minimal 51e5d6c7a29 which I provided, rather than try to fix up the existing on-stack logic. Looking at that commit, there is another bug in LOAD_C_CLOBBERED, where passing compat=0 xc=0 corrupts %rcx with whatever was on the stack for %r10 > This is against Xen 4.6. I believe it is also applicable to 4.7. > > xen/arch/x86/x86_64/compat/entry.S | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/xen/arch/x86/x86_64/compat/entry.S > b/xen/arch/x86/x86_64/compat/entry.S > index bc1f509672..b99b142e45 100644 > --- a/xen/arch/x86/x86_64/compat/entry.S > +++ b/xen/arch/x86/x86_64/compat/entry.S > @@ -56,7 +56,7 @@ UNLIKELY_END(msi_check) > xchgl %ecx,%esi /* Arg 2, Arg 4 */ > movl %edx,%edx /* Arg 3 */ > movl %edi,%r8d /* Arg 5 */ > - movl %ebp,%r9d /* Arg 6 */ > + movl UREGS_rbp(%rsp),%r9d /* Arg 6 */ > movl UREGS_rbx(%rsp),%edi /* Arg 1 */ This looks correct, (but there is a good reason why I purged this code from the codebase 3 releases ago). ~Andrew > #define SHADOW_BYTES 0 /* No on-stack shadow state */ > #endif _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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