On 2024-09-25 11:01, Ard Biesheuvel wrote:
From: Ard Biesheuvel <ardb@xxxxxxxxxx>
Calling C code via a different mapping than it was linked at is
problematic, because the compiler assumes that RIP-relative and absolute
symbol references are interchangeable. GCC in particular may use
RIP-relative per-CPU variable references even when not using -fpic.
So call xen_prepare_pvh() via its kernel virtual mapping on x86_64, so
that those RIP-relative references produce the correct values. This
matches the pre-existing behavior for i386, which also invokes
xen_prepare_pvh() via the kernel virtual mapping before invoking
startup_32 with paging disabled again.
Fixes: 7243b93345f7 ("xen/pvh: Bootstrap PVH guest")
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Tested-by: Jason Andryuk <jason.andryuk@xxxxxxx>
Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>
I found that before this change xen_prepare_pvh() would call through
some pv_ops function pointers into the kernel virtual mapping.
Regards,
Jason
