Commit e8fbc0d9 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Juergen Gross
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x86/pvh: Call C code via the kernel virtual mapping 



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: 7243b933 ("xen/pvh: Bootstrap PVH guest")
Tested-by: default avatarJason Andryuk <jason.andryuk@amd.com>
Reviewed-by: default avatarJason Andryuk <jason.andryuk@amd.com>
Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Message-ID: <20241009160438.3884381-8-ardb+git@google.com>
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
parent 81983758

arch/x86/platform/pvh/head.S

+8 −1
Original line number Diff line number Diff line
@@ -172,7 +172,14 @@ SYM_CODE_START_LOCAL(pvh_start_xen) 
	movq %rbp, %rbx

	subq $_pa(pvh_start_xen), %rbx

	movq %rbx, phys_base(%rip)

	call xen_prepare_pvh



	/* Call xen_prepare_pvh() via the kernel virtual mapping */

	leaq xen_prepare_pvh(%rip), %rax

	subq phys_base(%rip), %rax

	addq $__START_KERNEL_map, %rax

	ANNOTATE_RETPOLINE_SAFE

	call *%rax



	/*

	 * Clear phys_base.  __startup_64 will *add* to its value,

	 * so reset to 0.