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x86/pvh: Call C code via the kernel virtual mapping

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commit e8fbc0d9ca upstream.

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: 7243b93345 ("xen/pvh: Bootstrap PVH guest")
Tested-by: Jason Andryuk <jason.andryuk@amd.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Message-ID: <20241009160438.3884381-8-ardb+git@google.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
[ Stable context update ]
Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ard Biesheuvel
2024-10-09 18:04:40 +02:00
committed by Greg Kroah-Hartman
parent 2b4479eb46
commit 0fd13033d4
1 changed files with 6 additions and 1 deletions
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arch/x86/platform/pvh/head.S
+6 -1
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@@ -100,7 +100,12 @@ SYM_CODE_START_LOCAL(pvh_start_xen)
xor %edx, %edx
wrmsr
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
/* startup_64 expects boot_params in %rsi. */
mov $_pa(pvh_bootparams), %rsi