6.6-stable review patch. If anyone has any objections, please let me know.
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From: Ard Biesheuvel ardb@kernel.org
[ Upstream commit e8fbc0d9cab6c1ee6403f42c0991b0c1d5dbc092 ]
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") 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 Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/platform/pvh/head.S | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S index c994ea58bdf7a..008a805522245 100644 --- a/arch/x86/platform/pvh/head.S +++ b/arch/x86/platform/pvh/head.S @@ -107,7 +107,14 @@ 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.