From: Ard Biesheuvel Date: Wed, 9 Oct 2024 16:04:40 +0000 (+0200) Subject: x86/pvh: Call C code via the kernel virtual mapping X-Git-Tag: v6.6.89~15 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0fd13033d4e7fcf3fe2a36e1c7dcef8a06795988;p=thirdparty%2Fkernel%2Fstable.git x86/pvh: Call C code via the kernel virtual mapping commit e8fbc0d9cab6c1ee6403f42c0991b0c1d5dbc092 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: 7243b93345f7 ("xen/pvh: Bootstrap PVH guest") Tested-by: Jason Andryuk Reviewed-by: Jason Andryuk Signed-off-by: Ard Biesheuvel Message-ID: <20241009160438.3884381-8-ardb+git@google.com> Signed-off-by: Juergen Gross [ Stable context update ] Signed-off-by: Jason Andryuk Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S index c4365a05ab83b..fc46b4dfbd747 100644 --- a/arch/x86/platform/pvh/head.S +++ b/arch/x86/platform/pvh/head.S @@ -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