From: Juergen Gross Date: Thu, 17 Oct 2024 13:27:31 +0000 (+0200) Subject: x86/xen: remove hypercall page X-Git-Tag: v6.1.121~3 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4c24703978b44d4bb95413a6b85c3254a5fa9bc1;p=thirdparty%2Fkernel%2Fstable.git x86/xen: remove hypercall page commit 7fa0da5373685e7ed249af3fa317ab1e1ba8b0a6 upstream. The hypercall page is no longer needed. It can be removed, as from the Xen perspective it is optional. But, from Linux's perspective, it removes naked RET instructions that escape the speculative protections that Call Depth Tracking and/or Untrain Ret are trying to achieve. This is part of XSA-466 / CVE-2024-53241. Reported-by: Andrew Cooper Signed-off-by: Juergen Gross Reviewed-by: Andrew Cooper Reviewed-by: Jan Beulich Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h index f165d9bfcc142..9b4eddd5833ae 100644 --- a/arch/x86/include/asm/xen/hypercall.h +++ b/arch/x86/include/asm/xen/hypercall.h @@ -88,8 +88,6 @@ struct xen_dm_op_buf; * there aren't more than 5 arguments...) */ -extern struct { char _entry[32]; } hypercall_page[]; - void xen_hypercall_func(void); DECLARE_STATIC_CALL(xen_hypercall, xen_hypercall_func); diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 6006c42876ea3..31f4a4dd8c62a 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -26,8 +26,6 @@ #include "smp.h" #include "pmu.h" -EXPORT_SYMBOL_GPL(hypercall_page); - DEFINE_STATIC_CALL(xen_hypercall, xen_hypercall_hvm); EXPORT_STATIC_CALL_TRAMP(xen_hypercall); diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c index 3ed6db6e805c2..3a453207f3c7f 100644 --- a/arch/x86/xen/enlighten_hvm.c +++ b/arch/x86/xen/enlighten_hvm.c @@ -108,15 +108,8 @@ static void __init init_hvm_pv_info(void) /* PVH set up hypercall page in xen_prepare_pvh(). */ if (xen_pvh_domain()) pv_info.name = "Xen PVH"; - else { - u64 pfn; - uint32_t msr; - + else pv_info.name = "Xen HVM"; - msr = cpuid_ebx(base + 2); - pfn = __pa(hypercall_page); - wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32)); - } xen_setup_features(); diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c index ada3868c02c23..00ee9399fd0c3 100644 --- a/arch/x86/xen/enlighten_pvh.c +++ b/arch/x86/xen/enlighten_pvh.c @@ -27,17 +27,10 @@ EXPORT_SYMBOL_GPL(xen_pvh); void __init xen_pvh_init(struct boot_params *boot_params) { - u32 msr; - u64 pfn; - xen_pvh = 1; xen_domain_type = XEN_HVM_DOMAIN; xen_start_flags = pvh_start_info.flags; - msr = cpuid_ebx(xen_cpuid_base() + 2); - pfn = __pa(hypercall_page); - wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32)); - if (xen_initial_domain()) x86_init.oem.arch_setup = xen_add_preferred_consoles; x86_init.oem.banner = xen_banner; diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index 3635065d7560b..1cf94caa7600c 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -22,28 +22,6 @@ #include #include -.pushsection .noinstr.text, "ax" - .balign PAGE_SIZE -SYM_CODE_START(hypercall_page) - .rept (PAGE_SIZE / 32) - UNWIND_HINT_FUNC - ANNOTATE_NOENDBR - ANNOTATE_UNRET_SAFE - ret - /* - * Xen will write the hypercall page, and sort out ENDBR. - */ - .skip 31, 0xcc - .endr - -#define HYPERCALL(n) \ - .equ xen_hypercall_##n, hypercall_page + __HYPERVISOR_##n * 32; \ - .type xen_hypercall_##n, @function; .size xen_hypercall_##n, 32 -#include -#undef HYPERCALL -SYM_CODE_END(hypercall_page) -.popsection - #ifdef CONFIG_XEN_PV __INIT SYM_CODE_START(startup_xen) @@ -176,7 +154,6 @@ SYM_FUNC_END(xen_hypercall_intel) #ifdef CONFIG_XEN_PV ELFNOTE(Xen, XEN_ELFNOTE_ENTRY, _ASM_PTR startup_xen) #endif - ELFNOTE(Xen, XEN_ELFNOTE_HYPERCALL_PAGE, _ASM_PTR hypercall_page) ELFNOTE(Xen, XEN_ELFNOTE_FEATURES, .ascii "!writable_page_tables|pae_pgdir_above_4gb") ELFNOTE(Xen, XEN_ELFNOTE_SUPPORTED_FEATURES,