From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Mon, 14 Feb 2022 12:12:13 +0000 (+0000)
Subject: x86/hvm: Use __initdata_cf_clobber for hvm_funcs
X-Git-Tag: archive/raspbian/4.17.0-1+rpi1^2~33^2~921
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=8bf7240842c765b6fa13095572aa77c38ff27acf;p=xen.git

x86/hvm: Use __initdata_cf_clobber for hvm_funcs

Now that all calls through hvm_funcs are fully altcall'd, harden all the svm
and vmx function pointer targets.  This drops 106 endbr64 instructions.

Clobbering does come with a theoretical risk.  The non-pointer fields of
{svm,vmx}_function_table can in theory happen to form a bit pattern matching a
pointer into .text at a legal endbr64 instruction, but this is expected to be
implausible for anything liable to pass code review.

While at it, move hvm_funcs into __ro_after_init now that this exists.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index cdd1529014..709a4191ef 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -88,7 +88,7 @@ unsigned int opt_hvm_debug_level __read_mostly;
 integer_param("hvm_debug", opt_hvm_debug_level);
 #endif
 
-struct hvm_function_table hvm_funcs __read_mostly;
+struct hvm_function_table __ro_after_init hvm_funcs;
 
 /*
  * The I/O permission bitmap is globally shared by all HVM guests except
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 63535a74b5..b80d4af6cb 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -2513,7 +2513,7 @@ static void cf_check svm_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
     }
 }
 
-static struct hvm_function_table __initdata svm_function_table = {
+static struct hvm_function_table __initdata_cf_clobber svm_function_table = {
     .name                 = "SVM",
     .cpu_up_prepare       = svm_cpu_up_prepare,
     .cpu_dead             = svm_cpu_dead,
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 41db538a9e..758df33218 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2473,7 +2473,7 @@ static void cf_check vmx_set_reg(struct vcpu *v, unsigned int reg, uint64_t val)
     vmx_vmcs_exit(v);
 }
 
-static struct hvm_function_table __initdata vmx_function_table = {
+static struct hvm_function_table __initdata_cf_clobber vmx_function_table = {
     .name                 = "VMX",
     .cpu_up_prepare       = vmx_cpu_up_prepare,
     .cpu_dead             = vmx_cpu_dead,