[PATCH v2 38/70] x86/nmi: CFI hardening

From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Xen-devel <xen-devel@lists.xenproject.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: [PATCH v2 38/70] x86/nmi: CFI hardening
Date: Mon, 14 Feb 2022 12:50:55 +0000	[thread overview]
Message-ID: <20220214125127.17985-39-andrew.cooper3@citrix.com> (raw)
In-Reply-To: <20220214125127.17985-1-andrew.cooper3@citrix.com>

Control Flow Integrity schemes use toolchain and optionally hardware support
to help protect against call/jump/return oriented programming attacks.

Use cf_check to annotate function pointer targets for the toolchain.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
---
 xen/arch/x86/alternative.c        | 4 ++--
 xen/arch/x86/cpu/microcode/core.c | 3 ++-
 xen/arch/x86/crash.c              | 3 ++-
 xen/arch/x86/livepatch.c          | 2 +-
 xen/arch/x86/oprofile/nmi_int.c   | 2 +-
 xen/arch/x86/traps.c              | 3 ++-
 6 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/alternative.c b/xen/arch/x86/alternative.c
index 1cb531c9df83..436047abe021 100644
--- a/xen/arch/x86/alternative.c
+++ b/xen/arch/x86/alternative.c
@@ -324,8 +324,8 @@ static unsigned int __initdata alt_done;
  * condition where an NMI hits while we are midway though patching some
  * instructions in the NMI path.
  */
-static int __init nmi_apply_alternatives(const struct cpu_user_regs *regs,
-                                         int cpu)
+static int __init cf_check nmi_apply_alternatives(
+    const struct cpu_user_regs *regs, int cpu)
 {
     /*
      * More than one NMI may occur between the two set_nmi_callback() below.
diff --git a/xen/arch/x86/cpu/microcode/core.c b/xen/arch/x86/cpu/microcode/core.c
index c07f68ba350e..f84dafa82693 100644
--- a/xen/arch/x86/cpu/microcode/core.c
+++ b/xen/arch/x86/cpu/microcode/core.c
@@ -376,7 +376,8 @@ static int primary_thread_work(const struct microcode_patch *patch)
     return ret;
 }
 
-static int microcode_nmi_callback(const struct cpu_user_regs *regs, int cpu)
+static int cf_check microcode_nmi_callback(
+    const struct cpu_user_regs *regs, int cpu)
 {
     unsigned int primary = cpumask_first(this_cpu(cpu_sibling_mask));
     int ret;
diff --git a/xen/arch/x86/crash.c b/xen/arch/x86/crash.c
index f6264946a681..c383f718f5bd 100644
--- a/xen/arch/x86/crash.c
+++ b/xen/arch/x86/crash.c
@@ -36,7 +36,8 @@ static unsigned int crashing_cpu;
 static DEFINE_PER_CPU_READ_MOSTLY(bool, crash_save_done);
 
 /* This becomes the NMI handler for non-crashing CPUs, when Xen is crashing. */
-static int noreturn do_nmi_crash(const struct cpu_user_regs *regs, int cpu)
+static int noreturn cf_check do_nmi_crash(
+    const struct cpu_user_regs *regs, int cpu)
 {
     stac();
 
diff --git a/xen/arch/x86/livepatch.c b/xen/arch/x86/livepatch.c
index d056b1ed8b41..37c9b8435eda 100644
--- a/xen/arch/x86/livepatch.c
+++ b/xen/arch/x86/livepatch.c
@@ -175,7 +175,7 @@ static nmi_callback_t *saved_nmi_callback;
  * Note that because of this NOP code the do_nmi is not safely patchable.
  * Also if we do receive 'real' NMIs we have lost them.
  */
-static int mask_nmi_callback(const struct cpu_user_regs *regs, int cpu)
+static int cf_check mask_nmi_callback(const struct cpu_user_regs *regs, int cpu)
 {
     /* TODO: Handle missing NMI/MCE.*/
     return 1;
diff --git a/xen/arch/x86/oprofile/nmi_int.c b/xen/arch/x86/oprofile/nmi_int.c
index 6ebe20bd1d3e..a90b72825818 100644
--- a/xen/arch/x86/oprofile/nmi_int.c
+++ b/xen/arch/x86/oprofile/nmi_int.c
@@ -95,7 +95,7 @@ bool nmi_oprofile_send_virq(void)
 	return v;
 }
 
-static int nmi_callback(const struct cpu_user_regs *regs, int cpu)
+static int cf_check nmi_callback(const struct cpu_user_regs *regs, int cpu)
 {
 	int xen_mode, ovf;
 
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 485bd66971db..7b957101934e 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -752,7 +752,8 @@ static cpumask_t show_state_mask;
 static bool opt_show_all;
 boolean_param("async-show-all", opt_show_all);
 
-static int nmi_show_execution_state(const struct cpu_user_regs *regs, int cpu)
+static int cf_check nmi_show_execution_state(
+    const struct cpu_user_regs *regs, int cpu)
 {
     if ( !cpumask_test_cpu(cpu, &show_state_mask) )
         return 0;
-- 
2.11.0


