From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Thu, 28 Oct 2021 12:48:54 +0000 (+0100)
Subject: x86/mtrr: CFI hardening
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=142923eaaf71f6cf38053da13c6dba598aff8839;p=people%2Ftklengyel%2Fxen.git

x86/mtrr: CFI hardening

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>
---

diff --git a/xen/arch/x86/cpu/mtrr/generic.c b/xen/arch/x86/cpu/mtrr/generic.c
index 7cf4cd01f3..47aaf76226 100644
--- a/xen/arch/x86/cpu/mtrr/generic.c
+++ b/xen/arch/x86/cpu/mtrr/generic.c
@@ -287,7 +287,8 @@ static void set_fixed_range(int msr, bool *changed, unsigned int *msrwords)
 	}
 }
 
-int generic_get_free_region(unsigned long base, unsigned long size, int replace_reg)
+int cf_check generic_get_free_region(
+    unsigned long base, unsigned long size, int replace_reg)
 /*  [SUMMARY] Get a free MTRR.
     <base> The starting (base) address of the region.
     <size> The size (in bytes) of the region.
@@ -309,8 +310,8 @@ int generic_get_free_region(unsigned long base, unsigned long size, int replace_
 	return -ENOSPC;
 }
 
-static void generic_get_mtrr(unsigned int reg, unsigned long *base,
-			     unsigned long *size, mtrr_type *type)
+static void cf_check generic_get_mtrr(
+    unsigned int reg, unsigned long *base, unsigned long *size, mtrr_type *type)
 {
 	uint64_t _mask, _base;
 
@@ -499,7 +500,7 @@ static void post_set(bool pge)
 	spin_unlock(&set_atomicity_lock);
 }
 
-static void generic_set_all(void)
+static void cf_check generic_set_all(void)
 {
 	unsigned long mask, count;
 	unsigned long flags;
@@ -522,8 +523,8 @@ static void generic_set_all(void)
 	}
 }
 
-static void generic_set_mtrr(unsigned int reg, unsigned long base,
-			     unsigned long size, mtrr_type type)
+static void cf_check generic_set_mtrr(
+    unsigned int reg, unsigned long base, unsigned long size, mtrr_type type)
 /*  [SUMMARY] Set variable MTRR register on the local CPU.
     <reg> The register to set.
     <base> The base address of the region.
@@ -566,7 +567,8 @@ static void generic_set_mtrr(unsigned int reg, unsigned long base,
 	local_irq_restore(flags);
 }
 
-int generic_validate_add_page(unsigned long base, unsigned long size, unsigned int type)
+int cf_check generic_validate_add_page(
+    unsigned long base, unsigned long size, unsigned int type)
 {
 	unsigned long lbase, last;
 
@@ -584,7 +586,7 @@ int generic_validate_add_page(unsigned long base, unsigned long size, unsigned i
 }
 
 
-static int generic_have_wrcomb(void)
+static int cf_check generic_have_wrcomb(void)
 {
 	unsigned long config;
 	rdmsrl(MSR_MTRRcap, config);
diff --git a/xen/arch/x86/cpu/mtrr/mtrr.h b/xen/arch/x86/cpu/mtrr/mtrr.h
index 9a406e6f61..c7fd44daab 100644
--- a/xen/arch/x86/cpu/mtrr/mtrr.h
+++ b/xen/arch/x86/cpu/mtrr/mtrr.h
@@ -24,10 +24,10 @@ struct mtrr_ops {
 	int	(*have_wrcomb)(void);
 };
 
-extern int generic_get_free_region(unsigned long base, unsigned long size,
-				   int replace_reg);
-extern int generic_validate_add_page(unsigned long base, unsigned long size,
-				     unsigned int type);
+int cf_check generic_get_free_region(
+    unsigned long base, unsigned long size, int replace_reg);
+int cf_check generic_validate_add_page(
+    unsigned long base, unsigned long size, unsigned int type);
 
 extern const struct mtrr_ops generic_mtrr_ops;