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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen stable-4.15] x86: Introduce support for CET-IBT
commit 96233cf87b4ead3f6480ed21c3ed2836dcc29418
Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Thu Oct 21 18:38:50 2021 +0100
Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Mar 25 17:10:38 2022 +0000
x86: Introduce support for CET-IBT
CET Indirect Branch Tracking is a hardware feature designed to provide
forward-edge control flow integrity, protecting against jump/call oriented
programming.
IBT requires the placement of endbr{32,64} instructions at the target of
every
indirect call/jmp, and every entrypoint.
It is necessary to check for both compiler and assembler support, as the
notrack prefix can be emitted in certain cases.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
(cherry picked from commit 3667f7f8f7c471e94e58cf35a95f09a0fe5c1290)
Note: For backports to 4.14 thru 4.16, we are deliberately not using
-mmanual-endbr as done in staging, as an intermediate approach which
is not too invasive to backport.
x86/cet: Force -fno-jump-tables for CET-IBT
Both GCC and Clang have a (mis)feature where, even with
-fcf-protection=branch, jump tables are created using a notrack jump rather
than using endbr's in each case statement.
This is incompatible with the safety properties we want in Xen, and enforced
by not setting MSR_S_CET.NOTRACK_EN. The consequence is a fatal #CP[endbr].
-fno-jump-tables is generally active as a side effect of
CONFIG_INDIRECT_THUNK (retpoline), but as of c/s 95d9ab461436 ("x86/Kconfig:
introduce option to select retpoline usage"), we explicitly support turning
retpoline off.
Fixes: 3667f7f8f7c4 ("x86: Introduce support for CET-IBT")
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
(cherry picked from commit 9d4a44380d273de22d5753883cbf5581795ff24d)
---
Config.mk | 1 -
xen/arch/x86/Kconfig | 17 +++++++++++++++++
xen/arch/x86/arch.mk | 9 +++++++++
xen/arch/x86/configs/pvshim_defconfig | 1 +
xen/include/asm-x86/asm-defns.h | 6 ++++++
xen/include/asm-x86/cpufeature.h | 1 +
xen/include/asm-x86/cpufeatures.h | 1 +
7 files changed, 35 insertions(+), 1 deletion(-)
diff --git a/Config.mk b/Config.mk
index f467b43beb..ae5eaecd62 100644
--- a/Config.mk
+++ b/Config.mk
@@ -205,7 +205,6 @@ APPEND_CFLAGS += $(foreach i, $(APPEND_INCLUDES), -I$(i))
EMBEDDED_EXTRA_CFLAGS := -nopie -fno-stack-protector -fno-stack-protector-all
EMBEDDED_EXTRA_CFLAGS += -fno-exceptions -fno-asynchronous-unwind-tables
-EMBEDDED_EXTRA_CFLAGS += -fcf-protection=none
XEN_EXTFILES_URL ?= http://xenbits.xen.org/xen-extfiles
# All the files at that location were downloaded from elsewhere on
diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 27cb793165..4fdb39af3e 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -38,6 +38,11 @@ config HAS_AS_CET_SS
# binutils >= 2.29 or LLVM >= 6
def_bool $(as-instr,wrssq %rax$(comma)0;setssbsy)
+config HAS_CC_CET_IBT
+ # GCC >= 9 and binutils >= 2.29
+ # Retpoline check to work around
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93654
+ def_bool $(cc-option,-fcf-protection=branch
-mindirect-branch=thunk-extern) && $(as-instr,endbr64)
+
menu "Architecture Features"
source "arch/Kconfig"
@@ -119,6 +124,18 @@ config XEN_SHSTK
When CET-SS is active, 32bit PV guests cannot be used. Backwards
compatiblity can be provided via the PV Shim mechanism.
+config XEN_IBT
+ bool "Supervisor Indirect Branch Tracking"
+ depends on HAS_CC_CET_IBT
+ default y
+ help
+ Control-flow Enforcement Technology (CET) is a set of features in
+ hardware designed to combat Return-oriented Programming (ROP, also
+ call/jump COP/JOP) attacks. Indirect Branch Tracking is one CET
+ feature designed to provide function pointer protection.
+
+ This option arranges for Xen to use CET-IBT for its own protection.
+
config SHADOW_PAGING
bool "Shadow Paging"
default !PV_SHIM_EXCLUSIVE
diff --git a/xen/arch/x86/arch.mk b/xen/arch/x86/arch.mk
index ce0c1a0e7f..033048ab6b 100644
--- a/xen/arch/x86/arch.mk
+++ b/xen/arch/x86/arch.mk
@@ -46,6 +46,15 @@ CFLAGS-$(CONFIG_INDIRECT_THUNK) +=
-mindirect-branch=thunk-extern
CFLAGS-$(CONFIG_INDIRECT_THUNK) += -mindirect-branch-register
CFLAGS-$(CONFIG_INDIRECT_THUNK) += -fno-jump-tables
+ifdef CONFIG_XEN_IBT
+# Force -fno-jump-tables to work around
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104816
+# https://github.com/llvm/llvm-project/issues/54247
+CFLAGS += -fcf-protection=branch -fno-jump-tables
+else
+$(call cc-option-add,CFLAGS,CC,-fcf-protection=none)
+endif
+
# If supported by the compiler, reduce stack alignment to 8 bytes. But allow
# this to be overridden elsewhere.
$(call cc-option-add,CFLAGS-stack-boundary,CC,-mpreferred-stack-boundary=3)
diff --git a/xen/arch/x86/configs/pvshim_defconfig
b/xen/arch/x86/configs/pvshim_defconfig
index cdf5776610..23ba51e728 100644
--- a/xen/arch/x86/configs/pvshim_defconfig
+++ b/xen/arch/x86/configs/pvshim_defconfig
@@ -9,6 +9,7 @@ CONFIG_EXPERT=y
CONFIG_SCHED_NULL=y
# Disable features not used by the PV shim
# CONFIG_XEN_SHSTK is not set
+# CONFIG_XEN_IBT is not set
# CONFIG_GRANT_TABLE is not set
# CONFIG_HYPFS is not set
# CONFIG_BIGMEM is not set
diff --git a/xen/include/asm-x86/asm-defns.h b/xen/include/asm-x86/asm-defns.h
index 505f39ad5f..8bd9007731 100644
--- a/xen/include/asm-x86/asm-defns.h
+++ b/xen/include/asm-x86/asm-defns.h
@@ -57,6 +57,12 @@
INDIRECT_BRANCH jmp \arg
.endm
+#ifdef CONFIG_XEN_IBT
+# define ENDBR64 endbr64
+#else
+# define ENDBR64
+#endif
+
.macro guest_access_mask_ptr ptr:req, scratch1:req, scratch2:req
#if defined(CONFIG_SPECULATIVE_HARDEN_GUEST_ACCESS)
/*
diff --git a/xen/include/asm-x86/cpufeature.h b/xen/include/asm-x86/cpufeature.h
index fe04d98fa1..460d38356c 100644
--- a/xen/include/asm-x86/cpufeature.h
+++ b/xen/include/asm-x86/cpufeature.h
@@ -153,6 +153,7 @@
#define cpu_has_lfence_dispatch boot_cpu_has(X86_FEATURE_LFENCE_DISPATCH)
#define cpu_has_xen_lbr boot_cpu_has(X86_FEATURE_XEN_LBR)
#define cpu_has_xen_shstk boot_cpu_has(X86_FEATURE_XEN_SHSTK)
+#define cpu_has_xen_ibt boot_cpu_has(X86_FEATURE_XEN_IBT)
#define cpu_has_msr_tsc_aux (cpu_has_rdtscp || cpu_has_rdpid)
diff --git a/xen/include/asm-x86/cpufeatures.h
b/xen/include/asm-x86/cpufeatures.h
index 6c8f432aee..fe2f97354f 100644
--- a/xen/include/asm-x86/cpufeatures.h
+++ b/xen/include/asm-x86/cpufeatures.h
@@ -39,6 +39,7 @@ XEN_CPUFEATURE(SC_VERW_PV, X86_SYNTH(23)) /* VERW used
by Xen for PV */
XEN_CPUFEATURE(SC_VERW_HVM, X86_SYNTH(24)) /* VERW used by Xen for HVM */
XEN_CPUFEATURE(SC_VERW_IDLE, X86_SYNTH(25)) /* VERW used by Xen for idle
*/
XEN_CPUFEATURE(XEN_SHSTK, X86_SYNTH(26)) /* Xen uses CET Shadow Stacks
*/
+XEN_CPUFEATURE(XEN_IBT, X86_SYNTH(27)) /* Xen uses CET Indirect
Branch Tracking */
/* Bug words follow the synthetic words. */
#define X86_NR_BUG 1
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.15
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