From 31bd2bbc5662f7a2d47f0b84ce286a40d98a883b Mon Sep 17 00:00:00 2001
From: Will Deacon <will.deacon@arm.com>
Date: Wed, 3 Jan 2018 11:17:58 +0000
Subject: [PATCH 11/24] arm64: Add skeleton to harden the branch predictor
against aliasing attacks
Git-commit: 0f15adbb2861ce6f75ccfc5a92b19eae0ef327d0
Patch-mainline: Queued
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
References: bsc#1068032
Aliasing attacks against CPU branch predictors can allow an attacker to
redirect speculative control flow on some CPUs and potentially divulge
information from one context to another.
This patch adds initial skeleton code behind a new Kconfig option to
enable implementation-specific mitigations against these attacks for
CPUs that are affected.
Co-developed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
arch/arm64/Kconfig | 17 +++++++++
arch/arm64/include/asm/cpucaps.h | 3 +-
arch/arm64/include/asm/mmu.h | 37 ++++++++++++++++++++
arch/arm64/include/asm/sysreg.h | 1 +
arch/arm64/kernel/Makefile | 4 +++
arch/arm64/kernel/bpi.S | 55 +++++++++++++++++++++++++++++
arch/arm64/kernel/cpu_errata.c | 74 ++++++++++++++++++++++++++++++++++++++++
arch/arm64/kernel/cpufeature.c | 1 +
arch/arm64/kernel/entry.S | 7 ++--
arch/arm64/mm/context.c | 2 ++
arch/arm64/mm/fault.c | 16 +++++++++
11 files changed, 214 insertions(+), 3 deletions(-)
create mode 100644 arch/arm64/kernel/bpi.S
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 20a7802fd5fc..0c2ad31ecf37 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -790,6 +790,23 @@ config UNMAP_KERNEL_AT_EL0
If unsure, say Y.
+config HARDEN_BRANCH_PREDICTOR
+ bool "Harden the branch predictor against aliasing attacks" if EXPERT
+ default y
+ help
+ Speculation attacks against some high-performance processors rely on
+ being able to manipulate the branch predictor for a victim context by
+ executing aliasing branches in the attacker context. Such attacks
+ can be partially mitigated against by clearing internal branch
+ predictor state and limiting the prediction logic in some situations.
+
+ This config option will take CPU-specific actions to harden the
+ branch predictor against aliasing attacks and may rely on specific
+ instruction sequences or control bits being set by the system
+ firmware.
+
+ If unsure, say Y.
+
menuconfig ARMV8_DEPRECATED
bool "Emulate deprecated/obsolete ARMv8 instructions"
depends on COMPAT
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 4337f4c729aa..2720d3d3492e 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -39,7 +39,8 @@
#define ARM64_WORKAROUND_QCOM_FALKOR_E1003 18
#define ARM64_WORKAROUND_858921 19
#define ARM64_UNMAP_KERNEL_AT_EL0 20
+#define ARM64_HARDEN_BRANCH_PREDICTOR 21
-#define ARM64_NCAPS 21
+#define ARM64_NCAPS 22
#endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 12f710c69b87..88c292d12a7a 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -40,6 +40,43 @@ static inline bool arm64_kernel_unmapped_at_el0(void)
cpus_have_const_cap(ARM64_UNMAP_KERNEL_AT_EL0);
}
+typedef void (*bp_hardening_cb_t)(void);
+
+struct bp_hardening_data {
+ int hyp_vectors_slot;
+ bp_hardening_cb_t fn;
+};
+
+#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
+extern char __bp_harden_hyp_vecs_start[], __bp_harden_hyp_vecs_end[];
+
+DECLARE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data);
+
+static inline struct bp_hardening_data *arm64_get_bp_hardening_data(void)
+{
+ return this_cpu_ptr(&bp_hardening_data);
+}
+
+static inline void arm64_apply_bp_hardening(void)
+{
+ struct bp_hardening_data *d;
+
+ if (!cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR))
+ return;
+
+ d = arm64_get_bp_hardening_data();
+ if (d->fn)
+ d->fn();
+}
+#else
+static inline struct bp_hardening_data *arm64_get_bp_hardening_data(void)
+{
+ return NULL;
+}
+
+static inline void arm64_apply_bp_hardening(void) { }
+#endif /* CONFIG_HARDEN_BRANCH_PREDICTOR */
+
extern void paging_init(void);
extern void bootmem_init(void);
extern void __iomem *early_io_map(phys_addr_t phys, unsigned long virt);
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 1849f621b397..cd27302a5007 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -315,6 +315,7 @@
/* id_aa64pfr0 */
#define ID_AA64PFR0_CSV3_SHIFT 60
+#define ID_AA64PFR0_CSV2_SHIFT 56
#define ID_AA64PFR0_GIC_SHIFT 24
#define ID_AA64PFR0_ASIMD_SHIFT 20
#define ID_AA64PFR0_FP_SHIFT 16
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 1dcb69d3d0e5..947b8a5fa874 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -54,6 +54,10 @@ arm64-obj-$(CONFIG_ARM64_RELOC_TEST) += arm64-reloc-test.o
arm64-reloc-test-y := reloc_test_core.o reloc_test_syms.o
arm64-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
+ifeq ($(CONFIG_KVM),y)
+arm64-obj-$(CONFIG_HARDEN_BRANCH_PREDICTOR) += bpi.o
+endif
+
obj-y += $(arm64-obj-y) vdso/ probes/
obj-m += $(arm64-obj-m)
head-y := head.o
diff --git a/arch/arm64/kernel/bpi.S b/arch/arm64/kernel/bpi.S
new file mode 100644
index 000000000000..06a931eb2673
--- /dev/null
+++ b/arch/arm64/kernel/bpi.S
@@ -0,0 +1,55 @@
+/*
+ * Contains CPU specific branch predictor invalidation sequences
+ *
+ * Copyright (C) 2018 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/linkage.h>
+
+.macro ventry target
+ .rept 31
+ nop
+ .endr
+ b \target
+.endm
+
+.macro vectors target
+ ventry \target + 0x000
+ ventry \target + 0x080
+ ventry \target + 0x100
+ ventry \target + 0x180
+
+ ventry \target + 0x200
+ ventry \target + 0x280
+ ventry \target + 0x300
+ ventry \target + 0x380
+
+ ventry \target + 0x400
+ ventry \target + 0x480
+ ventry \target + 0x500
+ ventry \target + 0x580
+
+ ventry \target + 0x600
+ ventry \target + 0x680
+ ventry \target + 0x700
+ ventry \target + 0x780
+.endm
+
+ .align 11
+ENTRY(__bp_harden_hyp_vecs_start)
+ .rept 4
+ vectors __kvm_hyp_vector
+ .endr
+ENTRY(__bp_harden_hyp_vecs_end)
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 2ed2a7657711..1e4393f39c39 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -46,6 +46,80 @@ static int cpu_enable_trap_ctr_access(void *__unused)
return 0;
}
+#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
+#include <asm/mmu_context.h>
+#include <asm/cacheflush.h>
+
+DEFINE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data);
+
+#ifdef CONFIG_KVM
+static void __copy_hyp_vect_bpi(int slot, const char *hyp_vecs_start,
+ const char *hyp_vecs_end)
+{
+ void *dst = lm_alias(__bp_harden_hyp_vecs_start + slot * SZ_2K);
+ int i;
+
+ for (i = 0; i < SZ_2K; i += 0x80)
+ memcpy(dst + i, hyp_vecs_start, hyp_vecs_end - hyp_vecs_start);
+
+ flush_icache_range((uintptr_t)dst, (uintptr_t)dst + SZ_2K);
+}
+
+static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
+ const char *hyp_vecs_start,
+ const char *hyp_vecs_end)
+{
+ static int last_slot = -1;
+ static DEFINE_SPINLOCK(bp_lock);
+ int cpu, slot = -1;
+
+ spin_lock(&bp_lock);
+ for_each_possible_cpu(cpu) {
+ if (per_cpu(bp_hardening_data.fn, cpu) == fn) {
+ slot = per_cpu(bp_hardening_data.hyp_vectors_slot, cpu);
+ break;
+ }
+ }
+
+ if (slot == -1) {
+ last_slot++;
+ BUG_ON(((__bp_harden_hyp_vecs_end - __bp_harden_hyp_vecs_start)
+ / SZ_2K) <= last_slot);
+ slot = last_slot;
+ __copy_hyp_vect_bpi(slot, hyp_vecs_start, hyp_vecs_end);
+ }
+
+ __this_cpu_write(bp_hardening_data.hyp_vectors_slot, slot);
+ __this_cpu_write(bp_hardening_data.fn, fn);
+ spin_unlock(&bp_lock);
+}
+#else
+static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
+ const char *hyp_vecs_start,
+ const char *hyp_vecs_end)
+{
+ __this_cpu_write(bp_hardening_data.fn, fn);
+}
+#endif /* CONFIG_KVM */
+
+static void install_bp_hardening_cb(const struct arm64_cpu_capabilities *entry,
+ bp_hardening_cb_t fn,
+ const char *hyp_vecs_start,
+ const char *hyp_vecs_end)
+{
+ u64 pfr0;
+
+ if (!entry->matches(entry, SCOPE_LOCAL_CPU))
+ return;
+
+ pfr0 = read_cpuid(ID_AA64PFR0_EL1);
+ if (cpuid_feature_extract_unsigned_field(pfr0, ID_AA64PFR0_CSV2_SHIFT))
+ return;
+
+ __install_bp_hardening_cb(fn, hyp_vecs_start, hyp_vecs_end);
+}
+#endif /* CONFIG_HARDEN_BRANCH_PREDICTOR */
+
#define MIDR_RANGE(model, min, max) \
.def_scope = SCOPE_LOCAL_CPU, \
.matches = is_affected_midr_range, \
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index afbee0761b0f..afc0b093554a 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -106,6 +106,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV3_SHIFT, 4, 0),
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV2_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_EXACT, ID_AA64PFR0_GIC_SHIFT, 4, 0),
S_ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_ASIMD_SHIFT, 4, ID_AA64PFR0_ASIMD_NI),
S_ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_FP_SHIFT, 4, ID_AA64PFR0_FP_NI),
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 38b5250e2c7c..d7fddfca1f72 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -718,12 +718,15 @@ el0_ia:
* Instruction abort handling
*/
mrs x26, far_el1
- enable_daif
+ enable_da_f
+#ifdef CONFIG_TRACE_IRQFLAGS
+ bl trace_hardirqs_off
+#endif
ct_user_exit
mov x0, x26
mov x1, x25
mov x2, sp
- bl do_mem_abort
+ bl do_el0_ia_bp_hardening
b ret_to_user
el0_fpsimd_acc:
/*
diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
index 6890bb6fc2ed..60280ea75820 100644
--- a/arch/arm64/mm/context.c
+++ b/arch/arm64/mm/context.c
@@ -243,6 +243,8 @@ asmlinkage void post_ttbr_update_workaround(void)
"ic iallu; dsb nsh; isb",
ARM64_WORKAROUND_CAVIUM_27456,
CONFIG_CAVIUM_ERRATUM_27456));
+
+ arm64_apply_bp_hardening();
}
static int asids_init(void)
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 85f5df20ce37..f0857353626f 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -669,6 +669,22 @@ asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
arm64_notify_die("", regs, &info, esr);
}
+asmlinkage void __exception do_el0_ia_bp_hardening(unsigned long addr,
+ unsigned int esr,
+ struct pt_regs *regs)
+{
+ /*
+ * We've taken an instruction abort from userspace and not yet
+ * re-enabled IRQs. If the address is a kernel address, apply
+ * BP hardening prior to enabling IRQs and pre-emption.
+ */
+ if (addr > TASK_SIZE)
+ arm64_apply_bp_hardening();
+
+ local_irq_enable();
+ do_mem_abort(addr, esr, regs);
+}
+
/*
* Handle stack alignment exceptions.
*/
--
2.11.0