From 9fa7b1a3e2bd501053cbae6a126d32e1d37865bd Mon Sep 17 00:00:00 2001
From: Marc Zyngier <marc.zyngier@arm.com>
Date: Tue, 29 May 2018 13:11:06 +0100
Subject: [PATCH 04/12] arm64: Call ARCH_WORKAROUND_2 on transitions between
EL0 and EL1
Git-commit: 8e2906245f1e3b0d027169d9f2e55ce0548cb96e
Patch-mainline: v4.18-rc1
References: bsc#1085308
In order for the kernel to protect itself, let's call the SSBD mitigation
implemented by the higher exception level (either hypervisor or firmware)
on each transition between userspace and kernel.
We must take the PSCI conduit into account in order to target the
right exception level, hence the introduction of a runtime patching
callback.
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Julien Grall <julien.grall@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
arch/arm64/kernel/cpu_errata.c | 24 ++++++++++++++++++++++++
arch/arm64/kernel/entry.S | 22 ++++++++++++++++++++++
include/linux/arm-smccc.h | 5 +++++
3 files changed, 51 insertions(+)
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 58028d9ebb1f..3394edc44ae8 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -214,6 +214,30 @@ static int qcom_enable_link_stack_sanitization(void *data)
}
#endif /* CONFIG_HARDEN_BRANCH_PREDICTOR */
+#ifdef CONFIG_ARM64_SSBD
+void __init arm64_update_smccc_conduit(struct alt_instr *alt,
+ __le32 *origptr, __le32 *updptr,
+ int nr_inst)
+{
+ u32 insn;
+
+ BUG_ON(nr_inst != 1);
+
+ switch (psci_ops.conduit) {
+ case PSCI_CONDUIT_HVC:
+ insn = aarch64_insn_get_hvc_value();
+ break;
+ case PSCI_CONDUIT_SMC:
+ insn = aarch64_insn_get_smc_value();
+ break;
+ default:
+ return;
+ }
+
+ *updptr = cpu_to_le32(insn);
+}
+#endif /* CONFIG_ARM64_SSBD */
+
#define MIDR_RANGE(model, min, max) \
.def_scope = SCOPE_LOCAL_CPU, \
.matches = is_affected_midr_range, \
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index cd3666e0b505..b3dcf1db3897 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -18,6 +18,7 @@
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include <linux/arm-smccc.h>
#include <linux/init.h>
#include <linux/linkage.h>
@@ -136,6 +137,18 @@ alternative_else_nop_endif
add \dst, \dst, #(\sym - .entry.tramp.text)
.endm
+ // This macro corrupts x0-x3. It is the caller's duty
+ // to save/restore them if required.
+ .macro apply_ssbd, state
+#ifdef CONFIG_ARM64_SSBD
+ mov w0, #ARM_SMCCC_ARCH_WORKAROUND_2
+ mov w1, #\state
+alternative_cb arm64_update_smccc_conduit
+ nop // Patched to SMC/HVC #0
+alternative_cb_end
+#endif
+ .endm
+
.macro kernel_entry, el, regsize = 64
.if \regsize == 32
mov w0, w0 // zero upper 32 bits of x0
@@ -162,6 +175,13 @@ alternative_else_nop_endif
ldr x19, [tsk, #TSK_TI_FLAGS] // since we can unmask debug
disable_step_tsk x19, x20 // exceptions when scheduling.
+ apply_ssbd 1
+
+#ifdef CONFIG_ARM64_SSBD
+ ldp x0, x1, [sp, #16 * 0]
+ ldp x2, x3, [sp, #16 * 1]
+#endif
+
mov x29, xzr // fp pointed to user-space
.else
add x21, sp, #S_FRAME_SIZE
@@ -304,6 +324,8 @@ alternative_if ARM64_WORKAROUND_845719
alternative_else_nop_endif
#endif
3:
+ apply_ssbd 0
+
.endif
msr elr_el1, x21 // set up the return data
diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index c89da86de99f..ca1d2cc2cdfa 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -80,6 +80,11 @@
ARM_SMCCC_SMC_32, \
0, 0x8000)
+#define ARM_SMCCC_ARCH_WORKAROUND_2 \
+ ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
+ ARM_SMCCC_SMC_32, \
+ 0, 0x7fff)
+
#ifndef __ASSEMBLY__
#include <linux/linkage.h>
--
2.11.0