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Subject[PATCH v4 16/17] arm64: Add ARM_SMCCC_ARCH_WORKAROUND_1 BP hardening support
Date
Add the detection and runtime code for ARM_SMCCC_ARCH_WORKAROUND_1.
It is lovely. Really.

Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm64/kernel/bpi.S | 20 +++++++++++++
arch/arm64/kernel/cpu_errata.c | 68 +++++++++++++++++++++++++++++++++++++++++-
2 files changed, 87 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/bpi.S b/arch/arm64/kernel/bpi.S
index 76225c2611ea..fdeed629f2c6 100644
--- a/arch/arm64/kernel/bpi.S
+++ b/arch/arm64/kernel/bpi.S
@@ -17,6 +17,7 @@
*/

#include <linux/linkage.h>
+#include <linux/arm-smccc.h>

.macro ventry target
.rept 31
@@ -85,3 +86,22 @@ ENTRY(__qcom_hyp_sanitize_link_stack_start)
.endr
ldp x29, x30, [sp], #16
ENTRY(__qcom_hyp_sanitize_link_stack_end)
+
+.macro smccc_workaround_1 inst
+ sub sp, sp, #(8 * 4)
+ stp x2, x3, [sp, #(8 * 0)]
+ stp x0, x1, [sp, #(8 * 2)]
+ mov w0, #ARM_SMCCC_ARCH_WORKAROUND_1
+ \inst #0
+ ldp x2, x3, [sp, #(8 * 0)]
+ ldp x0, x1, [sp, #(8 * 2)]
+ add sp, sp, #(8 * 4)
+.endm
+
+ENTRY(__smccc_workaround_1_smc_start)
+ smccc_workaround_1 smc
+ENTRY(__smccc_workaround_1_smc_end)
+
+ENTRY(__smccc_workaround_1_hvc_start)
+ smccc_workaround_1 hvc
+ENTRY(__smccc_workaround_1_hvc_end)
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index ed6881882231..9e77809a3b23 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -70,6 +70,10 @@ DEFINE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data);
extern char __psci_hyp_bp_inval_start[], __psci_hyp_bp_inval_end[];
extern char __qcom_hyp_sanitize_link_stack_start[];
extern char __qcom_hyp_sanitize_link_stack_end[];
+extern char __smccc_workaround_1_smc_start[];
+extern char __smccc_workaround_1_smc_end[];
+extern char __smccc_workaround_1_hvc_start[];
+extern char __smccc_workaround_1_hvc_end[];

static void __copy_hyp_vect_bpi(int slot, const char *hyp_vecs_start,
const char *hyp_vecs_end)
@@ -116,6 +120,10 @@ static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
#define __psci_hyp_bp_inval_end NULL
#define __qcom_hyp_sanitize_link_stack_start NULL
#define __qcom_hyp_sanitize_link_stack_end NULL
+#define __smccc_workaround_1_smc_start NULL
+#define __smccc_workaround_1_smc_end NULL
+#define __smccc_workaround_1_hvc_start NULL
+#define __smccc_workaround_1_hvc_end NULL

static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
const char *hyp_vecs_start,
@@ -142,17 +150,75 @@ static void install_bp_hardening_cb(const struct arm64_cpu_capabilities *entry,
__install_bp_hardening_cb(fn, hyp_vecs_start, hyp_vecs_end);
}

+#include <uapi/linux/psci.h>
+#include <linux/arm-smccc.h>
#include <linux/psci.h>

+static void call_smc_arch_workaround_1(void)
+{
+ arm_smccc_1_1_smc(ARM_SMCCC_ARCH_WORKAROUND_1, NULL);
+}
+
+static void call_hvc_arch_workaround_1(void)
+{
+ arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_WORKAROUND_1, NULL);
+}
+
+static bool check_smccc_arch_workaround_1(const struct arm64_cpu_capabilities *entry)
+{
+ bp_hardening_cb_t cb;
+ void *smccc_start, *smccc_end;
+ struct arm_smccc_res res;
+
+ if (!entry->matches(entry, SCOPE_LOCAL_CPU))
+ return false;
+
+ if (psci_ops.smccc_version == SMCCC_VERSION_1_0)
+ return false;
+
+ switch (psci_ops.conduit) {
+ case PSCI_CONDUIT_HVC:
+ arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+ ARM_SMCCC_ARCH_WORKAROUND_1, &res);
+ if (res.a0)
+ return false;
+ cb = call_hvc_arch_workaround_1;
+ smccc_start = __smccc_workaround_1_hvc_start;
+ smccc_end = __smccc_workaround_1_hvc_end;
+ break;
+
+ case PSCI_CONDUIT_SMC:
+ arm_smccc_1_1_smc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+ ARM_SMCCC_ARCH_WORKAROUND_1, &res);
+ if (res.a0)
+ return false;
+ cb = call_smc_arch_workaround_1;
+ smccc_start = __smccc_workaround_1_smc_start;
+ smccc_end = __smccc_workaround_1_smc_end;
+ break;
+
+ default:
+ return false;
+ }
+
+ install_bp_hardening_cb(entry, cb, smccc_start, smccc_end);
+
+ return true;
+}
+
static int enable_psci_bp_hardening(void *data)
{
const struct arm64_cpu_capabilities *entry = data;

- if (psci_ops.get_version)
+ if (psci_ops.get_version) {
+ if (check_smccc_arch_workaround_1(entry))
+ return 0;
+
install_bp_hardening_cb(entry,
(bp_hardening_cb_t)psci_ops.get_version,
__psci_hyp_bp_inval_start,
__psci_hyp_bp_inval_end);
+ }

return 0;
}
--
2.14.2
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