Commit a43ae4df authored by Marc Zyngier's avatar Marc Zyngier Committed by Catalin Marinas

arm64: Add 'ssbd' command-line option

On a system where the firmware implements ARCH_WORKAROUND_2,
it may be useful to either permanently enable or disable the
workaround for cases where the user decides that they'd rather
not get a trap overhead, and keep the mitigation permanently
on or off instead of switching it on exception entry/exit.

In any case, default to the mitigation being enabled.
Reviewed-by: default avatarJulien Grall <julien.grall@arm.com>
Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent a725e3dd
......@@ -4047,6 +4047,23 @@
expediting. Set to zero to disable automatic
expediting.
ssbd= [ARM64,HW]
Speculative Store Bypass Disable control
On CPUs that are vulnerable to the Speculative
Store Bypass vulnerability and offer a
firmware based mitigation, this parameter
indicates how the mitigation should be used:
force-on: Unconditionally enable mitigation for
for both kernel and userspace
force-off: Unconditionally disable mitigation for
for both kernel and userspace
kernel: Always enable mitigation in the
kernel, and offer a prctl interface
to allow userspace to register its
interest in being mitigated too.
stack_guard_gap= [MM]
override the default stack gap protection. The value
is in page units and it defines how many pages prior
......
......@@ -537,6 +537,12 @@ static inline u64 read_zcr_features(void)
return zcr;
}
#define ARM64_SSBD_UNKNOWN -1
#define ARM64_SSBD_FORCE_DISABLE 0
#define ARM64_SSBD_KERNEL 1
#define ARM64_SSBD_FORCE_ENABLE 2
#define ARM64_SSBD_MITIGATED 3
#endif /* __ASSEMBLY__ */
#endif
......@@ -235,6 +235,38 @@ enable_smccc_arch_workaround_1(const struct arm64_cpu_capabilities *entry)
#ifdef CONFIG_ARM64_SSBD
DEFINE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);
int ssbd_state __read_mostly = ARM64_SSBD_KERNEL;
static const struct ssbd_options {
const char *str;
int state;
} ssbd_options[] = {
{ "force-on", ARM64_SSBD_FORCE_ENABLE, },
{ "force-off", ARM64_SSBD_FORCE_DISABLE, },
{ "kernel", ARM64_SSBD_KERNEL, },
};
static int __init ssbd_cfg(char *buf)
{
int i;
if (!buf || !buf[0])
return -EINVAL;
for (i = 0; i < ARRAY_SIZE(ssbd_options); i++) {
int len = strlen(ssbd_options[i].str);
if (strncmp(buf, ssbd_options[i].str, len))
continue;
ssbd_state = ssbd_options[i].state;
return 0;
}
return -EINVAL;
}
early_param("ssbd", ssbd_cfg);
void __init arm64_update_smccc_conduit(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr,
int nr_inst)
......@@ -278,44 +310,83 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry,
int scope)
{
struct arm_smccc_res res;
bool supported = true;
bool required = true;
s32 val;
WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
if (psci_ops.smccc_version == SMCCC_VERSION_1_0)
if (psci_ops.smccc_version == SMCCC_VERSION_1_0) {
ssbd_state = ARM64_SSBD_UNKNOWN;
return false;
}
/*
* The probe function return value is either negative
* (unsupported or mitigated), positive (unaffected), or zero
* (requires mitigation). We only need to do anything in the
* last case.
*/
switch (psci_ops.conduit) {
case PSCI_CONDUIT_HVC:
arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
ARM_SMCCC_ARCH_WORKAROUND_2, &res);
if ((int)res.a0 != 0)
supported = false;
break;
case PSCI_CONDUIT_SMC:
arm_smccc_1_1_smc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
ARM_SMCCC_ARCH_WORKAROUND_2, &res);
if ((int)res.a0 != 0)
supported = false;
break;
default:
supported = false;
ssbd_state = ARM64_SSBD_UNKNOWN;
return false;
}
if (supported) {
__this_cpu_write(arm64_ssbd_callback_required, 1);
val = (s32)res.a0;
switch (val) {
case SMCCC_RET_NOT_SUPPORTED:
ssbd_state = ARM64_SSBD_UNKNOWN;
return false;
case SMCCC_RET_NOT_REQUIRED:
pr_info_once("%s mitigation not required\n", entry->desc);
ssbd_state = ARM64_SSBD_MITIGATED;
return false;
case SMCCC_RET_SUCCESS:
required = true;
break;
case 1: /* Mitigation not required on this CPU */
required = false;
break;
default:
WARN_ON(1);
return false;
}
switch (ssbd_state) {
case ARM64_SSBD_FORCE_DISABLE:
pr_info_once("%s disabled from command-line\n", entry->desc);
arm64_set_ssbd_mitigation(false);
required = false;
break;
case ARM64_SSBD_KERNEL:
if (required) {
__this_cpu_write(arm64_ssbd_callback_required, 1);
arm64_set_ssbd_mitigation(true);
}
break;
case ARM64_SSBD_FORCE_ENABLE:
pr_info_once("%s forced from command-line\n", entry->desc);
arm64_set_ssbd_mitigation(true);
required = true;
break;
default:
WARN_ON(1);
break;
}
return supported;
return required;
}
#endif /* CONFIG_ARM64_SSBD */
......
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