1 // SPDX-License-Identifier: GPL-2.0-only
6  *   https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability
20 #include <linux/arm-smccc.h>
69  * - Mitigated in hardware and advertised by ID_AA64PFR0_EL1.CSV2.
70  * - Mitigated in hardware and listed in our "safe list".
71  * - Mitigated in software by firmware.
72  * - Mitigated in software by a CPU-specific dance in the kernel and a
73  *   firmware call at EL2.
74  * - Vulnerable.
94 		pr_info_once("spectre-v2 mitigation disabled by command line option\n");  in spectre_v2_mitigations_off()
188 	 * the door when we're a guest. Skip the hyp-vectors work.  in install_bp_hardening_cb()
254 	 * Prefer a CPU-specific workaround if it exists. Note that we  in spectre_v2_enable_fw_mitigation()
255 	 * still rely on firmware for the mitigation at EL2.  in spectre_v2_enable_fw_mitigation()
276  * Spectre-v3a.
299 		data->slot += HYP_VECTOR_INDIRECT;  in spectre_v3a_enable_mitigation()
308  * - Mitigated in hardware and listed in our "safe list".
309  * - Mitigated in hardware via PSTATE.SSBS.
310  * - Mitigated in software by firmware (sometimes referred to as SSBD).
315  * on a per-task basis, but can also be forced on for the kernel, necessitating
316  * both context-switch *and* entry/exit hooks. To make it even worse, some CPUs
318  * being stale when re-entering the kernel. The usual big.LITTLE caveats apply,
319  * so you can have systems that have both firmware and SSBS mitigations. This
322  * be opt-in for userspace. Yes, really, the cure is worse than the disease.
324  * The only good part is that if the firmware mitigation is present, then it is
326  * vulnerable CPU if one of the boot CPUs is using the firmware mitigation.
328  * Give me a VAX-11/780 any day of the week...
332 /* This is the per-cpu state tracking whether we need to talk to firmware */
347 	{ "force-on",	SPECTRE_V4_POLICY_MITIGATION_ENABLED, },
348 	{ "force-off",	SPECTRE_V4_POLICY_MITIGATION_DISABLED, },
356 		return -EINVAL;  in parse_spectre_v4_param()
361 		if (strncmp(str, param->str, strlen(param->str)))  in parse_spectre_v4_param()
364 		__spectre_v4_policy = param->policy;  in parse_spectre_v4_param()
368 	return -EINVAL;  in parse_spectre_v4_param()
385 		pr_info_once("spectre-v4 mitigation disabled by command-line option\n");  in spectre_v4_mitigations_off()
487 		regs->pstate |= PSR_SSBS_BIT;  in ssbs_emulation_handler()
489 		regs->pstate &= ~PSR_SSBS_BIT;  in ssbs_emulation_handler()
528 	/* SCTLR_EL1.DSSBS was initialised to 0 during boot */  in spectre_v4_enable_hw_mitigation()
534  * Patch a branch over the Spectre-v4 mitigation code with a NOP so that
535  * we fallthrough and check whether firmware needs to be called on this CPU.
541 	BUG_ON(nr_inst != 1); /* Branch -> NOP */  in spectre_v4_patch_fw_mitigation_enable()
554  * Patch a NOP in the Spectre-v4 mitigation code with an SMC/HVC instruction
555  * to call into firmware to adjust the mitigation state.
563 	BUG_ON(nr_inst != 1); /* NOP -> HVC/SMC */  in spectre_v4_patch_fw_mitigation_conduit()
618 		regs->pstate |= bit;  in __update_pstate_ssbs()
620 		regs->pstate &= ~bit;  in __update_pstate_ssbs()
626 	bool ssbs = false, kthread = tsk->flags & PF_KTHREAD;  in spectre_v4_enable_task_mitigation()
637  * The Spectre-v4 mitigation can be controlled via a prctl() from userspace.
664 		 * re-enabled.  in ssbd_prctl_set()
667 			return -EPERM;  in ssbd_prctl_set()
671 		 * off and we again prevent it from being re-enabled.  in ssbd_prctl_set()
674 			return -EPERM;  in ssbd_prctl_set()
685 			return -EPERM;  in ssbd_prctl_set()
693 			return -EPERM;  in ssbd_prctl_set()
706 			return -EPERM;  in ssbd_prctl_set()
713 		return -ERANGE;  in ssbd_prctl_set()
727 		return -ENODEV;  in arch_prctl_spec_ctrl_set()
770 		return -ENODEV;  in arch_prctl_spec_ctrl_get()