cpufeature.c

 * Check for CPU features that are used in early boot
 * based on the Boot CPU value.
 */
static void check_early_cpu_features(void)
{
	verify_cpu_run_el();
	verify_cpu_asid_bits();
}

static void
verify_local_elf_hwcaps(const struct arm64_cpu_capabilities *caps)
{

	for (; caps->matches; caps++)
		if (cpus_have_elf_hwcap(caps) && !caps->matches(caps, SCOPE_LOCAL_CPU)) {
			pr_crit("CPU%d: missing HWCAP: %s\n",
					smp_processor_id(), caps->desc);
			cpu_die_early();
		}
}

static void
verify_local_cpu_features(const struct arm64_cpu_capabilities *caps)
{
	for (; caps->matches; caps++) {
		if (!cpus_have_cap(caps->capability))
			continue;
		/*
		 * If the new CPU misses an advertised feature, we cannot proceed
		 * further, park the cpu.
		 */
		if (!caps->matches(caps, SCOPE_LOCAL_CPU)) {
			pr_crit("CPU%d: missing feature: %s\n",
					smp_processor_id(), caps->desc);
			cpu_die_early();
		}
		if (caps->enable)
			caps->enable(NULL);
	}
}

/*
 * Run through the enabled system capabilities and enable() it on this CPU.
 * The capabilities were decided based on the available CPUs at the boot time.
 * Any new CPU should match the system wide status of the capability. If the
 * new CPU doesn't have a capability which the system now has enabled, we
 * cannot do anything to fix it up and could cause unexpected failures. So
 * we park the CPU.
 */
static void verify_local_cpu_capabilities(void)
{
	verify_local_cpu_errata_workarounds();
	verify_local_cpu_features(arm64_features);
	verify_local_elf_hwcaps(arm64_elf_hwcaps);
	if (system_supports_32bit_el0())
		verify_local_elf_hwcaps(compat_elf_hwcaps);
}

void check_local_cpu_capabilities(void)
{
	/*
	 * All secondary CPUs should conform to the early CPU features
	 * in use by the kernel based on boot CPU.
	 */
	check_early_cpu_features();

	/*
	 * If we haven't finalised the system capabilities, this CPU gets
	 * a chance to update the errata work arounds.
	 * Otherwise, this CPU should verify that it has all the system
	 * advertised capabilities.
	 */
	if (!sys_caps_initialised)
		update_cpu_errata_workarounds();
	else
		verify_local_cpu_capabilities();
}

static void __init setup_feature_capabilities(void)
{
	update_cpu_capabilities(arm64_features, "detected feature:");
	enable_cpu_capabilities(arm64_features);
}

/*
 * Check if the current CPU has a given feature capability.
 * Should be called from non-preemptible context.
 */
bool this_cpu_has_cap(unsigned int cap)
{
	const struct arm64_cpu_capabilities *caps;

	if (WARN_ON(preemptible()))
		return false;

	for (caps = arm64_features; caps->desc; caps++)
		if (caps->capability == cap && caps->matches)
			return caps->matches(caps, SCOPE_LOCAL_CPU);

	return false;
}

void __init setup_cpu_features(void)
{
	u32 cwg;
	int cls;

	/* Set the CPU feature capabilies */
	setup_feature_capabilities();
	enable_errata_workarounds();
	setup_elf_hwcaps(arm64_elf_hwcaps);

	if (system_supports_32bit_el0())
		setup_elf_hwcaps(compat_elf_hwcaps);

	/* Advertise that we have computed the system capabilities */
	set_sys_caps_initialised();

	/*
	 * Check for sane CTR_EL0.CWG value.
	 */
	cwg = cache_type_cwg();
	cls = cache_line_size();
	if (!cwg)
		pr_warn("No Cache Writeback Granule information, assuming cache line size %d\n",
			cls);
	if (L1_CACHE_BYTES < cls)
		pr_warn("L1_CACHE_BYTES smaller than the Cache Writeback Granule (%d < %d)\n",
			L1_CACHE_BYTES, cls);
}

static bool __maybe_unused
cpufeature_pan_not_uao(const struct arm64_cpu_capabilities *entry, int __unused)
{
	return (cpus_have_const_cap(ARM64_HAS_PAN) && !cpus_have_const_cap(ARM64_HAS_UAO));
}

/*
 * We emulate only the following system register space.
 * Op0 = 0x3, CRn = 0x0, Op1 = 0x0, CRm = [0, 4 - 7]
 * See Table C5-6 System instruction encodings for System register accesses,
 * ARMv8 ARM(ARM DDI 0487A.f) for more details.
 */
static inline bool __attribute_const__ is_emulated(u32 id)
{
	return (sys_reg_Op0(id) == 0x3 &&
		sys_reg_CRn(id) == 0x0 &&
		sys_reg_Op1(id) == 0x0 &&
		(sys_reg_CRm(id) == 0 ||
		 ((sys_reg_CRm(id) >= 4) && (sys_reg_CRm(id) <= 7))));
}

/*
 * With CRm == 0, reg should be one of :
 * MIDR_EL1, MPIDR_EL1 or REVIDR_EL1.
 */
static inline int emulate_id_reg(u32 id, u64 *valp)
{
	switch (id) {
	case SYS_MIDR_EL1:
		*valp = read_cpuid_id();
		break;
	case SYS_MPIDR_EL1:
		*valp = SYS_MPIDR_SAFE_VAL;
		break;
	case SYS_REVIDR_EL1:
		/* IMPLEMENTATION DEFINED values are emulated with 0 */
		*valp = 0;
		break;
	default:
		return -EINVAL;
	}

	return 0;
}

static int emulate_sys_reg(u32 id, u64 *valp)
{
	struct arm64_ftr_reg *regp;

	if (!is_emulated(id))
		return -EINVAL;

	if (sys_reg_CRm(id) == 0)
		return emulate_id_reg(id, valp);

	regp = get_arm64_ftr_reg(id);
	if (regp)
		*valp = arm64_ftr_reg_user_value(regp);
	else
		/*
		 * The untracked registers are either IMPLEMENTATION DEFINED
		 * (e.g, ID_AFR0_EL1) or reserved RAZ.
		 */
		*valp = 0;
	return 0;
}

static int emulate_mrs(struct pt_regs *regs, u32 insn)
{
	int rc;
	u32 sys_reg, dst;
	u64 val;

	/*
	 * sys_reg values are defined as used in mrs/msr instruction.
	 * shift the imm value to get the encoding.
	 */
	sys_reg = (u32)aarch64_insn_decode_immediate(AARCH64_INSN_IMM_16, insn) << 5;
	rc = emulate_sys_reg(sys_reg, &val);
	if (!rc) {
		dst = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RT, insn);
		regs->user_regs.regs[dst] = val;
		regs->pc += 4;
	}

	return rc;
}

static struct undef_hook mrs_hook = {
	.instr_mask = 0xfff00000,
	.instr_val  = 0xd5300000,
	.pstate_mask = COMPAT_PSR_MODE_MASK,
	.pstate_val = PSR_MODE_EL0t,
	.fn = emulate_mrs,
};

static int __init enable_mrs_emulation(void)
{
	register_undef_hook(&mrs_hook);
	return 0;
}

late_initcall(enable_mrs_emulation);