1 files changed, 401 insertions, 0 deletions
diff --git a/arch/arm64/kernel/pi/idreg-override.c b/arch/arm64/kernel/pi/idreg-override.c
new file mode 100644
index 000000000000..aad399796e81
--- /dev/null
+++ b/arch/arm64/kernel/pi/idreg-override.c
@@ -0,0 +1,401 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Early cpufeature override framework
+ *
+ * Copyright (C) 2020 Google LLC
+ * Author: Marc Zyngier <maz@kernel.org>
+ */
+
+#include <linux/ctype.h>
+#include <linux/kernel.h>
+#include <linux/libfdt.h>
+
+#include <asm/cacheflush.h>
+#include <asm/cpufeature.h>
+#include <asm/setup.h>
+
+#include "pi.h"
+
+#define FTR_DESC_NAME_LEN	20
+#define FTR_DESC_FIELD_LEN	10
+#define FTR_ALIAS_NAME_LEN	30
+#define FTR_ALIAS_OPTION_LEN	116
+
+static u64 __boot_status __initdata;
+
+typedef bool filter_t(u64 val);
+
+struct ftr_set_desc {
+	char 				name[FTR_DESC_NAME_LEN];
+	PREL64(struct arm64_ftr_override, override);
+	struct {
+		char			name[FTR_DESC_FIELD_LEN];
+		u8			shift;
+		u8			width;
+		PREL64(filter_t,	filter);
+	} 				fields[];
+};
+
+#define FIELD(n, s, f)	{ .name = n, .shift = s, .width = 4, .filter = f }
+
+static bool __init mmfr1_vh_filter(u64 val)
+{
+	/*
+	 * If we ever reach this point while running VHE, we're
+	 * guaranteed to be on one of these funky, VHE-stuck CPUs. If
+	 * the user was trying to force nVHE on us, proceed with
+	 * attitude adjustment.
+	 */
+	return !(__boot_status == (BOOT_CPU_FLAG_E2H | BOOT_CPU_MODE_EL2) &&
+		 val == 0);
+}
+
+static const struct ftr_set_desc mmfr1 __prel64_initconst = {
+	.name		= "id_aa64mmfr1",
+	.override	= &id_aa64mmfr1_override,
+	.fields		= {
+		FIELD("vh", ID_AA64MMFR1_EL1_VH_SHIFT, mmfr1_vh_filter),
+		{}
+	},
+};
+
+
+static bool __init mmfr2_varange_filter(u64 val)
+{
+	int __maybe_unused feat;
+
+	if (val)
+		return false;
+
+#ifdef CONFIG_ARM64_LPA2
+	feat = cpuid_feature_extract_signed_field(read_sysreg(id_aa64mmfr0_el1),
+						  ID_AA64MMFR0_EL1_TGRAN_SHIFT);
+	if (feat >= ID_AA64MMFR0_EL1_TGRAN_LPA2) {
+		id_aa64mmfr0_override.val |=
+			(ID_AA64MMFR0_EL1_TGRAN_LPA2 - 1) << ID_AA64MMFR0_EL1_TGRAN_SHIFT;
+		id_aa64mmfr0_override.mask |= 0xfU << ID_AA64MMFR0_EL1_TGRAN_SHIFT;
+	}
+#endif
+	return true;
+}
+
+static const struct ftr_set_desc mmfr2 __prel64_initconst = {
+	.name		= "id_aa64mmfr2",
+	.override	= &id_aa64mmfr2_override,
+	.fields		= {
+		FIELD("varange", ID_AA64MMFR2_EL1_VARange_SHIFT, mmfr2_varange_filter),
+		{}
+	},
+};
+
+static bool __init pfr0_sve_filter(u64 val)
+{
+	/*
+	 * Disabling SVE also means disabling all the features that
+	 * are associated with it. The easiest way to do it is just to
+	 * override id_aa64zfr0_el1 to be 0.
+	 */
+	if (!val) {
+		id_aa64zfr0_override.val = 0;
+		id_aa64zfr0_override.mask = GENMASK(63, 0);
+	}
+
+	return true;
+}
+
+static const struct ftr_set_desc pfr0 __prel64_initconst = {
+	.name		= "id_aa64pfr0",
+	.override	= &id_aa64pfr0_override,
+	.fields		= {
+	        FIELD("sve", ID_AA64PFR0_EL1_SVE_SHIFT, pfr0_sve_filter),
+		{}
+	},
+};
+
+static bool __init pfr1_sme_filter(u64 val)
+{
+	/*
+	 * Similarly to SVE, disabling SME also means disabling all
+	 * the features that are associated with it. Just set
+	 * id_aa64smfr0_el1 to 0 and don't look back.
+	 */
+	if (!val) {
+		id_aa64smfr0_override.val = 0;
+		id_aa64smfr0_override.mask = GENMASK(63, 0);
+	}
+
+	return true;
+}
+
+static const struct ftr_set_desc pfr1 __prel64_initconst = {
+	.name		= "id_aa64pfr1",
+	.override	= &id_aa64pfr1_override,
+	.fields		= {
+		FIELD("bt", ID_AA64PFR1_EL1_BT_SHIFT, NULL ),
+		FIELD("mte", ID_AA64PFR1_EL1_MTE_SHIFT, NULL),
+		FIELD("sme", ID_AA64PFR1_EL1_SME_SHIFT, pfr1_sme_filter),
+		{}
+	},
+};
+
+static const struct ftr_set_desc isar1 __prel64_initconst = {
+	.name		= "id_aa64isar1",
+	.override	= &id_aa64isar1_override,
+	.fields		= {
+		FIELD("gpi", ID_AA64ISAR1_EL1_GPI_SHIFT, NULL),
+		FIELD("gpa", ID_AA64ISAR1_EL1_GPA_SHIFT, NULL),
+		FIELD("api", ID_AA64ISAR1_EL1_API_SHIFT, NULL),
+		FIELD("apa", ID_AA64ISAR1_EL1_APA_SHIFT, NULL),
+		{}
+	},
+};
+
+static const struct ftr_set_desc isar2 __prel64_initconst = {
+	.name		= "id_aa64isar2",
+	.override	= &id_aa64isar2_override,
+	.fields		= {
+		FIELD("gpa3", ID_AA64ISAR2_EL1_GPA3_SHIFT, NULL),
+		FIELD("apa3", ID_AA64ISAR2_EL1_APA3_SHIFT, NULL),
+		FIELD("mops", ID_AA64ISAR2_EL1_MOPS_SHIFT, NULL),
+		{}
+	},
+};
+
+static const struct ftr_set_desc smfr0 __prel64_initconst = {
+	.name		= "id_aa64smfr0",
+	.override	= &id_aa64smfr0_override,
+	.fields		= {
+		FIELD("smever", ID_AA64SMFR0_EL1_SMEver_SHIFT, NULL),
+		/* FA64 is a one bit field... :-/ */
+		{ "fa64", ID_AA64SMFR0_EL1_FA64_SHIFT, 1, },
+		{}
+	},
+};
+
+static bool __init hvhe_filter(u64 val)
+{
+	u64 mmfr1 = read_sysreg(id_aa64mmfr1_el1);
+
+	return (val == 1 &&
+		lower_32_bits(__boot_status) == BOOT_CPU_MODE_EL2 &&
+		cpuid_feature_extract_unsigned_field(mmfr1,
+						     ID_AA64MMFR1_EL1_VH_SHIFT));
+}
+
+static const struct ftr_set_desc sw_features __prel64_initconst = {
+	.name		= "arm64_sw",
+	.override	= &arm64_sw_feature_override,
+	.fields		= {
+		FIELD("nokaslr", ARM64_SW_FEATURE_OVERRIDE_NOKASLR, NULL),
+		FIELD("hvhe", ARM64_SW_FEATURE_OVERRIDE_HVHE, hvhe_filter),
+		FIELD("rodataoff", ARM64_SW_FEATURE_OVERRIDE_RODATA_OFF, NULL),
+		{}
+	},
+};
+
+static const
+PREL64(const struct ftr_set_desc, reg) regs[] __prel64_initconst = {
+	{ &mmfr1	},
+	{ &mmfr2	},
+	{ &pfr0 	},
+	{ &pfr1 	},
+	{ &isar1	},
+	{ &isar2	},
+	{ &smfr0	},
+	{ &sw_features	},
+};
+
+static const struct {
+	char	alias[FTR_ALIAS_NAME_LEN];
+	char	feature[FTR_ALIAS_OPTION_LEN];
+} aliases[] __initconst = {
+	{ "kvm_arm.mode=nvhe",		"id_aa64mmfr1.vh=0" },
+	{ "kvm_arm.mode=protected",	"id_aa64mmfr1.vh=0" },
+	{ "arm64.nosve",		"id_aa64pfr0.sve=0" },
+	{ "arm64.nosme",		"id_aa64pfr1.sme=0" },
+	{ "arm64.nobti",		"id_aa64pfr1.bt=0" },
+	{ "arm64.nopauth",
+	  "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
+	  "id_aa64isar1.api=0 id_aa64isar1.apa=0 "
+	  "id_aa64isar2.gpa3=0 id_aa64isar2.apa3=0"	   },
+	{ "arm64.nomops",		"id_aa64isar2.mops=0" },
+	{ "arm64.nomte",		"id_aa64pfr1.mte=0" },
+	{ "nokaslr",			"arm64_sw.nokaslr=1" },
+	{ "rodata=off",			"arm64_sw.rodataoff=1" },
+	{ "arm64.nolva",		"id_aa64mmfr2.varange=0" },
+};
+
+static int __init parse_hexdigit(const char *p, u64 *v)
+{
+	// skip "0x" if it comes next
+	if (p[0] == '0' && tolower(p[1]) == 'x')
+		p += 2;
+
+	// check whether the RHS is a single hex digit
+	if (!isxdigit(p[0]) || (p[1] && !isspace(p[1])))
+		return -EINVAL;
+
+	*v = tolower(*p) - (isdigit(*p) ? '0' : 'a' - 10);
+	return 0;
+}
+
+static int __init find_field(const char *cmdline, char *opt, int len,
+			     const struct ftr_set_desc *reg, int f, u64 *v)
+{
+	int flen = strlen(reg->fields[f].name);
+
+	// append '<fieldname>=' to obtain '<name>.<fieldname>='
+	memcpy(opt + len, reg->fields[f].name, flen);
+	len += flen;
+	opt[len++] = '=';
+
+	if (memcmp(cmdline, opt, len))
+		return -1;
+
+	return parse_hexdigit(cmdline + len, v);
+}
+
+static void __init match_options(const char *cmdline)
+{
+	char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2];
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(regs); i++) {
+		const struct ftr_set_desc *reg = prel64_pointer(regs[i].reg);
+		struct arm64_ftr_override *override;
+		int len = strlen(reg->name);
+		int f;
+
+		override = prel64_pointer(reg->override);
+
+		// set opt[] to '<name>.'
+		memcpy(opt, reg->name, len);
+		opt[len++] = '.';
+
+		for (f = 0; reg->fields[f].name[0] != '\0'; f++) {
+			u64 shift = reg->fields[f].shift;
+			u64 width = reg->fields[f].width ?: 4;
+			u64 mask = GENMASK_ULL(shift + width - 1, shift);
+			bool (*filter)(u64 val);
+			u64 v;
+
+			if (find_field(cmdline, opt, len, reg, f, &v))
+				continue;
+
+			/*
+			 * If an override gets filtered out, advertise
+			 * it by setting the value to the all-ones while
+			 * clearing the mask... Yes, this is fragile.
+			 */
+			filter = prel64_pointer(reg->fields[f].filter);
+			if (filter && !filter(v)) {
+				override->val  |= mask;
+				override->mask &= ~mask;
+				continue;
+			}
+
+			override->val  &= ~mask;
+			override->val  |= (v << shift) & mask;
+			override->mask |= mask;
+
+			return;
+		}
+	}
+}
+
+static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
+{
+	do {
+		char buf[256];
+		size_t len;
+		int i;
+
+		cmdline = skip_spaces(cmdline);
+
+		/* terminate on "--" appearing on the command line by itself */
+		if (cmdline[0] == '-' && cmdline[1] == '-' && isspace(cmdline[2]))
+			return;
+
+		for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++) {
+			if (len >= sizeof(buf) - 1)
+				break;
+			if (cmdline[len] == '-')
+				buf[len] = '_';
+			else
+				buf[len] = cmdline[len];
+		}
+		if (!len)
+			return;
+
+		buf[len] = 0;
+
+		cmdline += len;
+
+		match_options(buf);
+
+		for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++)
+			if (!memcmp(buf, aliases[i].alias, len + 1))
+				__parse_cmdline(aliases[i].feature, false);
+	} while (1);
+}
+
+static __init const u8 *get_bootargs_cmdline(const void *fdt, int node)
+{
+	static char const bootargs[] __initconst = "bootargs";
+	const u8 *prop;
+
+	if (node < 0)
+		return NULL;
+
+	prop = fdt_getprop(fdt, node, bootargs, NULL);
+	if (!prop)
+		return NULL;
+
+	return strlen(prop) ? prop : NULL;
+}
+
+static __init void parse_cmdline(const void *fdt, int chosen)
+{
+	static char const cmdline[] __initconst = CONFIG_CMDLINE;
+	const u8 *prop = get_bootargs_cmdline(fdt, chosen);
+
+	if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
+		__parse_cmdline(cmdline, true);
+
+	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
+		__parse_cmdline(prop, true);
+}
+
+void __init init_feature_override(u64 boot_status, const void *fdt,
+				  int chosen)
+{
+	struct arm64_ftr_override *override;
+	const struct ftr_set_desc *reg;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(regs); i++) {
+		reg = prel64_pointer(regs[i].reg);
+		override = prel64_pointer(reg->override);
+
+		override->val  = 0;
+		override->mask = 0;
+	}
+
+	__boot_status = boot_status;
+
+	parse_cmdline(fdt, chosen);
+
+	for (i = 0; i < ARRAY_SIZE(regs); i++) {
+		reg = prel64_pointer(regs[i].reg);
+		override = prel64_pointer(reg->override);
+		dcache_clean_inval_poc((unsigned long)override,
+				       (unsigned long)(override + 1));
+	}
+}
+
+char * __init skip_spaces(const char *str)
+{
+	while (isspace(*str))
+		++str;
+	return (char *)str;
+}