[mirror_ubuntu-jammy-kernel.git] / arch / x86 / kernel / cpu / bugs.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 1994  Linus Torvalds
 *
 *  Cyrix stuff, June 1998 by:
 *	- Rafael R. Reilova (moved everything from head.S),
 *        <rreilova@ececs.uc.edu>
 *	- Channing Corn (tests & fixes),
 *	- Andrew D. Balsa (code cleanup).
 */
#include <linux/init.h>
#include <linux/utsname.h>
#include <linux/cpu.h>
#include <linux/module.h>

#include <asm/nospec-branch.h>
#include <asm/cmdline.h>
#include <asm/bugs.h>
#include <asm/processor.h>
#include <asm/processor-flags.h>
#include <asm/fpu/internal.h>
#include <asm/msr.h>
#include <asm/paravirt.h>
#include <asm/alternative.h>
#include <asm/pgtable.h>
#include <asm/set_memory.h>
#include <asm/intel-family.h>

static void __init spectre_v2_select_mitigation(void);

void __init check_bugs(void)
{
	identify_boot_cpu();

	if (!IS_ENABLED(CONFIG_SMP)) {
		pr_info("CPU: ");
		print_cpu_info(&boot_cpu_data);
	}

	/* Select the proper spectre mitigation before patching alternatives */
	spectre_v2_select_mitigation();

#ifdef CONFIG_X86_32
	/*
	 * Check whether we are able to run this kernel safely on SMP.
	 *
	 * - i386 is no longer supported.
	 * - In order to run on anything without a TSC, we need to be
	 *   compiled for a i486.
	 */
	if (boot_cpu_data.x86 < 4)
		panic("Kernel requires i486+ for 'invlpg' and other features");

	init_utsname()->machine[1] =
		'0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
	alternative_instructions();

	fpu__init_check_bugs();
#else /* CONFIG_X86_64 */
	alternative_instructions();

	/*
	 * Make sure the first 2MB area is not mapped by huge pages
	 * There are typically fixed size MTRRs in there and overlapping
	 * MTRRs into large pages causes slow downs.
	 *
	 * Right now we don't do that with gbpages because there seems
	 * very little benefit for that case.
	 */
	if (!direct_gbpages)
		set_memory_4k((unsigned long)__va(0), 1);
#endif
}

/* The kernel command line selection */
enum spectre_v2_mitigation_cmd {
	SPECTRE_V2_CMD_NONE,
	SPECTRE_V2_CMD_AUTO,
	SPECTRE_V2_CMD_FORCE,
	SPECTRE_V2_CMD_RETPOLINE,
	SPECTRE_V2_CMD_RETPOLINE_GENERIC,
	SPECTRE_V2_CMD_RETPOLINE_AMD,
};

static const char *spectre_v2_strings[] = {
	[SPECTRE_V2_NONE]			= "Vulnerable",
	[SPECTRE_V2_RETPOLINE_MINIMAL]		= "Vulnerable: Minimal generic ASM retpoline",
	[SPECTRE_V2_RETPOLINE_MINIMAL_AMD]	= "Vulnerable: Minimal AMD ASM retpoline",
	[SPECTRE_V2_RETPOLINE_GENERIC]		= "Mitigation: Full generic retpoline",
	[SPECTRE_V2_RETPOLINE_AMD]		= "Mitigation: Full AMD retpoline",
};

#undef pr_fmt
#define pr_fmt(fmt)     "Spectre V2 : " fmt

static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE;

#ifdef RETPOLINE
static bool spectre_v2_bad_module;

bool retpoline_module_ok(bool has_retpoline)
{
	if (spectre_v2_enabled == SPECTRE_V2_NONE || has_retpoline)
		return true;

	pr_err("System may be vulnerable to spectre v2\n");
	spectre_v2_bad_module = true;
	return false;
}

static inline const char *spectre_v2_module_string(void)
{
	return spectre_v2_bad_module ? " - vulnerable module loaded" : "";
}
#else
static inline const char *spectre_v2_module_string(void) { return ""; }
#endif

static void __init spec2_print_if_insecure(const char *reason)
{
	if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
		pr_info("%s selected on command line.\n", reason);
}

static void __init spec2_print_if_secure(const char *reason)
{
	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
		pr_info("%s selected on command line.\n", reason);
}

static inline bool retp_compiler(void)
{
	return __is_defined(RETPOLINE);
}

static inline bool match_option(const char *arg, int arglen, const char *opt)
{
	int len = strlen(opt);

	return len == arglen && !strncmp(arg, opt, len);
}

static const struct {
	const char *option;
	enum spectre_v2_mitigation_cmd cmd;
	bool secure;
} mitigation_options[] = {
	{ "off",               SPECTRE_V2_CMD_NONE,              false },
	{ "on",                SPECTRE_V2_CMD_FORCE,             true },
	{ "retpoline",         SPECTRE_V2_CMD_RETPOLINE,         false },
	{ "retpoline,amd",     SPECTRE_V2_CMD_RETPOLINE_AMD,     false },
	{ "retpoline,generic", SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
	{ "auto",              SPECTRE_V2_CMD_AUTO,              false },
};

static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
{
	char arg[20];
	int ret, i;
	enum spectre_v2_mitigation_cmd cmd = SPECTRE_V2_CMD_AUTO;

	if (cmdline_find_option_bool(boot_command_line, "nospectre_v2"))
		return SPECTRE_V2_CMD_NONE;
	else {
		ret = cmdline_find_option(boot_command_line, "spectre_v2", arg,
					  sizeof(arg));
		if (ret < 0)
			return SPECTRE_V2_CMD_AUTO;

		for (i = 0; i < ARRAY_SIZE(mitigation_options); i++) {
			if (!match_option(arg, ret, mitigation_options[i].option))
				continue;
			cmd = mitigation_options[i].cmd;
			break;
		}

		if (i >= ARRAY_SIZE(mitigation_options)) {
			pr_err("unknown option (%s). Switching to AUTO select\n",
			       mitigation_options[i].option);
			return SPECTRE_V2_CMD_AUTO;
		}
	}

	if ((cmd == SPECTRE_V2_CMD_RETPOLINE ||
	     cmd == SPECTRE_V2_CMD_RETPOLINE_AMD ||
	     cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC) &&
	    !IS_ENABLED(CONFIG_RETPOLINE)) {
		pr_err("%s selected but not compiled in. Switching to AUTO select\n",
		       mitigation_options[i].option);
		return SPECTRE_V2_CMD_AUTO;
	}

	if (cmd == SPECTRE_V2_CMD_RETPOLINE_AMD &&
	    boot_cpu_data.x86_vendor != X86_VENDOR_AMD) {
		pr_err("retpoline,amd selected but CPU is not AMD. Switching to AUTO select\n");
		return SPECTRE_V2_CMD_AUTO;
	}

	if (mitigation_options[i].secure)
		spec2_print_if_secure(mitigation_options[i].option);
	else
		spec2_print_if_insecure(mitigation_options[i].option);

	return cmd;
}

/* Check for Skylake-like CPUs (for RSB handling) */
static bool __init is_skylake_era(void)
{
	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
	    boot_cpu_data.x86 == 6) {
		switch (boot_cpu_data.x86_model) {
		case INTEL_FAM6_SKYLAKE_MOBILE:
		case INTEL_FAM6_SKYLAKE_DESKTOP:
		case INTEL_FAM6_SKYLAKE_X:
		case INTEL_FAM6_KABYLAKE_MOBILE:
		case INTEL_FAM6_KABYLAKE_DESKTOP:
			return true;
		}
	}
	return false;
}

static void __init spectre_v2_select_mitigation(void)
{
	enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline();
	enum spectre_v2_mitigation mode = SPECTRE_V2_NONE;

	/*
	 * If the CPU is not affected and the command line mode is NONE or AUTO
	 * then nothing to do.
	 */
	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) &&
	    (cmd == SPECTRE_V2_CMD_NONE || cmd == SPECTRE_V2_CMD_AUTO))
		return;

	switch (cmd) {
	case SPECTRE_V2_CMD_NONE:
		return;

	case SPECTRE_V2_CMD_FORCE:
	case SPECTRE_V2_CMD_AUTO:
		if (IS_ENABLED(CONFIG_RETPOLINE))
			goto retpoline_auto;
		break;
	case SPECTRE_V2_CMD_RETPOLINE_AMD:
		if (IS_ENABLED(CONFIG_RETPOLINE))
			goto retpoline_amd;
		break;
	case SPECTRE_V2_CMD_RETPOLINE_GENERIC:
		if (IS_ENABLED(CONFIG_RETPOLINE))
			goto retpoline_generic;
		break;
	case SPECTRE_V2_CMD_RETPOLINE:
		if (IS_ENABLED(CONFIG_RETPOLINE))
			goto retpoline_auto;
		break;
	}
	pr_err("kernel not compiled with retpoline; no mitigation available!");
	return;

retpoline_auto:
	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
	retpoline_amd:
		if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
			pr_err("LFENCE not serializing. Switching to generic retpoline\n");
			goto retpoline_generic;
		}
		mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_AMD :
					 SPECTRE_V2_RETPOLINE_MINIMAL_AMD;
		setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);
		setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
	} else {
	retpoline_generic:
		mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_GENERIC :
					 SPECTRE_V2_RETPOLINE_MINIMAL;
		setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
	}

	spectre_v2_enabled = mode;
	pr_info("%s\n", spectre_v2_strings[mode]);

	/*
	 * If neither SMEP or KPTI are available, there is a risk of
	 * hitting userspace addresses in the RSB after a context switch
	 * from a shallow call stack to a deeper one. To prevent this fill
	 * the entire RSB, even when using IBRS.
	 *
	 * Skylake era CPUs have a separate issue with *underflow* of the
	 * RSB, when they will predict 'ret' targets from the generic BTB.
	 * The proper mitigation for this is IBRS. If IBRS is not supported
	 * or deactivated in favour of retpolines the RSB fill on context
	 * switch is required.
	 */
	if ((!boot_cpu_has(X86_FEATURE_PTI) &&
	     !boot_cpu_has(X86_FEATURE_SMEP)) || is_skylake_era()) {
		setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
		pr_info("Filling RSB on context switch\n");
	}

	/* Initialize Indirect Branch Prediction Barrier if supported */
	if (boot_cpu_has(X86_FEATURE_IBPB)) {
		setup_force_cpu_cap(X86_FEATURE_USE_IBPB);
		pr_info("Enabling Indirect Branch Prediction Barrier\n");
	}
}

#undef pr_fmt

#ifdef CONFIG_SYSFS
ssize_t cpu_show_meltdown(struct device *dev,
			  struct device_attribute *attr, char *buf)
{
	if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN))
		return sprintf(buf, "Not affected\n");
	if (boot_cpu_has(X86_FEATURE_PTI))
		return sprintf(buf, "Mitigation: PTI\n");
	return sprintf(buf, "Vulnerable\n");
}

ssize_t cpu_show_spectre_v1(struct device *dev,
			    struct device_attribute *attr, char *buf)
{
	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1))
		return sprintf(buf, "Not affected\n");
	return sprintf(buf, "Mitigation: __user pointer sanitization\n");
}

ssize_t cpu_show_spectre_v2(struct device *dev,
			    struct device_attribute *attr, char *buf)
{
	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
		return sprintf(buf, "Not affected\n");

	return sprintf(buf, "%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
		       boot_cpu_has(X86_FEATURE_USE_IBPB) ? ", IBPB" : "",
		       spectre_v2_module_string());
}
#endif
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
1353ebb4	2	/*
1353ebb4 JF	3	* Copyright (C) 1994 Linus Torvalds
	4	*
	5	* Cyrix stuff, June 1998 by:
	6	* - Rafael R. Reilova (moved everything from head.S),
	7	* <rreilova@ececs.uc.edu>
	8	* - Channing Corn (tests & fixes),
	9	* - Andrew D. Balsa (code cleanup).
	10	*/
	11	#include <linux/init.h>
	12	#include <linux/utsname.h>
61dc0f55	13	#include <linux/cpu.h>
caf7501a	14	#include <linux/module.h>
da285121 DW	15
	16	#include <asm/nospec-branch.h>
	17	#include <asm/cmdline.h>
91eb1b79	18	#include <asm/bugs.h>
1353ebb4	19	#include <asm/processor.h>
7ebad705	20	#include <asm/processor-flags.h>
952f07ec	21	#include <asm/fpu/internal.h>
1353ebb4 JF	22	#include <asm/msr.h>
	23	#include <asm/paravirt.h>
	24	#include <asm/alternative.h>
62a67e12	25	#include <asm/pgtable.h>
d1163651	26	#include <asm/set_memory.h>
c995efd5	27	#include <asm/intel-family.h>
1353ebb4	28
da285121 DW	29	static void __init spectre_v2_select_mitigation(void);
da285121 DW	30
1353ebb4 JF	31	void __init check_bugs(void)
	32	{
	33	identify_boot_cpu();
55a36b65	34
62a67e12 BP	35	if (!IS_ENABLED(CONFIG_SMP)) {
	36	pr_info("CPU: ");
	37	print_cpu_info(&boot_cpu_data);
	38	}
	39
da285121 DW	40	/* Select the proper spectre mitigation before patching alternatives */
	41	spectre_v2_select_mitigation();
	42
62a67e12	43	#ifdef CONFIG_X86_32
55a36b65 BP	44	/*
	45	* Check whether we are able to run this kernel safely on SMP.
	46	*
	47	* - i386 is no longer supported.
	48	* - In order to run on anything without a TSC, we need to be
	49	* compiled for a i486.
	50	*/
	51	if (boot_cpu_data.x86 < 4)
	52	panic("Kernel requires i486+ for 'invlpg' and other features");
	53
bfe4bb15 MV	54	init_utsname()->machine[1] =
bfe4bb15 MV	55	'0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
1353ebb4	56	alternative_instructions();
304bceda	57
4d164092	58	fpu__init_check_bugs();
62a67e12 BP	59	#else /* CONFIG_X86_64 */
	60	alternative_instructions();
	61
	62	/*
	63	* Make sure the first 2MB area is not mapped by huge pages
	64	* There are typically fixed size MTRRs in there and overlapping
	65	* MTRRs into large pages causes slow downs.
	66	*
	67	* Right now we don't do that with gbpages because there seems
	68	* very little benefit for that case.
	69	*/
	70	if (!direct_gbpages)
	71	set_memory_4k((unsigned long)__va(0), 1);
	72	#endif
1353ebb4	73	}
61dc0f55	74
da285121 DW	75	/* The kernel command line selection */
	76	enum spectre_v2_mitigation_cmd {
	77	SPECTRE_V2_CMD_NONE,
	78	SPECTRE_V2_CMD_AUTO,
	79	SPECTRE_V2_CMD_FORCE,
	80	SPECTRE_V2_CMD_RETPOLINE,
	81	SPECTRE_V2_CMD_RETPOLINE_GENERIC,
	82	SPECTRE_V2_CMD_RETPOLINE_AMD,
	83	};
	84
	85	static const char *spectre_v2_strings[] = {
	86	[SPECTRE_V2_NONE] = "Vulnerable",
	87	[SPECTRE_V2_RETPOLINE_MINIMAL] = "Vulnerable: Minimal generic ASM retpoline",
	88	[SPECTRE_V2_RETPOLINE_MINIMAL_AMD] = "Vulnerable: Minimal AMD ASM retpoline",
	89	[SPECTRE_V2_RETPOLINE_GENERIC] = "Mitigation: Full generic retpoline",
	90	[SPECTRE_V2_RETPOLINE_AMD] = "Mitigation: Full AMD retpoline",
	91	};
	92
	93	#undef pr_fmt
55fa19d3	94	#define pr_fmt(fmt) "Spectre V2 : " fmt
da285121 DW	95
da285121 DW	96	static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE;
caf7501a AK	97
caf7501a AK	98	#ifdef RETPOLINE
e383095c TG	99	static bool spectre_v2_bad_module;
e383095c TG	100
caf7501a AK	101	bool retpoline_module_ok(bool has_retpoline)
	102	{
	103	if (spectre_v2_enabled == SPECTRE_V2_NONE \|\| has_retpoline)
	104	return true;
	105
e698dcdf	106	pr_err("System may be vulnerable to spectre v2\n");
caf7501a AK	107	spectre_v2_bad_module = true;
	108	return false;
	109	}
e383095c TG	110
	111	static inline const char *spectre_v2_module_string(void)
	112	{
	113	return spectre_v2_bad_module ? " - vulnerable module loaded" : "";
	114	}
	115	#else
	116	static inline const char *spectre_v2_module_string(void) { return ""; }
caf7501a	117	#endif
da285121 DW	118
	119	static void __init spec2_print_if_insecure(const char *reason)
	120	{
	121	if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
9005c683	122	pr_info("%s selected on command line.\n", reason);
da285121 DW	123	}
	124
	125	static void __init spec2_print_if_secure(const char *reason)
	126	{
	127	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
9005c683	128	pr_info("%s selected on command line.\n", reason);
da285121 DW	129	}
	130
	131	static inline bool retp_compiler(void)
	132	{
	133	return __is_defined(RETPOLINE);
	134	}
	135
	136	static inline bool match_option(const char arg, int arglen, const char opt)
	137	{
	138	int len = strlen(opt);
	139
	140	return len == arglen && !strncmp(arg, opt, len);
	141	}
	142
9005c683 KA	143	static const struct {
	144	const char *option;
	145	enum spectre_v2_mitigation_cmd cmd;
	146	bool secure;
	147	} mitigation_options[] = {
	148	{ "off", SPECTRE_V2_CMD_NONE, false },
	149	{ "on", SPECTRE_V2_CMD_FORCE, true },
	150	{ "retpoline", SPECTRE_V2_CMD_RETPOLINE, false },
	151	{ "retpoline,amd", SPECTRE_V2_CMD_RETPOLINE_AMD, false },
	152	{ "retpoline,generic", SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
	153	{ "auto", SPECTRE_V2_CMD_AUTO, false },
	154	};
	155
da285121 DW	156	static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
	157	{
	158	char arg[20];
9005c683 KA	159	int ret, i;
	160	enum spectre_v2_mitigation_cmd cmd = SPECTRE_V2_CMD_AUTO;
	161
	162	if (cmdline_find_option_bool(boot_command_line, "nospectre_v2"))
	163	return SPECTRE_V2_CMD_NONE;
	164	else {
	165	ret = cmdline_find_option(boot_command_line, "spectre_v2", arg,
	166	sizeof(arg));
	167	if (ret < 0)
	168	return SPECTRE_V2_CMD_AUTO;
	169
	170	for (i = 0; i < ARRAY_SIZE(mitigation_options); i++) {
	171	if (!match_option(arg, ret, mitigation_options[i].option))
	172	continue;
	173	cmd = mitigation_options[i].cmd;
	174	break;
	175	}
	176
	177	if (i >= ARRAY_SIZE(mitigation_options)) {
	178	pr_err("unknown option (%s). Switching to AUTO select\n",
	179	mitigation_options[i].option);
da285121 DW	180	return SPECTRE_V2_CMD_AUTO;
	181	}
	182	}
	183
9005c683 KA	184	if ((cmd == SPECTRE_V2_CMD_RETPOLINE \|\|
	185	cmd == SPECTRE_V2_CMD_RETPOLINE_AMD \|\|
	186	cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC) &&
	187	!IS_ENABLED(CONFIG_RETPOLINE)) {
	188	pr_err("%s selected but not compiled in. Switching to AUTO select\n",
	189	mitigation_options[i].option);
da285121	190	return SPECTRE_V2_CMD_AUTO;
9005c683 KA	191	}
	192
	193	if (cmd == SPECTRE_V2_CMD_RETPOLINE_AMD &&
	194	boot_cpu_data.x86_vendor != X86_VENDOR_AMD) {
	195	pr_err("retpoline,amd selected but CPU is not AMD. Switching to AUTO select\n");
	196	return SPECTRE_V2_CMD_AUTO;
	197	}
	198
	199	if (mitigation_options[i].secure)
	200	spec2_print_if_secure(mitigation_options[i].option);
	201	else
	202	spec2_print_if_insecure(mitigation_options[i].option);
	203
	204	return cmd;
da285121 DW	205	}
da285121 DW	206
c995efd5 DW	207	/* Check for Skylake-like CPUs (for RSB handling) */
	208	static bool __init is_skylake_era(void)
	209	{
	210	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
	211	boot_cpu_data.x86 == 6) {
	212	switch (boot_cpu_data.x86_model) {
	213	case INTEL_FAM6_SKYLAKE_MOBILE:
	214	case INTEL_FAM6_SKYLAKE_DESKTOP:
	215	case INTEL_FAM6_SKYLAKE_X:
	216	case INTEL_FAM6_KABYLAKE_MOBILE:
	217	case INTEL_FAM6_KABYLAKE_DESKTOP:
	218	return true;
	219	}
	220	}
	221	return false;
	222	}
	223
da285121 DW	224	static void __init spectre_v2_select_mitigation(void)
	225	{
	226	enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline();
	227	enum spectre_v2_mitigation mode = SPECTRE_V2_NONE;
	228
	229	/*
	230	* If the CPU is not affected and the command line mode is NONE or AUTO
	231	* then nothing to do.
	232	*/
	233	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) &&
	234	(cmd == SPECTRE_V2_CMD_NONE \|\| cmd == SPECTRE_V2_CMD_AUTO))
	235	return;
	236
	237	switch (cmd) {
	238	case SPECTRE_V2_CMD_NONE:
	239	return;
	240
	241	case SPECTRE_V2_CMD_FORCE:
da285121	242	case SPECTRE_V2_CMD_AUTO:
9471eee9 DL	243	if (IS_ENABLED(CONFIG_RETPOLINE))
	244	goto retpoline_auto;
	245	break;
da285121 DW	246	case SPECTRE_V2_CMD_RETPOLINE_AMD:
	247	if (IS_ENABLED(CONFIG_RETPOLINE))
	248	goto retpoline_amd;
	249	break;
	250	case SPECTRE_V2_CMD_RETPOLINE_GENERIC:
	251	if (IS_ENABLED(CONFIG_RETPOLINE))
	252	goto retpoline_generic;
	253	break;
	254	case SPECTRE_V2_CMD_RETPOLINE:
	255	if (IS_ENABLED(CONFIG_RETPOLINE))
	256	goto retpoline_auto;
	257	break;
	258	}
	259	pr_err("kernel not compiled with retpoline; no mitigation available!");
	260	return;
	261
	262	retpoline_auto:
	263	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
	264	retpoline_amd:
	265	if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
	266	pr_err("LFENCE not serializing. Switching to generic retpoline\n");
	267	goto retpoline_generic;
	268	}
	269	mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_AMD :
	270	SPECTRE_V2_RETPOLINE_MINIMAL_AMD;
	271	setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);
	272	setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
	273	} else {
	274	retpoline_generic:
	275	mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_GENERIC :
	276	SPECTRE_V2_RETPOLINE_MINIMAL;
	277	setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
	278	}
	279
	280	spectre_v2_enabled = mode;
	281	pr_info("%s\n", spectre_v2_strings[mode]);
c995efd5 DW	282
	283	/*
	284	* If neither SMEP or KPTI are available, there is a risk of
	285	* hitting userspace addresses in the RSB after a context switch
	286	* from a shallow call stack to a deeper one. To prevent this fill
	287	* the entire RSB, even when using IBRS.
	288	*
	289	* Skylake era CPUs have a separate issue with underflow of the
	290	* RSB, when they will predict 'ret' targets from the generic BTB.
	291	* The proper mitigation for this is IBRS. If IBRS is not supported
	292	* or deactivated in favour of retpolines the RSB fill on context
	293	* switch is required.
	294	*/
	295	if ((!boot_cpu_has(X86_FEATURE_PTI) &&
	296	!boot_cpu_has(X86_FEATURE_SMEP)) \|\| is_skylake_era()) {
	297	setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
	298	pr_info("Filling RSB on context switch\n");
	299	}
20ffa1ca DW	300
20ffa1ca DW	301	/* Initialize Indirect Branch Prediction Barrier if supported */
2961298e DW	302	if (boot_cpu_has(X86_FEATURE_IBPB)) {
2961298e DW	303	setup_force_cpu_cap(X86_FEATURE_USE_IBPB);
20ffa1ca DW	304	pr_info("Enabling Indirect Branch Prediction Barrier\n");
20ffa1ca DW	305	}
da285121 DW	306	}
	307
	308	#undef pr_fmt
	309
61dc0f55 TG	310	#ifdef CONFIG_SYSFS
	311	ssize_t cpu_show_meltdown(struct device *dev,
	312	struct device_attribute attr, char buf)
	313	{
	314	if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN))
	315	return sprintf(buf, "Not affected\n");
	316	if (boot_cpu_has(X86_FEATURE_PTI))
	317	return sprintf(buf, "Mitigation: PTI\n");
	318	return sprintf(buf, "Vulnerable\n");
	319	}
	320
	321	ssize_t cpu_show_spectre_v1(struct device *dev,
	322	struct device_attribute attr, char buf)
	323	{
	324	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1))
	325	return sprintf(buf, "Not affected\n");
edfbae53	326	return sprintf(buf, "Mitigation: __user pointer sanitization\n");
61dc0f55 TG	327	}
	328
	329	ssize_t cpu_show_spectre_v2(struct device *dev,
	330	struct device_attribute attr, char buf)
	331	{
	332	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
	333	return sprintf(buf, "Not affected\n");
da285121	334
20ffa1ca	335	return sprintf(buf, "%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
2961298e	336	boot_cpu_has(X86_FEATURE_USE_IBPB) ? ", IBPB" : "",
e383095c	337	spectre_v2_module_string());
61dc0f55 TG	338	}
61dc0f55 TG	339	#endif