/sys/devices/system/cpu/vulnerabilities/mds
/sys/devices/system/cpu/vulnerabilities/meltdown
/sys/devices/system/cpu/vulnerabilities/mmio_stale_data
+ /sys/devices/system/cpu/vulnerabilities/reg_file_data_sampling
/sys/devices/system/cpu/vulnerabilities/retbleed
/sys/devices/system/cpu/vulnerabilities/spec_store_bypass
/sys/devices/system/cpu/vulnerabilities/spectre_v1
The filter can be disabled or changed to another
driver later using sysfs.
+ reg_file_data_sampling=
+ [X86] Controls mitigation for Register File Data
+ Sampling (RFDS) vulnerability. RFDS is a CPU
+ vulnerability which may allow userspace to infer
+ kernel data values previously stored in floating point
+ registers, vector registers, or integer registers.
+ RFDS only affects Intel Atom processors.
+
+ on: Turns ON the mitigation.
+ off: Turns OFF the mitigation.
+
+ This parameter overrides the compile time default set
+ by CONFIG_MITIGATION_RFDS. Mitigation cannot be
+ disabled when other VERW based mitigations (like MDS)
+ are enabled. In order to disable RFDS mitigation all
+ VERW based mitigations need to be disabled.
+
+ For details see:
+ Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
+
driver_async_probe= [KNL]
List of driver names to be probed asynchronously. *
matches with all driver names. If * is specified, the
nospectre_bhb [ARM64]
nospectre_v1 [X86,PPC]
nospectre_v2 [X86,PPC,S390,ARM64]
+ reg_file_data_sampling=off [X86]
retbleed=off [X86]
spec_store_bypass_disable=off [X86,PPC]
spectre_v2_user=off [X86]
If in doubt, say N.
+config MITIGATION_RFDS
+ bool "RFDS Mitigation"
+ depends on CPU_SUP_INTEL
+ default y
+ help
+ Enable mitigation for Register File Data Sampling (RFDS) by default.
+ RFDS is a hardware vulnerability which affects Intel Atom CPUs. It
+ allows unprivileged speculative access to stale data previously
+ stored in floating point, vector and integer registers.
+ See also <file:Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst>
+
endif
config ARCH_HAS_ADD_PAGES
/* BUG word 2 */
#define X86_BUG_SRSO X86_BUG(1*32 + 0) /* AMD SRSO bug */
#define X86_BUG_DIV0 X86_BUG(1*32 + 1) /* AMD DIV0 speculation bug */
+#define X86_BUG_RFDS X86_BUG(1*32 + 2) /* CPU is vulnerable to Register File Data Sampling */
#endif /* _ASM_X86_CPUFEATURES_H */
* CPU is not vulnerable to Gather
* Data Sampling (GDS).
*/
+#define ARCH_CAP_RFDS_NO BIT(27) /*
+ * Not susceptible to Register
+ * File Data Sampling.
+ */
+#define ARCH_CAP_RFDS_CLEAR BIT(28) /*
+ * VERW clears CPU Register
+ * File.
+ */
#define ARCH_CAP_XAPIC_DISABLE BIT(21) /*
* IA32_XAPIC_DISABLE_STATUS MSR
}
early_param("mmio_stale_data", mmio_stale_data_parse_cmdline);
+#undef pr_fmt
+#define pr_fmt(fmt) "Register File Data Sampling: " fmt
+
+enum rfds_mitigations {
+ RFDS_MITIGATION_OFF,
+ RFDS_MITIGATION_VERW,
+ RFDS_MITIGATION_UCODE_NEEDED,
+};
+
+/* Default mitigation for Register File Data Sampling */
+static enum rfds_mitigations rfds_mitigation __ro_after_init =
+ IS_ENABLED(CONFIG_MITIGATION_RFDS) ? RFDS_MITIGATION_VERW : RFDS_MITIGATION_OFF;
+
+static const char * const rfds_strings[] = {
+ [RFDS_MITIGATION_OFF] = "Vulnerable",
+ [RFDS_MITIGATION_VERW] = "Mitigation: Clear Register File",
+ [RFDS_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode",
+};
+
+static void __init rfds_select_mitigation(void)
+{
+ if (!boot_cpu_has_bug(X86_BUG_RFDS) || cpu_mitigations_off()) {
+ rfds_mitigation = RFDS_MITIGATION_OFF;
+ return;
+ }
+ if (rfds_mitigation == RFDS_MITIGATION_OFF)
+ return;
+
+ if (x86_read_arch_cap_msr() & ARCH_CAP_RFDS_CLEAR)
+ setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
+ else
+ rfds_mitigation = RFDS_MITIGATION_UCODE_NEEDED;
+}
+
+static __init int rfds_parse_cmdline(char *str)
+{
+ if (!str)
+ return -EINVAL;
+
+ if (!boot_cpu_has_bug(X86_BUG_RFDS))
+ return 0;
+
+ if (!strcmp(str, "off"))
+ rfds_mitigation = RFDS_MITIGATION_OFF;
+ else if (!strcmp(str, "on"))
+ rfds_mitigation = RFDS_MITIGATION_VERW;
+
+ return 0;
+}
+early_param("reg_file_data_sampling", rfds_parse_cmdline);
+
#undef pr_fmt
#define pr_fmt(fmt) "" fmt
mmio_mitigation = MMIO_MITIGATION_VERW;
mmio_select_mitigation();
}
+ if (rfds_mitigation == RFDS_MITIGATION_OFF &&
+ boot_cpu_has_bug(X86_BUG_RFDS)) {
+ rfds_mitigation = RFDS_MITIGATION_VERW;
+ rfds_select_mitigation();
+ }
out:
if (boot_cpu_has_bug(X86_BUG_MDS))
pr_info("MDS: %s\n", mds_strings[mds_mitigation]);
pr_info("MMIO Stale Data: %s\n", mmio_strings[mmio_mitigation]);
else if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
pr_info("MMIO Stale Data: Unknown: No mitigations\n");
+ if (boot_cpu_has_bug(X86_BUG_RFDS))
+ pr_info("Register File Data Sampling: %s\n", rfds_strings[rfds_mitigation]);
}
static void __init md_clear_select_mitigation(void)
mds_select_mitigation();
taa_select_mitigation();
mmio_select_mitigation();
+ rfds_select_mitigation();
/*
- * As MDS, TAA and MMIO Stale Data mitigations are inter-related, update
- * and print their mitigation after MDS, TAA and MMIO Stale Data
- * mitigation selection is done.
+ * As these mitigations are inter-related and rely on VERW instruction
+ * to clear the microarchitural buffers, update and print their status
+ * after mitigation selection is done for each of these vulnerabilities.
*/
md_clear_update_mitigation();
}
sched_smt_active() ? "vulnerable" : "disabled");
}
+static ssize_t rfds_show_state(char *buf)
+{
+ return sysfs_emit(buf, "%s\n", rfds_strings[rfds_mitigation]);
+}
+
static char *stibp_state(void)
{
if (spectre_v2_in_eibrs_mode(spectre_v2_enabled))
case X86_BUG_SRSO:
return srso_show_state(buf);
+ case X86_BUG_RFDS:
+ return rfds_show_state(buf);
+
default:
break;
}
{
return cpu_show_common(dev, attr, buf, X86_BUG_SRSO);
}
+
+ssize_t cpu_show_reg_file_data_sampling(struct device *dev, struct device_attribute *attr, char *buf)
+{
+ return cpu_show_common(dev, attr, buf, X86_BUG_RFDS);
+}
#endif
#define SRSO BIT(5)
/* CPU is affected by GDS */
#define GDS BIT(6)
+/* CPU is affected by Register File Data Sampling */
+#define RFDS BIT(7)
static const struct x86_cpu_id cpu_vuln_blacklist[] __initconst = {
VULNBL_INTEL_STEPPINGS(IVYBRIDGE, X86_STEPPING_ANY, SRBDS),
VULNBL_INTEL_STEPPINGS(TIGERLAKE, X86_STEPPING_ANY, GDS),
VULNBL_INTEL_STEPPINGS(LAKEFIELD, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RETBLEED),
VULNBL_INTEL_STEPPINGS(ROCKETLAKE, X86_STEPPING_ANY, MMIO | RETBLEED | GDS),
- VULNBL_INTEL_STEPPINGS(ATOM_TREMONT, X86_STEPPING_ANY, MMIO | MMIO_SBDS),
- VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_D, X86_STEPPING_ANY, MMIO),
- VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS),
+ VULNBL_INTEL_STEPPINGS(ALDERLAKE, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(ALDERLAKE_L, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(RAPTORLAKE, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(RAPTORLAKE_P, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(RAPTORLAKE_S, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(ALDERLAKE_N, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(ATOM_TREMONT, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RFDS),
+ VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_D, X86_STEPPING_ANY, MMIO | RFDS),
+ VULNBL_INTEL_STEPPINGS(ATOM_TREMONT_L, X86_STEPPING_ANY, MMIO | MMIO_SBDS | RFDS),
+ VULNBL_INTEL_STEPPINGS(ATOM_GOLDMONT, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(ATOM_GOLDMONT_D, X86_STEPPING_ANY, RFDS),
+ VULNBL_INTEL_STEPPINGS(ATOM_GOLDMONT_PLUS, X86_STEPPING_ANY, RFDS),
VULNBL_AMD(0x15, RETBLEED),
VULNBL_AMD(0x16, RETBLEED),
ia32_cap & ARCH_CAP_SBDR_SSDP_NO);
}
+static bool __init vulnerable_to_rfds(u64 ia32_cap)
+{
+ /* The "immunity" bit trumps everything else: */
+ if (ia32_cap & ARCH_CAP_RFDS_NO)
+ return false;
+
+ /*
+ * VMMs set ARCH_CAP_RFDS_CLEAR for processors not in the blacklist to
+ * indicate that mitigation is needed because guest is running on a
+ * vulnerable hardware or may migrate to such hardware:
+ */
+ if (ia32_cap & ARCH_CAP_RFDS_CLEAR)
+ return true;
+
+ /* Only consult the blacklist when there is no enumeration: */
+ return cpu_matches(cpu_vuln_blacklist, RFDS);
+}
+
static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
{
u64 ia32_cap = x86_read_arch_cap_msr();
setup_force_cpu_bug(X86_BUG_SRSO);
}
+ if (vulnerable_to_rfds(ia32_cap))
+ setup_force_cpu_bug(X86_BUG_RFDS);
+
if (cpu_matches(cpu_vuln_whitelist, NO_MELTDOWN))
return;
return sysfs_emit(buf, "Not affected\n");
}
+ssize_t __weak cpu_show_reg_file_data_sampling(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "Not affected\n");
+}
+
static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);
static DEVICE_ATTR(retbleed, 0444, cpu_show_retbleed, NULL);
static DEVICE_ATTR(gather_data_sampling, 0444, cpu_show_gds, NULL);
static DEVICE_ATTR(spec_rstack_overflow, 0444, cpu_show_spec_rstack_overflow, NULL);
+static DEVICE_ATTR(reg_file_data_sampling, 0444, cpu_show_reg_file_data_sampling, NULL);
static struct attribute *cpu_root_vulnerabilities_attrs[] = {
&dev_attr_meltdown.attr,
&dev_attr_retbleed.attr,
&dev_attr_gather_data_sampling.attr,
&dev_attr_spec_rstack_overflow.attr,
+ &dev_attr_reg_file_data_sampling.attr,
NULL
};
struct device_attribute *attr, char *buf);
extern ssize_t cpu_show_gds(struct device *dev,
struct device_attribute *attr, char *buf);
+extern ssize_t cpu_show_reg_file_data_sampling(struct device *dev,
+ struct device_attribute *attr, char *buf);
extern __printf(4, 5)
struct device *cpu_device_create(struct device *parent, void *drvdata,
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