#include <linux/utsname.h>
#include <linux/cpu.h>
#include <linux/smp.h>
+#include <linux/nospec.h>
+#include <linux/prctl.h>
-#include <asm/nospec-branch.h>
+#include <asm/spec-ctrl.h>
#include <asm/cmdline.h>
#include <asm/bugs.h>
#include <asm/processor.h>
* Our boot-time value of the SPEC_CTRL MSR. We read it once so that any
* writes to SPEC_CTRL contain whatever reserved bits have been set.
*/
-static u64 __ro_after_init x86_spec_ctrl_base;
+u64 __ro_after_init x86_spec_ctrl_base;
+
+/*
+ * The vendor and possibly platform specific bits which can be modified in
+ * x86_spec_ctrl_base.
+ */
+static u64 __ro_after_init x86_spec_ctrl_mask = ~SPEC_CTRL_IBRS;
+
+/*
+ * AMD specific MSR info for Speculative Store Bypass control.
+ * x86_amd_ls_cfg_ssbd_mask is initialized in identify_boot_cpu().
+ */
+u64 __ro_after_init x86_amd_ls_cfg_base;
+u64 __ro_after_init x86_amd_ls_cfg_ssbd_mask;
void __init check_bugs(void)
{
/*
* Read the SPEC_CTRL MSR to account for reserved bits which may
- * have unknown values.
+ * have unknown values. AMD64_LS_CFG MSR is cached in the early AMD
+ * init code as it is not enumerated and depends on the family.
*/
if (ibrs_inuse)
rdmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
#undef pr_fmt
#define pr_fmt(fmt) "Spectre V2 mitigation: " fmt
-static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE;
+static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
+ SPECTRE_V2_NONE;
void x86_spec_ctrl_set(u64 val)
{
- if (val & ~SPEC_CTRL_IBRS)
+ if (val & x86_spec_ctrl_mask)
WARN_ONCE(1, "SPEC_CTRL MSR value 0x%16llx is unknown.\n", val);
else
wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base | val);
u64 x86_spec_ctrl_get_default(void)
{
- return x86_spec_ctrl_base;
+ u64 msrval = x86_spec_ctrl_base;
+
+ if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
+ msrval |= ssbd_tif_to_spec_ctrl(current_thread_info()->flags);
+ return msrval;
}
EXPORT_SYMBOL_GPL(x86_spec_ctrl_get_default);
void x86_spec_ctrl_set_guest(u64 guest_spec_ctrl)
{
+ u64 host = x86_spec_ctrl_base;
+
if (!ibrs_inuse)
return;
- if (x86_spec_ctrl_base != guest_spec_ctrl)
+
+ if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
+ host |= ssbd_tif_to_spec_ctrl(current_thread_info()->flags);
+
+ if (host != guest_spec_ctrl)
wrmsrl(MSR_IA32_SPEC_CTRL, guest_spec_ctrl);
}
EXPORT_SYMBOL_GPL(x86_spec_ctrl_set_guest);
void x86_spec_ctrl_restore_host(u64 guest_spec_ctrl)
{
+ u64 host = x86_spec_ctrl_base;
+
if (!ibrs_inuse)
return;
- if (x86_spec_ctrl_base != guest_spec_ctrl)
- wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
+
+ if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
+ host |= ssbd_tif_to_spec_ctrl(current_thread_info()->flags);
+
+ if (host != guest_spec_ctrl)
+ wrmsrl(MSR_IA32_SPEC_CTRL, host);
}
EXPORT_SYMBOL_GPL(x86_spec_ctrl_restore_host);
+static void x86_amd_ssb_disable(void)
+{
+ u64 msrval = x86_amd_ls_cfg_base | x86_amd_ls_cfg_ssbd_mask;
+
+ if (boot_cpu_has(X86_FEATURE_AMD_SSBD))
+ wrmsrl(MSR_AMD64_LS_CFG, msrval);
+}
+
static void __init spec2_print_if_insecure(const char *reason)
{
if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
#undef pr_fmt
#define pr_fmt(fmt) "Speculative Store Bypass: " fmt
-static enum ssb_mitigation ssb_mode = SPEC_STORE_BYPASS_NONE;
+static enum ssb_mitigation ssb_mode __ro_after_init = SPEC_STORE_BYPASS_NONE;
/* The kernel command line selection */
enum ssb_mitigation_cmd {
SPEC_STORE_BYPASS_CMD_NONE,
SPEC_STORE_BYPASS_CMD_AUTO,
SPEC_STORE_BYPASS_CMD_ON,
+ SPEC_STORE_BYPASS_CMD_PRCTL,
+ SPEC_STORE_BYPASS_CMD_SECCOMP,
};
static const char *ssb_strings[] = {
[SPEC_STORE_BYPASS_NONE] = "Vulnerable",
- [SPEC_STORE_BYPASS_DISABLE] = "Mitigation: Speculative Store Bypass disabled"
+ [SPEC_STORE_BYPASS_DISABLE] = "Mitigation: Speculative Store Bypass disabled",
+ [SPEC_STORE_BYPASS_PRCTL] = "Mitigation: Speculative Store Bypass disabled via prctl",
+ [SPEC_STORE_BYPASS_SECCOMP] = "Mitigation: Speculative Store Bypass disabled via prctl and seccomp",
};
static const struct {
const char *option;
enum ssb_mitigation_cmd cmd;
} ssb_mitigation_options[] = {
- { "auto", SPEC_STORE_BYPASS_CMD_AUTO }, /* Platform decides */
- { "on", SPEC_STORE_BYPASS_CMD_ON }, /* Disable Speculative Store Bypass */
- { "off", SPEC_STORE_BYPASS_CMD_NONE }, /* Don't touch Speculative Store Bypass */
+ { "auto", SPEC_STORE_BYPASS_CMD_AUTO }, /* Platform decides */
+ { "on", SPEC_STORE_BYPASS_CMD_ON }, /* Disable Speculative Store Bypass */
+ { "off", SPEC_STORE_BYPASS_CMD_NONE }, /* Don't touch Speculative Store Bypass */
+ { "prctl", SPEC_STORE_BYPASS_CMD_PRCTL }, /* Disable Speculative Store Bypass via prctl */
+ { "seccomp", SPEC_STORE_BYPASS_CMD_SECCOMP }, /* Disable Speculative Store Bypass via prctl and seccomp */
};
static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void)
return cmd;
}
-static enum ssb_mitigation_cmd __init __ssb_select_mitigation(void)
+static enum ssb_mitigation __init __ssb_select_mitigation(void)
{
enum ssb_mitigation mode = SPEC_STORE_BYPASS_NONE;
enum ssb_mitigation_cmd cmd;
- if (!boot_cpu_has(X86_FEATURE_RDS))
+ if (!boot_cpu_has(X86_FEATURE_SSBD))
return mode;
cmd = ssb_parse_cmdline();
switch (cmd) {
case SPEC_STORE_BYPASS_CMD_AUTO:
+ case SPEC_STORE_BYPASS_CMD_SECCOMP:
+ /*
+ * Choose prctl+seccomp as the default mode if seccomp is
+ * enabled.
+ */
+ if (IS_ENABLED(CONFIG_SECCOMP))
+ mode = SPEC_STORE_BYPASS_SECCOMP;
+ else
+ mode = SPEC_STORE_BYPASS_PRCTL;
+ break;
case SPEC_STORE_BYPASS_CMD_ON:
mode = SPEC_STORE_BYPASS_DISABLE;
break;
+ case SPEC_STORE_BYPASS_CMD_PRCTL:
+ mode = SPEC_STORE_BYPASS_PRCTL;
+ break;
case SPEC_STORE_BYPASS_CMD_NONE:
break;
}
- if (mode != SPEC_STORE_BYPASS_NONE)
+ /*
+ * We have three CPU feature flags that are in play here:
+ * - X86_BUG_SPEC_STORE_BYPASS - CPU is susceptible.
+ * - X86_FEATURE_SSBD - CPU is able to turn off speculative store bypass
+ * - X86_FEATURE_SPEC_STORE_BYPASS_DISABLE - engage the mitigation
+ */
+ if (mode == SPEC_STORE_BYPASS_DISABLE) {
setup_force_cpu_cap(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE);
+ /*
+ * Intel uses the SPEC CTRL MSR Bit(2) for this, while AMD uses
+ * a completely different MSR and bit dependent on family.
+ */
+ switch (boot_cpu_data.x86_vendor) {
+ case X86_VENDOR_INTEL:
+ x86_spec_ctrl_base |= SPEC_CTRL_SSBD;
+ x86_spec_ctrl_mask &= ~SPEC_CTRL_SSBD;
+ x86_spec_ctrl_set(SPEC_CTRL_SSBD);
+ break;
+ case X86_VENDOR_AMD:
+ x86_amd_ssb_disable();
+ break;
+ }
+ }
+
return mode;
}
}
#undef pr_fmt
+#define pr_fmt(fmt) "Speculation prctl: " fmt
+
+static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl)
+{
+ bool update;
+
+ if (ssb_mode != SPEC_STORE_BYPASS_PRCTL &&
+ ssb_mode != SPEC_STORE_BYPASS_SECCOMP)
+ return -ENXIO;
+
+ switch (ctrl) {
+ case PR_SPEC_ENABLE:
+ /* If speculation is force disabled, enable is not allowed */
+ if (task_spec_ssb_force_disable(task))
+ return -EPERM;
+ task_clear_spec_ssb_disable(task);
+ update = test_and_clear_tsk_thread_flag(task, TIF_SSBD);
+ break;
+ case PR_SPEC_DISABLE:
+ task_set_spec_ssb_disable(task);
+ update = !test_and_set_tsk_thread_flag(task, TIF_SSBD);
+ break;
+ case PR_SPEC_FORCE_DISABLE:
+ task_set_spec_ssb_disable(task);
+ task_set_spec_ssb_force_disable(task);
+ update = !test_and_set_tsk_thread_flag(task, TIF_SSBD);
+ break;
+ default:
+ return -ERANGE;
+ }
+
+ /*
+ * If being set on non-current task, delay setting the CPU
+ * mitigation until it is next scheduled.
+ */
+ if (task == current && update)
+ speculative_store_bypass_update();
+
+ return 0;
+}
+
+int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
+ unsigned long ctrl)
+{
+ switch (which) {
+ case PR_SPEC_STORE_BYPASS:
+ return ssb_prctl_set(task, ctrl);
+ default:
+ return -ENODEV;
+ }
+}
+
+#ifdef CONFIG_SECCOMP
+void arch_seccomp_spec_mitigate(struct task_struct *task)
+{
+ if (ssb_mode == SPEC_STORE_BYPASS_SECCOMP)
+ ssb_prctl_set(task, PR_SPEC_FORCE_DISABLE);
+}
+#endif
+
+static int ssb_prctl_get(struct task_struct *task)
+{
+ switch (ssb_mode) {
+ case SPEC_STORE_BYPASS_DISABLE:
+ return PR_SPEC_DISABLE;
+ case SPEC_STORE_BYPASS_SECCOMP:
+ case SPEC_STORE_BYPASS_PRCTL:
+ if (task_spec_ssb_force_disable(task))
+ return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
+ if (task_spec_ssb_disable(task))
+ return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
+ return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
+ default:
+ if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
+ return PR_SPEC_ENABLE;
+ return PR_SPEC_NOT_AFFECTED;
+ }
+}
+
+int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
+{
+ switch (which) {
+ case PR_SPEC_STORE_BYPASS:
+ return ssb_prctl_get(task);
+ default:
+ return -ENODEV;
+ }
+}
+
+void x86_spec_ctrl_setup_ap(void)
+{
+ if (ibrs_inuse)
+ x86_spec_ctrl_set(x86_spec_ctrl_base & ~x86_spec_ctrl_mask);
+
+ if (ssb_mode == SPEC_STORE_BYPASS_DISABLE)
+ x86_amd_ssb_disable();
+}
#ifdef CONFIG_SYSFS
ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
projects / mirror_ubuntu-artful-kernel.git / blobdiff