u64 __ro_after_init x86_amd_ls_cfg_base;
u64 __ro_after_init x86_amd_ls_cfg_ssbd_mask;
+/* Control conditional STIPB in switch_to() */
+DEFINE_STATIC_KEY_FALSE(switch_to_cond_stibp);
+
void __init check_bugs(void)
{
identify_boot_cpu();
static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
SPECTRE_V2_NONE;
+static enum spectre_v2_user_mitigation spectre_v2_user __ro_after_init =
+ SPECTRE_V2_USER_NONE;
+
#ifdef RETPOLINE
static bool spectre_v2_bad_module;
SPECTRE_V2_CMD_RETPOLINE_AMD,
};
+enum spectre_v2_user_cmd {
+ SPECTRE_V2_USER_CMD_NONE,
+ SPECTRE_V2_USER_CMD_AUTO,
+ SPECTRE_V2_USER_CMD_FORCE,
+};
+
+static const char * const spectre_v2_user_strings[] = {
+ [SPECTRE_V2_USER_NONE] = "User space: Vulnerable",
+ [SPECTRE_V2_USER_STRICT] = "User space: Mitigation: STIBP protection",
+};
+
+static const struct {
+ const char *option;
+ enum spectre_v2_user_cmd cmd;
+ bool secure;
+} v2_user_options[] __initdata = {
+ { "auto", SPECTRE_V2_USER_CMD_AUTO, false },
+ { "off", SPECTRE_V2_USER_CMD_NONE, false },
+ { "on", SPECTRE_V2_USER_CMD_FORCE, true },
+};
+
+static void __init spec_v2_user_print_cond(const char *reason, bool secure)
+{
+ if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure)
+ pr_info("spectre_v2_user=%s forced on command line.\n", reason);
+}
+
+static enum spectre_v2_user_cmd __init
+spectre_v2_parse_user_cmdline(enum spectre_v2_mitigation_cmd v2_cmd)
+{
+ char arg[20];
+ int ret, i;
+
+ switch (v2_cmd) {
+ case SPECTRE_V2_CMD_NONE:
+ return SPECTRE_V2_USER_CMD_NONE;
+ case SPECTRE_V2_CMD_FORCE:
+ return SPECTRE_V2_USER_CMD_FORCE;
+ default:
+ break;
+ }
+
+ ret = cmdline_find_option(boot_command_line, "spectre_v2_user",
+ arg, sizeof(arg));
+ if (ret < 0)
+ return SPECTRE_V2_USER_CMD_AUTO;
+
+ for (i = 0; i < ARRAY_SIZE(v2_user_options); i++) {
+ if (match_option(arg, ret, v2_user_options[i].option)) {
+ spec_v2_user_print_cond(v2_user_options[i].option,
+ v2_user_options[i].secure);
+ return v2_user_options[i].cmd;
+ }
+ }
+
+ pr_err("Unknown user space protection option (%s). Switching to AUTO select\n", arg);
+ return SPECTRE_V2_USER_CMD_AUTO;
+}
+
+static void __init
+spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
+{
+ enum spectre_v2_user_mitigation mode = SPECTRE_V2_USER_NONE;
+ bool smt_possible = IS_ENABLED(CONFIG_SMP);
+
+ if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP))
+ return;
+
+ if (cpu_smt_control == CPU_SMT_FORCE_DISABLED ||
+ cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
+ smt_possible = false;
+
+ switch (spectre_v2_parse_user_cmdline(v2_cmd)) {
+ case SPECTRE_V2_USER_CMD_AUTO:
+ case SPECTRE_V2_USER_CMD_NONE:
+ goto set_mode;
+ case SPECTRE_V2_USER_CMD_FORCE:
+ mode = SPECTRE_V2_USER_STRICT;
+ break;
+ }
+
+ /* Initialize Indirect Branch Prediction Barrier */
+ if (boot_cpu_has(X86_FEATURE_IBPB)) {
+ setup_force_cpu_cap(X86_FEATURE_USE_IBPB);
+ pr_info("Spectre v2 mitigation: Enabling Indirect Branch Prediction Barrier\n");
+ }
+
+ /* If enhanced IBRS is enabled no STIPB required */
+ if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
+ return;
+
+set_mode:
+ spectre_v2_user = mode;
+ /* Only print the STIBP mode when SMT possible */
+ if (smt_possible)
+ pr_info("%s\n", spectre_v2_user_strings[mode]);
+}
+
static const char * const spectre_v2_strings[] = {
[SPECTRE_V2_NONE] = "Vulnerable",
[SPECTRE_V2_RETPOLINE_GENERIC] = "Mitigation: Full generic retpoline",
setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
pr_info("Spectre v2 / SpectreRSB mitigation: 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("Spectre v2 mitigation: Enabling Indirect Branch Prediction Barrier\n");
- }
-
/*
* Retpoline means the kernel is safe because it has no indirect
* branches. Enhanced IBRS protects firmware too, so, enable restricted
pr_info("Enabling Restricted Speculation for firmware calls\n");
}
+ /* Set up IBPB and STIBP depending on the general spectre V2 command */
+ spectre_v2_user_select_mitigation(cmd);
+
/* Enable STIBP if appropriate */
arch_smt_update();
}
static bool stibp_needed(void)
{
- if (spectre_v2_enabled == SPECTRE_V2_NONE)
- return false;
-
/* Enhanced IBRS makes using STIBP unnecessary. */
if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
return false;
- if (!boot_cpu_has(X86_FEATURE_STIBP))
- return false;
-
- return true;
+ /* Check for strict user mitigation mode */
+ return spectre_v2_user == SPECTRE_V2_USER_STRICT;
}
static void update_stibp_msr(void *info)
if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
return "";
- if (x86_spec_ctrl_base & SPEC_CTRL_STIBP)
- return ", STIBP";
- else
- return "";
+ switch (spectre_v2_user) {
+ case SPECTRE_V2_USER_NONE:
+ return ", STIBP: disabled";
+ case SPECTRE_V2_USER_STRICT:
+ return ", STIBP: forced";
+ }
+ return "";
}
static char *ibpb_state(void)
projects / mirror_ubuntu-bionic-kernel.git / blobdiff