3 files changed, 73 insertions, 0 deletions

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index c651f91e5eab..2cfc483e8342 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -178,6 +178,7 @@ enum spectre_v2_mitigation {
 enum spectre_v2_user_mitigation {
 	SPECTRE_V2_USER_NONE,
 	SPECTRE_V2_USER_STRICT,
+	SPECTRE_V2_USER_PRCTL,
 };
 
 /* The Speculative Store Bypass disable variants */
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 73accc32e314..c47d55485646 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -561,6 +561,8 @@ void arch_smt_update(void)
 	case SPECTRE_V2_USER_STRICT:
 		update_stibp_strict();
 		break;
+	case SPECTRE_V2_USER_PRCTL:
+		break;
 	}
 
 	mutex_unlock(&spec_ctrl_mutex);
@@ -747,12 +749,50 @@ static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl)
 	return 0;
 }
 
+static int ib_prctl_set(struct task_struct *task, unsigned long ctrl)
+{
+	switch (ctrl) {
+	case PR_SPEC_ENABLE:
+		if (spectre_v2_user == SPECTRE_V2_USER_NONE)
+			return 0;
+		/*
+		 * Indirect branch speculation is always disabled in strict
+		 * mode.
+		 */
+		if (spectre_v2_user == SPECTRE_V2_USER_STRICT)
+			return -EPERM;
+		task_clear_spec_ib_disable(task);
+		task_update_spec_tif(task);
+		break;
+	case PR_SPEC_DISABLE:
+	case PR_SPEC_FORCE_DISABLE:
+		/*
+		 * Indirect branch speculation is always allowed when
+		 * mitigation is force disabled.
+		 */
+		if (spectre_v2_user == SPECTRE_V2_USER_NONE)
+			return -EPERM;
+		if (spectre_v2_user == SPECTRE_V2_USER_STRICT)
+			return 0;
+		task_set_spec_ib_disable(task);
+		if (ctrl == PR_SPEC_FORCE_DISABLE)
+			task_set_spec_ib_force_disable(task);
+		task_update_spec_tif(task);
+		break;
+	default:
+		return -ERANGE;
+	}
+	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);
+	case PR_SPEC_INDIRECT_BRANCH:
+		return ib_prctl_set(task, ctrl);
 	default:
 		return -ENODEV;
 	}
@@ -785,11 +825,34 @@ static int ssb_prctl_get(struct task_struct *task)
 	}
 }
 
+static int ib_prctl_get(struct task_struct *task)
+{
+	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
+		return PR_SPEC_NOT_AFFECTED;
+
+	switch (spectre_v2_user) {
+	case SPECTRE_V2_USER_NONE:
+		return PR_SPEC_ENABLE;
+	case SPECTRE_V2_USER_PRCTL:
+		if (task_spec_ib_force_disable(task))
+			return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
+		if (task_spec_ib_disable(task))
+			return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
+		return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
+	case SPECTRE_V2_USER_STRICT:
+		return PR_SPEC_DISABLE;
+	default:
+		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);
+	case PR_SPEC_INDIRECT_BRANCH:
+		return ib_prctl_get(task);
 	default:
 		return -ENODEV;
 	}
@@ -886,6 +949,8 @@ static char *stibp_state(void)
 		return ", STIBP: disabled";
 	case SPECTRE_V2_USER_STRICT:
 		return ", STIBP: forced";
+	case SPECTRE_V2_USER_PRCTL:
+		return "";
 	}
 	return "";
 }
@@ -898,6 +963,8 @@ static char *ibpb_state(void)
 			return ", IBPB: disabled";
 		case SPECTRE_V2_USER_STRICT:
 			return ", IBPB: always-on";
+		case SPECTRE_V2_USER_PRCTL:
+			return "";
 		}
 	}
 	return "";
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 4aa3b5ebbce5..64090c943f05 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -372,6 +372,11 @@ static unsigned long speculation_ctrl_update_tif(struct task_struct *tsk)
 			set_tsk_thread_flag(tsk, TIF_SSBD);
 		else
 			clear_tsk_thread_flag(tsk, TIF_SSBD);
+
+		if (task_spec_ib_disable(tsk))
+			set_tsk_thread_flag(tsk, TIF_SPEC_IB);
+		else
+			clear_tsk_thread_flag(tsk, TIF_SPEC_IB);
 	}
 	/* Return the updated threadinfo flags*/
 	return task_thread_info(tsk)->flags;