Merge branch 'for-next/ghostbusters' into for-next/core

Fix and subsequently rewrite Spectre mitigations, including the addition
of support for PR_SPEC_DISABLE_NOEXEC.

(Will Deacon and Marc Zyngier)
* for-next/ghostbusters: (22 commits)
  arm64: Add support for PR_SPEC_DISABLE_NOEXEC prctl() option
  arm64: Pull in task_stack_page() to Spectre-v4 mitigation code
  KVM: arm64: Allow patching EL2 vectors even with KASLR is not enabled
  arm64: Get rid of arm64_ssbd_state
  KVM: arm64: Convert ARCH_WORKAROUND_2 to arm64_get_spectre_v4_state()
  KVM: arm64: Get rid of kvm_arm_have_ssbd()
  KVM: arm64: Simplify handling of ARCH_WORKAROUND_2
  arm64: Rewrite Spectre-v4 mitigation code
  arm64: Move SSBD prctl() handler alongside other spectre mitigation code
  arm64: Rename ARM64_SSBD to ARM64_SPECTRE_V4
  arm64: Treat SSBS as a non-strict system feature
  arm64: Group start_thread() functions together
  KVM: arm64: Set CSV2 for guests on hardware unaffected by Spectre-v2
  arm64: Rewrite Spectre-v2 mitigation code
  arm64: Introduce separate file for spectre mitigations and reporting
  arm64: Rename ARM64_HARDEN_BRANCH_PREDICTOR to ARM64_SPECTRE_V2
  KVM: arm64: Simplify install_bp_hardening_cb()
  KVM: arm64: Replace CONFIG_KVM_INDIRECT_VECTORS with CONFIG_RANDOMIZE_BASE
  arm64: Remove Spectre-related CONFIG_* options
  arm64: Run ARCH_WORKAROUND_2 enabling code on all CPUs
  ...

1 files changed, 9 insertions, 14 deletions

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index f1804496b935..085d8ca39e47 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -21,6 +21,7 @@
 #include <linux/lockdep.h>
 #include <linux/mman.h>
 #include <linux/mm.h>
+#include <linux/nospec.h>
 #include <linux/stddef.h>
 #include <linux/sysctl.h>
 #include <linux/unistd.h>
@@ -421,8 +422,7 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
 		    cpus_have_const_cap(ARM64_HAS_UAO))
 			childregs->pstate |= PSR_UAO_BIT;
 
-		if (arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE)
-			set_ssbs_bit(childregs);
+		spectre_v4_enable_task_mitigation(p);
 
 		if (system_uses_irq_prio_masking())
 			childregs->pmr_save = GIC_PRIO_IRQON;
@@ -472,8 +472,6 @@ void uao_thread_switch(struct task_struct *next)
  */
 static void ssbs_thread_switch(struct task_struct *next)
 {
-	struct pt_regs *regs = task_pt_regs(next);
-
 	/*
 	 * Nothing to do for kernel threads, but 'regs' may be junk
 	 * (e.g. idle task) so check the flags and bail early.
@@ -485,18 +483,10 @@ static void ssbs_thread_switch(struct task_struct *next)
 	 * If all CPUs implement the SSBS extension, then we just need to
 	 * context-switch the PSTATE field.
 	 */
-	if (cpu_have_feature(cpu_feature(SSBS)))
-		return;
-
-	/* If the mitigation is enabled, then we leave SSBS clear. */
-	if ((arm64_get_ssbd_state() == ARM64_SSBD_FORCE_ENABLE) ||
-	    test_tsk_thread_flag(next, TIF_SSBD))
+	if (cpus_have_const_cap(ARM64_SSBS))
 		return;
 
-	if (compat_user_mode(regs))
-		set_compat_ssbs_bit(regs);
-	else if (user_mode(regs))
-		set_ssbs_bit(regs);
+	spectre_v4_enable_task_mitigation(next);
 }
 
 /*
@@ -620,6 +610,11 @@ void arch_setup_new_exec(void)
 	current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0;
 
 	ptrauth_thread_init_user(current);
+
+	if (task_spec_ssb_noexec(current)) {
+		arch_prctl_spec_ctrl_set(current, PR_SPEC_STORE_BYPASS,
+					 PR_SPEC_ENABLE);
+	}
 }
 
 #ifdef CONFIG_ARM64_TAGGED_ADDR_ABI