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-rw-r--r--arch/arm64/kernel/process.c29
1 files changed, 28 insertions, 1 deletions
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 8d836d0abc96..f674f28df663 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -398,7 +398,7 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
childregs->pstate |= PSR_UAO_BIT;
if (arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE)
- childregs->pstate |= PSR_SSBS_BIT;
+ set_ssbs_bit(childregs);
if (system_uses_irq_prio_masking())
childregs->pmr_save = GIC_PRIO_IRQON;
@@ -443,6 +443,32 @@ void uao_thread_switch(struct task_struct *next)
}
/*
+ * Force SSBS state on context-switch, since it may be lost after migrating
+ * from a CPU which treats the bit as RES0 in a heterogeneous system.
+ */
+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.
+ */
+ if (unlikely(next->flags & PF_KTHREAD))
+ 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))
+ return;
+
+ if (compat_user_mode(regs))
+ set_compat_ssbs_bit(regs);
+ else if (user_mode(regs))
+ set_ssbs_bit(regs);
+}
+
+/*
* We store our current task in sp_el0, which is clobbered by userspace. Keep a
* shadow copy so that we can restore this upon entry from userspace.
*
@@ -471,6 +497,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
entry_task_switch(next);
uao_thread_switch(next);
ptrauth_thread_switch(next);
+ ssbs_thread_switch(next);
/*
* Complete any pending TLB or cache maintenance on this CPU in case