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-rw-r--r--arch/arm64/kernel/process.c50
1 files changed, 33 insertions, 17 deletions
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index a47462def04b..71f788cd2b18 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -17,6 +17,7 @@
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/kernel.h>
+#include <linux/lockdep.h>
#include <linux/mm.h>
#include <linux/stddef.h>
#include <linux/sysctl.h>
@@ -44,6 +45,7 @@
#include <asm/alternative.h>
#include <asm/arch_gicv3.h>
#include <asm/compat.h>
+#include <asm/cpufeature.h>
#include <asm/cacheflush.h>
#include <asm/exec.h>
#include <asm/fpsimd.h>
@@ -332,22 +334,27 @@ void arch_release_task_struct(struct task_struct *tsk)
fpsimd_release_task(tsk);
}
-/*
- * src and dst may temporarily have aliased sve_state after task_struct
- * is copied. We cannot fix this properly here, because src may have
- * live SVE state and dst's thread_info may not exist yet, so tweaking
- * either src's or dst's TIF_SVE is not safe.
- *
- * The unaliasing is done in copy_thread() instead. This works because
- * dst is not schedulable or traceable until both of these functions
- * have been called.
- */
int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
if (current->mm)
fpsimd_preserve_current_state();
*dst = *src;
+ /* We rely on the above assignment to initialize dst's thread_flags: */
+ BUILD_BUG_ON(!IS_ENABLED(CONFIG_THREAD_INFO_IN_TASK));
+
+ /*
+ * Detach src's sve_state (if any) from dst so that it does not
+ * get erroneously used or freed prematurely. dst's sve_state
+ * will be allocated on demand later on if dst uses SVE.
+ * For consistency, also clear TIF_SVE here: this could be done
+ * later in copy_process(), but to avoid tripping up future
+ * maintainers it is best not to leave TIF_SVE and sve_state in
+ * an inconsistent state, even temporarily.
+ */
+ dst->thread.sve_state = NULL;
+ clear_tsk_thread_flag(dst, TIF_SVE);
+
return 0;
}
@@ -361,13 +368,6 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
memset(&p->thread.cpu_context, 0, sizeof(struct cpu_context));
/*
- * Unalias p->thread.sve_state (if any) from the parent task
- * and disable discard SVE state for p:
- */
- clear_tsk_thread_flag(p, TIF_SVE);
- p->thread.sve_state = NULL;
-
- /*
* In case p was allocated the same task_struct pointer as some
* other recently-exited task, make sure p is disassociated from
* any cpu that may have run that now-exited task recently.
@@ -633,3 +633,19 @@ static int __init tagged_addr_init(void)
core_initcall(tagged_addr_init);
#endif /* CONFIG_ARM64_TAGGED_ADDR_ABI */
+
+asmlinkage void __sched arm64_preempt_schedule_irq(void)
+{
+ lockdep_assert_irqs_disabled();
+
+ /*
+ * Preempting a task from an IRQ means we leave copies of PSTATE
+ * on the stack. cpufeature's enable calls may modify PSTATE, but
+ * resuming one of these preempted tasks would undo those changes.
+ *
+ * Only allow a task to be preempted once cpufeatures have been
+ * enabled.
+ */
+ if (static_branch_likely(&arm64_const_caps_ready))
+ preempt_schedule_irq();
+}