1 files changed, 43 insertions, 41 deletions

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index aacf2f5559a8..5369e649fa79 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -40,6 +40,7 @@
 #include <linux/percpu.h>
 #include <linux/thread_info.h>
 #include <linux/prctl.h>
+#include <linux/stacktrace.h>
 
 #include <asm/alternative.h>
 #include <asm/compat.h>
@@ -439,34 +440,26 @@ static void entry_task_switch(struct task_struct *next)
 
 /*
  * ARM erratum 1418040 handling, affecting the 32bit view of CNTVCT.
- * Assuming the virtual counter is enabled at the beginning of times:
- *
- * - disable access when switching from a 64bit task to a 32bit task
- * - enable access when switching from a 32bit task to a 64bit task
+ * Ensure access is disabled when switching to a 32bit task, ensure
+ * access is enabled when switching to a 64bit task.
  */
-static void erratum_1418040_thread_switch(struct task_struct *prev,
-					  struct task_struct *next)
+static void erratum_1418040_thread_switch(struct task_struct *next)
 {
-	bool prev32, next32;
-	u64 val;
-
-	if (!IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040))
-		return;
-
-	prev32 = is_compat_thread(task_thread_info(prev));
-	next32 = is_compat_thread(task_thread_info(next));
-
-	if (prev32 == next32 || !this_cpu_has_cap(ARM64_WORKAROUND_1418040))
+	if (!IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040) ||
+	    !this_cpu_has_cap(ARM64_WORKAROUND_1418040))
 		return;
 
-	val = read_sysreg(cntkctl_el1);
-
-	if (!next32)
-		val |= ARCH_TIMER_USR_VCT_ACCESS_EN;
+	if (is_compat_thread(task_thread_info(next)))
+		sysreg_clear_set(cntkctl_el1, ARCH_TIMER_USR_VCT_ACCESS_EN, 0);
 	else
-		val &= ~ARCH_TIMER_USR_VCT_ACCESS_EN;
+		sysreg_clear_set(cntkctl_el1, 0, ARCH_TIMER_USR_VCT_ACCESS_EN);
+}
 
-	write_sysreg(val, cntkctl_el1);
+static void erratum_1418040_new_exec(void)
+{
+	preempt_disable();
+	erratum_1418040_thread_switch(current);
+	preempt_enable();
 }
 
 /*
@@ -490,7 +483,8 @@ void update_sctlr_el1(u64 sctlr)
 /*
  * Thread switching.
  */
-__notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
+__notrace_funcgraph __sched
+struct task_struct *__switch_to(struct task_struct *prev,
 				struct task_struct *next)
 {
 	struct task_struct *last;
@@ -501,7 +495,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
 	contextidr_thread_switch(next);
 	entry_task_switch(next);
 	ssbs_thread_switch(next);
-	erratum_1418040_thread_switch(prev, next);
+	erratum_1418040_thread_switch(next);
 	ptrauth_thread_switch_user(next);
 
 	/*
@@ -528,30 +522,37 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
 	return last;
 }
 
+struct wchan_info {
+	unsigned long	pc;
+	int		count;
+};
+
+static bool get_wchan_cb(void *arg, unsigned long pc)
+{
+	struct wchan_info *wchan_info = arg;
+
+	if (!in_sched_functions(pc)) {
+		wchan_info->pc = pc;
+		return false;
+	}
+	return wchan_info->count++ < 16;
+}
+
 unsigned long __get_wchan(struct task_struct *p)
 {
-	struct stackframe frame;
-	unsigned long stack_page, ret = 0;
-	int count = 0;
+	struct wchan_info wchan_info = {
+		.pc = 0,
+		.count = 0,
+	};
 
-	stack_page = (unsigned long)try_get_task_stack(p);
-	if (!stack_page)
+	if (!try_get_task_stack(p))
 		return 0;
 
-	start_backtrace(&frame, thread_saved_fp(p), thread_saved_pc(p));
-
-	do {
-		if (unwind_frame(p, &frame))
-			goto out;
-		if (!in_sched_functions(frame.pc)) {
-			ret = frame.pc;
-			goto out;
-		}
-	} while (count++ < 16);
+	arch_stack_walk(get_wchan_cb, &wchan_info, p, NULL);
 
-out:
 	put_task_stack(p);
-	return ret;
+
+	return wchan_info.pc;
 }
 
 unsigned long arch_align_stack(unsigned long sp)
@@ -611,6 +612,7 @@ void arch_setup_new_exec(void)
 	current->mm->context.flags = mmflags;
 	ptrauth_thread_init_user();
 	mte_thread_init_user();
+	erratum_1418040_new_exec();
 
 	if (task_spec_ssb_noexec(current)) {
 		arch_prctl_spec_ctrl_set(current, PR_SPEC_STORE_BYPASS,