v4.19.13 snapshot.
diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
new file mode 100644
index 0000000..7627455
--- /dev/null
+++ b/arch/x86/kernel/stacktrace.c
@@ -0,0 +1,229 @@
+/*
+ * Stack trace management functions
+ *
+ * Copyright (C) 2006-2009 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ */
+#include <linux/sched.h>
+#include <linux/sched/debug.h>
+#include <linux/sched/task_stack.h>
+#include <linux/stacktrace.h>
+#include <linux/export.h>
+#include <linux/uaccess.h>
+#include <asm/stacktrace.h>
+#include <asm/unwind.h>
+
+static int save_stack_address(struct stack_trace *trace, unsigned long addr,
+ bool nosched)
+{
+ if (nosched && in_sched_functions(addr))
+ return 0;
+
+ if (trace->skip > 0) {
+ trace->skip--;
+ return 0;
+ }
+
+ if (trace->nr_entries >= trace->max_entries)
+ return -1;
+
+ trace->entries[trace->nr_entries++] = addr;
+ return 0;
+}
+
+static void noinline __save_stack_trace(struct stack_trace *trace,
+ struct task_struct *task, struct pt_regs *regs,
+ bool nosched)
+{
+ struct unwind_state state;
+ unsigned long addr;
+
+ if (regs)
+ save_stack_address(trace, regs->ip, nosched);
+
+ for (unwind_start(&state, task, regs, NULL); !unwind_done(&state);
+ unwind_next_frame(&state)) {
+ addr = unwind_get_return_address(&state);
+ if (!addr || save_stack_address(trace, addr, nosched))
+ break;
+ }
+
+ if (trace->nr_entries < trace->max_entries)
+ trace->entries[trace->nr_entries++] = ULONG_MAX;
+}
+
+/*
+ * Save stack-backtrace addresses into a stack_trace buffer.
+ */
+void save_stack_trace(struct stack_trace *trace)
+{
+ trace->skip++;
+ __save_stack_trace(trace, current, NULL, false);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace);
+
+void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
+{
+ __save_stack_trace(trace, current, regs, false);
+}
+
+void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+{
+ if (!try_get_task_stack(tsk))
+ return;
+
+ if (tsk == current)
+ trace->skip++;
+ __save_stack_trace(trace, tsk, NULL, true);
+
+ put_task_stack(tsk);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
+
+#ifdef CONFIG_HAVE_RELIABLE_STACKTRACE
+
+static int __always_inline
+__save_stack_trace_reliable(struct stack_trace *trace,
+ struct task_struct *task)
+{
+ struct unwind_state state;
+ struct pt_regs *regs;
+ unsigned long addr;
+
+ for (unwind_start(&state, task, NULL, NULL);
+ !unwind_done(&state) && !unwind_error(&state);
+ unwind_next_frame(&state)) {
+
+ regs = unwind_get_entry_regs(&state, NULL);
+ if (regs) {
+ /* Success path for user tasks */
+ if (user_mode(regs))
+ goto success;
+
+ /*
+ * Kernel mode registers on the stack indicate an
+ * in-kernel interrupt or exception (e.g., preemption
+ * or a page fault), which can make frame pointers
+ * unreliable.
+ */
+
+ if (IS_ENABLED(CONFIG_FRAME_POINTER))
+ return -EINVAL;
+ }
+
+ addr = unwind_get_return_address(&state);
+
+ /*
+ * A NULL or invalid return address probably means there's some
+ * generated code which __kernel_text_address() doesn't know
+ * about.
+ */
+ if (!addr)
+ return -EINVAL;
+
+ if (save_stack_address(trace, addr, false))
+ return -EINVAL;
+ }
+
+ /* Check for stack corruption */
+ if (unwind_error(&state))
+ return -EINVAL;
+
+ /* Success path for non-user tasks, i.e. kthreads and idle tasks */
+ if (!(task->flags & (PF_KTHREAD | PF_IDLE)))
+ return -EINVAL;
+
+success:
+ if (trace->nr_entries < trace->max_entries)
+ trace->entries[trace->nr_entries++] = ULONG_MAX;
+
+ return 0;
+}
+
+/*
+ * This function returns an error if it detects any unreliable features of the
+ * stack. Otherwise it guarantees that the stack trace is reliable.
+ *
+ * If the task is not 'current', the caller *must* ensure the task is inactive.
+ */
+int save_stack_trace_tsk_reliable(struct task_struct *tsk,
+ struct stack_trace *trace)
+{
+ int ret;
+
+ /*
+ * If the task doesn't have a stack (e.g., a zombie), the stack is
+ * "reliably" empty.
+ */
+ if (!try_get_task_stack(tsk))
+ return 0;
+
+ ret = __save_stack_trace_reliable(trace, tsk);
+
+ put_task_stack(tsk);
+
+ return ret;
+}
+#endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */
+
+/* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */
+
+struct stack_frame_user {
+ const void __user *next_fp;
+ unsigned long ret_addr;
+};
+
+static int
+copy_stack_frame(const void __user *fp, struct stack_frame_user *frame)
+{
+ int ret;
+
+ if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
+ return 0;
+
+ ret = 1;
+ pagefault_disable();
+ if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
+ ret = 0;
+ pagefault_enable();
+
+ return ret;
+}
+
+static inline void __save_stack_trace_user(struct stack_trace *trace)
+{
+ const struct pt_regs *regs = task_pt_regs(current);
+ const void __user *fp = (const void __user *)regs->bp;
+
+ if (trace->nr_entries < trace->max_entries)
+ trace->entries[trace->nr_entries++] = regs->ip;
+
+ while (trace->nr_entries < trace->max_entries) {
+ struct stack_frame_user frame;
+
+ frame.next_fp = NULL;
+ frame.ret_addr = 0;
+ if (!copy_stack_frame(fp, &frame))
+ break;
+ if ((unsigned long)fp < regs->sp)
+ break;
+ if (frame.ret_addr) {
+ trace->entries[trace->nr_entries++] =
+ frame.ret_addr;
+ }
+ if (fp == frame.next_fp)
+ break;
+ fp = frame.next_fp;
+ }
+}
+
+void save_stack_trace_user(struct stack_trace *trace)
+{
+ /*
+ * Trace user stack if we are not a kernel thread
+ */
+ if (current->mm) {
+ __save_stack_trace_user(trace);
+ }
+ if (trace->nr_entries < trace->max_entries)
+ trace->entries[trace->nr_entries++] = ULONG_MAX;
+}