x86: Fix __get_wchan() for !STACKTRACE

mainline inclusion
from mainline-v5.16-rc1
commit 5d1ceb39
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5BKYL
CVE: NA

--------------------------------

Use asm/unwind.h to implement wchan, since we cannot always rely on
STACKTRACE=y.

Fixes: bc9bbb81 ("x86: Fix get_wchan() to support the ORC unwinder")
Reported-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NKees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20211022152104.137058575@infradead.orgSigned-off-by: NLin Yujun <linyujun809@huawei.com>
Reviewed-by: NZhang Jianhua <chris.zjh@huawei.com>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

arch/x86/kernel/process.c

@@ -39,6 +39,7 @@
 #include <asm/desc.h>
 #include <asm/prctl.h>
 #include <asm/spec-ctrl.h>
+#include <asm/unwind.h>
 
 #include "process.h"
 
@@ -787,58 +788,23 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
  */
 unsigned long get_wchan(struct task_struct *p)
 {
-	unsigned long start, bottom, top, sp, fp, ip, ret = 0;
-	int count = 0;
+	struct unwind_state state;
+	unsigned long addr = 0;
 
 	if (!p || p == current || p->state == TASK_RUNNING)
 		return 0;
 
-	if (!try_get_task_stack(p))
-		return 0;
-
-	start = (unsigned long)task_stack_page(p);
-	if (!start)
-		goto out;
-
-	/*
-	 * Layout of the stack page:
-	 *
-	 * ----------- topmax = start + THREAD_SIZE - sizeof(unsigned long)
-	 * PADDING
-	 * ----------- top = topmax - TOP_OF_KERNEL_STACK_PADDING
-	 * stack
-	 * ----------- bottom = start
-	 *
-	 * The tasks stack pointer points at the location where the
-	 * framepointer is stored. The data on the stack is:
-	 * ... IP FP ... IP FP
-	 *
-	 * We need to read FP and IP, so we need to adjust the upper
-	 * bound by another unsigned long.
-	 */
-	top = start + THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING;
-	top -= 2 * sizeof(unsigned long);
-	bottom = start;
-
-	sp = READ_ONCE(p->thread.sp);
-	if (sp < bottom || sp > top)
-		goto out;
-
-	fp = READ_ONCE_NOCHECK(((struct inactive_task_frame *)sp)->bp);
-	do {
-		if (fp < bottom || fp > top)
-			goto out;
-		ip = READ_ONCE_NOCHECK(*(unsigned long *)(fp + sizeof(unsigned long)));
-		if (!in_sched_functions(ip)) {
-			ret = ip;
-			goto out;
-		}
-		fp = READ_ONCE_NOCHECK(*(unsigned long *)fp);
-	} while (count++ < 16 && p->state != TASK_RUNNING);
+	for (unwind_start(&state, p, NULL, NULL); !unwind_done(&state);
+	     unwind_next_frame(&state)) {
+	        addr = unwind_get_return_address(&state);
+	        if (!addr)
+	                break;
+	        if (in_sched_functions(addr))
+	                continue;
+	        break;
+	}
 
-out:
-	put_task_stack(p);
-	return ret;
+	return addr;
 }
 
 long do_arch_prctl_common(struct task_struct *task, int option,