arm64: fix backtraces of KASAN kernel dumpfile truncated

We met "bt" command on KASAN kernel vmcore display truncated backtraces
like this:

  crash> bt
  PID: 4131   TASK: ffff8001521df000  CPU: 3   COMMAND: "bash"
   #0 [ffff2000224b0cb0] machine_kexec_prepare at ffff2000200bff4c

After digging the root cause, it turns out that arm64_in_kdump_text()
found wrong bt->bptr at "machine_kexec" branch.

Disassemble machine_kexec() of KASAN vmlinux (gcc 7.3.0):

  crash> dis -x machine_kexec
  0xffff2000200bff50 <machine_kexec>:     stp     x29, x30, [sp,#-208]!
  0xffff2000200bff54 <machine_kexec+0x4>: mov     x29, sp
  0xffff2000200bff58 <machine_kexec+0x8>: stp     x19, x20, [sp,#16]
  0xffff2000200bff5c <machine_kexec+0xc>: str     x24, [sp,#56]
  0xffff2000200bff60 <machine_kexec+0x10>:        str     x26, [sp,#72]
  0xffff2000200bff64 <machine_kexec+0x14>:        mov     x2, #0x8ab3
  0xffff2000200bff68 <machine_kexec+0x18>:        add     x1, x29, #0x70
  0xffff2000200bff6c <machine_kexec+0x1c>:        lsr     x1, x1, #3
  0xffff2000200bff70 <machine_kexec+0x20>:        movk    x2, #0x41b5, lsl #16
  0xffff2000200bff74 <machine_kexec+0x24>:        mov     x19, #0x200000000000
  0xffff2000200bff78 <machine_kexec+0x28>:        adrp    x3, 0xffff2000224b0000
  0xffff2000200bff7c <machine_kexec+0x2c>:        movk    x19, #0xdfff, lsl #48
  0xffff2000200bff80 <machine_kexec+0x30>:        add     x3, x3, #0xcb0
  0xffff2000200bff84 <machine_kexec+0x34>:        add     x4, x1, x19
  0xffff2000200bff88 <machine_kexec+0x38>:        stp     x2, x3, [x29,#112]
  0xffff2000200bff8c <machine_kexec+0x3c>:        adrp    x2, 0xffff2000200bf000 <swsusp_arch_resume+0x1e8>
  0xffff2000200bff90 <machine_kexec+0x40>:        add     x2, x2, #0xf50
  0xffff2000200bff94 <machine_kexec+0x44>:        str     x2, [x29,#128]
  0xffff2000200bff98 <machine_kexec+0x48>:        mov     w2, #0xf1f1f1f1
  0xffff2000200bff9c <machine_kexec+0x4c>:        str     w2, [x1,x19]
  0xffff2000200bffa0 <machine_kexec+0x50>:        mov     w2, #0xf200
  0xffff2000200bffa4 <machine_kexec+0x54>:        mov     w1, #0xf3f3f3f3
  0xffff2000200bffa8 <machine_kexec+0x58>:        movk    w2, #0xf2f2, lsl #16
  0xffff2000200bffac <machine_kexec+0x5c>:        stp     w2, w1, [x4,#4]

We notice that:
1. machine_kexec() start address is 0xffff2000200bff50
2. the instruction at machine_kexec+0x44 stores the same value
   0xffff2000200bff50 (comes from 0xffff2000200bf000 + 0xf50)
   into stack postion [x29,#128].

When arm64_in_kdump_text() searches for LR from stack, it met
0xffff2000200bff50 firstly, so got wrong bt->bptr.

We know that the real LR is always greater than the start address
of a function, so let's fix it by changing the search conditon to
(*ptr > xxx_start) && (*ptr < xxx_end).

Signed-off-by: Ding Hui <[email protected]>

arm64.c

@@ -3479,7 +3479,7 @@ arm64_in_kdump_text(struct bt_info *bt, struct arm64_stackframe *frame)
 	ms = machdep->machspec;
 	for (ptr = start - 8; ptr >= base; ptr--) {
 		if (bt->flags & BT_OPT_BACK_TRACE) {
-			if ((*ptr >= ms->crash_kexec_start) &&
+			if ((*ptr > ms->crash_kexec_start) &&
 			    (*ptr < ms->crash_kexec_end) &&
 			    INSTACK(*(ptr - 1), bt)) {
 				bt->bptr = ((ulong)(ptr - 1) - (ulong)base)
@@ -3488,7 +3488,7 @@ arm64_in_kdump_text(struct bt_info *bt, struct arm64_stackframe *frame)
 					fprintf(fp, "%lx: %lx (crash_kexec)\n", bt->bptr, *ptr);
 				return TRUE;
 			}
-			if ((*ptr >= ms->crash_save_cpu_start) &&
+			if ((*ptr > ms->crash_save_cpu_start) &&
 			    (*ptr < ms->crash_save_cpu_end) &&
 			    INSTACK(*(ptr - 1), bt)) {
 				bt->bptr = ((ulong)(ptr - 1) - (ulong)base)
@@ -3498,14 +3498,14 @@ arm64_in_kdump_text(struct bt_info *bt, struct arm64_stackframe *frame)
 				return TRUE;
 			}
 		} else {
-			if ((*ptr >= ms->machine_kexec_start) && (*ptr < ms->machine_kexec_end)) {
+			if ((*ptr > ms->machine_kexec_start) && (*ptr < ms->machine_kexec_end)) {
 				bt->bptr = ((ulong)ptr - (ulong)base)
 					   + task_to_stackbase(bt->tc->task);
 				if (CRASHDEBUG(1))
 					fprintf(fp, "%lx: %lx (machine_kexec)\n", bt->bptr, *ptr);
 				return TRUE;
 			}
-			if ((*ptr >= ms->crash_kexec_start) && (*ptr < ms->crash_kexec_end)) {
+			if ((*ptr > ms->crash_kexec_start) && (*ptr < ms->crash_kexec_end)) {
 				/*
 				 *  Stash the first crash_kexec frame in case the machine_kexec
 				 *  frame is not found.
@@ -3519,7 +3519,7 @@ arm64_in_kdump_text(struct bt_info *bt, struct arm64_stackframe *frame)
 				}
 				continue;
 			}
-			if ((*ptr >= ms->crash_save_cpu_start) && (*ptr < ms->crash_save_cpu_end)) {
+			if ((*ptr > ms->crash_save_cpu_start) && (*ptr < ms->crash_save_cpu_end)) {
 				bt->bptr = ((ulong)ptr - (ulong)base)
 					   + task_to_stackbase(bt->tc->task);
 				if (CRASHDEBUG(1))
@@ -3566,7 +3566,7 @@ arm64_in_kdump_text_on_irq_stack(struct bt_info *bt)
 
 	for (ptr = start - 8; ptr >= base; ptr--) {
 		if (bt->flags & BT_OPT_BACK_TRACE) {
-			if ((*ptr >= ms->crash_kexec_start) &&
+			if ((*ptr > ms->crash_kexec_start) &&
 			    (*ptr < ms->crash_kexec_end) &&
 			    INSTACK(*(ptr - 1), bt)) {
 				bt->bptr = ((ulong)(ptr - 1) - (ulong)base) + stackbase;
@@ -3576,7 +3576,7 @@ arm64_in_kdump_text_on_irq_stack(struct bt_info *bt)
 				FREEBUF(stackbuf);
 				return TRUE;
 			}
-			if ((*ptr >= ms->crash_save_cpu_start) &&
+			if ((*ptr > ms->crash_save_cpu_start) &&
 			    (*ptr < ms->crash_save_cpu_end) &&
 			    INSTACK(*(ptr - 1), bt)) {
 				bt->bptr = ((ulong)(ptr - 1) - (ulong)base) + stackbase;
@@ -3587,15 +3587,15 @@ arm64_in_kdump_text_on_irq_stack(struct bt_info *bt)
 				return TRUE;
 			}
 		} else {
-			if ((*ptr >= ms->crash_kexec_start) && (*ptr < ms->crash_kexec_end)) {
+			if ((*ptr > ms->crash_kexec_start) && (*ptr < ms->crash_kexec_end)) {
 				bt->bptr = ((ulong)ptr - (ulong)base) + stackbase;
 				if (CRASHDEBUG(1))
 					fprintf(fp, "%lx: %lx (crash_kexec on IRQ stack)\n", 
 						bt->bptr, *ptr);
 				FREEBUF(stackbuf);
 				return TRUE;
 			}
-			if ((*ptr >= ms->crash_save_cpu_start) && (*ptr < ms->crash_save_cpu_end)) {
+			if ((*ptr > ms->crash_save_cpu_start) && (*ptr < ms->crash_save_cpu_end)) {
 				bt->bptr = ((ulong)ptr - (ulong)base) + stackbase;
 				if (CRASHDEBUG(1))
 					fprintf(fp, "%lx: %lx (crash_save_cpu on IRQ stack)\n",