v4.19.13 snapshot.
diff --git a/arch/alpha/lib/dbg_stackkill.S b/arch/alpha/lib/dbg_stackkill.S
new file mode 100644
index 0000000..6d9197e
--- /dev/null
+++ b/arch/alpha/lib/dbg_stackkill.S
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * arch/alpha/lib/dbg_stackkill.S
+ * Contributed by Richard Henderson (rth@cygnus.com)
+ *
+ * Clobber the balance of the kernel stack, hoping to catch
+ * uninitialized local variables in the act.
+ */
+
+#include <asm/asm-offsets.h>
+
+ .text
+ .set noat
+
+ .align 5
+ .globl _mcount
+ .ent _mcount
+_mcount:
+ .frame $30, 0, $28, 0
+ .prologue 0
+
+ ldi $0, 0xdeadbeef
+ lda $2, -STACK_SIZE
+ sll $0, 32, $1
+ and $30, $2, $2
+ or $0, $1, $0
+ lda $2, TASK_SIZE($2)
+ cmpult $2, $30, $1
+ beq $1, 2f
+1: stq $0, 0($2)
+ addq $2, 8, $2
+ cmpult $2, $30, $1
+ bne $1, 1b
+2: ret ($28)
+
+ .end _mcount