Index: lib/libc/arch/x86_64/sys/__sigtramp2.S
===================================================================
RCS file: /cvsroot/src/lib/libc/arch/x86_64/sys/__sigtramp2.S,v
retrieving revision 1.7
diff -u -r1.7 __sigtramp2.S
--- lib/libc/arch/x86_64/sys/__sigtramp2.S	2 Dec 2019 01:38:54 -0000	1.7
+++ lib/libc/arch/x86_64/sys/__sigtramp2.S	12 Oct 2020 00:42:16 -0000
@@ -43,6 +43,36 @@
  */
 NENTRY(__sigtramp_siginfo_2)
 	.cfi_startproc
+	.cfi_signal_frame
+	/*
+	 * Specify the virtual register CFA - call frame address - which is
+	 * pretty much the stack-pointer before entry and then specify the other
+	 * registers as offests from that address.
+	 */
+	.cfi_def_cfa 15, 0	/* R15, offset=0 */
+	/*
+	 * The Register rN is a raw register number used in CFI.
+	 * The value is the offset of the register in ucontext_t.
+	 *
+	 * For RAX it is: offsetof(ucontext_t, uc_mcontext.__gregs[_REG_RAX]).
+	 */
+	.cfi_offset 0,168	/* RAX */
+	.cfi_offset 1,72	/* RDX */
+	.cfi_offset 2,80	/* RCX */
+	.cfi_offset 3,160	/* RBX */
+	.cfi_offset 4,64	/* RSI */
+	.cfi_offset 5,56	/* RDI */
+	.cfi_offset 6,152	/* RBP */
+	/* The unwinder will use the CFA to restore RSP. */
+	.cfi_offset 8,88	/* R8 */
+	.cfi_offset 9,96	/* R9 */
+	.cfi_offset 10,104	/* R10 */
+	.cfi_offset 11,112	/* R11 */
+	.cfi_offset 12,120	/* R12 */
+	.cfi_offset 13,128	/* R13 */
+	.cfi_offset 14,136	/* R14 */
+	.cfi_offset 15,144	/* R15 */
+	.cfi_offset 16,224	/* RIP */
 	.cfi_def_cfa rsp, 8
 	movq	%r15,%rdi
 	movq	$SYS_setcontext, %rax