Implement _Unwind_Resume in libc on top of <unwind-link.h>

Temporarily move the arm _Unwind_Resume implementation to the file
used by libpthread.  It will be ported to <unwind-link.h> along with
the rest of nptl.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 46 insertions, 2 deletions

diff --git a/sysdeps/arm/pt-arm-unwind-resume.S b/sysdeps/arm/pt-arm-unwind-resume.S
index 7cb555c02b..d579848696 100644
--- a/sysdeps/arm/pt-arm-unwind-resume.S
+++ b/sysdeps/arm/pt-arm-unwind-resume.S
@@ -1,2 +1,46 @@
-#define __libgcc_s_init	pthread_cancel_init
-#include <arm-unwind-resume.S>
+/* _Unwind_Resume wrapper for ARM EABI.
+   Copyright (C) 2015-2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+
+/* This is just implementing exactly what the C version does.
+   We do it in assembly just to ensure that we get an unmolested tail
+   call to the libgcc function, which is necessary for the ARM unwinder.  */
+
+ENTRY (_Unwind_Resume)
+	LDR_HIDDEN (ip, ip, __libgcc_s_resume, 0)
+	cmp	ip, #0
+	beq	1f
+0:	PTR_DEMANGLE (ip, ip, r2, r3)
+	bx	ip
+
+	/* We need to save and restore LR (for our own return address)
+	   and R0 (for the argument to _Unwind_Resume) around the call.  */
+1:	push	{r0, lr}
+	cfi_adjust_cfa_offset (8)
+	cfi_rel_offset (r0, 0)
+	cfi_rel_offset (lr, 4)
+	bl	pthread_cancel_init
+	pop	{r0, lr}
+	cfi_adjust_cfa_offset (-8)
+	cfi_restore (r0)
+	cfi_restore (lr)
+
+	LDR_HIDDEN (ip, ip, __libgcc_s_resume, 0)
+	b	0b
+END (_Unwind_Resume)