xtensa: implement user context manipulation functions

Implement getcontext, makecontext, setcontext and swapcontext.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

1 files changed, 116 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/xtensa/setcontext.S b/libc/sysdeps/linux/xtensa/setcontext.S
new file mode 100644
index 000000000..4df7cc049
--- /dev/null
+++ b/libc/sysdeps/linux/xtensa/setcontext.S
@@ -0,0 +1,116 @@
+/* Copyright (C) 2018 - 2022 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+#include "ucontext_i.h"
+
+#if defined(__XTENSA_CALL0_ABI__)
+ENTRY(__setcontext)
+	addi	sp, sp, -16
+	s32i	a0, sp, 0
+	s32i	a2, sp, 4
+
+	addi	a3, a2, UCONTEXT_SIGMASK
+	movi	a4, 0
+	movi	a2, SIG_SETMASK
+	movi	a5, JUMPTARGET (sigprocmask)
+	callx0	a5
+	bnez	a2, .Lerror
+
+	l32i	a2, sp, 4
+	l32i	a0, a2, MCONTEXT_SC_PC
+	l32i	a1, a2, MCONTEXT_SC_A_0 + 4
+
+	/* load callee-saved registers from the context */
+	l32i	a12, a2, MCONTEXT_SC_A_0 + 48
+	l32i	a13, a2, MCONTEXT_SC_A_0 + 52
+	l32i	a14, a2, MCONTEXT_SC_A_0 + 56
+	l32i	a15, a2, MCONTEXT_SC_A_0 + 60
+	movi	a2, 0
+	ret
+.Lerror:
+	l32i	a0, sp, 0
+	addi	sp, sp, 16
+	ret
+END(__setcontext)
+#elif defined(__XTENSA_WINDOWED_ABI__)
+ENTRY(__setcontext)
+	movi	a6, SIG_SETMASK
+	addi	a7, a2, UCONTEXT_SIGMASK
+	movi	a8, 0
+	movi	a4, JUMPTARGET (sigprocmask)
+	callx4	a4
+	bnez	a6, .Lerror
+	movi	a4, __window_spill
+	callx4	a4
+
+	l32i	a0, a2, MCONTEXT_SC_PC
+
+	/* copy registers a0..a3 to spill area */
+	addi	a3, a1, -16
+	l32i	a4, a2, MCONTEXT_SC_A_0 + 0
+	l32i	a5, a2, MCONTEXT_SC_A_0 + 4
+	l32i	a6, a2, MCONTEXT_SC_A_0 + 8
+	l32i	a7, a2, MCONTEXT_SC_A_0 + 12
+	s32i	a4, a3, 0
+	s32i	a5, a3, 4
+	s32i	a6, a3, 8
+	s32i	a7, a3, 12
+
+	/* if it was call4 then register setup is done */
+	extui	a4, a0, 30, 2
+	bltui	a4, 2, 1f
+
+	/* otherwise load spill overflow area address into a3 */
+	addi	a3, a5, -16
+	l32i	a3, a3, 4
+	addi	a3, a3, -32
+	beqi	a4, 2, 2f
+
+	/* copy registers a8..a11 to spill overflow area */
+	addi	a3, a3, -16
+	l32i	a4, a2, MCONTEXT_SC_A_0 + 32
+	l32i	a5, a2, MCONTEXT_SC_A_0 + 36
+	l32i	a6, a2, MCONTEXT_SC_A_0 + 40
+	l32i	a7, a2, MCONTEXT_SC_A_0 + 44
+	s32i	a4, a3, 16
+	s32i	a5, a3, 20
+	s32i	a6, a3, 24
+	s32i	a7, a3, 28
+
+	/* copy registers a4..a7 to spill overflow area */
+2:
+	l32i	a4, a2, MCONTEXT_SC_A_0 + 16
+	l32i	a5, a2, MCONTEXT_SC_A_0 + 20
+	l32i	a6, a2, MCONTEXT_SC_A_0 + 24
+	l32i	a7, a2, MCONTEXT_SC_A_0 + 28
+	s32i	a4, a3, 0
+	s32i	a5, a3, 4
+	s32i	a6, a3, 8
+	s32i	a7, a3, 12
+1:
+	movi	a2, 0
+	retw
+.Lerror:
+	mov	a2, a6
+	retw
+END(__setcontext)
+#else
+#error Unsupported Xtensa ABI
+#endif
+
+weak_alias (__setcontext, setcontext)