1 files changed, 100 insertions, 0 deletions
diff --git a/libc/sysdeps/linux/xtensa/__start_context.S b/libc/sysdeps/linux/xtensa/__start_context.S
new file mode 100644
index 000000000..a30d7b618
--- /dev/null
+++ b/libc/sysdeps/linux/xtensa/__start_context.S
@@ -0,0 +1,100 @@
+/* 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>
+
+#if defined(__XTENSA_CALL0_ABI__)
+/*
+ * There's no entry instruction, makecontext sets up ucontext_t as if
+ * getcontext was called above and is about to return here.
+ * Registers on entry to this function:
+ *   a12: func to call
+ *   a13: ucp->uc_link, next context to activate if func returns
+ *   a14: func argc
+ */
+	.literal_position
+
+ENTRY_PREFIX(__start_context)
+
+	beqz	a14, 1f
+
+	/* load func arguments 0..1 from stack and free that space */
+	l32i	a2, a1, 8
+	l32i	a3, a1, 12
+	addi	a1, a1, 16
+	bltui	a14, 3, 1f
+
+	/* load func arguments 2..5 from stack and free that space */
+	l32i	a4, a1, 0
+	l32i	a5, a1, 4
+	l32i	a6, a1, 8
+	l32i	a7, a1, 12
+	addi	a1, a1, 16
+	/* func arguments 6..argc - 1 are now at the top of the stack */
+1:
+	callx0	a12
+	beqz	a13, 1f
+	mov	a2, a13
+	movi	a4, JUMPTARGET (setcontext)
+	callx0	a4
+1:
+	movi	a4, JUMPTARGET (_exit)
+	movi	a2, 0
+	callx0	a4
+	ill
+END(__start_context)
+#elif defined(__XTENSA_WINDOWED_ABI__)
+/*
+ * There's no entry instruction, makecontext sets up ucontext_t as if
+ * getcontext was called above and is about to return here.
+ * Registers on entry to this function:
+ *   a2: func to call
+ *   a3: ucp->uc_link, next context to activate if func returns
+ *   a4: func argc
+ *   a5..a7: func arguments 0..2
+ */
+	.literal_position
+
+ENTRY_PREFIX(__start_context)
+
+	mov	a10, a5
+	mov	a11, a6
+	mov	a12, a7
+	bltui	a4, 4, 1f
+
+	/* load func arguments 3..5 from stack and free that space */
+	l32i	a13, a1, 4
+	l32i	a14, a1, 8
+	l32i	a15, a1, 12
+	addi	a5, a1, 16
+	movsp	a1, a5
+	/* func arguments 6..argc - 1 are now at the top of the stack */
+1:
+	callx8	a2
+	beqz	a3, 1f
+	mov	a6, a3
+	movi	a4, JUMPTARGET (setcontext)
+	callx4	a4
+1:
+	movi	a4, JUMPTARGET (_exit)
+	movi	a6, 0
+	callx4	a4
+	ill
+END(__start_context)
+#else
+#error Unsupported Xtensa ABI
+#endif