add experimental aarch64 support

Ported over from GNU C Library and runtime tested in Qemu.

1 files changed, 89 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/aarch64/crt1.S b/libc/sysdeps/linux/aarch64/crt1.S
new file mode 100644
index 000000000..09d0327ac
--- /dev/null
+++ b/libc/sysdeps/linux/aarch64/crt1.S
@@ -0,0 +1,89 @@
+/* Copyright (C) 1995-2016 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/>.  */
+
+/* This is the canonical entry point, usually the first thing in the text
+   segment.
+
+   Note that the code in the .init section has already been run.
+   This includes _init and _libc_init
+
+
+   At this entry point, most registers' values are unspecified, except:
+
+   x0		Contains a function pointer to be registered with `atexit'.
+		This is how the dynamic linker arranges to have DT_FINI
+		functions called for shared libraries that have been loaded
+		before this code runs.
+
+   sp		The stack contains the arguments and environment:
+		0(sp)			argc
+		8(sp)			argv[0]
+		...
+		(8*argc)(sp)		NULL
+		(8*(argc+1))(sp)	envp[0]
+		...
+					NULL
+ */
+
+	.text
+	.globl _start
+	.type _start,#function
+_start:
+	/* Create an initial frame with 0 LR and FP */
+	mov	x29, #0
+	mov	x30, #0
+
+	/* Setup _fini in argument register */
+	mov	x5, x0
+
+	/* Load argc and a pointer to argv */
+	ldr	x1, [sp, #0]
+	add	x2, sp, #8
+
+	/* Setup stack limit in argument register */
+	mov	x6, sp
+
+#ifdef __PIC__
+        adrp    x0, :got:main
+	ldr     x0, [x0, #:got_lo12:main]
+
+        adrp    x3, :got:_init
+	ldr     x3, [x3, #:got_lo12:_init]
+
+        adrp    x4, :got:_fini
+	ldr     x4, [x4, #:got_lo12:_fini]
+#else
+	/* Set up the other arguments in registers */
+	ldr	x0, =main
+	ldr	x3, =_init
+	ldr	x4, =_fini
+#endif
+
+	/* Let the libc call main and exit with its return code.  */
+	bl	__uClibc_main
+
+	/* should never get here....*/
+	bl	abort
+
+	/* Define a symbol for the first piece of initialized data.  */
+	.data
+	.globl __data_start
+__data_start:
+	.long 0
+	.weak data_start
+	data_start = __data_start