CoCalc -- arch-arm.h

GitHub Repository: torvalds/linux
Path: blob/master/tools/include/nolibc/arch-arm.h
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/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
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/*
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 * ARM specific definitions for NOLIBC
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 * Copyright (C) 2017-2022 Willy Tarreau <[email protected]>
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 */
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#ifndef _NOLIBC_ARCH_ARM_H
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#define _NOLIBC_ARCH_ARM_H
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#include "compiler.h"
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#include "crt.h"
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/* Syscalls for ARM in ARM or Thumb modes :
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 *   - registers are 32-bit
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 *   - stack is 8-byte aligned
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 *     ( http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka4127.html)
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 *   - syscall number is passed in r7
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 *   - arguments are in r0, r1, r2, r3, r4, r5
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 *   - the system call is performed by calling svc #0
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 *   - syscall return comes in r0.
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 *   - only lr is clobbered.
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 *   - the arguments are cast to long and assigned into the target registers
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 *     which are then simply passed as registers to the asm code, so that we
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 *     don't have to experience issues with register constraints.
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 *   - the syscall number is always specified last in order to allow to force
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 *     some registers before (gcc refuses a %-register at the last position).
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 *   - in thumb mode without -fomit-frame-pointer, r7 is also used to store the
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 *     frame pointer, and we cannot directly assign it as a register variable,
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 *     nor can we clobber it. Instead we assign the r6 register and swap it
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 *     with r7 before calling svc, and r6 is marked as clobbered.
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 *     We're just using any regular register which we assign to r7 after saving
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 *     it.
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 *
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 * Also, ARM supports the old_select syscall if newselect is not available
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 */
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#define __ARCH_WANT_SYS_OLD_SELECT
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#if (defined(__THUMBEB__) || defined(__THUMBEL__)) && \
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    !defined(NOLIBC_OMIT_FRAME_POINTER)
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/* swap r6,r7 needed in Thumb mode since we can't use nor clobber r7 */
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#define _NOLIBC_SYSCALL_REG         "r6"
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#define _NOLIBC_THUMB_SET_R7        "eor r7, r6\neor r6, r7\neor r7, r6\n"
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#define _NOLIBC_THUMB_RESTORE_R7    "mov r7, r6\n"
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#else  /* we're in ARM mode */
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/* in Arm mode we can directly use r7 */
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#define _NOLIBC_SYSCALL_REG         "r7"
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#define _NOLIBC_THUMB_SET_R7        ""
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#define _NOLIBC_THUMB_RESTORE_R7    ""
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#endif /* end THUMB */
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#define my_syscall0(num)                                                      \
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({                                                                            \
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	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
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	register long _arg1 __asm__ ("r0");                                   \
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									      \
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	__asm__ volatile (                                                    \
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		_NOLIBC_THUMB_SET_R7                                          \
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		"svc #0\n"                                                    \
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		_NOLIBC_THUMB_RESTORE_R7                                      \
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		: "=r"(_arg1), "=r"(_num)                                     \
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		: "r"(_arg1),                                                 \
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		  "r"(_num)                                                   \
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		: "memory", "cc", "lr"                                        \
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	);                                                                    \
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	_arg1;                                                                \
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})
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#define my_syscall1(num, arg1)                                                \
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({                                                                            \
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	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
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	register long _arg1 __asm__ ("r0") = (long)(arg1);                    \
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									      \
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	__asm__ volatile (                                                    \
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		_NOLIBC_THUMB_SET_R7                                          \
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		"svc #0\n"                                                    \
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		_NOLIBC_THUMB_RESTORE_R7                                      \
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		: "=r"(_arg1), "=r" (_num)                                    \
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		: "r"(_arg1),                                                 \
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		  "r"(_num)                                                   \
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		: "memory", "cc", "lr"                                        \
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	);                                                                    \
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	_arg1;                                                                \
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})
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#define my_syscall2(num, arg1, arg2)                                          \
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({                                                                            \
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	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
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	register long _arg1 __asm__ ("r0") = (long)(arg1);                    \
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	register long _arg2 __asm__ ("r1") = (long)(arg2);                    \
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									      \
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	__asm__ volatile (                                                    \
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		_NOLIBC_THUMB_SET_R7                                          \
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		"svc #0\n"                                                    \
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		_NOLIBC_THUMB_RESTORE_R7                                      \
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		: "=r"(_arg1), "=r" (_num)                                    \
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		: "r"(_arg1), "r"(_arg2),                                     \
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		  "r"(_num)                                                   \
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		: "memory", "cc", "lr"                                        \
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	);                                                                    \
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	_arg1;                                                                \
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})
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#define my_syscall3(num, arg1, arg2, arg3)                                    \
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({                                                                            \
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	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
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	register long _arg1 __asm__ ("r0") = (long)(arg1);                    \
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	register long _arg2 __asm__ ("r1") = (long)(arg2);                    \
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	register long _arg3 __asm__ ("r2") = (long)(arg3);                    \
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									      \
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	__asm__ volatile (                                                    \
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		_NOLIBC_THUMB_SET_R7                                          \
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		"svc #0\n"                                                    \
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		_NOLIBC_THUMB_RESTORE_R7                                      \
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		: "=r"(_arg1), "=r" (_num)                                    \
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		: "r"(_arg1), "r"(_arg2), "r"(_arg3),                         \
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		  "r"(_num)                                                   \
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		: "memory", "cc", "lr"                                        \
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	);                                                                    \
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	_arg1;                                                                \
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})
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#define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
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({                                                                            \
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	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
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	register long _arg1 __asm__ ("r0") = (long)(arg1);                    \
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	register long _arg2 __asm__ ("r1") = (long)(arg2);                    \
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	register long _arg3 __asm__ ("r2") = (long)(arg3);                    \
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	register long _arg4 __asm__ ("r3") = (long)(arg4);                    \
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									      \
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	__asm__ volatile (                                                    \
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		_NOLIBC_THUMB_SET_R7                                          \
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		"svc #0\n"                                                    \
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		_NOLIBC_THUMB_RESTORE_R7                                      \
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		: "=r"(_arg1), "=r" (_num)                                    \
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		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4),             \
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		  "r"(_num)                                                   \
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		: "memory", "cc", "lr"                                        \
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	);                                                                    \
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	_arg1;                                                                \
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})
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#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)                        \
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({                                                                            \
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	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
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	register long _arg1 __asm__ ("r0") = (long)(arg1);                    \
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	register long _arg2 __asm__ ("r1") = (long)(arg2);                    \
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	register long _arg3 __asm__ ("r2") = (long)(arg3);                    \
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	register long _arg4 __asm__ ("r3") = (long)(arg4);                    \
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	register long _arg5 __asm__ ("r4") = (long)(arg5);                    \
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									      \
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	__asm__ volatile (                                                    \
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		_NOLIBC_THUMB_SET_R7                                          \
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		"svc #0\n"                                                    \
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		_NOLIBC_THUMB_RESTORE_R7                                      \
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		: "=r"(_arg1), "=r" (_num)                                    \
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		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
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		  "r"(_num)                                                   \
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		: "memory", "cc", "lr"                                        \
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	);                                                                    \
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	_arg1;                                                                \
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})
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#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6)                  \
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({                                                                            \
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	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
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	register long _arg1 __asm__ ("r0") = (long)(arg1);                    \
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	register long _arg2 __asm__ ("r1") = (long)(arg2);                    \
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	register long _arg3 __asm__ ("r2") = (long)(arg3);                    \
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	register long _arg4 __asm__ ("r3") = (long)(arg4);                    \
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	register long _arg5 __asm__ ("r4") = (long)(arg5);                    \
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	register long _arg6 __asm__ ("r5") = (long)(arg6);                    \
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									      \
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	__asm__ volatile (                                                    \
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		_NOLIBC_THUMB_SET_R7                                          \
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		"svc #0\n"                                                    \
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		_NOLIBC_THUMB_RESTORE_R7                                      \
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		: "=r"(_arg1), "=r" (_num)                                    \
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		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
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		  "r"(_arg6), "r"(_num)                                       \
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		: "memory", "cc", "lr"                                        \
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	);                                                                    \
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	_arg1;                                                                \
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})
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/* startup code */
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void __attribute__((weak, noreturn)) __nolibc_entrypoint __no_stack_protector _start(void)
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{
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	__asm__ volatile (
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		"mov r0, sp\n"          /* save stack pointer to %r0, as arg1 of _start_c */
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		"bl  _start_c\n"        /* transfer to c runtime                          */
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	);
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	__nolibc_entrypoint_epilogue();
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}
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#endif /* _NOLIBC_ARCH_ARM_H */
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