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a6f29a2c41
The environ is retrieved from the _start code and is easy to store at this moment. Let's declare the variable weak and store the value into it. By not being static it will be visible to all units. By being weak, if some programs already declared it, they will continue to be able to use it. This was tested in arm and thumb1 and thumb2 modes, and for each mode, both with environ inherited from _start and extracted from envp. Signed-off-by: Willy Tarreau <w@1wt.eu> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
229 lines
11 KiB
C
229 lines
11 KiB
C
/* 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 <w@1wt.eu>
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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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/* The struct returned by the stat() syscall, 32-bit only, the syscall returns
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* exactly 56 bytes (stops before the unused array). In big endian, the format
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* differs as devices are returned as short only.
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*/
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struct sys_stat_struct {
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#if defined(__ARMEB__)
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unsigned short st_dev;
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unsigned short __pad1;
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#else
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unsigned long st_dev;
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#endif
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unsigned long st_ino;
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unsigned short st_mode;
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unsigned short st_nlink;
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unsigned short st_uid;
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unsigned short st_gid;
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#if defined(__ARMEB__)
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unsigned short st_rdev;
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unsigned short __pad2;
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#else
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unsigned long st_rdev;
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#endif
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unsigned long st_size;
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unsigned long st_blksize;
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unsigned long st_blocks;
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unsigned long st_atime;
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unsigned long st_atime_nsec;
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unsigned long st_mtime;
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unsigned long st_mtime_nsec;
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unsigned long st_ctime;
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unsigned long st_ctime_nsec;
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unsigned long __unused[2];
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};
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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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char **environ __attribute__((weak));
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/* startup code */
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void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void)
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{
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__asm__ volatile (
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"pop {%r0}\n" // argc was in the stack
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"mov %r1, %sp\n" // argv = sp
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"add %r2, %r0, $1\n" // envp = (argc + 1) ...
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"lsl %r2, %r2, $2\n" // * 4 ...
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"add %r2, %r2, %r1\n" // + argv
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"ldr %r3, 1f\n" // r3 = &environ (see below)
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"str %r2, [r3]\n" // store envp into environ
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"mov %r3, $8\n" // AAPCS : sp must be 8-byte aligned in the
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"neg %r3, %r3\n" // callee, and bl doesn't push (lr=pc)
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"and %r3, %r3, %r1\n" // so we do sp = r1(=sp) & r3(=-8);
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"mov %sp, %r3\n" //
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"bl main\n" // main() returns the status code, we'll exit with it.
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"movs r7, $1\n" // NR_exit == 1
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"svc $0x00\n"
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".align 2\n" // below are the pointers to a few variables
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"1:\n"
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".word environ\n"
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);
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__builtin_unreachable();
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}
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#endif // _NOLIBC_ARCH_ARM_H
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