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/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
* ARM specific definitions for NOLIBC
* Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
*/
#ifndef _NOLIBC_ARCH_ARM_H
#define _NOLIBC_ARCH_ARM_H
#include "compiler.h"
#include "crt.h"
/* Syscalls for ARM in ARM or Thumb modes :
* - registers are 32-bit
* - stack is 8-byte aligned
* ( http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka4127.html)
* - syscall number is passed in r7
* - arguments are in r0, r1, r2, r3, r4, r5
* - the system call is performed by calling svc #0
* - syscall return comes in r0.
* - only lr is clobbered.
* - the arguments are cast to long and assigned into the target registers
* which are then simply passed as registers to the asm code, so that we
* don't have to experience issues with register constraints.
* - the syscall number is always specified last in order to allow to force
* some registers before (gcc refuses a %-register at the last position).
* - in thumb mode without -fomit-frame-pointer, r7 is also used to store the
* frame pointer, and we cannot directly assign it as a register variable,
* nor can we clobber it. Instead we assign the r6 register and swap it
* with r7 before calling svc, and r6 is marked as clobbered.
* We're just using any regular register which we assign to r7 after saving
* it.
*
* Also, ARM supports the old_select syscall if newselect is not available
*/
#define __ARCH_WANT_SYS_OLD_SELECT
#if (defined(__THUMBEB__) || defined(__THUMBEL__)) && \
!defined(NOLIBC_OMIT_FRAME_POINTER)
/* swap r6,r7 needed in Thumb mode since we can't use nor clobber r7 */
#define _NOLIBC_SYSCALL_REG "r6"
#define _NOLIBC_THUMB_SET_R7 "eor r7, r6\neor r6, r7\neor r7, r6\n"
#define _NOLIBC_THUMB_RESTORE_R7 "mov r7, r6\n"
#else /* we're in ARM mode */
/* in Arm mode we can directly use r7 */
#define _NOLIBC_SYSCALL_REG "r7"
#define _NOLIBC_THUMB_SET_R7 ""
#define _NOLIBC_THUMB_RESTORE_R7 ""
#endif /* end THUMB */
#define my_syscall0(num) \
({ \
register long _num __asm__(_NOLIBC_SYSCALL_REG) = (num); \
register long _arg1 __asm__ ("r0"); \
\
__asm__ volatile ( \
_NOLIBC_THUMB_SET_R7 \
"svc #0\n" \
_NOLIBC_THUMB_RESTORE_R7 \
: "=r"(_arg1), "=r"(_num) \
: "r"(_arg1), \
"r"(_num) \
: "memory", "cc", "lr" \
); \
_arg1; \
})
#define my_syscall1(num, arg1) \
({ \
register long _num __asm__(_NOLIBC_SYSCALL_REG) = (num); \
register long _arg1 __asm__ ("r0") = (long)(arg1); \
\
__asm__ volatile ( \
_NOLIBC_THUMB_SET_R7 \
"svc #0\n" \
_NOLIBC_THUMB_RESTORE_R7 \
: "=r"(_arg1), "=r" (_num) \
: "r"(_arg1), \
"r"(_num) \
: "memory", "cc", "lr" \
); \
_arg1; \
})
#define my_syscall2(num, arg1, arg2) \
({ \
register long _num __asm__(_NOLIBC_SYSCALL_REG) = (num); \
register long _arg1 __asm__ ("r0") = (long)(arg1); \
register long _arg2 __asm__ ("r1") = (long)(arg2); \
\
__asm__ volatile ( \
_NOLIBC_THUMB_SET_R7 \
"svc #0\n" \
_NOLIBC_THUMB_RESTORE_R7 \
: "=r"(_arg1), "=r" (_num) \
: "r"(_arg1), "r"(_arg2), \
"r"(_num) \
: "memory", "cc", "lr" \
); \
_arg1; \
})
#define my_syscall3(num, arg1, arg2, arg3) \
({ \
register long _num __asm__(_NOLIBC_SYSCALL_REG) = (num); \
register long _arg1 __asm__ ("r0") = (long)(arg1); \
register long _arg2 __asm__ ("r1") = (long)(arg2); \
register long _arg3 __asm__ ("r2") = (long)(arg3); \
\
__asm__ volatile ( \
_NOLIBC_THUMB_SET_R7 \
"svc #0\n" \
_NOLIBC_THUMB_RESTORE_R7 \
: "=r"(_arg1), "=r" (_num) \
: "r"(_arg1), "r"(_arg2), "r"(_arg3), \
"r"(_num) \
: "memory", "cc", "lr" \
); \
_arg1; \
})
#define my_syscall4(num, arg1, arg2, arg3, arg4) \
({ \
register long _num __asm__(_NOLIBC_SYSCALL_REG) = (num); \
register long _arg1 __asm__ ("r0") = (long)(arg1); \
register long _arg2 __asm__ ("r1") = (long)(arg2); \
register long _arg3 __asm__ ("r2") = (long)(arg3); \
register long _arg4 __asm__ ("r3") = (long)(arg4); \
\
__asm__ volatile ( \
_NOLIBC_THUMB_SET_R7 \
"svc #0\n" \
_NOLIBC_THUMB_RESTORE_R7 \
: "=r"(_arg1), "=r" (_num) \
: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \
"r"(_num) \
: "memory", "cc", "lr" \
); \
_arg1; \
})
#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \
({ \
register long _num __asm__(_NOLIBC_SYSCALL_REG) = (num); \
register long _arg1 __asm__ ("r0") = (long)(arg1); \
register long _arg2 __asm__ ("r1") = (long)(arg2); \
register long _arg3 __asm__ ("r2") = (long)(arg3); \
register long _arg4 __asm__ ("r3") = (long)(arg4); \
register long _arg5 __asm__ ("r4") = (long)(arg5); \
\
__asm__ volatile ( \
_NOLIBC_THUMB_SET_R7 \
"svc #0\n" \
_NOLIBC_THUMB_RESTORE_R7 \
: "=r"(_arg1), "=r" (_num) \
: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
"r"(_num) \
: "memory", "cc", "lr" \
); \
_arg1; \
})
#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \
({ \
register long _num __asm__(_NOLIBC_SYSCALL_REG) = (num); \
register long _arg1 __asm__ ("r0") = (long)(arg1); \
register long _arg2 __asm__ ("r1") = (long)(arg2); \
register long _arg3 __asm__ ("r2") = (long)(arg3); \
register long _arg4 __asm__ ("r3") = (long)(arg4); \
register long _arg5 __asm__ ("r4") = (long)(arg5); \
register long _arg6 __asm__ ("r5") = (long)(arg6); \
\
__asm__ volatile ( \
_NOLIBC_THUMB_SET_R7 \
"svc #0\n" \
_NOLIBC_THUMB_RESTORE_R7 \
: "=r"(_arg1), "=r" (_num) \
: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
"r"(_arg6), "r"(_num) \
: "memory", "cc", "lr" \
); \
_arg1; \
})
/* startup code */
void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
{
__asm__ volatile (
"mov %r0, sp\n" /* save stack pointer to %r0, as arg1 of _start_c */
"and ip, %r0, #-8\n" /* sp must be 8-byte aligned in the callee */
"mov sp, ip\n"
"bl _start_c\n" /* transfer to c runtime */
);
__builtin_unreachable();
}
#endif /* _NOLIBC_ARCH_ARM_H */
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