200 lines
10 KiB
C
200 lines
10 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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#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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"and ip, r0, #-8\n" /* sp must be 8-byte aligned in the callee */
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"mov sp, ip\n"
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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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