2022-02-07 16:23:17 +00:00
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/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
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/*
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* RISCV (32 and 64) 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_RISCV_H
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#define _NOLIBC_ARCH_RISCV_H
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struct sys_stat_struct {
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unsigned long st_dev; /* Device. */
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unsigned long st_ino; /* File serial number. */
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unsigned int st_mode; /* File mode. */
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unsigned int st_nlink; /* Link count. */
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unsigned int st_uid; /* User ID of the file's owner. */
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unsigned int st_gid; /* Group ID of the file's group. */
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unsigned long st_rdev; /* Device number, if device. */
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unsigned long __pad1;
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long st_size; /* Size of file, in bytes. */
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int st_blksize; /* Optimal block size for I/O. */
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int __pad2;
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long st_blocks; /* Number 512-byte blocks allocated. */
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long st_atime; /* Time of last access. */
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unsigned long st_atime_nsec;
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long st_mtime; /* Time of last modification. */
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unsigned long st_mtime_nsec;
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long st_ctime; /* Time of last status change. */
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unsigned long st_ctime_nsec;
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unsigned int __unused4;
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unsigned int __unused5;
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};
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#if __riscv_xlen == 64
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#define PTRLOG "3"
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#define SZREG "8"
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#elif __riscv_xlen == 32
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#define PTRLOG "2"
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#define SZREG "4"
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#endif
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/* Syscalls for RISCV :
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* - stack is 16-byte aligned
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* - syscall number is passed in a7
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* - arguments are in a0, a1, a2, a3, a4, a5
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* - the system call is performed by calling ecall
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* - syscall return comes in a0
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* - the arguments are cast to long and assigned into the target
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* registers which are then simply passed as registers to the asm code,
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* so that we don't have to experience issues with register constraints.
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*
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* On riscv, select() is not implemented so we have to use pselect6().
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*/
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#define __ARCH_WANT_SYS_PSELECT6
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#define my_syscall0(num) \
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({ \
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2022-03-29 10:17:30 +00:00
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register long _num __asm__ ("a7") = (num); \
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register long _arg1 __asm__ ("a0"); \
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2022-02-07 16:23:17 +00:00
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\
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2022-03-29 10:17:30 +00:00
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__asm__ volatile ( \
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2022-02-07 16:23:17 +00:00
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"ecall\n\t" \
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: "=r"(_arg1) \
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: "r"(_num) \
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: "memory", "cc" \
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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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2022-03-29 10:17:30 +00:00
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register long _num __asm__ ("a7") = (num); \
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register long _arg1 __asm__ ("a0") = (long)(arg1); \
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2022-02-07 16:23:17 +00:00
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\
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2022-03-29 10:17:30 +00:00
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__asm__ volatile ( \
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2022-02-07 16:23:17 +00:00
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"ecall\n" \
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: "+r"(_arg1) \
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: "r"(_num) \
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: "memory", "cc" \
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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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2022-03-29 10:17:30 +00:00
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register long _num __asm__ ("a7") = (num); \
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register long _arg1 __asm__ ("a0") = (long)(arg1); \
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register long _arg2 __asm__ ("a1") = (long)(arg2); \
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2022-02-07 16:23:17 +00:00
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\
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__asm__ volatile ( \
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2022-02-07 16:23:17 +00:00
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"ecall\n" \
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: "+r"(_arg1) \
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: "r"(_arg2), \
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"r"(_num) \
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: "memory", "cc" \
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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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2022-03-29 10:17:30 +00:00
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register long _num __asm__ ("a7") = (num); \
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register long _arg1 __asm__ ("a0") = (long)(arg1); \
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register long _arg2 __asm__ ("a1") = (long)(arg2); \
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register long _arg3 __asm__ ("a2") = (long)(arg3); \
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2022-02-07 16:23:17 +00:00
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\
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2022-03-29 10:17:30 +00:00
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__asm__ volatile ( \
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2022-02-07 16:23:17 +00:00
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"ecall\n\t" \
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: "+r"(_arg1) \
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: "r"(_arg2), "r"(_arg3), \
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"r"(_num) \
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: "memory", "cc" \
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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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2022-03-29 10:17:30 +00:00
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register long _num __asm__ ("a7") = (num); \
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register long _arg1 __asm__ ("a0") = (long)(arg1); \
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register long _arg2 __asm__ ("a1") = (long)(arg2); \
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register long _arg3 __asm__ ("a2") = (long)(arg3); \
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register long _arg4 __asm__ ("a3") = (long)(arg4); \
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2022-02-07 16:23:17 +00:00
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\
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2022-03-29 10:17:30 +00:00
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__asm__ volatile ( \
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2022-02-07 16:23:17 +00:00
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"ecall\n" \
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: "+r"(_arg1) \
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: "r"(_arg2), "r"(_arg3), "r"(_arg4), \
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"r"(_num) \
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: "memory", "cc" \
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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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2022-03-29 10:17:30 +00:00
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register long _num __asm__ ("a7") = (num); \
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register long _arg1 __asm__ ("a0") = (long)(arg1); \
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register long _arg2 __asm__ ("a1") = (long)(arg2); \
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register long _arg3 __asm__ ("a2") = (long)(arg3); \
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register long _arg4 __asm__ ("a3") = (long)(arg4); \
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register long _arg5 __asm__ ("a4") = (long)(arg5); \
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2022-02-07 16:23:17 +00:00
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\
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2022-03-29 10:17:30 +00:00
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__asm__ volatile ( \
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2022-02-07 16:23:17 +00:00
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"ecall\n" \
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: "+r"(_arg1) \
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: "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
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"r"(_num) \
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: "memory", "cc" \
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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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2022-03-29 10:17:30 +00:00
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register long _num __asm__ ("a7") = (num); \
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register long _arg1 __asm__ ("a0") = (long)(arg1); \
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register long _arg2 __asm__ ("a1") = (long)(arg2); \
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register long _arg3 __asm__ ("a2") = (long)(arg3); \
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register long _arg4 __asm__ ("a3") = (long)(arg4); \
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register long _arg5 __asm__ ("a4") = (long)(arg5); \
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register long _arg6 __asm__ ("a5") = (long)(arg6); \
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2022-02-07 16:23:17 +00:00
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\
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2022-03-29 10:17:30 +00:00
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__asm__ volatile ( \
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2022-02-07 16:23:17 +00:00
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"ecall\n" \
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: "+r"(_arg1) \
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: "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), "r"(_arg6), \
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"r"(_num) \
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: "memory", "cc" \
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); \
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_arg1; \
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})
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2023-01-10 07:24:23 +00:00
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char **environ __attribute__((weak));
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2023-01-10 07:24:29 +00:00
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const unsigned long *_auxv __attribute__((weak));
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2023-01-10 07:24:23 +00:00
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2022-02-07 16:23:17 +00:00
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/* startup code */
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tools/nolibc: make compiler and assembler agree on the section around _start
The out-of-block asm() statement carrying _start does not allow the
compiler to know what section the assembly code is being emitted to,
and there's no easy way to push/pop the current section and restore
it. It sometimes causes issues depending on the include files ordering
and compiler optimizations. For example if a variable is declared
immediately before the asm() block and another one after, the compiler
assumes that the current section is still .bss and doesn't re-emit it,
making the second variable appear inside the .text section instead.
Forcing .bss at the end of the _start block doesn't work either because
at certain optimizations the compiler may reorder blocks and will make
some real code appear just after this block.
A significant number of solutions were attempted, but many of them were
still sensitive to section reordering. In the end, the best way to make
sure the compiler and assembler agree on the current section is to place
this code inside a function. Here the function is directly called _start
and configured not to emit a frame-pointer, hence to have no prologue.
If some future architectures would still emit some prologue, another
working approach consists in naming the function differently and placing
the _start label inside the asm statement. But the current solution is
simpler.
It was tested with nolibc-test at -O,-O0,-O2,-O3,-Os for arm,arm64,i386,
mips,riscv,s390 and x86_64.
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2023-01-10 07:24:13 +00:00
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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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".option push\n"
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".option norelax\n"
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"lla gp, __global_pointer$\n"
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".option pop\n"
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"lw a0, 0(sp)\n" // argc (a0) was in the stack
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"add a1, sp, "SZREG"\n" // argv (a1) = sp
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"slli a2, a0, "PTRLOG"\n" // envp (a2) = SZREG*argc ...
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"add a2, a2, "SZREG"\n" // + SZREG (skip null)
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"add a2,a2,a1\n" // + argv
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2023-01-10 07:24:29 +00:00
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"add a3, a2, zero\n" // iterate a3 over envp to find auxv (after NULL)
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"0:\n" // do {
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"ld a4, 0(a3)\n" // a4 = *a3;
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"add a3, a3, "SZREG"\n" // a3 += sizeof(void*);
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"bne a4, zero, 0b\n" // } while (a4);
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"lui a4, %hi(_auxv)\n" // a4 = &_auxv (high bits)
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"sd a3, %lo(_auxv)(a4)\n" // store a3 into _auxv
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2023-01-10 07:24:23 +00:00
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"lui a3, %hi(environ)\n" // a3 = &environ (high bits)
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"sd a2,%lo(environ)(a3)\n" // store envp(a2) into environ
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tools/nolibc: make compiler and assembler agree on the section around _start
The out-of-block asm() statement carrying _start does not allow the
compiler to know what section the assembly code is being emitted to,
and there's no easy way to push/pop the current section and restore
it. It sometimes causes issues depending on the include files ordering
and compiler optimizations. For example if a variable is declared
immediately before the asm() block and another one after, the compiler
assumes that the current section is still .bss and doesn't re-emit it,
making the second variable appear inside the .text section instead.
Forcing .bss at the end of the _start block doesn't work either because
at certain optimizations the compiler may reorder blocks and will make
some real code appear just after this block.
A significant number of solutions were attempted, but many of them were
still sensitive to section reordering. In the end, the best way to make
sure the compiler and assembler agree on the current section is to place
this code inside a function. Here the function is directly called _start
and configured not to emit a frame-pointer, hence to have no prologue.
If some future architectures would still emit some prologue, another
working approach consists in naming the function differently and placing
the _start label inside the asm statement. But the current solution is
simpler.
It was tested with nolibc-test at -O,-O0,-O2,-O3,-Os for arm,arm64,i386,
mips,riscv,s390 and x86_64.
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2023-01-10 07:24:13 +00:00
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"andi sp,a1,-16\n" // sp must be 16-byte aligned
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"call main\n" // main() returns the status code, we'll exit with it.
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"li a7, 93\n" // NR_exit == 93
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"ecall\n"
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);
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__builtin_unreachable();
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}
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2022-02-07 16:23:17 +00:00
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#endif // _NOLIBC_ARCH_RISCV_H
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