2022-02-07 17:23:17 +01:00
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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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2023-05-21 11:36:34 +02:00
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#include "compiler.h"
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2023-07-16 02:31:12 +08:00
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#include "crt.h"
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2022-02-07 17:23:17 +01:00
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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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#define my_syscall0(num) \
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({ \
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2022-03-29 17:17:30 +07:00
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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 17:23:17 +01:00
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\
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2023-07-07 22:52:09 +08:00
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__asm__ volatile ( \
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2022-02-07 17:23:17 +01:00
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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 17:17:30 +07:00
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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 17:23:17 +01:00
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\
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2023-07-07 22:52:09 +08:00
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__asm__ volatile ( \
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2022-02-07 17:23:17 +01:00
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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 17:17:30 +07:00
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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 17:23:17 +01:00
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\
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2023-07-07 22:52:09 +08:00
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__asm__ volatile ( \
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2022-02-07 17:23:17 +01:00
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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 17:17:30 +07:00
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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 17:23:17 +01:00
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\
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2023-07-07 22:52:09 +08:00
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__asm__ volatile ( \
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2022-02-07 17:23:17 +01:00
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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 17:17:30 +07:00
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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 17:23:17 +01:00
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\
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2023-07-07 22:52:09 +08:00
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__asm__ volatile ( \
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2022-02-07 17:23:17 +01:00
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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 17:17:30 +07:00
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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 17:23:17 +01:00
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\
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2023-07-07 22:52:09 +08:00
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__asm__ volatile ( \
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2022-02-07 17:23:17 +01:00
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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 17:17:30 +07:00
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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 17:23:17 +01:00
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\
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2023-07-07 22:52:09 +08:00
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__asm__ volatile ( \
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2022-02-07 17:23:17 +01:00
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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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/* startup code */
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2023-07-16 02:18:54 +08:00
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void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
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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 08:24:13 +01:00
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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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2023-07-16 02:31:12 +08:00
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"lla gp, __global_pointer$\n"
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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 08:24:13 +01:00
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".option pop\n"
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2023-07-16 02:31:12 +08:00
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"mv a0, sp\n" /* save stack pointer to a0, as arg1 of _start_c */
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"andi sp, a0, -16\n" /* sp must be 16-byte aligned */
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"call _start_c\n" /* transfer to c runtime */
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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 08:24:13 +01:00
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);
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__builtin_unreachable();
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}
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2022-02-07 17:23:17 +01:00
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2023-04-06 21:54:49 +00:00
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#endif /* _NOLIBC_ARCH_RISCV_H */
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