2022-02-08 00:23:17 +08:00
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/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
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/*
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* x86_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_X86_64_H
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#define _NOLIBC_ARCH_X86_64_H
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2023-05-21 17:36:34 +08:00
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#include "compiler.h"
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2023-07-16 02:27:49 +08:00
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#include "crt.h"
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2023-05-21 17:36:34 +08:00
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2022-02-08 00:23:17 +08:00
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/* Syscalls for x86_64 :
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* - registers are 64-bit
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* - syscall number is passed in rax
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* - arguments are in rdi, rsi, rdx, r10, r8, r9 respectively
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* - the system call is performed by calling the syscall instruction
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* - syscall return comes in rax
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* - rcx and r11 are clobbered, others are preserved.
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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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* - see also x86-64 ABI section A.2 AMD64 Linux Kernel Conventions, A.2.1
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* Calling Conventions.
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*
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2022-03-29 18:17:29 +08:00
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* Link x86-64 ABI: https://gitlab.com/x86-psABIs/x86-64-ABI/-/wikis/home
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2022-02-08 00:23:17 +08:00
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*
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*/
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#define my_syscall0(num) \
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({ \
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long _ret; \
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2022-03-29 18:17:30 +08:00
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register long _num __asm__ ("rax") = (num); \
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2023-07-07 22:50:34 +08:00
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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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2022-02-08 00:23:17 +08:00
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"syscall\n" \
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: "=a"(_ret) \
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: "0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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})
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#define my_syscall1(num, arg1) \
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({ \
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long _ret; \
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2022-03-29 18:17:30 +08:00
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register long _num __asm__ ("rax") = (num); \
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register long _arg1 __asm__ ("rdi") = (long)(arg1); \
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\
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__asm__ volatile ( \
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"syscall\n" \
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: "=a"(_ret) \
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: "r"(_arg1), \
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"0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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})
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#define my_syscall2(num, arg1, arg2) \
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({ \
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long _ret; \
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2022-03-29 18:17:30 +08:00
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register long _num __asm__ ("rax") = (num); \
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register long _arg1 __asm__ ("rdi") = (long)(arg1); \
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register long _arg2 __asm__ ("rsi") = (long)(arg2); \
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\
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__asm__ volatile ( \
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2022-02-08 00:23:17 +08:00
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"syscall\n" \
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: "=a"(_ret) \
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: "r"(_arg1), "r"(_arg2), \
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"0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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})
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#define my_syscall3(num, arg1, arg2, arg3) \
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({ \
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long _ret; \
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2022-03-29 18:17:30 +08:00
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register long _num __asm__ ("rax") = (num); \
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register long _arg1 __asm__ ("rdi") = (long)(arg1); \
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register long _arg2 __asm__ ("rsi") = (long)(arg2); \
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register long _arg3 __asm__ ("rdx") = (long)(arg3); \
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\
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__asm__ volatile ( \
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2022-02-08 00:23:17 +08:00
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"syscall\n" \
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: "=a"(_ret) \
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: "r"(_arg1), "r"(_arg2), "r"(_arg3), \
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"0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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})
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#define my_syscall4(num, arg1, arg2, arg3, arg4) \
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({ \
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long _ret; \
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2022-03-29 18:17:30 +08:00
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register long _num __asm__ ("rax") = (num); \
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register long _arg1 __asm__ ("rdi") = (long)(arg1); \
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register long _arg2 __asm__ ("rsi") = (long)(arg2); \
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register long _arg3 __asm__ ("rdx") = (long)(arg3); \
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register long _arg4 __asm__ ("r10") = (long)(arg4); \
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2023-07-07 22:50:34 +08:00
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\
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__asm__ volatile ( \
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"syscall\n" \
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: "=a"(_ret) \
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: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \
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"0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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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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long _ret; \
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2022-03-29 18:17:30 +08:00
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register long _num __asm__ ("rax") = (num); \
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register long _arg1 __asm__ ("rdi") = (long)(arg1); \
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register long _arg2 __asm__ ("rsi") = (long)(arg2); \
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register long _arg3 __asm__ ("rdx") = (long)(arg3); \
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register long _arg4 __asm__ ("r10") = (long)(arg4); \
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register long _arg5 __asm__ ("r8") = (long)(arg5); \
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\
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__asm__ volatile ( \
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"syscall\n" \
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: "=a"(_ret) \
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: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
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"0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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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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long _ret; \
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2022-03-29 18:17:30 +08:00
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register long _num __asm__ ("rax") = (num); \
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register long _arg1 __asm__ ("rdi") = (long)(arg1); \
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register long _arg2 __asm__ ("rsi") = (long)(arg2); \
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register long _arg3 __asm__ ("rdx") = (long)(arg3); \
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register long _arg4 __asm__ ("r10") = (long)(arg4); \
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register long _arg5 __asm__ ("r8") = (long)(arg5); \
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register long _arg6 __asm__ ("r9") = (long)(arg6); \
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2023-07-07 22:50:34 +08:00
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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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2022-02-08 00:23:17 +08:00
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"syscall\n" \
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: "=a"(_ret) \
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: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
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"r"(_arg6), "0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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})
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/* startup code */
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/*
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* x86-64 System V ABI mandates:
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* 1) %rsp must be 16-byte aligned right before the function call.
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* 2) The deepest stack frame should be zero (the %rbp).
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*
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*/
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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 15:24:13 +08:00
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{
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__asm__ volatile (
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2023-07-16 02:27:49 +08:00
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"xor %ebp, %ebp\n" /* zero the stack frame */
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"mov %rsp, %rdi\n" /* save stack pointer to %rdi, as arg1 of _start_c */
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"and $-16, %rsp\n" /* %rsp must be 16-byte aligned before call */
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"call _start_c\n" /* transfer to c runtime */
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"hlt\n" /* ensure it does not return */
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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 15:24:13 +08:00
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);
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__builtin_unreachable();
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}
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2022-02-08 00:23:17 +08:00
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2023-04-07 05:54:49 +08:00
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#endif /* _NOLIBC_ARCH_X86_64_H */
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