mirror of
https://github.com/opencontainers/runc.git
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Rodrigo Campos
90f5da651a
Linux repo has under `tools/include/nolibc` very simple include files that we can use to generate very small binaries that don't depend on libc. To make things even better, since Linux 6.6 it supports all the architectures we support in runc, which is just beautiful. The runc-dmz binary on x86_64 before this patch (on my debian host) was taking 636K, with this patch it takes only 8K. Signed-off-by: Rodrigo Campos <rodrigoca@microsoft.com>
179 lines
8.6 KiB
C
179 lines
8.6 KiB
C
/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
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/*
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* i386 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_I386_H
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#define _NOLIBC_ARCH_I386_H
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#include "compiler.h"
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#include "crt.h"
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/* Syscalls for i386 :
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* - mostly similar to x86_64
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* - registers are 32-bit
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* - syscall number is passed in eax
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* - arguments are in ebx, ecx, edx, esi, edi, ebp respectively
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* - all registers are preserved (except eax of course)
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* - the system call is performed by calling int $0x80
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* - syscall return comes in eax
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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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*
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* Also, i386 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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#define my_syscall0(num) \
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({ \
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long _ret; \
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register long _num __asm__ ("eax") = (num); \
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\
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__asm__ volatile ( \
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"int $0x80\n" \
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: "=a" (_ret) \
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: "0"(_num) \
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: "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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register long _num __asm__ ("eax") = (num); \
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register long _arg1 __asm__ ("ebx") = (long)(arg1); \
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\
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__asm__ volatile ( \
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"int $0x80\n" \
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: "=a" (_ret) \
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: "r"(_arg1), \
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"0"(_num) \
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: "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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register long _num __asm__ ("eax") = (num); \
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register long _arg1 __asm__ ("ebx") = (long)(arg1); \
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register long _arg2 __asm__ ("ecx") = (long)(arg2); \
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\
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__asm__ volatile ( \
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"int $0x80\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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: "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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register long _num __asm__ ("eax") = (num); \
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register long _arg1 __asm__ ("ebx") = (long)(arg1); \
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register long _arg2 __asm__ ("ecx") = (long)(arg2); \
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register long _arg3 __asm__ ("edx") = (long)(arg3); \
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\
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__asm__ volatile ( \
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"int $0x80\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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: "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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register long _num __asm__ ("eax") = (num); \
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register long _arg1 __asm__ ("ebx") = (long)(arg1); \
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register long _arg2 __asm__ ("ecx") = (long)(arg2); \
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register long _arg3 __asm__ ("edx") = (long)(arg3); \
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register long _arg4 __asm__ ("esi") = (long)(arg4); \
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\
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__asm__ volatile ( \
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"int $0x80\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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: "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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register long _num __asm__ ("eax") = (num); \
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register long _arg1 __asm__ ("ebx") = (long)(arg1); \
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register long _arg2 __asm__ ("ecx") = (long)(arg2); \
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register long _arg3 __asm__ ("edx") = (long)(arg3); \
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register long _arg4 __asm__ ("esi") = (long)(arg4); \
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register long _arg5 __asm__ ("edi") = (long)(arg5); \
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\
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__asm__ volatile ( \
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"int $0x80\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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: "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 _eax = (long)(num); \
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long _arg6 = (long)(arg6); /* Always in memory */ \
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__asm__ volatile ( \
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"pushl %[_arg6]\n\t" \
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"pushl %%ebp\n\t" \
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"movl 4(%%esp),%%ebp\n\t" \
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"int $0x80\n\t" \
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"popl %%ebp\n\t" \
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"addl $4,%%esp\n\t" \
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: "+a"(_eax) /* %eax */ \
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: "b"(arg1), /* %ebx */ \
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"c"(arg2), /* %ecx */ \
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"d"(arg3), /* %edx */ \
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"S"(arg4), /* %esi */ \
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"D"(arg5), /* %edi */ \
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[_arg6]"m"(_arg6) /* memory */ \
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: "memory", "cc" \
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); \
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_eax; \
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})
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/* startup code */
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/*
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* i386 System V ABI mandates:
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* 1) last pushed argument must be 16-byte aligned.
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* 2) The deepest stack frame should be set to zero
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*
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*/
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void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
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{
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__asm__ volatile (
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"xor %ebp, %ebp\n" /* zero the stack frame */
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"mov %esp, %eax\n" /* save stack pointer to %eax, as arg1 of _start_c */
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"and $-16, %esp\n" /* last pushed argument must be 16-byte aligned */
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"push %eax\n" /* push arg1 on stack to support plain stack modes too */
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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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);
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__builtin_unreachable();
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}
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#endif /* _NOLIBC_ARCH_I386_H */
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