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d873a364ef
The ABI mandates that the %esp register must be a multiple of 16 when executing a 'call' instruction. Commit2ab446336b("tools/nolibc: i386: shrink _start with _start_c") simplified the _start function, but it didn't take care of the %esp alignment, causing SIGSEGV on SSE and AVX programs that use aligned move instruction (e.g., movdqa, movaps, and vmovdqa). The 'and $-16, %esp' aligns the %esp at a multiple of 16. Then 'push %eax' will subtract the %esp by 4; thus, it breaks the 16-byte alignment. Make sure the %esp is correctly aligned after the push by subtracting 12 before the push. Extra: Add 'add $12, %esp' before the 'and $-16, %esp' to avoid over-estimating for particular cases as suggested by Willy. A test program to validate the %esp alignment on _start can be found at: https://lore.kernel.org/lkml/ZOoindMFj1UKqo+s@biznet-home.integral.gnuweeb.org [ Thomas: trim Fixes tag commit id ] Cc: Zhangjin Wu <falcon@tinylab.org> Fixes:2ab446336b("tools/nolibc: i386: shrink _start with _start_c") Reported-by: Nicholas Rosenberg <inori@vnlx.org> Acked-by: Thomas Weißschuh <linux@weissschuh.net> Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org> Reviewed-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org> Signed-off-by: Willy Tarreau <w@1wt.eu> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
181 lines
8.8 KiB
C
181 lines
8.8 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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"add $12, %esp\n" /* avoid over-estimating after the 'and' & 'sub' below */
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"and $-16, %esp\n" /* the %esp must be 16-byte aligned on 'call' */
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"sub $12, %esp\n" /* sub 12 to keep it aligned after the push %eax */
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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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