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9ff72da471
This patch implements a new posix_spawn{p} implementation for Linux. The main difference is it uses the clone syscall directly with CLONE_VM and CLONE_VFORK flags and a direct allocated stack. The new stack and start function solves most the vfork limitation (possible parent clobber due stack spilling). The remaning issue are related to signal handling: 1. That no signal handlers must run in child context, to avoid corrupt parent's state. 2. Child must synchronize with parent to enforce stack deallocation and to possible return execv issues. The first one is solved by blocking all signals in child, even NPTL-internal ones (SIGCANCEL and SIGSETXID). The second issue is done by a stack allocation in parent and a synchronization with using a pipe or waitpid (in case or error). The pipe has the advantage of allowing the child signal an exec error (checked with new tst-spawn2 test). There is an inherent race condition in pipe2 usage for architectures that do not support the syscall directly. In such cases the a pipe plus fctnl is used instead and it may lead to file descriptor leak in parent (as decribed by fcntl documentation). The child process stack is allocate with a mmap with MAP_STACK flag using default architecture stack size. Although it is slower than use a stack buffer from parent, it allows some slack for the compatibility code to run scripts with no shebang (which may use a buffer with size depending of argument list count). Performance should be similar to the vfork default posix implementation and way faster than fork path (vfork on mostly linux ports are basically clone with CLONE_VM plus CLONE_VFORK). The only difference is the syscalls required for the stack allocation/deallocation. It fixes BZ#10354, BZ#14750, and BZ#18433. Tested on i386, x86_64, powerpc64le, and aarch64. [BZ #14750] [BZ #10354] [BZ #18433] * include/sched.h (__clone): Add hidden prototype. (__clone2): Likewise. * include/unistd.h (__dup): Likewise. * posix/Makefile (tests): Add tst-spawn2. * posix/tst-spawn2.c: New file. * sysdeps/posix/dup.c (__dup): Add hidden definition. * sysdeps/unix/sysv/linux/aarch64/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/alpha/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/arm/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/hppa/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/i386/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/ia64/clone2.S (__clone): Likewise. * sysdeps/unix/sysv/linux/m68k/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/microblaze/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/mips/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/nios2/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/powerpc/powerpc32/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/s390/s390-32/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/s390/s390-64/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/sh/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/sparc/sparc32/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/sparc/sparc64/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/tile/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/x86_64/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/nptl-signals.h (____nptl_is_internal_signal): New function. * sysdeps/unix/sysv/linux/spawni.c: New file.
144 lines
3.5 KiB
ArmAsm
144 lines
3.5 KiB
ArmAsm
/* Copyright (C) 1996-2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Richard Henderson (rth@tamu.edu)
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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/* clone() is even more special than fork() as it mucks with stacks
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and invokes a function in the right context after its all over. */
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#include <sysdep.h>
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#define _ERRNO_H 1
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#include <bits/errno.h>
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#include <asm-syntax.h>
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/* int clone(int (*fn)(void *arg), void *child_stack, int flags, void *arg,
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pid_t *ptid, struct user_desc *tls, pid_t *ctid); */
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#define PARMS 4 /* no space for saved regs */
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#define FUNC PARMS
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#define STACK FUNC+4
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#define FLAGS STACK+4
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#define ARG FLAGS+4
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#define PTID ARG+4
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#define TLS PTID+4
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#define CTID TLS+4
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#define __NR_clone 120
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#define SYS_clone 120
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#define CLONE_VM 0x00000100
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#define CLONE_THREAD 0x00010000
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.text
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ENTRY (__clone)
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/* Sanity check arguments. */
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movl $-EINVAL,%eax
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movl FUNC(%esp),%ecx /* no NULL function pointers */
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testl %ecx,%ecx
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jz SYSCALL_ERROR_LABEL
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movl STACK(%esp),%ecx /* no NULL stack pointers */
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testl %ecx,%ecx
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jz SYSCALL_ERROR_LABEL
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/* Insert the argument onto the new stack. Make sure the new
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thread is started with an alignment of (mod 16). */
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andl $0xfffffff0, %ecx
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subl $28,%ecx
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movl ARG(%esp),%eax /* no negative argument counts */
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movl %eax,12(%ecx)
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/* Save the function pointer as the zeroth argument.
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It will be popped off in the child in the ebx frobbing below. */
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movl FUNC(%esp),%eax
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movl %eax,8(%ecx)
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/* Don't leak any information. */
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movl $0,4(%ecx)
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/* Do the system call */
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pushl %ebx
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cfi_adjust_cfa_offset (4)
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pushl %esi
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cfi_adjust_cfa_offset (4)
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pushl %edi
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cfi_adjust_cfa_offset (4)
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movl TLS+12(%esp),%esi
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cfi_rel_offset (esi, 4)
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movl PTID+12(%esp),%edx
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movl FLAGS+12(%esp),%ebx
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cfi_rel_offset (ebx, 8)
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movl CTID+12(%esp),%edi
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cfi_rel_offset (edi, 0)
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movl $SYS_ify(clone),%eax
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/* Remember the flag value. */
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movl %ebx, (%ecx)
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/* End FDE now, because in the child the unwind info will be
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wrong. */
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cfi_endproc
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int $0x80
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popl %edi
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popl %esi
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popl %ebx
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test %eax,%eax
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jl SYSCALL_ERROR_LABEL
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jz L(thread_start)
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ret
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L(thread_start):
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cfi_startproc;
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/* Clearing frame pointer is insufficient, use CFI. */
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cfi_undefined (eip);
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/* Note: %esi is zero. */
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movl %esi,%ebp /* terminate the stack frame */
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testl $CLONE_THREAD, %edi
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je L(newpid)
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L(haspid):
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call *%ebx
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#ifdef PIC
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call L(here)
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L(here):
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popl %ebx
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addl $_GLOBAL_OFFSET_TABLE_+[.-L(here)], %ebx
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#endif
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movl %eax, %ebx
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movl $SYS_ify(exit), %eax
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ENTER_KERNEL
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.subsection 2
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L(newpid):
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testl $CLONE_VM, %edi
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movl $-1, %eax
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jne L(nomoregetpid)
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movl $SYS_ify(getpid), %eax
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ENTER_KERNEL
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L(nomoregetpid):
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movl %eax, %gs:PID
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movl %eax, %gs:TID
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jmp L(haspid)
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.previous
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cfi_endproc;
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cfi_startproc
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PSEUDO_END (__clone)
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libc_hidden_def (__clone)
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weak_alias (__clone, clone)
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