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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.
188 lines
7.1 KiB
C
188 lines
7.1 KiB
C
#ifndef _UNISTD_H
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# include <posix/unistd.h>
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# ifndef _ISOMAC
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__BEGIN_DECLS
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libc_hidden_proto (_exit, __noreturn__)
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rtld_hidden_proto (_exit, __noreturn__)
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libc_hidden_proto (alarm)
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libc_hidden_proto (confstr)
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libc_hidden_proto (execl)
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libc_hidden_proto (execle)
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libc_hidden_proto (execlp)
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libc_hidden_proto (execvp)
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libc_hidden_proto (getpid)
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libc_hidden_proto (getsid)
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libc_hidden_proto (getdomainname)
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extern __typeof (getlogin_r) __getlogin_r __nonnull ((1));
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libc_hidden_proto (__getlogin_r)
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libc_hidden_proto (getlogin_r)
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libc_hidden_proto (seteuid)
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libc_hidden_proto (setegid)
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libc_hidden_proto (tcgetpgrp)
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libc_hidden_proto (readlinkat)
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/* Now define the internal interfaces. */
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extern int __access (const char *__name, int __type);
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extern int __euidaccess (const char *__name, int __type);
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extern __off64_t __lseek64 (int __fd, __off64_t __offset, int __whence);
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extern __off_t __lseek (int __fd, __off_t __offset, int __whence);
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libc_hidden_proto (__lseek)
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extern __off_t __libc_lseek (int __fd, __off_t __offset, int __whence);
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extern __off64_t __libc_lseek64 (int __fd, __off64_t __offset, int __whence);
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extern ssize_t __pread (int __fd, void *__buf, size_t __nbytes,
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__off_t __offset);
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extern ssize_t __libc_pread (int __fd, void *__buf, size_t __nbytes,
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__off_t __offset);
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extern ssize_t __pread64 (int __fd, void *__buf, size_t __nbytes,
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__off64_t __offset);
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extern ssize_t __libc_pread64 (int __fd, void *__buf, size_t __nbytes,
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__off64_t __offset);
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extern ssize_t __pwrite (int __fd, const void *__buf, size_t __n,
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__off_t __offset);
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extern ssize_t __libc_pwrite (int __fd, const void *__buf, size_t __n,
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__off_t __offset);
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extern ssize_t __pwrite64 (int __fd, const void *__buf, size_t __n,
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__off64_t __offset);
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libc_hidden_proto (__pwrite64)
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extern ssize_t __libc_pwrite64 (int __fd, const void *__buf, size_t __n,
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__off64_t __offset) attribute_hidden;
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extern ssize_t __libc_read (int __fd, void *__buf, size_t __n);
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libc_hidden_proto (__libc_read)
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extern ssize_t __libc_write (int __fd, const void *__buf, size_t __n);
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libc_hidden_proto (__libc_write)
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extern int __pipe (int __pipedes[2]);
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libc_hidden_proto (__pipe)
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extern int __pipe2 (int __pipedes[2], int __flags);
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extern unsigned int __sleep (unsigned int __seconds);
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extern int __chown (const char *__file,
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__uid_t __owner, __gid_t __group);
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libc_hidden_proto (__chown)
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extern int __fchown (int __fd,
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__uid_t __owner, __gid_t __group);
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extern int __lchown (const char *__file, __uid_t __owner,
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__gid_t __group);
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extern int __chdir (const char *__path);
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extern int __fchdir (int __fd);
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extern char *__getcwd (char *__buf, size_t __size);
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extern int __rmdir (const char *__path);
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extern int __execvpe (const char *file, char *const argv[],
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char *const envp[]);
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/* Get the canonical absolute name of the named directory, and put it in SIZE
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bytes of BUF. Returns NULL if the directory couldn't be determined or
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SIZE was too small. If successful, returns BUF. In GNU, if BUF is
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NULL, an array is allocated with `malloc'; the array is SIZE bytes long,
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unless SIZE <= 0, in which case it is as big as necessary. */
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char *__canonicalize_directory_name_internal (const char *__thisdir,
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char *__buf,
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size_t __size) attribute_hidden;
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extern int __dup (int __fd);
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libc_hidden_proto (__dup)
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extern int __dup2 (int __fd, int __fd2);
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libc_hidden_proto (__dup2)
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extern int __dup3 (int __fd, int __fd2, int flags);
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libc_hidden_proto (__dup3)
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extern int __execve (const char *__path, char *const __argv[],
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char *const __envp[]);
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extern long int __pathconf (const char *__path, int __name);
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extern long int __fpathconf (int __fd, int __name);
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extern long int __sysconf (int __name);
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libc_hidden_proto (__sysconf)
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extern __pid_t __getpid (void);
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libc_hidden_proto (__getpid)
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extern __pid_t __getppid (void);
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extern __pid_t __setsid (void);
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extern __uid_t __getuid (void);
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extern __uid_t __geteuid (void);
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extern __gid_t __getgid (void);
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extern __gid_t __getegid (void);
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extern int __getgroups (int __size, __gid_t __list[]);
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libc_hidden_proto (__getpgid)
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extern int __group_member (__gid_t __gid);
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extern int __setuid (__uid_t __uid);
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extern int __setreuid (__uid_t __ruid, __uid_t __euid);
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extern int __setgid (__gid_t __gid);
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extern int __setpgid (__pid_t __pid, __pid_t __pgid);
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libc_hidden_proto (__setpgid)
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extern int __setregid (__gid_t __rgid, __gid_t __egid);
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extern int __getresuid (__uid_t *__ruid, __uid_t *__euid, __uid_t *__suid);
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extern int __getresgid (__gid_t *__rgid, __gid_t *__egid, __gid_t *__sgid);
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extern int __setresuid (__uid_t __ruid, __uid_t __euid, __uid_t __suid);
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extern int __setresgid (__gid_t __rgid, __gid_t __egid, __gid_t __sgid);
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libc_hidden_proto (__getresuid)
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libc_hidden_proto (__getresgid)
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libc_hidden_proto (__setresuid)
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libc_hidden_proto (__setresgid)
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extern __pid_t __vfork (void);
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libc_hidden_proto (__vfork)
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extern int __ttyname_r (int __fd, char *__buf, size_t __buflen);
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extern int __isatty (int __fd);
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extern int __link (const char *__from, const char *__to);
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extern int __symlink (const char *__from, const char *__to);
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extern ssize_t __readlink (const char *__path, char *__buf, size_t __len);
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extern int __unlink (const char *__name);
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extern int __gethostname (char *__name, size_t __len);
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extern int __profil (unsigned short int *__sample_buffer, size_t __size,
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size_t __offset, unsigned int __scale);
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extern int __getdtablesize (void);
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extern int __brk (void *__addr);
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extern int __close (int __fd);
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libc_hidden_proto (__close)
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extern int __libc_close (int __fd);
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extern ssize_t __read (int __fd, void *__buf, size_t __nbytes);
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libc_hidden_proto (__read)
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extern ssize_t __write (int __fd, const void *__buf, size_t __n);
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libc_hidden_proto (__write)
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extern __pid_t __fork (void);
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libc_hidden_proto (__fork)
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extern int __getpagesize (void) __attribute__ ((__const__));
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libc_hidden_proto (__getpagesize)
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extern int __ftruncate (int __fd, __off_t __length);
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extern int __ftruncate64 (int __fd, __off64_t __length);
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extern int __truncate (const char *path, __off_t __length);
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extern void *__sbrk (intptr_t __delta);
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libc_hidden_proto (__sbrk)
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/* This variable is set nonzero at startup if the process's effective
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IDs differ from its real IDs, or it is otherwise indicated that
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extra security should be used. When this is set the dynamic linker
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and some functions contained in the C library ignore various
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environment variables that normally affect them. */
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extern int __libc_enable_secure attribute_relro;
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extern int __libc_enable_secure_decided;
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rtld_hidden_proto (__libc_enable_secure)
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/* Various internal function. */
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extern void __libc_check_standard_fds (void) attribute_hidden;
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/* Internal name for fork function. */
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extern __pid_t __libc_fork (void);
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/* Suspend the process until a signal arrives.
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This always returns -1 and sets `errno' to EINTR. */
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extern int __libc_pause (void);
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/* Not cancelable variant. */
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extern int __pause_nocancel (void) attribute_hidden;
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extern int __have_pipe2 attribute_hidden;
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extern int __have_dup3 attribute_hidden;
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extern int __getlogin_r_loginuid (char *name, size_t namesize)
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attribute_hidden;
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# if IS_IN (rtld)
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# include <dl-unistd.h>
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# endif
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__END_DECLS
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# endif
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#endif
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