Date: Thu, 16 Apr 2009 22:30:02 GMT From: Jilles Tjoelker <jilles@stack.nl> To: freebsd-standards@FreeBSD.org Subject: Re: kern/27835: [libc] execve() doesn't conform to execve(2) spec in syscall manual Message-ID: <200904162230.n3GMU2lL042689@freefall.freebsd.org>
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The following reply was made to PR kern/27835; it has been noted by GNATS.
From: Jilles Tjoelker <jilles@stack.nl>
To: bug-followup@FreeBSD.org, jyliu@163.net
Cc:
Subject: Re: kern/27835: [libc] execve() doesn't conform to execve(2) spec
in syscall manual
Date: Fri, 17 Apr 2009 00:26:57 +0200
POSIX says that passing 0 arguments in execve() is allowed, but an
application doing it is not strictly POSIX compliant, and that
applications must handle being started with 0 arguments. The Solaris 10
man page says something similar.
The test program fails with EFAULT on 7.x, but passing 0 arguments is
still possible by changing the execve call to
execve("/bin/sh", (char*[]){ NULL }, NULL)
That change is good because a null pointer for argv yields undefined
behaviour (like any function parameter outside the permitted domain).
Another reason not to apply the patch to the kernel is that it uses
EINVAL which POSIX already defines for a different purpose that seems
useful to me: to indicate binaries with correct permissions and a valid
file format that are not supported (e.g. wrong architecture). This
situation currently results in ENOEXEC. Implementing the POSIX EINVAL
could improve the 'Syntax error: "(" unexpected' message you get when
trying to execute an ELF binary for the wrong architecture in sh; some
other shells and the execlp(3) and execvp(3) libc functions also assume
an executable is a shell script when they get ENOEXEC.
--
Jilles Tjoelker
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