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Re: The time(2) man page conflicts with glibc
- From: Rich Felker <dalias at libc dot org>
- To: Zack Weinberg <zackw at panix dot com>, "H.J. Lu" <hjl dot tools at gmail dot com>, "Michael Kerrisk (man-pages)" <mtk dot manpages at gmail dot com>, libc-alpha <libc-alpha at sourceware dot org>, linux-man <linux-man at vger dot kernel dot org>
- Date: Wed, 16 Dec 2015 16:59:56 -0500
- Subject: Re: The time(2) man page conflicts with glibc
- Authentication-results: sourceware.org; auth=none
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On Wed, Dec 16, 2015 at 03:34:32PM -0500, Mike Frysinger wrote:
> On 16 Dec 2015 02:08, Rich Felker wrote:
> > On Tue, Dec 15, 2015 at 01:38:26PM -0500, Mike Frysinger wrote:
> > > On 15 Dec 2015 10:19, Zack Weinberg wrote:
> > > > On Tue, Dec 15, 2015 at 9:55 AM, Mike Frysinger wrote:
> > > > > On 15 Dec 2015 09:14, Zack Weinberg wrote:
> > > > >> Given the extreme obsolescence of the argument to `time`, I would
> > > > >> recommend that the *kernel* be changed to fire an actual SIGSEGV
> > > > >> instead of returning -EFAULT from the syscall version of `time`, and
> > > > >> then that can be the documented behavior, with the historic behavior
> > > > >> relegated to the BUGS section of the manpage.
> > > > >
> > > > > meh. it would be out of character for the kernel to do this.
> > > >
> > > > Why?
> > >
> > > because it returns EFAULT for other syscalls when you pass bad pointers.
> > > projects like LTP utilize that to verify edge case functionality.
> > Programs could also be calling the syscall directly (using syscall()
> > or asm) and using it as a (very cheap, fail-safe) way to verify that
> > an address is writable before attempting to write to it. Breaking this
> > would be a kernel API regression. However the library function time()
> > has UB for invalid pointers and no obligation to support them.
> sure, but that still doesn't mean the kernel should be sending SEGV.
> which is what this subthread was about.
The kernel is not causing SIGSEGV as far as I can tell; it's purely
the library function time that's causing this.