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Re: The time(2) man page conflicts with glibc

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.


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