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. -mike
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