On Tue, May 26, 2015 at 04:42:36PM -0400, Jarod Wilson wrote: > On 5/8/2015 8:28 AM, Alexey Dobriyan wrote: > > /proc/$PID/cmdline truncates output at PAGE_SIZE. It is easy to see with > > > > $ cat /proc/self/cmdline $(seq 1037) 2>/dev/null > > > > However, command line size was never limited to PAGE_SIZE but to 128 KB and > > relatively recently limitation was removed altogether. > > > > People noticed and ask questions: > > http://stackoverflow.com/questions/199130/how-do-i-increase-the-proc-pid-cmdline-4096-byte-limit > > > > seq file interface is not OK, because it kmalloc's for whole output and > > open + read(, 1) + sleep will pin arbitrary amounts of kernel memory. > > To not do that, limit must be imposed which is incompatible with > > arbitrary sized command lines. > > > > I apologize for hairy code, but this it direct consequence of command line > > layout in memory and hacks to support things like "init [3]". > > > > The loops are "unrolled" otherwise it is either macros which hide > > control flow or functions with 7-8 arguments with equal line count. > > > > There should be real setproctitle(2) or something. > > > > Signed-off-by: Alexey Dobriyan <adobri...@gmail.com> > > Tested-by: Jarod Wilson <ja...@redhat.com> > > Acked-by: Jarod Wilson <ja...@redhat.com> > > Should have tested on more than just x86, it appears. We've started > hammering on this internally across all arches, and its exploded > multiple times on ppc64 now: > > [ 2717.074699] ------------[ cut here ]------------ > [ 2717.074787] kernel BUG at fs/proc/base.c:244!
> OE-------------- 3.10.0-255.el7.ppc64.debug #1 Which BUG_ON is this? BUG_ON(*pos < 0); BUG_ON(arg_start > arg_end); BUG_ON(env_start > env_end); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/