On May 26, 2015, at 5:24 PM, Alexey Dobriyan <adobri...@gmail.com> wrote: > >> 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);
Ah, sorry, right, might not be exactly the same with the back-up ported version... It was the env_start > env_end one. -- Jarod Wilson-- 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/
