The /proc/PID/coredump_filter mechanism makes it easy to tweak the per-process setting to control ELF core dump style details. This setting is per-process (per-mm) and inherited by children.

But as a user, the /proc interface is insane. It prints a magical hex value (without a leading 0x, to make it sneaky), which you'll be damn lucky to figure out from reading Documentation/filesystems/proc.txt. Then you get to set it to another such magical value, which is in decimal unless you add a leading 0x (cat /proc/x/coredump_filter > /proc/y/coredump_filter does not copy the setting, go team).

I have kicking around this half-assed bash script that I don't care to bother making really presentable. Where should it live? In the upstream kernel's scripts/? (Then noone would ever see it for sure.) In util-linux-ng? Or what? Someone want to take it off my hands?

Thanks, Roland

#!/bin/bash # # Usage: chcorefilter - PID... prints [pmfse]+ string for each PID # chcorefilter [pmfse]+ PID... changes filter bits for each PID # # Each bit set says a flavor of mapping that should be included in core dumps. # The setting for a process is inherited by its new children. # # p anonymous Private memory # m anonymous shared Memory # f private File mapping # s Shared file mapping # e ELF headers (first page of ELF-looking untouched file mapping) # # Default setting upstream is 'pm', Fedora >= 8 default is 'pme'. # GDB < 6.7 will be confused by the core files from +e settings. # # A fancier command would take +e or -e to set/clear just some # bits relative to the current setting. #

get_filter() { local pid=$1 local f f=`cat /proc/$pid/coredump_filter` || exit ((f=0x$f))

local s='' ((($f & 1) == 0)) || s="${s}p" ((($f & 2) == 0)) || s="${s}m" ((($f & 4) == 0)) || s="${s}f" ((($f & 8) == 0)) || s="${s}s" ((($f & 16) == 0)) || s="${s}e"

filter_dec=$f filter_str=${s:-.} }

set_filter() { local pid=$1 local val=$2 printf "0x%x\n" $val > /proc/$pid/coredump_filter || exit }

if [ $# -eq 0 ]; then exec sed '1d;/^#/!q' $0 fi

if [ "x$1" = x- ]; then shift for pid; do get_filter $pid if [ $# -gt 1 ]; then echo "${pid}: ${filter_str}" else echo "$filter_str" fi done exit 0 fi

arg="$1" shift

case "$arg" in -*) op='&=~'; arg=${arg#?} ;; +*) op='|=' ; arg=${arg#?} ;; .) op='=' ; arg=${arg#?} ;; *) op='=' ;; esac

val=0 until [ -z "$arg" ]; do case "$arg" in p*) ((val |= 1));; # anonymous Private memory m*) ((val |= 2));; # anonymous shared Memory f*) ((val |= 4));; # private File mapping s*) ((val |= 8));; # Shared file mapping e*) ((val |= 16));; # ELF headers *) bogon; break ;; esac arg=${arg#?} done

for pid; do get_filter $pid ((filter_dec $op $val)) set_filter $pid $filter_dec done