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Re: core dump

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From:
Andy Bach
Date:
September 3, 2019 16:08
Subject:
Re: core dump
Message ID:
SN6PR09MB3790BB48BC80A9B64DF312B0C0B90@SN6PR09MB3790.namprd09.prod.outlook.com
On my box, man core shows how to dump core using ctrl-backslash
$ perl
^\Quit (core dumped)

It also gives the example of creating a pipeline for core handling (.c file text below):
        $ cc -o core_pattern_pipe_test core_pattern_pipe_test.c
           $ su
           Password:
           # echo "|$PWD/core_pattern_pipe_test %p UID=%u GID=%g sig=%s" > \
               /proc/sys/kernel/core_pattern
           # exit
           $ sleep 100
           ^\                     # type control-backslash
           Quit (core dumped)
           $ cat core.info
           argc=5
           argc[0]=</home/mtk/core_pattern_pipe_test>
           argc[1]=<20575>
           argc[2]=<UID=1000>
           argc[3]=<GID=100>
           argc[4]=<sig=3>
           Total bytes in core dump: 282624

I used just
$ perl
^\Quit (core dumped)
$ cat core.info
argc=5
argc[0]=</usr/local/bin/core_pipe_test>
argc[1]=<3804>
argc[2]=<UID=1000>
argc[3]=<GID=1000>
argc[4]=<sig=3>
Total bytes in core dump: 602112


  /* core_pattern_pipe_test.c */

       #define _GNU_SOURCE
       #include <sys/stat.h>
       #include <fcntl.h>
       #include <limits.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <unistd.h>

       #define BUF_SIZE 1024

       int
       main(int argc, char *argv[])
       {
           int tot, j;
           ssize_t nread;
           char buf[BUF_SIZE];
           FILE *fp;
           char cwd[PATH_MAX];

           /* Change our current working directory to that of the
              crashing process */

           snprintf(cwd, PATH_MAX, "/proc/%s/cwd", argv[1]);
           chdir(cwd);

           /* Write output to file "core.info" in that directory */

           fp = fopen("core.info", "w+");
           if (fp == NULL)
               exit(EXIT_FAILURE);

           /* Display command-line arguments given to core_pattern
              pipe program */

           fprintf(fp, "argc=%d\n", argc);
           for (j = 0; j < argc; j++)
               fprintf(fp, "argc[%d]=<%s>\n", j, argv[j]);

           /* Count bytes in standard input (the core dump) */

           tot = 0;
           while ((nread = read(STDIN_FILENO, buf, BUF_SIZE)) > 0)
               tot += nread;
           fprintf(fp, "Total bytes in core dump: %d\n", tot);

           fclose(fp);
           exit(EXIT_SUCCESS);
       }

________________________________
From: ToddAndMargo via perl6-users <perl6-users@perl.org>
Sent: Friday, August 30, 2019 7:21 PM
To: perl6-users@perl.org <perl6-users@perl.org>
Subject: Re: core dump

On 8/9/19 3:41 PM, ToddAndMargo via perl6-users wrote:
> Hi All,
>
> Fedora 30
> rakudo-0.2019.03-2.fc30.x86_64
>
> I have a weird question.  I need to simulate a core
> dump under a bash (ulimit) shell.
>
> Any of you guys know who to get Perl to crash with a
> core dump?
>
> I need to prove that core dumps are not
> active on my system.  Or if I am mistaken.
>
>
> Many thanks,
> -T
>

Follow up:

      To trigger a core dump:
          $ kill -s SIGSEGV PID     Subsitute your PID
          $ kill -s SIGSEGV $$      Will kill your current shell


Since core dumps have changed significantly under Fedora 30
(systemd), anyone wants my full notes, please ping me
on the subject line and respond on this thread.

-T

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