[Crash-utility] [PATCH] extension: get socket receive queue into a file
Dave Anderson
anderson at redhat.com
Tue Apr 22 15:26:03 UTC 2014
Thanks Qiao -- I've posted the module in the extensions page:
http://people.redhat.com/anderson/extensions.html#SOCKQ
Dave
----- Original Message -----
> syslog() can be used to send messages to the system logger, and a socket is
> used to do the deliverying. So such a situation may be existed that the message
> is sent to the socket, but not received by syslogd yet. This module is used to
> dump the messages left in the socket.
>
> This module has been tested on RHEL5/6 x86/x64. The following program is used
> to generate a kdump core that got log messages left in socket.
>
> 1. compile the following c program to a.out
> <cut>
>
> int main(int argc, char **argv)
> {
> char buf[256];
> int i = 0;
>
> for (i = 0; i < 1; i++) {
> openlog("syslog", LOG_CONS , 0);
> sprintf(buf, "[TEST] a very long test message is appropriate, but I
> do "
> "not know such a message (No.%d)\n", i);
> syslog(LOG_INFO, buf);
> closelog();
> }
>
> return 0;
> }
> <cut>
>
> 2. run the following bash code to panic and generate a kdump core
> <cut>
> i=0
> while [[ $i -lt 1000 ]];do
> ./a.out &
> echo $i
> i=$((i+1))
> done
> echo c > /proc/sysrq-trigger
> i=0
> while [[ $i -lt 1000 ]];do
> ./a.out &
> echo $i
> i=$((i+1))
> done
> <cut>
>
> 3. run crash with the vmcore generated in step 2 and load sockq module. Then
> run command like below to get left log message
> <cut>
> crash> ps | grep syslog
> 1121 1 0 ffff880037ac2080 IN 0.2 249080 1740 rsyslogd
> 1123 1 1 ffff880037a00040 RU 0.2 249080 1740 rsyslogd
> 1124 1 1 ffff8800375f9540 IN 0.2 249080 1740 rsyslogd
> crash> files 1121
> PID: 1121 TASK: ffff880037ac2080 CPU: 0 COMMAND: "rsyslogd"
> ROOT: / CWD: /
> FD FILE DENTRY INODE TYPE PATH
> 0 ffff88003e0d0b40 ffff88003ef29a80 ffff88003ef8c688 SOCK
> 1 ffff88003d8f1140 ffff88003efc3800 ffff88003d3d44c0 REG /var/log/messages
> 2 ffff88003d859180 ffff88003efadb40 ffff88003d3d40c0 REG /var/log/secure
> 3 ffff88003d8590c0 ffff88003ef29b40 ffff88003ef917f8 REG /proc/kmsg
> 4 ffff88003dfd1b40 ffff88003d1a7500 ffff88003d004cc0 REG /var/log/maillog
> 5 ffff88003dee7180 ffff88003d0b6980 ffff88003d0048c0 REG /var/log/cron
>
> crash> sockq ffff88003e0d0b40 out
> crash> cat out
> <14>Apr 17 16:32:56 syslog: [TEST] a very long test message is appropriate,
> but I do not know such a message (No.48)
> <14>Apr 17 16:32:56 syslog: [TEST] a very long test message is appropriate,
> but I do not know such a message (No.44)
> <14>Apr 17 16:32:56 syslog: [TEST] a very long test message is appropriate,
> but I do not know such a message (No.12)
> <14>Apr 17 16:32:56 syslog: [TEST] a very long test message is appropriate,
> but I do not know such a message (No.13)
> <14>Apr 17 16:32:56 syslog: [TEST] a very long test message is appropriate,
> but I do not know such a message (No.21)
> <14>Apr 17 16:32:56 syslog: [TEST] a very long test message is appropriate,
> but I do not know such a message (No.21)
> <14>Apr 17 16:32:56 syslog: [TEST] a very long test message is appropriate,
> but I do not know such a message (No.18)
> <14>Apr 17 16:32:56 syslog: [TEST] a very long test message is appropriate,
> but I do not know such a message (No.1)
> <14>Apr 17 16:32:56 syslog: [TEST] a very long test message is appropriate,
> but I do not know such a message (No.18)
> <14>Apr 17 16:32:56 syslog: [TEST] a very long test message is appropriate,
> but I do not know such a message (No.18)
> <14>Apr 17 16:32:56 syslog: [TEST] a very long test message is appropriate,
> but I do not know such a message (No.2)
> crash>
> <cut>
>
> Signed-off-by: Qiao Nuohan <qiaonuohan at cn.fujitsu.com>
> ---
> extensions/sockq.c | 203
> +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 203 insertions(+)
> create mode 100644 extensions/sockq.c
>
> diff --git a/extensions/sockq.c b/extensions/sockq.c
> new file mode 100644
> index 0000000..3784413
> --- /dev/null
> +++ b/extensions/sockq.c
> @@ -0,0 +1,203 @@
> +/* sockq.c - sockq extension module for crash
> + *
> + * Copyright (C) 2014 FUJITSU LIMITED
> + * Author: Qiao Nuohan <qiaonuohan at cn.fujitsu.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + */
> +
> +#include "defs.h" /* From the crash source top-level directory */
> +
> +void sockq_init(void); /* constructor function */
> +void sockq_fini(void); /* destructor function (optional) */
> +
> +void cmd_sockq(void); /* Declare the commands and their help data. */
> +char *help_sockq[];
> +
> +static struct command_table_entry command_table[] = {
> + { "sockq", cmd_sockq, help_sockq, 0}, /* One or more commands, */
> + { NULL }, /* terminated by NULL, */
> +};
> +
> +char *help_sockq[] = {
> +"sockq", /* command name */
> +"get socket receive queue into a file", /* short description */
> +"file_address outfile", /* argument synopsis */
> +
> +" This command gets the data from the socket receive queue.",
> +" ",
> +" file_address A hexadecimal value of socket's file structure
> address.",
> +" outfile A name of output file. If the file already exists,",
> +" it is overwritten.",
> +NULL
> +};
> +
> +void __attribute__((constructor))
> +sockq_init(void) /* Register the command set. */
> +{
> + register_extension(command_table);
> +}
> +
> +/*
> + * This function is called if the shared object is unloaded.
> + * If desired, perform any cleanups here.
> + */
> +void __attribute__((destructor))
> +sockq_fini(void) { }
> +
> +static int
> +get_member_data(ulonglong addr, char *name, char *member, void* buf)
> +{
> + ulong member_offset;
> +
> + member_offset = MEMBER_OFFSET(name, member);
> +
> + if (!readmem(addr + member_offset, KVADDR, buf,
> + MEMBER_SIZE(name, member), name, FAULT_ON_ERROR))
> + return FALSE;
> +
> + return TRUE;
> +}
> +
> +/*
> + * write receive data in the specified file
> + */
> +static int
> +write_data(int fd, char *buf, ulong addr, ulong size)
> +{
> + ulong wsize;
> +
> + while (size > 0) {
> + /* size of the buffer is pagesize */
> + wsize = (size > PAGESIZE()) ? PAGESIZE() : size;
> +
> + if (!readmem(addr, KVADDR, buf, wsize, "vaddr", FAULT_ON_ERROR)) {
> + fprintf(fp, "cannot read data from packet buffer\n");
> + return 1;
> + }
> +
> + if (write(fd, buf, wsize) < 0) {
> + fprintf(fp, "cannot write data in a file\n");
> + return 1;
> + }
> +
> + addr += wsize;
> + size -= wsize;
> + }
> +
> + return 0;
> +}
> +
> +int
> +do_sockq(ulong file_addr, char *output_file, int fd)
> +{
> + int rc = 1;
> + ulong pd, sk;
> + uint qlen;
> + char *buf = NULL;
> + ulong next, head;
> + unsigned int len;
> + ulong wnext;
> +
> + if (!get_member_data(file_addr, "file", "private_data", &pd)) {
> + fprintf(fp, "cannot get private_datad of file structure\n");
> + goto cleanup;
> + }
> +
> + if (!get_member_data(pd, "socket", "sk", &sk)) {
> + fprintf(fp, "cannot get sk of socket structure\n");
> + goto cleanup;
> + }
> +
> + if (!get_member_data(sk + MEMBER_OFFSET("sock", "sk_receive_queue"),
> + "sk_buff_head", "next", &next)) {
> + fprintf(fp, "cannot get the first queue of sock structure\n");
> + goto cleanup;
> + }
> +
> + if (!get_member_data(sk + MEMBER_OFFSET("sock", "sk_receive_queue"),
> + "sk_buff_head", "qlen", &qlen)) {
> + fprintf(fp, "cannot get the number of queue list\n");
> + goto cleanup;
> + }
> +
> + /* create a output file */
> + if (output_file != NULL &&
> + (fd = open(output_file,
> + O_WRONLY | O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR)) < 0) {
> + fprintf(fp, "cannot create %s\n", output_file);
> + goto cleanup;
> + }
> +
> + if (qlen == 0) {
> + /* receive queue is empty */
> + rc = 0;
> + goto cleanup;
> + }
> +
> + /* get work area */
> + buf = GETBUF(PAGESIZE());
> +
> + while (qlen-- > 0) {
> + /* get packet buffer are info */
> + if (!get_member_data(next, "sk_buff", "head", &head)) {
> + fprintf(fp, "cannot head of sk_buff structure\n");
> + goto cleanup;
> + }
> +
> + if (!get_member_data(next, "sk_buff", "len", &len)) {
> + fprintf(fp, "cannot tail of sk_buff structure\n");
> + goto cleanup;
> + }
> +
> + /* write data in the output file */
> + if (write_data(fd, buf, head, len))
> + goto cleanup;
> +
> + /* next receive queue */
> + wnext = next;
> + if (!get_member_data(wnext, "sk_buff", "next", &next)) {
> + fprintf(fp, "cannot get next of sk_buff structure\n");
> + goto cleanup;
> + }
> + }
> +
> + /* all process normally ends */
> + rc = 0;
> +
> +cleanup:
> + if (output_file != NULL)
> + close(fd);
> + if (buf)
> + FREEBUF(buf);
> +
> + return rc;
> +}
> +
> +void
> +cmd_sockq(void)
> +{
> + ulong file_addr;
> +
> + if (argcnt != 3)
> + cmd_usage(pc->curcmd, SYNOPSIS);
> +
> + optind++;
> + file_addr = htol(args[optind], FAULT_ON_ERROR, NULL);
> +
> + optind++;
> + if (strlen(args[optind]) > PATH_MAX) {
> + fprintf(fp, "cannot create specified output file\n");
> + return;
> + }
> +
> + do_sockq(file_addr, args[optind], -1);
> +}
> --
> 1.8.5.3
>
> --
> Crash-utility mailing list
> Crash-utility at redhat.com
> https://www.redhat.com/mailman/listinfo/crash-utility
>
More information about the Crash-utility
mailing list