Re: [PATCH v6 1/6] introduce the kdump logger from the dracut

[Kairui Song]

On Tue, Oct 20, 2020 at 10:46 AM Lianbo Jiang <lijiang(a)redhat.com&gt; wrote:
>  Currently, all messages are directly printed to the console, sometimes,
>  we also need to output these messages to the journal log according to
>  the log level.
>
>  In view of this, introduce the kdump logger from the dracut module.
>
>  Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com&gt;
>  ---
>   kdump-logger.sh | 344 ++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 344 insertions(+)
>   create mode 100755 kdump-logger.sh
>
>  diff --git a/kdump-logger.sh b/kdump-logger.sh
>  new file mode 100755
>  index 000000000000..c2c5c35820e1
>  --- /dev/null
>  +++ b/kdump-logger.sh
>  @@ -0,0 +1,344 @@
>  +#!/bin/bash
>  +#
>  +# This comes from the dracut-logger.sh
>  +#
>  +# The logger defined 6 logging levels:
>  +#   - dtrace() (6)
>  +#     The TRACE Level designates finer-grained informational events than the
>  +#     DEBUG.
>  +#   - ddebug (5)
>  +#     The DEBUG Level designates fine-grained informational events that are most
>  +#     useful to debug an application.
>  +#   - dinfo (4)
>  +#     The INFO level designates informational messages that highlight the
>  +#     progress of the application at coarse-grained level.
>  +#   - dwarn (3)
>  +#     The WARN level designates potentially harmful situations.
>  +#   - derror (2)
>  +#     The ERROR level designates error events that might still allow the
>  +#     application to continue running.
>  +#   - dfatal (1)
>  +#     The FATAL level designates very severe error events that will presumably
>  +#     lead the application to abort.
>  +#
>  +# Logging is controlled by following global variables:
>  +#   - @var kdump_stdloglvl - logging level to standard error (console output)
>  +#   - @var kdump_sysloglvl - logging level to syslog (by logger command)
>  +#   - @var kdump_kmsgloglvl - logging level to /dev/kmsg (only for boot-time)
>  +#
>  +# If any of the variables is not set, this function set it to default:
>  +#   - @var kdump_stdloglvl = 4 (info)
>  +#   - @var kdump_sysloglvl = 4 (info)
>  +#   - @var kdump_kmsgloglvl = 0 (no logging)
>  +#
>  +# First of all you have to start with dlog_init() function which initializes
>  +# required variables. Don't call any other logging function before that one!
>  +#
>  +# @brief Initializes Logger.
>  +# @retval 1 if something has gone wrong
>  +# @retval 0 on success.
>  +#
>  +dlog_init() {
>  +    local ret=0; local errmsg
>  +    [ -z "$kdump_stdloglvl" ] && kdump_stdloglvl=4
>  +    [ -z "$kdump_sysloglvl" ] && kdump_sysloglvl=4
>  +    [ -z "$kdump_kmsgloglvl" ] && kdump_kmsgloglvl=0
>  +    # Skip initialization if it's already done.
>  +    [ -n "$kdump_maxloglvl" ] && return 0
>  +
>  +    if [[ $UID -ne 0 ]]; then
>  +        kdump_kmsgloglvl=0
>  +        kdump_sysloglvl=0
>  +    fi
>  +
>  +    if [[ $kdump_sysloglvl -gt 0 ]]; then
>  +        if [[ -d /run/systemd/journal ]] \
>  +            && type -P systemd-cat &>/dev/null \
>  +            && systemctl --quiet is-active systemd-journald.socket
> &>/dev/null; then
>  +            readonly _systemdcatfile="/var/tmp/systemd-cat"
>  +            mkfifo "$_systemdcatfile" &>/dev/null
>  +            readonly _dlogfd=15
>  +            systemd-cat -t 'kdump' --level-prefix=true
> <"$_systemdcatfile" &
>  +            exec 15>"$_systemdcatfile"
>  +        elif ! [ -S /dev/log -a -w /dev/log ] || ! command -v logger >/dev/null;
> then
>  +            # We cannot log to syslog, so turn this facility off.
>  +            kdump_kmsgloglvl=$kdump_sysloglvl
>  +            kdump_sysloglvl=0
>  +            ret=1
>  +            errmsg="No '/dev/log' or 'logger' included for syslog
> logging"
>  +        fi
>  +    fi
>  +
>  +    if [[ $kdump_sysloglvl -gt 0 ]] || [[ $kdump_kmsgloglvl -gt 0 ]]; then
>  +        if [ -n "$dracutbasedir" ]; then 
Hi Lianbo, I think this dracut
related code should be dropped.

From dracut comment, syslogfacility is set either to 'user' (when
building initramfs) or 'daemon' (when booting).
I thin we can either just drop it, as usually we  already know where
the log comes from, or maybe we can use /proc/vmcore to judge if it's
the kdump kernel.


>  +            readonly kdump_syslogfacility=user
>  +        else
>  +            readonly kdump_syslogfacility=daemon
>  +        fi
>  +        export kdump_syslogfacility
>  +    fi
>  +
>  +    local lvl; local maxloglvl_l=0
>  +    for lvl in $kdump_stdloglvl $kdump_sysloglvl $kdump_kmsgloglvl; do
>  +        [[ $lvl -gt $maxloglvl_l ]] && maxloglvl_l=$lvl
>  +    done
>  +    readonly kdump_maxloglvl=$maxloglvl_l
>  +    export kdump_maxloglvl
>  +
>  +
>  +    if [[ $kdump_stdloglvl -lt 6 ]] && [[ $kdump_kmsgloglvl -lt 6 ]] &&
> [[ $kdump_sysloglvl -lt 6 ]]; then
>  +        unset dtrace
>  +        dtrace() { :; };
>  +    fi
>  +
>  +    if [[ $kdump_stdloglvl -lt 5 ]] && [[ $kdump_kmsgloglvl -lt 5 ]] &&
> [[ $kdump_sysloglvl -lt 5 ]]; then
>  +        unset ddebug
>  +        ddebug() { :; };
>  +    fi
>  +
>  +    if [[ $kdump_stdloglvl -lt 4 ]] && [[ $kdump_kmsgloglvl -lt 4 ]] &&
> [[ $kdump_sysloglvl -lt 4 ]]; then
>  +        unset dinfo
>  +        dinfo() { :; };
>  +    fi
>  +
>  +    if [[ $kdump_stdloglvl -lt 3 ]] && [[ $kdump_kmsgloglvl -lt 3 ]] &&
> [[ $kdump_sysloglvl -lt 3 ]]; then
>  +        unset dwarn
>  +        dwarn() { :; };
>  +        unset dwarning
>  +        dwarning() { :; };
>  +    fi
>  +
>  +    if [[ $kdump_stdloglvl -lt 2 ]] && [[ $kdump_kmsgloglvl -lt 2 ]] &&
> [[ $kdump_sysloglvl -lt 2 ]]; then
>  +        unset derror
>  +        derror() { :; };
>  +    fi
>  +
>  +    if [[ $kdump_stdloglvl -lt 1 ]] && [[ $kdump_kmsgloglvl -lt 1 ]] &&
> [[ $kdump_sysloglvl -lt 1 ]]; then
>  +        unset dfatal
>  +        dfatal() { :; };
>  +    fi
>  +
>  +    [ -n "$errmsg" ] && derror "$errmsg"
>  +
>  +    return $ret
>  +}
>  +
>  +## @brief Converts numeric logging level to the first letter of level name.
>  +#
>  +# @param lvl Numeric logging level in range from 1 to 6.
>  +# @retval 1 if @a lvl is out of range.
>  +# @retval 0 if @a lvl is correct.
>  +# @result Echoes first letter of level name.
>  +_lvl2char() {
>  +    case "$1" in
>  +        1) echo F;;
>  +        2) echo E;;
>  +        3) echo W;;
>  +        4) echo I;;
>  +        5) echo D;;
>  +        6) echo T;;
>  +        *) return 1;;
>  +    esac
>  +}
>  +
>  +## @brief Converts numeric level to logger priority defined by POSIX.2.
>  +#
>  +# @param lvl Numeric logging level in range from 1 to 6.
>  +# @retval 1 if @a lvl is out of range.
>  +# @retval 0 if @a lvl is correct.
>  +# @result Echoes logger priority.
>  +_lvl2syspri() {
>  +    printf $kdump_syslogfacility.
>  +    case "$1" in
>  +        1) echo crit;;
>  +        2) echo error;;
>  +        3) echo warning;;
>  +        4) echo info;;
>  +        5) echo debug;;
>  +        6) echo debug;;
>  +        *) return 1;;
>  +    esac
>  +}
>  +
>  +## @brief Converts logger numeric level to syslog log level
>  +#
>  +# @param lvl Numeric logging level in range from 1 to 6.
>  +# @retval 1 if @a lvl is out of range.
>  +# @retval 0 if @a lvl is correct.
>  +# @result Echoes kernel console numeric log level
>  +#
>  +# Conversion is done as follows:
>  +#
>  +# <tt>
>  +#   none     -> LOG_EMERG (0)
>  +#   none     -> LOG_ALERT (1)
>  +#   FATAL(1) -> LOG_CRIT (2)
>  +#   ERROR(2) -> LOG_ERR (3)
>  +#   WARN(3)  -> LOG_WARNING (4)
>  +#   none     -> LOG_NOTICE (5)
>  +#   INFO(4)  -> LOG_INFO (6)
>  +#   DEBUG(5) -> LOG_DEBUG (7)
>  +#   TRACE(6) /
>  +# </tt>
>  +#
>  +# @see /usr/include/sys/syslog.h
>  +_dlvl2syslvl() {
>  +    local lvl
>  +
>  +    case "$1" in
>  +        1) lvl=2;;
>  +        2) lvl=3;;
>  +        3) lvl=4;;
>  +        4) lvl=6;;
>  +        5) lvl=7;;
>  +        6) lvl=7;;
>  +        *) return 1;;
>  +    esac
>  +
>  +    [ "$kdump_syslogfacility" = user ] && echo $((8+$lvl)) || echo
> $((24+$lvl))
>  +}
>  +
>  +## @brief Prints to stderr and/or writes to file, to syslog and/or /dev/kmsg
>  +# given message with given level (priority).
>  +#
>  +# @param lvl Numeric logging level.
>  +# @param msg Message.
>  +# @retval 0 It's always returned, even if logging failed.
>  +#
>  +# @note This function is not supposed to be called manually. Please use
>  +# dtrace(), ddebug(), or others instead which wrap this one.
>  +#
>  +# This is core logging function which logs given message to standard error, file
>  +# and/or syslog (with POSIX shell command <tt>logger</tt>) and/or to
> /dev/kmsg.
>  +# The format is following:
>  +#
>  +# <tt>X: some message</tt>
>  +#
>  +# where @c X is the first letter of logging level. See module description for
>  +# details on that.
>  +#
>  +# Message to syslog is sent with tag @c kdump. Priorities are mapped as
>  +# following:
>  +#   - @c FATAL to @c crit
>  +#   - @c ERROR to @c error
>  +#   - @c WARN to @c warning
>  +#   - @c INFO to @c info
>  +#   - @c DEBUG and @c TRACE both to @c debug
>  +_do_dlog() {
>  +    local lvl="$1"; shift
>  +    local lvlc=$(_lvl2char "$lvl") || return 0
>  +    local msg="$*"
>  +    local lmsg="$lvlc: $*"
>  +
>  +    [[ $lvl -le $kdump_stdloglvl ]] && printf -- 'kdump: %s\n'
> "$msg" >&2
>  +
>  +    if [[ $lvl -le $kdump_sysloglvl ]]; then
>  +        if [[ "$_dlogfd" ]]; then
>  +            printf -- "<%s>%s\n" "$(($(_dlvl2syslvl $lvl) &
> 7))" "$msg" >&$_dlogfd
>  +        else
>  +            logger -t "kdump[$$]" -p $(_lvl2syspri $lvl) -- "$msg"
>  +        fi
>  +    fi
>  +
>  +    [[ $lvl -le $kdump_kmsgloglvl ]] && \
>  +        echo "<$(_dlvl2syslvl $lvl)>kdump[$$] $msg" >/dev/kmsg
>  +}
>  +
>  +## @brief Internal helper function for _do_dlog()
>  +#
>  +# @param lvl Numeric logging level.
>  +# @param msg Message.
>  +# @retval 0 It's always returned, even if logging failed.
>  +#
>  +# @note This function is not supposed to be called manually. Please use
>  +# dtrace(), ddebug(), or others instead which wrap this one.
>  +#
>  +# This function calls _do_dlog() either with parameter msg, or if
>  +# none is given, it will read standard input and will use every line as
>  +# a message.
>  +#
>  +# This enables:
>  +# dwarn "This is a warning"
>  +# echo "This is a warning" | dwarn
>  +dlog() {
>  +    [ -z "$kdump_maxloglvl" ] && return 0
>  +    [[ $1 -le $kdump_maxloglvl ]] || return 0
>  +
>  +    if [[ $# -gt 1 ]]; then
>  +        _do_dlog "$@"
>  +    else
>  +        while read line || [ -n "$line" ]; do
>  +            _do_dlog "$1" "$line"
>  +        done
>  +    fi
>  +}
>  +
>  +## @brief Logs message at TRACE level (6)
>  +#
>  +# @param msg Message.
>  +# @retval 0 It's always returned, even if logging failed.
>  +dtrace() {
>  +    set +x
>  +    dlog 6 "$@"
>  +    [ -n "$debug" ] && set -x || :
>  +}
>  +
>  +## @brief Logs message at DEBUG level (5)
>  +#
>  +# @param msg Message.
>  +# @retval 0 It's always returned, even if logging failed.
>  +ddebug() {
>  +    set +x
>  +    dlog 5 "$@"
>  +    [ -n "$debug" ] && set -x || :
>  +}
>  +
>  +## @brief Logs message at INFO level (4)
>  +#
>  +# @param msg Message.
>  +# @retval 0 It's always returned, even if logging failed.
>  +dinfo() {
>  +    set +x
>  +    dlog 4 "$@"
>  +    [ -n "$debug" ] && set -x || :
>  +}
>  +
>  +## @brief Logs message at WARN level (3)
>  +#
>  +# @param msg Message.
>  +# @retval 0 It's always returned, even if logging failed.
>  +dwarn() {
>  +    set +x
>  +    dlog 3 "$@"
>  +    [ -n "$debug" ] && set -x || :
>  +}
>  +
>  +## @brief It's an alias to dwarn() function.
>  +#
>  +# @param msg Message.
>  +# @retval 0 It's always returned, even if logging failed.
>  +dwarning() {
>  +    set +x
>  +    dwarn "$@"
>  +    [ -n "$debug" ] && set -x || :
>  +}
>  +
>  +## @brief Logs message at ERROR level (2)
>  +#
>  +# @param msg Message.
>  +# @retval 0 It's always returned, even if logging failed.
>  +derror() {
>  +    set +x
>  +    dlog 2 "$@"
>  +    [ -n "$debug" ] && set -x || :
>  +}
>  +
>  +## @brief Logs message at FATAL level (1)
>  +#
>  +# @param msg Message.
>  +# @retval 0 It's always returned, even if logging failed.
>  +dfatal() {
>  +    set +x
>  +    dlog 1 "$@"
>  +    [ -n "$debug" ] && set -x || :
>  +}
>  --
>  2.17.1
>  

--
Best Regards,
Kairui Song