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    Subject[PATCH 3.19 135/175] kdb: Avoid printing KERN_ levels to consoles
    Date
    3.19-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Daniel Thompson <daniel.thompson@linaro.org>

    commit f7d4ca8bbfda23b4f1eae9b6757ff64166b093d5 upstream.

    Currently when kdb traps printk messages then the raw log level prefix
    (consisting of '\001' followed by a numeral) does not get stripped off
    before the message is issued to the various I/O handlers supported by
    kdb. This causes annoying visual noise as well as causing problems
    grepping for ^. It is also a change of behaviour compared to normal usage
    of printk() usage. For example <SysRq>-h ends up with different output to
    that of kdb's "sr h".

    This patch addresses the problem by stripping log levels from messages
    before they are issued to the I/O handlers. printk() which can also
    act as an i/o handler in some cases is special cased; if the caller
    provided a log level then the prefix will be preserved when sent to
    printk().

    The addition of non-printable characters to the output of kdb commands is a
    regression, albeit and extremely elderly one, introduced by commit
    04d2c8c83d0e ("printk: convert the format for KERN_<LEVEL> to a 2 byte
    pattern"). Note also that this patch does *not* restore the original
    behaviour from v3.5. Instead it makes printk() from within a kdb command
    display the message without any prefix (i.e. like printk() normally does).

    Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
    Cc: Joe Perches <joe@perches.com>
    Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    include/linux/kdb.h | 8 +++++++-
    kernel/debug/kdb/kdb_io.c | 22 +++++++++++++---------
    kernel/printk/printk.c | 2 +-
    3 files changed, 21 insertions(+), 11 deletions(-)

    --- a/include/linux/kdb.h
    +++ b/include/linux/kdb.h
    @@ -156,8 +156,14 @@ typedef enum {
    KDB_REASON_SYSTEM_NMI, /* In NMI due to SYSTEM cmd; regs valid */
    } kdb_reason_t;

    +enum kdb_msgsrc {
    + KDB_MSGSRC_INTERNAL, /* direct call to kdb_printf() */
    + KDB_MSGSRC_PRINTK, /* trapped from printk() */
    +};
    +
    extern int kdb_trap_printk;
    -extern __printf(1, 0) int vkdb_printf(const char *fmt, va_list args);
    +extern __printf(2, 0) int vkdb_printf(enum kdb_msgsrc src, const char *fmt,
    + va_list args);
    extern __printf(1, 2) int kdb_printf(const char *, ...);
    typedef __printf(1, 2) int (*kdb_printf_t)(const char *, ...);

    --- a/kernel/debug/kdb/kdb_io.c
    +++ b/kernel/debug/kdb/kdb_io.c
    @@ -548,7 +548,7 @@ static int kdb_search_string(char *searc
    return 0;
    }

    -int vkdb_printf(const char *fmt, va_list ap)
    +int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap)
    {
    int diag;
    int linecount;
    @@ -691,19 +691,20 @@ kdb_printit:
    * Write to all consoles.
    */
    retlen = strlen(kdb_buffer);
    + cp = (char *) printk_skip_level(kdb_buffer);
    if (!dbg_kdb_mode && kgdb_connected) {
    - gdbstub_msg_write(kdb_buffer, retlen);
    + gdbstub_msg_write(cp, retlen - (cp - kdb_buffer));
    } else {
    if (dbg_io_ops && !dbg_io_ops->is_console) {
    - len = retlen;
    - cp = kdb_buffer;
    + len = retlen - (cp - kdb_buffer);
    + cp2 = cp;
    while (len--) {
    - dbg_io_ops->write_char(*cp);
    - cp++;
    + dbg_io_ops->write_char(*cp2);
    + cp2++;
    }
    }
    while (c) {
    - c->write(c, kdb_buffer, retlen);
    + c->write(c, cp, retlen - (cp - kdb_buffer));
    touch_nmi_watchdog();
    c = c->next;
    }
    @@ -711,7 +712,10 @@ kdb_printit:
    if (logging) {
    saved_loglevel = console_loglevel;
    console_loglevel = CONSOLE_LOGLEVEL_SILENT;
    - printk(KERN_INFO "%s", kdb_buffer);
    + if (printk_get_level(kdb_buffer) || src == KDB_MSGSRC_PRINTK)
    + printk("%s", kdb_buffer);
    + else
    + pr_info("%s", kdb_buffer);
    }

    if (KDB_STATE(PAGER)) {
    @@ -844,7 +848,7 @@ int kdb_printf(const char *fmt, ...)
    int r;

    va_start(ap, fmt);
    - r = vkdb_printf(fmt, ap);
    + r = vkdb_printf(KDB_MSGSRC_INTERNAL, fmt, ap);
    va_end(ap);

    return r;
    --- a/kernel/printk/printk.c
    +++ b/kernel/printk/printk.c
    @@ -1811,7 +1811,7 @@ int vprintk_default(const char *fmt, va_

    #ifdef CONFIG_KGDB_KDB
    if (unlikely(kdb_trap_printk)) {
    - r = vkdb_printf(fmt, args);
    + r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
    return r;
    }
    #endif



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