kdb,vt_console: Fix missed data due to pager overruns

commit 17b572e82032bc246324ce136696656b66d4e3f1 upstream.

It is possible to miss data when using the kdb pager.  The kdb pager
does not pay attention to the maximum column constraint of the screen
or serial terminal.  This result is not incrementing the shown lines
correctly and the pager will print more lines that fit on the screen.
Obviously that is less than useful when using a VGA console where you
cannot scroll back.

The pager will now look at the kdb_buffer string to see how many
characters are printed.  It might not be perfect considering you can
output ASCII that might move the cursor position, but it is a
substantially better approximation for viewing dmesg and trace logs.

This also means that the vt screen needs to set the kdb COLUMNS
variable.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 2156188db4a64e73d41d8a7aa5cc8d4980f356e1..18d06be8c9bd27c87edf28c67d6554fd47db5ca2 100644 (file)
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -3475,6 +3475,19 @@ int con_debug_enter(struct vc_data *vc)
                        kdb_set(2, setargs);
                }
        }
+       if (vc->vc_cols < 999) {
+               int colcount;
+               char cols[4];
+               const char *setargs[3] = {
+                       "set",
+                       "COLUMNS",
+                       cols,
+               };
+               if (kdbgetintenv(setargs[0], &colcount)) {
+                       snprintf(cols, 4, "%i", vc->vc_cols);
+                       kdb_set(2, setargs);
+               }
+       }
 #endif /* CONFIG_KGDB_KDB */
        return ret;
 }

diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index bb9520f0f6ff8e607d0b08b2561efa62f4ba3b8d..572e604c56213d53420d17acca489df443821d65 100644 (file)
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -552,6 +552,7 @@ int vkdb_printf(const char *fmt, va_list ap)
 {
        int diag;
        int linecount;
+       int colcount;
        int logging, saved_loglevel = 0;
        int saved_trap_printk;
        int got_printf_lock = 0;
@@ -584,6 +585,10 @@ int vkdb_printf(const char *fmt, va_list ap)
        if (diag || linecount <= 1)
                linecount = 24;
 
+       diag = kdbgetintenv("COLUMNS", &colcount);
+       if (diag || colcount <= 1)
+               colcount = 80;
+
        diag = kdbgetintenv("LOGGING", &logging);
        if (diag)
                logging = 0;
@@ -690,7 +695,7 @@ kdb_printit:
                gdbstub_msg_write(kdb_buffer, retlen);
        } else {
                if (dbg_io_ops && !dbg_io_ops->is_console) {
-                       len = strlen(kdb_buffer);
+                       len = retlen;
                        cp = kdb_buffer;
                        while (len--) {
                                dbg_io_ops->write_char(*cp);
@@ -709,11 +714,29 @@ kdb_printit:
                printk(KERN_INFO "%s", kdb_buffer);
        }
 
-       if (KDB_STATE(PAGER) && strchr(kdb_buffer, '\n'))
-               kdb_nextline++;
+       if (KDB_STATE(PAGER)) {
+               /*
+                * Check printed string to decide how to bump the
+                * kdb_nextline to control when the more prompt should
+                * show up.
+                */
+               int got = 0;
+               len = retlen;
+               while (len--) {
+                       if (kdb_buffer[len] == '\n') {
+                               kdb_nextline++;
+                               got = 0;
+                       } else if (kdb_buffer[len] == '\r') {
+                               got = 0;
+                       } else {
+                               got++;
+                       }
+               }
+               kdb_nextline += got / (colcount + 1);
+       }
 
        /* check for having reached the LINES number of printed lines */
-       if (kdb_nextline == linecount) {
+       if (kdb_nextline >= linecount) {
                char buf1[16] = "";
 #if defined(CONFIG_SMP)
                char buf2[32];
@@ -776,7 +799,7 @@ kdb_printit:
                        kdb_grepping_flag = 0;
                        kdb_printf("\n");
                } else if (buf1[0] == ' ') {
-                       kdb_printf("\n");
+                       kdb_printf("\r");
                        suspend_grep = 1; /* for this recursion */
                } else if (buf1[0] == '\n') {
                        kdb_nextline = linecount - 1;