4.20-stable review patch. If anyone has any objections, please let me know.
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From: Nicolas Pitre nicolas.pitre@linaro.org
commit 6609cff65c5b184ab889880ef5d41189611ea05f upstream.
When kernel messages are printed to the console, they appear blank on the unicode screen. This is because vt_console_print() is lacking a call to vc_uniscr_putc(). However the later function assumes vc->vc_x is always up to date when called, which is not the case here as vt_console_print() uses it to mark the beginning of the display update.
This patch reworks (and simplifies) vt_console_print() so that vc->vc_x is always valid and keeps the start of display update in a local variable instead, which finally allows for adding the missing vc_uniscr_putc() call.
Signed-off-by: Nicolas Pitre nico@linaro.org Cc: stable@vger.kernel.org # v4.19+ Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/tty/vt/vt.c | 47 +++++++++++++++-------------------------------- 1 file changed, 15 insertions(+), 32 deletions(-)
--- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -2884,8 +2884,7 @@ static void vt_console_print(struct cons unsigned char c; static DEFINE_SPINLOCK(printing_lock); const ushort *start; - ushort cnt = 0; - ushort myx; + ushort start_x, cnt; int kmsg_console;
/* console busy or not yet initialized */ @@ -2898,10 +2897,6 @@ static void vt_console_print(struct cons if (kmsg_console && vc_cons_allocated(kmsg_console - 1)) vc = vc_cons[kmsg_console - 1].d;
- /* read `x' only after setting currcons properly (otherwise - the `x' macro will read the x of the foreground console). */ - myx = vc->vc_x; - if (!vc_cons_allocated(fg_console)) { /* impossible */ /* printk("vt_console_print: tty %d not allocated ??\n", currcons+1); */ @@ -2916,53 +2911,41 @@ static void vt_console_print(struct cons hide_cursor(vc);
start = (ushort *)vc->vc_pos; - - /* Contrived structure to try to emulate original need_wrap behaviour - * Problems caused when we have need_wrap set on '\n' character */ + start_x = vc->vc_x; + cnt = 0; while (count--) { c = *b++; if (c == 10 || c == 13 || c == 8 || vc->vc_need_wrap) { - if (cnt > 0) { - if (con_is_visible(vc)) - vc->vc_sw->con_putcs(vc, start, cnt, vc->vc_y, vc->vc_x); - vc->vc_x += cnt; - if (vc->vc_need_wrap) - vc->vc_x--; - cnt = 0; - } + if (cnt && con_is_visible(vc)) + vc->vc_sw->con_putcs(vc, start, cnt, vc->vc_y, start_x); + cnt = 0; if (c == 8) { /* backspace */ bs(vc); start = (ushort *)vc->vc_pos; - myx = vc->vc_x; + start_x = vc->vc_x; continue; } if (c != 13) lf(vc); cr(vc); start = (ushort *)vc->vc_pos; - myx = vc->vc_x; + start_x = vc->vc_x; if (c == 10 || c == 13) continue; } + vc_uniscr_putc(vc, c); scr_writew((vc->vc_attr << 8) + c, (unsigned short *)vc->vc_pos); notify_write(vc, c); cnt++; - if (myx == vc->vc_cols - 1) { - vc->vc_need_wrap = 1; - continue; - } - vc->vc_pos += 2; - myx++; - } - if (cnt > 0) { - if (con_is_visible(vc)) - vc->vc_sw->con_putcs(vc, start, cnt, vc->vc_y, vc->vc_x); - vc->vc_x += cnt; - if (vc->vc_x == vc->vc_cols) { - vc->vc_x--; + if (vc->vc_x == vc->vc_cols - 1) { vc->vc_need_wrap = 1; + } else { + vc->vc_pos += 2; + vc->vc_x++; } } + if (cnt && con_is_visible(vc)) + vc->vc_sw->con_putcs(vc, start, cnt, vc->vc_y, start_x); set_cursor(vc); notify_update(vc);