Hi Tomi,
I thought I'd let you, Tomi, (and all the others) know what the patch
does:
There is currently a single scrollback buffer (vgacon_scrollback) that
contains the text of the current console. When you switch the console it
is cleared and re-used for the new console.
My patch simply replaced the single scrollback buffer with an array of
scrollback buffers. One for each console.
A quick shout out to everybody else: Tomi told me today that he is
currently short on time to review this patch, so any Reviewed-by or
Tested-by would be very appreciated.
Bye,
Manuel
On Mo, 2016-09-19 at 00:06 +0200, Manuel Schölling wrote:
> Add a scrollback buffers for each VGA console. The benefit is that
> the scrollback history is not flushed when switching between consoles
> but is persistent.
> The buffers are allocated on demand when a new console is opened.
>
> It always annoys me when I switch back to a console and I can just
> read half of an error backtrace. This should fix issues like these.
>
> This breaks tools like clear_console that rely on flushing the
> scrollback history by switching back and forth between consoles
> which is why this feature is disabled by default.
> Use the escape sequence \e[3J instead for flushing the buffer.
>
> Signed-off-by: Manuel Schölling <manuel.schoell...@gmx.de>
> ---
> Changes in v3:
> - Add config option for this feature
> - Fallback to old scrollback buffer if kcalloc() fails
> - Remove ioctl() call again and add documentation about existing
> escape sequence to flush the scrollback buffer
> Changes in v2:
> - Add ioctl() call to flush scrollback buffer
> - (Patch v2 was not labeled as such, sorry)
> ---
> drivers/video/console/Kconfig | 23 +++++-
> drivers/video/console/vgacon.c | 160
> +++++++++++++++++++++++++++--------------
> 2 files changed, 128 insertions(+), 55 deletions(-)
>
> diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
> index 38da6e2..67e52f0 100644
> --- a/drivers/video/console/Kconfig
> +++ b/drivers/video/console/Kconfig
> @@ -43,9 +43,26 @@ config VGACON_SOFT_SCROLLBACK_SIZE
> range 1 1024
> default "64"
> help
> - Enter the amount of System RAM to allocate for the scrollback
> - buffer. Each 64KB will give you approximately 16 80x25
> - screenfuls of scrollback buffer
> + Enter the amount of System RAM to allocate for scrollback
> + buffers of VGA consoles. Each 64KB will give you approximately
> + 16 80x25 screenfuls of scrollback buffer.
> +
> +config VGACON_SOFT_SCROLLBACK_FOR_EACH_CONSOLE
> + bool "Persistent Scrollback History for each console"
> + depends on VGACON_SOFT_SCROLLBACK
> + default n
> + help
> + Say Y here if for each VGA console a scrollback buffer should
> + be allocated. The scrollback history will persist when switching
> + between consoles. If you say N here, scrollback is only supported
> + for the active VGA console and scrollback history will be flushed
> + when switching between consoles.
> +
> + This breaks legacy versions of tools like clear_console which
> + might cause security issues.
> + Use the escape sequence \e[3J instead if this feature is activated.
> +
> + If you use a RAM-constrained system, say N here.
>
> config MDA_CONSOLE
> depends on !M68K && !PARISC && ISA
> diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
> index 1157661..e70e8fe 100644
> --- a/drivers/video/console/vgacon.c
> +++ b/drivers/video/console/vgacon.c
> @@ -1,5 +1,5 @@
> /*
> - * linux/drivers/video/vgacon.c -- Low level VGA based console driver
> + * linux/drivers/video/console/vgacon.c -- Low level VGA based console
> driver
> *
> * Created 28 Sep 1997 by Geert Uytterhoeven
> *
> @@ -181,70 +181,125 @@ static inline void vga_set_mem_top(struct vc_data *c)
>
> #ifdef CONFIG_VGACON_SOFT_SCROLLBACK
> /* software scrollback */
> -static void *vgacon_scrollback;
> -static int vgacon_scrollback_tail;
> -static int vgacon_scrollback_size;
> -static int vgacon_scrollback_rows;
> -static int vgacon_scrollback_cnt;
> -static int vgacon_scrollback_cur;
> -static int vgacon_scrollback_save;
> -static int vgacon_scrollback_restore;
> -
> -static void vgacon_scrollback_init(int pitch)
> +struct vgacon_scrollback_info {
> + void *data;
> + int tail;
> + int size;
> + int rows;
> + int cnt;
> + int cur;
> + int save;
> + int restore;
> +};
> +static struct vgacon_scrollback_info *vgacon_scrollback_cur;
> +#ifdef CONFIG_VGACON_SOFT_SCROLLBACK_FOR_EACH_CONSOLE
> +static struct vgacon_scrollback_info vgacon_scrollbacks[MAX_NR_CONSOLES];
> +#else
> +static struct vgacon_scrollback_info vgacon_scrollbacks[1];
> +#endif
> +
> +static void vgacon_scrollback_reset(size_t reset_size)
> {
> - int rows = CONFIG_VGACON_SOFT_SCROLLBACK_SIZE * 1024/pitch;
> -
> - if (vgacon_scrollback) {
> - vgacon_scrollback_cnt = 0;
> - vgacon_scrollback_tail = 0;
> - vgacon_scrollback_cur = 0;
> - vgacon_scrollback_rows = rows - 1;
> - vgacon_scrollback_size = rows * pitch;
> + if (vgacon_scrollback_cur->data && reset_size > 0)
> + memset(vgacon_scrollback_cur->data, 0, reset_size);
> +
> + vgacon_scrollback_cur->cnt = 0;
> + vgacon_scrollback_cur->tail = 0;
> + vgacon_scrollback_cur->cur = 0;
> +}
> +
> +static void vgacon_scrollback_init(int vc_num)
> +{
> + int pitch = vga_video_num_columns * 2;
> + size_t size = CONFIG_VGACON_SOFT_SCROLLBACK_SIZE * 1024;
> + int rows = size/pitch;
> + void *data;
> +
> + data = kcalloc(CONFIG_VGACON_SOFT_SCROLLBACK_SIZE, 1024, GFP_NOWAIT);
> + if (data) {
> + vgacon_scrollbacks[vc_num].data = data;
> + vgacon_scrollback_cur = &vgacon_scrollbacks[vc_num];
> +
> + vgacon_scrollback_cur->rows = rows - 1;
> + vgacon_scrollback_cur->size = rows * pitch;
> +
> + vgacon_scrollback_reset(0);
> + } else {
> + pr_warn("VGAcon: failed to allocate memory for scrollback.
> Trying to reuse previous buffer.\n");
> + /* Leave vgacon_scrollback_cur untouched but reset its content
> */
> + vgacon_scrollback_reset(size);
> }
> }
>
> +static void vgacon_switch_scrollback(int vc_num)
> +{
> +#ifdef CONFIG_VGACON_SOFT_SCROLLBACK_FOR_EACH_CONSOLE
> + if (!vgacon_scrollbacks[vc_num].data)
> + vgacon_scrollback_init(vc_num);
> + else
> + vgacon_scrollback_cur = &vgacon_scrollbacks[vc_num];
> +#else
> + vc_num = 0;
> +
> + if (!vgacon_scrollbacks[vc_num].data)
> + vgacon_scrollback_init(vc_num);
> + else {
> + size_t size = CONFIG_VGACON_SOFT_SCROLLBACK_SIZE * 1024;
> +
> + vgacon_scrollback_reset(size);
> + }
> +#endif
> +}
> +
> static void vgacon_scrollback_startup(void)
> {
> - vgacon_scrollback = kcalloc(CONFIG_VGACON_SOFT_SCROLLBACK_SIZE, 1024,
> GFP_NOWAIT);
> - vgacon_scrollback_init(vga_video_num_columns * 2);
> + int i;
> +
> + for (i = 0; i < ARRAY_SIZE(vgacon_scrollbacks); ++i)
> + vgacon_scrollbacks[i].data = NULL;
> +
> + vgacon_scrollback_cur = &vgacon_scrollbacks[0];
> + vgacon_scrollback_init(0);
> }
>
> static void vgacon_scrollback_update(struct vc_data *c, int t, int count)
> {
> void *p;
>
> - if (!vgacon_scrollback_size || c->vc_num != fg_console)
> + if (!vgacon_scrollback_cur->data || !vgacon_scrollback_cur->size)
> return;
>
> p = (void *) (c->vc_origin + t * c->vc_size_row);
>
> while (count--) {
> - scr_memcpyw(vgacon_scrollback + vgacon_scrollback_tail,
> + scr_memcpyw(vgacon_scrollback_cur->data +
> + vgacon_scrollback_cur->tail,
> p, c->vc_size_row);
> - vgacon_scrollback_cnt++;
> +
> + vgacon_scrollback_cur->cnt++;
> p += c->vc_size_row;
> - vgacon_scrollback_tail += c->vc_size_row;
> + vgacon_scrollback_cur->tail += c->vc_size_row;
>
> - if (vgacon_scrollback_tail >= vgacon_scrollback_size)
> - vgacon_scrollback_tail = 0;
> + if (vgacon_scrollback_cur->tail >= vgacon_scrollback_cur->size)
> + vgacon_scrollback_cur->tail = 0;
>
> - if (vgacon_scrollback_cnt > vgacon_scrollback_rows)
> - vgacon_scrollback_cnt = vgacon_scrollback_rows;
> + if (vgacon_scrollback_cur->cnt > vgacon_scrollback_cur->rows)
> + vgacon_scrollback_cur->cnt =
> vgacon_scrollback_cur->rows;
>
> - vgacon_scrollback_cur = vgacon_scrollback_cnt;
> + vgacon_scrollback_cur->cur = vgacon_scrollback_cur->cnt;
> }
> }
>
> static void vgacon_restore_screen(struct vc_data *c)
> {
> - vgacon_scrollback_save = 0;
> + vgacon_scrollback_cur->save = 0;
>
> - if (!vga_is_gfx && !vgacon_scrollback_restore) {
> + if (!vga_is_gfx && !vgacon_scrollback_cur->restore) {
> scr_memcpyw((u16 *) c->vc_origin, (u16 *) c->vc_screenbuf,
> c->vc_screenbuf_size > vga_vram_size ?
> vga_vram_size : c->vc_screenbuf_size);
> - vgacon_scrollback_restore = 1;
> - vgacon_scrollback_cur = vgacon_scrollback_cnt;
> + vgacon_scrollback_cur->restore = 1;
> + vgacon_scrollback_cur->cur = vgacon_scrollback_cur->cnt;
> }
> }
>
> @@ -258,41 +313,41 @@ static void vgacon_scrolldelta(struct vc_data *c, int
> lines)
> return;
> }
>
> - if (!vgacon_scrollback)
> + if (!vgacon_scrollback_cur->data)
> return;
>
> - if (!vgacon_scrollback_save) {
> + if (!vgacon_scrollback_cur->save) {
> vgacon_cursor(c, CM_ERASE);
> vgacon_save_screen(c);
> - vgacon_scrollback_save = 1;
> + vgacon_scrollback_cur->save = 1;
> }
>
> - vgacon_scrollback_restore = 0;
> - start = vgacon_scrollback_cur + lines;
> + vgacon_scrollback_cur->restore = 0;
> + start = vgacon_scrollback_cur->cur + lines;
> end = start + abs(lines);
>
> if (start < 0)
> start = 0;
>
> - if (start > vgacon_scrollback_cnt)
> - start = vgacon_scrollback_cnt;
> + if (start > vgacon_scrollback_cur->cnt)
> + start = vgacon_scrollback_cur->cnt;
>
> if (end < 0)
> end = 0;
>
> - if (end > vgacon_scrollback_cnt)
> - end = vgacon_scrollback_cnt;
> + if (end > vgacon_scrollback_cur->cnt)
> + end = vgacon_scrollback_cur->cnt;
>
> - vgacon_scrollback_cur = start;
> + vgacon_scrollback_cur->cur = start;
> count = end - start;
> - soff = vgacon_scrollback_tail - ((vgacon_scrollback_cnt - end) *
> - c->vc_size_row);
> + soff = vgacon_scrollback_cur->tail - (c->vc_size_row *
> + (vgacon_scrollback_cur->cnt - end));
> soff -= count * c->vc_size_row;
>
> if (soff < 0)
> - soff += vgacon_scrollback_size;
> + soff += vgacon_scrollback_cur->size;
>
> - count = vgacon_scrollback_cnt - start;
> + count = vgacon_scrollback_cur->cnt - start;
>
> if (count > c->vc_rows)
> count = c->vc_rows;
> @@ -306,13 +361,13 @@ static void vgacon_scrolldelta(struct vc_data *c, int
> lines)
>
> count *= c->vc_size_row;
> /* how much memory to end of buffer left? */
> - copysize = min(count, vgacon_scrollback_size - soff);
> - scr_memcpyw(d, vgacon_scrollback + soff, copysize);
> + copysize = min(count, vgacon_scrollback_cur->size - soff);
> + scr_memcpyw(d, vgacon_scrollback_cur->data + soff, copysize);
> d += copysize;
> count -= copysize;
>
> if (count) {
> - scr_memcpyw(d, vgacon_scrollback, count);
> + scr_memcpyw(d, vgacon_scrollback_cur->data, count);
> d += count;
> }
>
> @@ -325,6 +380,7 @@ static void vgacon_scrolldelta(struct vc_data *c, int
> lines)
> #define vgacon_scrollback_startup(...) do { } while (0)
> #define vgacon_scrollback_init(...) do { } while (0)
> #define vgacon_scrollback_update(...) do { } while (0)
> +#define vgacon_switch_scrollback(...) do { } while (0)
>
> static void vgacon_restore_screen(struct vc_data *c)
> {
> @@ -839,7 +895,7 @@ static int vgacon_switch(struct vc_data *c)
> vgacon_doresize(c, c->vc_cols, c->vc_rows);
> }
>
> - vgacon_scrollback_init(c->vc_size_row);
> + vgacon_switch_scrollback(c->vc_num);
> return 0; /* Redrawing not needed */
> }
>
