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 */
}
--
2.1.4
