[PATCH 0/2] Persistent scrollback buffers for all VGA consoles

[PATCH 0/2] Persistent scrollback buffers for all VGA consoles

[Manuel Schölling]

Another attempt to add persistent scrollback buffers for all VGA consol=
es,
so the buffer is not flushed when swithing back and forth between conso=
les.

Note that breaks tools like bash's clear_console and thus might have
security implications:
clear_console relies on this 'anti-feature' of the kernel to clear the =
buffer
when consoles are switched.

To offer a way for userland tools to flush the buffer my second patch a=
dds
a ioctl call for that.
Also this feature is disabled by default and security implications are =
clearly
stated in its documentation.

Manuel Sch=C3=B6lling (2):
  console: Add persistent scrollback buffers for all VGA consoles
  console: Add ioctl for flushing the scrollback buffer

 drivers/tty/vt/vt_ioctl.c               |  20 ++++
 drivers/usb/misc/sisusbvga/sisusb_con.c |   1 +
 drivers/video/console/Kconfig           |  22 +++-
 drivers/video/console/dummycon.c        |   1 +
 drivers/video/console/mdacon.c          |   6 +
 drivers/video/console/newport_con.c     |   1 +
 drivers/video/console/sticon.c          |   7 ++
 drivers/video/console/vgacon.c          | 195 ++++++++++++++++++++++--=
--------
 include/linux/console.h                 |   1 +
 include/uapi/linux/vt.h                 |   1 +
 10 files changed, 194 insertions(+), 61 deletions(-)

--=20
2.1.4

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[PATCH 0/2] Persistent scrollback buffers for all VGA consoles

[Manuel Schölling]

Another attempt to add persistent scrollback buffers for all VGA consol=
es,
so the buffer is not flushed when swithing back and forth between conso=
les.

Note that breaks tools like bash's clear_console and thus might have
security implications:
clear_console relies on this 'anti-feature' of the kernel to clear the =
buffer
when consoles are switched.

To offer a way for userland tools to flush the buffer my second patch a=
dds
a ioctl call for that.
Also this feature is disabled by default and security implications are =
clearly
stated in its documentation.

Manuel Sch=C3=B6lling (2):
  console: Add persistent scrollback buffers for all VGA consoles
  console: Add ioctl for flushing the scrollback buffer

 drivers/tty/vt/vt_ioctl.c               |  20 ++++
 drivers/usb/misc/sisusbvga/sisusb_con.c |   1 +
 drivers/video/console/Kconfig           |  22 +++-
 drivers/video/console/dummycon.c        |   1 +
 drivers/video/console/mdacon.c          |   6 +
 drivers/video/console/newport_con.c     |   1 +
 drivers/video/console/sticon.c          |   7 ++
 drivers/video/console/vgacon.c          | 195 ++++++++++++++++++++++--=
--------
 include/linux/console.h                 |   1 +
 include/uapi/linux/vt.h                 |   1 +
 10 files changed, 194 insertions(+), 61 deletions(-)

--=20
2.1.4

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[PATCH 1/2] console: Add persistent scrollback buffers for all VGA consoles

[Manuel Schölling]

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.

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.

Signed-off-by: Manuel Sch=C3=B6lling <manuel.schoelling@gmx.de>
---
 drivers/video/console/Kconfig  |  22 +++++-
 drivers/video/console/vgacon.c | 172 +++++++++++++++++++++++++++------=
--------
 2 files changed, 133 insertions(+), 61 deletions(-)

diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kcon=
fig
index 38da6e2..f101a63 100644
--- a/drivers/video/console/Kconfig
+++ b/drivers/video/console/Kconfig
@@ -43,9 +43,25 @@ 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 raise security issues.
+
+	  If you use a RAM-constrained system, say N here.
=20
 config MDA_CONSOLE
 	depends on !M68K && !PARISC && ISA
diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vga=
con.c
index 517f565..6c0b9ba 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 consol=
e driver
  *
  *	Created 28 Sep 1997 by Geert Uytterhoeven
  *
@@ -106,12 +106,12 @@ static unsigned char	vga_hardscroll_enabled	__rea=
d_mostly;
 static unsigned char	vga_hardscroll_user_enable __read_mostly =3D 1;
 static unsigned char	vga_font_is_default =3D 1;
 static int		vga_vesa_blanked;
-static int 		vga_palette_blanked;
-static int 		vga_is_gfx;
-static int 		vga_512_chars;
-static int 		vga_video_font_height;
-static int 		vga_scan_lines		__read_mostly;
-static unsigned int 	vga_rolled_over;
+static int		vga_palette_blanked;
+static int		vga_is_gfx;
+static int		vga_512_chars;
+static int		vga_video_font_height;
+static int		vga_scan_lines		__read_mostly;
+static unsigned int	vga_rolled_over;
=20
 static int vgacon_text_mode_force;
=20
@@ -182,70 +182,125 @@ static inline void vga_set_mem_top(struct vc_dat=
a *c)
=20
 #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_CONSOLE=
S];
+#else
+static struct vgacon_scrollback_info vgacon_scrollbacks[1];
+#endif
+
+static void vgacon_scrollback_reset(size_t reset_size)
 {
-	int rows =3D CONFIG_VGACON_SOFT_SCROLLBACK_SIZE * 1024/pitch;
-
-	if (vgacon_scrollback) {
-		vgacon_scrollback_cnt  =3D 0;
-		vgacon_scrollback_tail =3D 0;
-		vgacon_scrollback_cur  =3D 0;
-		vgacon_scrollback_rows =3D rows - 1;
-		vgacon_scrollback_size =3D rows * pitch;
+	if (vgacon_scrollback_cur->data && reset_size > 0)
+		memset(vgacon_scrollback_cur->data, 0, reset_size);
+
+	vgacon_scrollback_cur->cnt  =3D 0;
+	vgacon_scrollback_cur->tail =3D 0;
+	vgacon_scrollback_cur->cur  =3D 0;
+}
+
+static void vgacon_scrollback_init(int vc_num)
+{
+	int pitch =3D vga_video_num_columns * 2;
+	size_t size =3D CONFIG_VGACON_SOFT_SCROLLBACK_SIZE * 1024;
+	int rows =3D size/pitch;
+	void *data;
+
+	data =3D kcalloc(CONFIG_VGACON_SOFT_SCROLLBACK_SIZE, 1024, GFP_NOWAIT=
);
+	if (data) {
+		vgacon_scrollbacks[vc_num].data =3D data;
+		vgacon_scrollback_cur =3D &vgacon_scrollbacks[vc_num];
+
+		vgacon_scrollback_cur->rows =3D rows - 1;
+		vgacon_scrollback_cur->size =3D 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);
 	}
 }
=20
+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 =3D &vgacon_scrollbacks[vc_num];
+#else
+	vc_num =3D 0;
+
+	if (!vgacon_scrollbacks[vc_num].data)
+		vgacon_scrollback_init(vc_num);
+	else {
+		size_t size =3D CONFIG_VGACON_SOFT_SCROLLBACK_SIZE * 1024;
+
+		vgacon_scrollback_reset(size);
+	}
+#endif
+}
+
 static void vgacon_scrollback_startup(void)
 {
-	vgacon_scrollback =3D kcalloc(CONFIG_VGACON_SOFT_SCROLLBACK_SIZE, 102=
4, GFP_NOWAIT);
-	vgacon_scrollback_init(vga_video_num_columns * 2);
+	int i;
+
+	for (i =3D 0; i < ARRAY_SIZE(vgacon_scrollbacks); ++i)
+		vgacon_scrollbacks[i].data =3D NULL;
+
+	vgacon_scrollback_cur =3D &vgacon_scrollbacks[0];
+	vgacon_scrollback_init(0);
 }
=20
 static void vgacon_scrollback_update(struct vc_data *c, int t, int cou=
nt)
 {
 	void *p;
=20
-	if (!vgacon_scrollback_size || c->vc_num !=3D fg_console)
+	if (!vgacon_scrollback_cur->data || !vgacon_scrollback_cur->size)
 		return;
=20
 	p =3D (void *) (c->vc_origin + t * c->vc_size_row);
=20
 	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 +=3D c->vc_size_row;
-		vgacon_scrollback_tail +=3D c->vc_size_row;
+		vgacon_scrollback_cur->tail +=3D c->vc_size_row;
=20
-		if (vgacon_scrollback_tail >=3D vgacon_scrollback_size)
-			vgacon_scrollback_tail =3D 0;
+		if (vgacon_scrollback_cur->tail >=3D vgacon_scrollback_cur->size)
+			vgacon_scrollback_cur->tail =3D 0;
=20
-		if (vgacon_scrollback_cnt > vgacon_scrollback_rows)
-			vgacon_scrollback_cnt =3D vgacon_scrollback_rows;
+		if (vgacon_scrollback_cur->cnt > vgacon_scrollback_cur->rows)
+			vgacon_scrollback_cur->cnt =3D vgacon_scrollback_cur->rows;
=20
-		vgacon_scrollback_cur =3D vgacon_scrollback_cnt;
+		vgacon_scrollback_cur->cur =3D vgacon_scrollback_cur->cnt;
 	}
 }
=20
 static void vgacon_restore_screen(struct vc_data *c)
 {
-	vgacon_scrollback_save =3D 0;
+	vgacon_scrollback_cur->save =3D 0;
=20
-	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 =3D 1;
-		vgacon_scrollback_cur =3D vgacon_scrollback_cnt;
+		vgacon_scrollback_cur->restore =3D 1;
+		vgacon_scrollback_cur->cur =3D vgacon_scrollback_cur->cnt;
 	}
 }
=20
@@ -259,41 +314,41 @@ static int vgacon_scrolldelta(struct vc_data *c, =
int lines)
 		return 1;
 	}
=20
-	if (!vgacon_scrollback)
+	if (!vgacon_scrollback_cur->data)
 		return 1;
=20
-	if (!vgacon_scrollback_save) {
+	if (!vgacon_scrollback_cur->save) {
 		vgacon_cursor(c, CM_ERASE);
 		vgacon_save_screen(c);
-		vgacon_scrollback_save =3D 1;
+		vgacon_scrollback_cur->save =3D 1;
 	}
=20
-	vgacon_scrollback_restore =3D 0;
-	start =3D vgacon_scrollback_cur + lines;
+	vgacon_scrollback_cur->restore =3D 0;
+	start =3D vgacon_scrollback_cur->cur + lines;
 	end =3D start + abs(lines);
=20
 	if (start < 0)
 		start =3D 0;
=20
-	if (start > vgacon_scrollback_cnt)
-		start =3D vgacon_scrollback_cnt;
+	if (start > vgacon_scrollback_cur->cnt)
+		start =3D vgacon_scrollback_cur->cnt;
=20
 	if (end < 0)
 		end =3D 0;
=20
-	if (end > vgacon_scrollback_cnt)
-		end =3D vgacon_scrollback_cnt;
+	if (end > vgacon_scrollback_cur->cnt)
+		end =3D vgacon_scrollback_cur->cnt;
=20
-	vgacon_scrollback_cur =3D start;
+	vgacon_scrollback_cur->cur =3D start;
 	count =3D end - start;
-	soff =3D vgacon_scrollback_tail - ((vgacon_scrollback_cnt - end) *
-					 c->vc_size_row);
+	soff =3D vgacon_scrollback_cur->tail;
+	soff -=3D ((vgacon_scrollback_cur->cnt - end) * c->vc_size_row);
 	soff -=3D count * c->vc_size_row;
=20
 	if (soff < 0)
-		soff +=3D vgacon_scrollback_size;
+		soff +=3D vgacon_scrollback_cur->size;
=20
-	count =3D vgacon_scrollback_cnt - start;
+	count =3D vgacon_scrollback_cur->cnt - start;
=20
 	if (count > c->vc_rows)
 		count =3D c->vc_rows;
@@ -307,13 +362,13 @@ static int vgacon_scrolldelta(struct vc_data *c, =
int lines)
=20
 		count *=3D c->vc_size_row;
 		/* how much memory to end of buffer left? */
-		copysize =3D min(count, vgacon_scrollback_size - soff);
-		scr_memcpyw(d, vgacon_scrollback + soff, copysize);
+		copysize =3D min(count, vgacon_scrollback_cur->size - soff);
+		scr_memcpyw(d, vgacon_scrollback_cur->data + soff, copysize);
 		d +=3D copysize;
 		count -=3D copysize;
=20
 		if (count) {
-			scr_memcpyw(d, vgacon_scrollback, count);
+			scr_memcpyw(d, vgacon_scrollback_cur->data, count);
 			d +=3D count;
 		}
=20
@@ -328,6 +383,7 @@ static int vgacon_scrolldelta(struct vc_data *c, in=
t 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)
=20
 static void vgacon_restore_screen(struct vc_data *c)
 {
@@ -843,7 +899,7 @@ static int vgacon_switch(struct vc_data *c)
 			vgacon_doresize(c, c->vc_cols, c->vc_rows);
 	}
=20
-	vgacon_scrollback_init(c->vc_size_row);
+	vgacon_switch_scrollback(c->vc_num);
 	return 0;		/* Redrawing not needed */
 }
=20
--=20
2.1.4

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[PATCH 2/2] console: Add ioctl for flushing the scrollback buffer

[Manuel Schölling]

Tools like clear_console rely on the fact that scrollback history is
flushed when switching back and forth between consoles.
Persistent scrollback buffers for each console breaks this, so this
patch adds a ioctl() callf for flushing the scrollback history.

Signed-off-by: Manuel Sch=C3=B6lling <manuel.schoelling@gmx.de>
---
 drivers/tty/vt/vt_ioctl.c               | 20 ++++++++++++++++++++
 drivers/usb/misc/sisusbvga/sisusb_con.c |  1 +
 drivers/video/console/dummycon.c        |  1 +
 drivers/video/console/mdacon.c          |  6 ++++++
 drivers/video/console/newport_con.c     |  1 +
 drivers/video/console/sticon.c          |  7 +++++++
 drivers/video/console/vgacon.c          | 23 +++++++++++++++++++++++
 include/linux/console.h                 |  1 +
 include/uapi/linux/vt.h                 |  1 +
 9 files changed, 61 insertions(+)

diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index 97d5a74..18adc23 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -903,6 +903,26 @@ int vt_ioctl(struct tty_struct *tty,
 		break;
 	}
=20
+	/*
+	 * flush the specified VT's scollback buffer
+	 */
+	case VT_FLUSH_SCROLLBACK: {
+		if (!perm)
+			return -EPERM;
+		if (arg =3D=3D 0 || arg > MAX_NR_CONSOLES)
+			ret =3D -ENXIO;
+		else {
+			struct vc_data *data =3D vc_cons[arg-1].d;
+
+			if (!data)
+				ret =3D -ENXIO;
+			else
+				ret =3D data->vc_sw->con_flush_scrollback(data);
+		}
+
+		break;
+	}
+
 	case PIO_FONT: {
 		if (!perm)
 			return -EPERM;
diff --git a/drivers/usb/misc/sisusbvga/sisusb_con.c b/drivers/usb/misc=
/sisusbvga/sisusb_con.c
index ace3430..cc5fc10 100644
--- a/drivers/usb/misc/sisusbvga/sisusb_con.c
+++ b/drivers/usb/misc/sisusbvga/sisusb_con.c
@@ -1442,6 +1442,7 @@ static const struct consw sisusb_dummy_con =3D {
 	.con_font_copy =3D	SISUSBCONDUMMY,
 	.con_set_palette =3D	SISUSBCONDUMMY,
 	.con_scrolldelta =3D	SISUSBCONDUMMY,
+	.con_flush_scrollback =3D SISUSBCONDUMMY,
 };
=20
 int
diff --git a/drivers/video/console/dummycon.c b/drivers/video/console/d=
ummycon.c
index 0efc52f..d2888e5 100644
--- a/drivers/video/console/dummycon.c
+++ b/drivers/video/console/dummycon.c
@@ -73,5 +73,6 @@ const struct consw dummy_con =3D {
     .con_font_copy =3D	DUMMY,
     .con_set_palette =3D	DUMMY,
     .con_scrolldelta =3D	DUMMY,
+    .con_flush_scrollback =3D DUMMY,
 };
 EXPORT_SYMBOL_GPL(dummy_con);
diff --git a/drivers/video/console/mdacon.c b/drivers/video/console/mda=
con.c
index 296e945..10ebcbe 100644
--- a/drivers/video/console/mdacon.c
+++ b/drivers/video/console/mdacon.c
@@ -510,6 +510,11 @@ static int mdacon_scrolldelta(struct vc_data *c, i=
nt lines)
 	return 0;
 }
=20
+static int mdacon_flush_scrollback(struct vc_data *c)
+{
+	return 0;
+}
+
 static void mdacon_cursor(struct vc_data *c, int mode)
 {
 	if (mode =3D=3D CM_ERASE) {
@@ -579,6 +584,7 @@ static const struct consw mda_con =3D {
 	.con_blank =3D		mdacon_blank,
 	.con_set_palette =3D	mdacon_set_palette,
 	.con_scrolldelta =3D	mdacon_scrolldelta,
+	.con_flush_scrollback =3D	mdacon_flush_scrollback,
 	.con_build_attr =3D	mdacon_build_attr,
 	.con_invert_region =3D	mdacon_invert_region,
 };
diff --git a/drivers/video/console/newport_con.c b/drivers/video/consol=
e/newport_con.c
index bb4e962..d04183c 100644
--- a/drivers/video/console/newport_con.c
+++ b/drivers/video/console/newport_con.c
@@ -738,6 +738,7 @@ const struct consw newport_con =3D {
 	.con_scrolldelta  =3D newport_scrolldelta,
 	.con_set_origin	  =3D DUMMY,
 	.con_save_screen  =3D DUMMY
+	.con_flush_scrollback =3D DUMMY,
 };
=20
 static int newport_probe(struct gio_device *dev,
diff --git a/drivers/video/console/sticon.c b/drivers/video/console/sti=
con.c
index 026fd12..46046d6 100644
--- a/drivers/video/console/sticon.c
+++ b/drivers/video/console/sticon.c
@@ -345,6 +345,12 @@ static void sticon_save_screen(struct vc_data *con=
p)
 {
 }
=20
+static int sticon_flush_scrollback(struct vc_data *c)
+{
+	return 0;
+}
+
+
 static const struct consw sti_con =3D {
 	.owner			=3D THIS_MODULE,
 	.con_startup		=3D sticon_startup,
@@ -360,6 +366,7 @@ static const struct consw sti_con =3D {
 	.con_blank		=3D sticon_blank,
 	.con_set_palette	=3D sticon_set_palette,
 	.con_scrolldelta	=3D sticon_scrolldelta,
+	.con_flush_scrollback	=3D sticon_flush_scrollback,
 	.con_set_origin		=3D sticon_set_origin,
 	.con_save_screen	=3D sticon_save_screen,=20
 	.con_build_attr		=3D sticon_build_attr,
diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vga=
con.c
index 6c0b9ba..b5ea94f 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -379,12 +379,34 @@ static int vgacon_scrolldelta(struct vc_data *c, =
int lines)
=20
 	return 1;
 }
+
+/* flush the scrollback buffer of a console */
+static int vgacon_flush_scrollback(struct vc_data *c)
+{
+	size_t size =3D CONFIG_VGACON_SOFT_SCROLLBACK_SIZE * 1024;
+	struct vgacon_scrollback_info *vgacon_scrollback_prev;
+
+	vgacon_scrollback_prev =3D vgacon_scrollback_cur;
+	vgacon_scrollback_cur =3D &vgacon_scrollbacks[c->vc_num];
+
+	if (vgacon_scrollback_cur !=3D NULL)
+		vgacon_scrollback_reset(size);
+
+	vgacon_scrollback_cur =3D vgacon_scrollback_prev;
+
+	return 0;
+}
 #else
 #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)
=20
+static int vgacon_flush_scrollback(struct vc_data *c)
+{
+	return 0;
+}
+
 static void vgacon_restore_screen(struct vc_data *c)
 {
 	if (c->vc_origin !=3D c->vc_visible_origin)
@@ -1492,6 +1514,7 @@ const struct consw vga_con =3D {
 	.con_resize =3D vgacon_resize,
 	.con_set_palette =3D vgacon_set_palette,
 	.con_scrolldelta =3D vgacon_scrolldelta,
+	.con_flush_scrollback =3D vgacon_flush_scrollback,
 	.con_set_origin =3D vgacon_set_origin,
 	.con_save_screen =3D vgacon_save_screen,
 	.con_build_attr =3D vgacon_build_attr,
diff --git a/include/linux/console.h b/include/linux/console.h
index e49cc1e..946ff20 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -49,6 +49,7 @@ struct consw {
 			       unsigned int);
 	int	(*con_set_palette)(struct vc_data *, unsigned char *);
 	int	(*con_scrolldelta)(struct vc_data *, int);
+	int	(*con_flush_scrollback)(struct vc_data *);
 	int	(*con_set_origin)(struct vc_data *);
 	void	(*con_save_screen)(struct vc_data *);
 	u8	(*con_build_attr)(struct vc_data *, u8, u8, u8, u8, u8, u8);
diff --git a/include/uapi/linux/vt.h b/include/uapi/linux/vt.h
index 978578b..b799541 100644
--- a/include/uapi/linux/vt.h
+++ b/include/uapi/linux/vt.h
@@ -83,5 +83,6 @@ struct vt_setactivate {
 };
=20
 #define VT_SETACTIVATE	0x560F	/* Activate and set the mode of a consol=
e */
+#define VT_FLUSH_SCROLLBACK	0x5610	/* Flush the scrollback buffer */
=20
 #endif /* _UAPI_LINUX_VT_H */
--=20
2.1.4

Re: [PATCH 2/2] console: Add ioctl for flushing the scrollback buffer

[kbuild test robot]

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Hi Manuel,

[auto build test ERROR on usb/usb-testing]
[also build test ERROR on v4.6-rc4 next-20160418]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:    https://github.com/0day-ci/linux/commits/Manuel-Sch-lling/Persistent-scrollback-buffers-for-all-VGA-consoles/20160419-040228
base:   https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
config: mips-allyesconfig (attached as .config)
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=mips 

All errors (new ones prefixed by >>):

>> drivers/video/console/newport_con.c:741:2: error: request for member 'con_flush_scrollback' in something not a structure or union
     .con_flush_scrollback = DUMMY,
     ^

vim +/con_flush_scrollback +741 drivers/video/console/newport_con.c

   735		.con_font_set	  = newport_font_set,
   736		.con_font_default = newport_font_default,
   737		.con_set_palette  = newport_set_palette,
   738		.con_scrolldelta  = newport_scrolldelta,
   739		.con_set_origin	  = DUMMY,
   740		.con_save_screen  = DUMMY
 > 741		.con_flush_scrollback = DUMMY,
   742	};
   743	
   744	static int newport_probe(struct gio_device *dev,

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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Re: [PATCH 0/2] Persistent scrollback buffers for all VGA consoles

[Jakub Wilk]

* Manuel Sch=F6lling <manuel.schoelling-Mmb7MZpHnFY@public.gmane.org>, 2016-04-18, 21:56:
>To offer a way for userland tools to flush the buffer my second patch=20
>adds a ioctl call for that.

In f8df13e0a901fe55631fed66562369b4dba40f8b, the escape sequence \e[3J=20
was added, which erases the whole display including the scroll-back=20
buffer. So the new ioctl shouldn't be necessary.

--=20
Jakub Wilk
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