| Message ID | 1474236417-27150-1-git-send-email-manuel.schoelling@gmx.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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.schoelling@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 */ > } > -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Sep 19, 2016 at 12:06:57AM +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.schoelling@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(-) I need someone else to at least test this, and give an acked-by for it... thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Sep 19, 2016 at 12:06:57AM +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. Hi, I have noticed your message on #kernelnewbies IRC channel. Thanks for the patch. This is definitely very useful, especially when you boot into rescue system and use raw console and not a fancy X11-based terminal app. > > 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. Personal feelings don't belong to commit messages. Previous paragraph is enough to express the purpose. > > 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. Have never heard of such tool as clear_console. Why mention it at all, where is it used, which are practical configurations which are broken in this way? Does this break clear(1)? > > Signed-off-by: Manuel Schölling <manuel.schoelling@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. Indentation amended, I don't know which way it should be, please double-check or mimic old indentation to stay on safe side. > + > +config VGACON_SOFT_SCROLLBACK_FOR_EACH_CONSOLE Feels like bad naming. What about VGACON_SOFT_SCROLLBACK_PERSISTENT? > + 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 Unnatural order of sentence IMHO, however I'm not native English. > + 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. I think you may put less text here. You can skip details like "buffer ... allocated", just explain the difference in behaviour. > + > + 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. See above. I'd drop this paragraph if clear(1) is not broken. > + > + If you use a RAM-constrained system, say N here. Which exactly cases to consider? I can't think of any practical one. You may want to help user to figure out if he should consider this by explaining that VGACON_SOFT_SCROLLBACK_SIZE is taken for each created tty device (right?). Or drop this line :) > > 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 Cosmetic changes in separate patch please. > * > * 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; > +}; Refactor in separate patch please. It would be much nicer if you make first patch in series which would gather all these variables into struct and uses it everywhere, leaving external behaviour the same. Then, in following patches, change the behaviour, one trait at a time. > +static struct vgacon_scrollback_info *vgacon_scrollback_cur; Could you use name vgacon_scrollback instead of new vgacon_scrollback_cur? It doesn't change anything conceptually, but is a bit shorter and seems to mean current scrollback context anyway, right? I think I see nothing to comment on below. Looking forward to see your reply. Would definitely like to test this when I have some time. -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
---
Changes in v4:
- Rename from VGACON_SOFT_SCROLLBACK_FOR_EACH_CONSOLE to
VGACON_SOFT_SCROLLBACK_PERSISTENT
- Split into two patches
- Rework documentation
- Remove cosmetic changes in comments (postponed)
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)
--
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Hi, I finally found the time to rework the patches, but there are a few things I want to discuss: > > 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. > > Have never heard of such tool as clear_console. Why mention it at all, > where is it used, which are practical configurations which are broken in > this way? clear_console(1) is part of Debian's bash package and (I think) a inofficial 'downstream' patch developed by Ubuntu [1]. There has been security concerns (which is also why I disabled this feature by default). However, if there might be security issues, I would strongly suggest to keep this part in the documentation - it does no harm anyway, does it? > Does this break clear(1)? No, my tests with clear(1) worked fine. > > - 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. > > Indentation amended, I don't know which way it should be, please > double-check or mimic old indentation to stay on safe side. Double-checked! That's at least how I read the docs. > > +static struct vgacon_scrollback_info *vgacon_scrollback_cur; > > Could you use name vgacon_scrollback instead of new > vgacon_scrollback_cur? It doesn't change anything conceptually, but is a > bit shorter and seems to mean current scrollback context anyway, right? > > I think I see nothing to comment on below. There is a already an array called 'vgacon_scrollbacks[N]', so I would not like to have two variables named 'vgacon_scrollback' and 'vgacon_scrollbacks'. Either {'vgacon_scrollback_cur' and 'vgacon_scrollbacks'} or {'vgacon_scrollback' and 'vgacon_scrollback_list'}. You can make a suggestion, if you like. All other point you mentioned where fixed as you suggested. Thanks again for your help, Andrey! Best, Manuel [1] http://manpages.ubuntu.com/manpages/xenial/en/man1/clear_console.1.html -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Well, that's embarrassing: I changed the order of some local commits
in the last minute, so my patches included a compiler error.
Changes in v4.1:
- Fix compiler error
Changes in v4:
- Rename from VGACON_SOFT_SCROLLBACK_FOR_EACH_CONSOLE to
VGACON_SOFT_SCROLLBACK_PERSISTENT
- Split into two patches
- Rework documentation
- Remove cosmetic changes in comments (postponed)
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)
Manuel Schölling (2):
console: Move scrollback data into its own struct
console: Add persistent scrollback buffers for all VGA consoles
drivers/video/console/Kconfig | 23 +++++-
drivers/video/console/vgacon.c | 158 ++++++++++++++++++++++++++++-------------
2 files changed, 127 insertions(+), 54 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 */ }
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.schoelling@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(-)