On 18.01.23 21:56, Heinrich Schuchardt wrote:
>
>
> Am 18. Januar 2023 21:44:58 MEZ schrieb Jan Kiszka <jan.kis...@siemens.com>:
>> From: Jan Kiszka <jan.kis...@siemens.com>
>>
>> Before clearing the screen, ensure that no previous output of firmware
>> or UEFI programs will be overwritten on serial devices or other
>> streaming consoles. This helps generating complete boot logs.
>>
>> Tested regarding multi-output against qemu-x86_defconfig. Still, there
>> were remaining concerns about side effects, so this is provided as an
>> opt-in feature.
>>
>> Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
>> ---
>> lib/efi_loader/Kconfig | 9 +++++++++
>> lib/efi_loader/efi_console.c | 10 +++++++++-
>> 2 files changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
>> index b498c72206f..b2c3250b4ad 100644
>> --- a/lib/efi_loader/Kconfig
>> +++ b/lib/efi_loader/Kconfig
>> @@ -124,6 +124,15 @@ config EFI_SET_TIME
>> Provide the SetTime() runtime service at boottime. This service
>> can be used by an EFI application to adjust the real time clock.
>>
>> +config EFI_SCROLL_ON_CLEAR_SCREEN
>> + bool "Avoid overwriting previous output on clear screen"
>> + help
>> + Instead of moving the cursor home when the console screen should be
>> + cleared, emit blank new lines so that previous output is scrolled
>> + out of sight rather than overwritten. This allows on serial consoles
>> + to capture complete boot logs (except for interactive menus etc.)
>> + and can ease debugging related issues.
>> +
>> config EFI_HAVE_CAPSULE_SUPPORT
>> bool
>>
>> diff --git a/lib/efi_loader/efi_console.c b/lib/efi_loader/efi_console.c
>> index 4d08dd3763a..e40c129d1b2 100644
>> --- a/lib/efi_loader/efi_console.c
>> +++ b/lib/efi_loader/efi_console.c
>> @@ -461,10 +461,18 @@ static efi_status_t EFIAPI efi_cout_set_attribute(
>> }
>>
>> /**
>> - * efi_cout_clear_screen() - clear screen
>> + * efi_clear_screen() - clear screen
>> */
>> static void efi_clear_screen(void)
>> {
>> + if (CONFIG_IS_ENABLED(EFI_SCROLL_ON_CLEAR_SCREEN)) {
>> + unsigned int row;
>> +
>> + /* Avoid overwriting previous outputs on streaming consoles */
>
> Thanks for making the behavior configurable.
>
> We cannot assume that the cursor is on the last line.
>
> Assume that the cursor is on the first line. Then the screen will still be
> deleted.
>
> Especially in GRUB the cursor often is in the upper half of the screen
>
> The cursor should be moved to the right lower corner before scrolling.
Can do, though logging interactive menus was not in scope (and can't be
solved this way anyway).
Jan
--
Siemens AG, Technology
Competence Center Embedded Linux
