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From: Pekka Enberg on 26 Apr 2010 05:40
Guenter Roeck kirjoitti:
> Ensure that early_printk() does not write into VGA memory space
> if there is not VGA device in the system.
>
> Signed-off-by: Guenter Roeck <guenter.roeck(a)ericsson.com>
> ---
> v3:
> Changes are now limited to early_printk.c. Functionality is retained, meaning
> there will still be output on the VGA console before setup_early_printk()
> is called, but only if a VGA device is known to exist in the system.
>
> arch/x86/kernel/early_printk.c | 17 +++++++++++++----
> 1 files changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
> index b9c830c..783cb25 100644
> --- a/arch/x86/kernel/early_printk.c
> +++ b/arch/x86/kernel/early_printk.c
> @@ -170,10 +170,13 @@ asmlinkage void early_printk(const char *fmt, ...)
> int n;
> va_list ap;
>
> - va_start(ap, fmt);
> - n = vscnprintf(buf, sizeof(buf), fmt, ap);
> - early_console->write(early_console, buf, n);
> - va_end(ap);
> + if (early_console && (early_console_initialized ||
> + boot_params.screen_info.orig_video_isVGA == 1)) {
> + va_start(ap, fmt);
> + n = vscnprintf(buf, sizeof(buf), fmt, ap);
> + early_console->write(early_console, buf, n);
> + va_end(ap);
> + }
> }
>
> static inline void early_console_register(struct console *con, int keep_early)
> @@ -233,6 +236,12 @@ static int __init setup_early_printk(char *buf)
> #endif
> buf++;
> }
> +
> + /* If there is no VGA device, don't try to use it as early console. */
> + if (early_console == &early_vga_console &&
> + boot_params.screen_info.orig_video_isVGA != 1)
> + early_console = NULL;

Wouldn't it be better to switch to, say, serial console here to avoid
the NULL check in early_printk()?

> +
> return 0;
> }
>
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