On Mon, Sep 11, 2017 at 01:18:16PM +0200, Gerd Hoffmann wrote:
[...]
> --- a/src/romlayout.S
> +++ b/src/romlayout.S
> @@ -434,7 +434,7 @@ entry_sercon:
> pushl $1f
> retl
> 1: cmpl %esp, %eax
> - jne 4f
> + jne 5f
> cmpb $0, sercon_enable // Test that sercon is enabled
> je 3f
>
> @@ -449,15 +449,17 @@ entry_sercon:
>
> // sercon disabled - verify not 0x03 modeset and otherwise exit
> 3: popl %eax
> + cmpw $0x0007, %ax
> + je 4f
> cmpw $0x0003, %ax
> - jne 5f
> - pushl %eax
> + jg 6f
> +4: pushl %eax
> jmp 2b
>
> // Running on broken x86emu - restore stack and exit
> -4: movl %eax, %esp
> +5: movl %eax, %esp
> popl %eax
> -5: popw %ds
> +6: popw %ds
> iretw
The asm could be simplified a bit:
// Serial console "hooked vga" entry point
DECLFUNC entry_sercon
entry_sercon:
// Setup for chain loading to real vga handler
pushfw
pushl %cs:sercon_real_vga_handler
// Set %ds to zonelow segment
cli
cld
pushw %ds
pushl %eax
movl $_zonelow_seg, %eax
movl %eax, %ds
// Test if the sercon handler can be called
movl %esp, %eax // Test for broken x86emu
pushl $1f
retl
1: cmpl %esp, %eax
jne 4f
cmpb $0, sercon_enable // Test that sercon is enabled
je 3f
// Call handle_sercon()
popl %eax
popw %ds
2: pushl $handle_sercon
#if CONFIG_ENTRY_EXTRASTACK
jmp irqentry_arg_extrastack
#else
jmp irqentry_arg
#endif
// sercon disabled - check for legacy text modeset and otherwise exit
3: popl %eax
popw %ds
cmpw $0x0007, %ax
jle 2b
iretw
// Running on broken x86emu - restore stack and exit
4: movl %eax, %esp
popl %eax
popw %ds
iretw
_______________________________________________
SeaBIOS mailing list
SeaBIOS@seabios.org
https://mail.coreboot.org/mailman/listinfo/seabios
