Re: [PATCH 1/3] x86, acpi: Eliminate saved_eip

[Denys Vlasenko]

On 06/16/2015 12:05 PM, Pavel Machek wrote:
> 
>> diff --git a/arch/x86/kernel/acpi/wakeup_32.S b/arch/x86/kernel/acpi/wakeup_32.S
>> index 665c6b7..eef2bd3 100644
>> --- a/arch/x86/kernel/acpi/wakeup_32.S
>> +++ b/arch/x86/kernel/acpi/wakeup_32.S
>> @@ -31,17 +31,11 @@ wakeup_pmode_return:
>>  
>>  	movl	%cs:saved_magic, %eax
>>  	cmpl	$0x12345678, %eax
>> -	jne	bogus_magic
>> -
>> -	# jump to place where we left off
>> -	movl	saved_eip, %eax
>> -	jmp	*%eax
>> -
>> +	je	ret_point
>>  bogus_magic:
> 
> Longjump is supposed to flush the prefetch, but hopefully nothing
> depends on that detail... ...
> 
> no.
> 
> https://en.wikibooks.org/wiki/X86_Assembly/Protected_Mode#Entering_Protected_Mode
> 
> longjump is supposed to be there. Sorry about that. I guess indirect
> jump is not neccessary, and we should add a comment there.

What "long jump"? It's not a far (segment:offset) jump, it's a near
jump (one which only changes the offset), indirect one through a register.

And we aren't switching to or from protected mode here.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/