[PATCH 2/4] powerpc/64: remove support for kernel-mode syscalls

[Nicholas Piggin]

Nicholas Piggin's on August 27, 2019 8:20 pm:
> Christophe Leroy's on August 27, 2019 4:13 pm:
>> 
>> 
>> Le 27/08/2019 à 05:30, Nicholas Piggin a écrit :
>>> There is support for the kernel to execute the 'sc 0' instruction and
>>> make a system call to itself. This is a relic that is unused in the
>>> tree, therefore untested. It's also highly questionable for modules to
>>> be doing this.
>> 
>> I like it.
>> 
>> I dropped support for that in PPC32 when I added fast-path syscalls.
> 
> Good, then we'll match again.
> 
>>> -	beq	2f			/* if from kernel mode */
>>>   #ifdef CONFIG_PPC_FSL_BOOK3E
>>>   START_BTB_FLUSH_SECTION
>>>   	BTB_FLUSH(r10)
>>>   END_BTB_FLUSH_SECTION
>>>   #endif
>>>   	ACCOUNT_CPU_USER_ENTRY(r13, r10, r11)
>>> -2:	std	r2,GPR2(r1)
> 
> Btw. there is a hunk which restores this optimisation but it leaked
> into a later patch, I'll move it back here.

I'm wrong. Now I look at it again, the hunk should be removed
completely of course.

Thanks,
Nick