Re: [patch V4 part 2 10/18] x86/entry/64: Check IF in __preempt_enable_notrace() thunk

[Thomas Gleixner]

Steven Rostedt <rostedt@xxxxxxxxxxx> writes:
> On Tue, 05 May 2020 15:41:22 +0200
> Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>
>> The preempt_enable_notrace() ASM thunk is called from tracing, entry code
>> RCU and other places which are already in or going to be in the noinstr
>> section which protects sensitve code from being instrumented.
>> 
>> Calls out of these sections happen with interrupts disabled, which is
>> handled in C code, but the push regs, call, pop regs sequence can be
>> completely avoided in this case.
>> 
>> This is also a preparatory step for annotating the call from the thunk to
>> preempt_enable_notrace() safe from a noinstr section.
>> 
>
> BTW, after applying this patch, I get the following error:
>
> /work/git/linux-test.git/arch/x86/entry/thunk_64.S: Assembler messages:
> /work/git/linux-test.git/arch/x86/entry/thunk_64.S:67: Error: invalid operands (*UND* and *UND* sections) for `+'
> /work/git/linux-test.git/arch/x86/entry/thunk_64.S:67: Error: invalid operands (*UND* and *ABS* sections) for `/'
> make[3]: *** [/work/git/linux-test.git/scripts/Makefile.build:349: arch/x86/entry/thunk_64.o] Error 1
> make[3]: *** Waiting for unfinished jobs....

Yes I know, but I'm going to drop that patch completely.