Re: [patch V6 19/37] x86/irq: Convey vector as argument and not in ptregs

[Josh Poimboeuf]

On Fri, May 22, 2020 at 02:48:53PM -0400, Boris Ostrovsky wrote:
> > Yes. They just make objtool very unhappy:
> >
> > arch/x86/entry/entry_64.o: warning: objtool: .entry.text+0xfd0: special:
> > can't find orig instruction
> >
> > Peter suggested to use:
> >
> >       .pos = .
> >       .byte..
> >       jmp
> >       .nops (pos + 8) - .
> 
> 
> Unfortunately this (.nops directive) only works for newer assemblers
> (2.31, per
> https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob_plain;f=gas/NEWS;h=9a3f352108e439754688e19e63a6235b38801182;hb=5eb617a71463fa6810cd14f57adfe7a1efc93a96)
> 
> 
> I have 2.27 and things don't go well.

A single nop should be fine, since gas will complain if it tries to move
the IP backwards.  (Also I'd vote for normal indentation instead of the
"assembler magic at 4 spaces" thing.)

.align 8
SYM_CODE_START(irq_entries_start)
	vector = FIRST_EXTERNAL_VECTOR
	.rept (FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR)
		pos = .
		UNWIND_HINT_IRET_REGS
		.byte	0x6a, vector
		jmp	asm_common_interrupt
		nop
		.  = pos + 8
		vector = vector + 1
	.endr
SYM_CODE_END(irq_entries_start)

-- 
Josh