[PATCH v2 09/10] arm64/BUG: Use BRK instruction for generic BUG traps

Mark Rutland
2015-07-14T11:09:05Z

On Tue, Jul 14, 2015 at 11:20:27AM +0100, Dave P Martin wrote:
> On Mon, Jul 13, 2015 at 05:56:39PM +0100, Mark Rutland wrote:
> > On Mon, Jul 13, 2015 at 05:51:51PM +0100, Dave P Martin wrote:
> > > On Mon, Jul 13, 2015 at 05:43:15PM +0100, Mark Rutland wrote:
>
> [...]
>
> > > > Given the reliance on the labels in the caller, I think it might make
> > >
> > > Not sure what you mean here, can you elaborate?
> >
> > We're relying on label "0:" in the caller/user of the macro when we emit
> > ".long 2b - 0b".
> >
> > I think it would be clearer if folded into the caller (even with the
> > inline ifdef this necessitates).
> >
> > Though I could be missing something here that renders that impossible.
>
> Before I respin the series, can you cast your eye over this
> alternative?
>
> I'm testing it now, but in any case it should make the conditional
> structure of the code clearer as per your suggestion.

I think that style of macro is certainly more legible when applied to
single lines, but I got a little confused when reading this before I
noticed that each __BUGVERBOSE use covered a few lines.

Thanks,
Mark.

>
> Cheers
> ---Dave
>
>
> [...]
>
> #ifdef CONFIG_DEBUG_BUGVERBOSE
> #define __BUGVERBOSE(x...) x
> #else
> #define __BUGVERBOSE(x...)
> #endif
>
> #define _BUG_FLAGS(flags, file, line) __BUG_FLAGS(flags, file, line)
>
> #define __BUG_FLAGS(flags, file, line) asm volatile ( \
> __BUGVERBOSE( ".pushsection .rodata.str,\"aMS\", at progbits,1\n" \
> "2: .string \"" file "\"\n\t" \
> ".popsection\n\t" ) \
> \
> ".pushsection __bug_table,\"a\"\n\t" \
> ".align 2\n\t" \
> "0: .long 1f - 0b\n\t" \
> __BUGVERBOSE( ".long 2b - 0b\n\t" \
> ".short " #line "\n\t" ) \
> ".short " #flags "\n\t" \
> ".popsection\n" \
> \
> "1: brk %[imm]" \
> :: [imm] "i" (BUG_BRK_IMM) \
> )
>
> #define BUG() do { \
> _BUG_FLAGS(0, __FILE__, __LINE__); \
> unreachable(); \
> } while (0)
>
> #define __WARN_TAINT(taint) \
> _BUG_FLAGS(BUGFLAG_TAINT(taint), __FILE__, __LINE__)
>
> …