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

[Dave Martin]

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.

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__)

[...]