Re: [PATCH v4 14/18] static_call: Add static_cond_call()

[Peter Zijlstra]

On Wed, May 06, 2020 at 01:09:24PM -0500, Josh Poimboeuf wrote:

> #define __ARCH_DEFINE_STATIC_CALL_TRAMP(name, insns)			\
> 	asm(".pushsection .static_call.text, \"ax\"		\n"	\
> 	    ".align 4						\n"	\
> 	    ".globl " STATIC_CALL_TRAMP_STR(name) "		\n"	\
> 	    STATIC_CALL_TRAMP_STR(name) ":			\n"	\
> 	    insns "						\n"	\
> 	    ".type " STATIC_CALL_TRAMP_STR(name) ", @function	\n"	\
> 	    ".size " STATIC_CALL_TRAMP_STR(name) ", . - " STATIC_CALL_TRAMP_STR(name) " \n" \
> 	    ".popsection					\n")
> 
> #define ARCH_DEFINE_STATIC_CALL_TRAMP(name, func)			\
> 	__ARCH_DEFINE_STATIC_CALL_TRAMP(name, "jmp.d32 " # func)

Note that this one is now:

	.byte 0xe9; .long #func - (. + 4);

due to clang not actually understanding jmp.d32 :-(

> #define ARCH_DEFINE_STATIC_CALL_RETTRAMP(name, func)			\
> 	__ARCH_DEFINE_STATIC_CALL_TRAMP(name, "ret; nop; nop; nop; nop")
> 
> I like it.  Makes it easy to see the differences between the tramps.

OK, ok.. changed :-)