On Fri, May 01, 2020 at 10:29:03PM +0200, Peter Zijlstra wrote: > +++ b/arch/x86/include/asm/static_call.h > @@ -30,4 +30,14 @@ > ".size " STATIC_CALL_TRAMP_STR(name) ", . - " > STATIC_CALL_TRAMP_STR(name) " \n" \ > ".popsection \n") > > +#define ARCH_DEFINE_STATIC_CALL_RETTRAMP(name) > \ > + asm(".pushsection .static_call.text, \"ax\" \n" \ > + ".align 4 \n" \ > + ".globl " STATIC_CALL_TRAMP_STR(name) " \n" \ > + STATIC_CALL_TRAMP_STR(name) ": \n" \ > + " ret; nop; nop; nop; nop; \n" \ > + ".type " STATIC_CALL_TRAMP_STR(name) ", @function \n" \ > + ".size " STATIC_CALL_TRAMP_STR(name) ", . - " > STATIC_CALL_TRAMP_STR(name) " \n" \ > + ".popsection \n") > +
The boilerplate in these two trampoline macros is identical except for the actual instructions, maybe there could be a shared __ARCH_DEFINE_STATIC_CALL_TRAMP(name, insns) macro which does most of the dirty work. > #endif /* _ASM_STATIC_CALL_H */ > --- a/arch/x86/kernel/static_call.c > +++ b/arch/x86/kernel/static_call.c > @@ -4,19 +4,41 @@ > #include <linux/bug.h> > #include <asm/text-patching.h> > > -static void __static_call_transform(void *insn, u8 opcode, void *func) > +enum insn_type { > + call = 0, /* site call */ > + nop = 1, /* site cond-call */ > + jmp = 2, /* tramp / site tail-call */ > + ret = 3, /* tramp / site cond-tail-call */ > +}; The lowercase enums threw me for a loop, I thought they were variables a few times. Starting a new enum trend? :-) > void arch_static_call_transform(void *site, void *tramp, void *func) > @@ -24,10 +46,10 @@ void arch_static_call_transform(void *si > mutex_lock(&text_mutex); > > if (tramp) > - __static_call_transform(tramp, JMP32_INSN_OPCODE, func); > + __static_call_transform(tramp, jmp + !func, func); > > if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site) > - __static_call_transform(site, CALL_INSN_OPCODE, func); > + __static_call_transform(site, !func, func); Clever enum math, but probably more robust to be ignorant of the values: if (tramp) __static_call_transform(tramp, func ? jmp : ret, func); if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site) __static_call_transform(site, func ? call : nop, func); > +++ b/include/linux/static_call.h > @@ -16,7 +16,9 @@ > * > * DECLARE_STATIC_CALL(name, func); > * DEFINE_STATIC_CALL(name, func); > + * DEFINE_STATIC_COND_CALL(name, typename); > * static_call(name)(args...); > + * static_cond_call(name)(args...) > * static_call_update(name, func); Missing semicolon, also an updated description/example would be useful. On that note, what do you think about tweaking the naming from DEFINE_STATIC_COND_CALL(name, typename); static_cond_call(name)(args...); to DEFINE_STATIC_CALL_NO_FUNC(name, typename); static_call_if_func(name)(args...); ? Seems clearer to me. They're still STATIC_CALLs, so it seems logical to keep those two words together. And NO_FUNC clarifies the initialized value. Similarly RETTRAMP could be ARCH_DEFINE_STATIC_CALL_NO_FUNC. -- Josh