Messages in this thread | | | Date | Thu, 10 Jan 2019 10:28:10 -0600 | From | Josh Poimboeuf <> | Subject | Re: [PATCH v3 3/6] x86/static_call: Add out-of-line static call implementation |
| |
On Thu, Jan 10, 2019 at 12:16:34AM +0000, Nadav Amit wrote: > > On Jan 9, 2019, at 2:59 PM, Josh Poimboeuf <jpoimboe@redhat.com> wrote: > > > > <snip> > > > + > > +void __ref arch_static_call_transform(void *site, void *tramp, void *func) > > +{ > > + s32 dest_relative; > > + unsigned char opcode; > > + void *(*poker)(void *, const void *, size_t); > > + void *insn = tramp; > > + > > + mutex_lock(&text_mutex); > > + > > + /* > > + * For x86-64, a 32-bit cross-modifying write to a call destination is > > + * safe as long as it's within a cache line. > > + */ > > + opcode = *(unsigned char *)insn; > > + if (opcode != 0xe8 && opcode != 0xe9) { > > + WARN_ONCE(1, "unexpected static call insn opcode 0x%x at %pS", > > + opcode, insn); > > + goto done; > > + } > > + > > + dest_relative = (long)(func) - (long)(insn + CALL_INSN_SIZE); > > + > > + poker = early_boot_irqs_disabled ? text_poke_early : text_poke; > > + poker(insn + 1, &dest_relative, sizeof(dest_relative)); > > + > > +done: > > + mutex_unlock(&text_mutex); > > +} > > +EXPORT_SYMBOL_GPL(arch_static_call_transform); > > Err… I was rewriting __jump_label_transform(), so if this code duplication can > be avoided, this would be great. > > (See https://lkml.org/lkml/2018/11/14/72 )
I don't see much code duplication, because __jump_label_transform() uses text_poke_bp(), whereas this uses text_poke().
It's true they both fall back to text_poke_early(), but I don't see any opportunities for sharing code there, unless we decide to go back to using breakpoints.
-- Josh
| |