From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752876AbdHRNnp (ORCPT ); Fri, 18 Aug 2017 09:43:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:58090 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752541AbdHRNnn (ORCPT ); Fri, 18 Aug 2017 09:43:43 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2532023951 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Fri, 18 Aug 2017 09:43:38 -0400 From: Steven Rostedt To: Ard Biesheuvel Cc: "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" , "H. Peter Anvin" , Arnd Bergmann , Heiko Carstens , Kees Cook , Will Deacon , Michael Ellerman , Thomas Garnier , Thomas Gleixner , "Serge E. Hallyn" , Bjorn Helgaas , Benjamin Herrenschmidt , Paul Mackerras , Catalin Marinas , Petr Mladek , Ingo Molnar , James Morris , Andrew Morton , Joe Perches , Nicolas Pitre , Martin Schwidefsky , Sergey Senozhatsky , Linus Torvalds , Andy Whitcroft , Jessica Yu Subject: Re: [PATCH v2 6/6] kernel: tracepoints: add support for relative references Message-ID: <20170818094338.5370cdad@gandalf.local.home> In-Reply-To: References: <20170818112624.24991-1-ard.biesheuvel@linaro.org> <20170818112624.24991-7-ard.biesheuvel@linaro.org> X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 18 Aug 2017 12:44:17 +0100 Ard Biesheuvel wrote: > On 18 August 2017 at 12:26, Ard Biesheuvel wrote: > > To avoid the need for relocating absolute references to tracepoint > > structures at boot time when running relocatable kernels (which may > > take a disproportionate amount of space), add the option to emit > > these tables as relative references instead. > > > > Cc: Steven Rostedt > > Cc: Ingo Molnar > > Signed-off-by: Ard Biesheuvel > > --- > > include/linux/tracepoint.h | 42 ++++++++++++++++++-- > > kernel/tracepoint.c | 7 +--- > > 2 files changed, 40 insertions(+), 9 deletions(-) > > > > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h > > index a26ffbe09e71..68701821933a 100644 > > --- a/include/linux/tracepoint.h > > +++ b/include/linux/tracepoint.h > > @@ -228,6 +228,42 @@ extern void syscall_unregfunc(void); > > return static_key_false(&__tracepoint_##name.key); \ > > } > > > > +#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS > > +#define __TRACEPOINT_ENTRY(name) \ > > + asm(" .section \"__tracepoints_ptrs\", \"a\"\n" \ > > + " .balign 4\n" \ > > + " .long " VMLINUX_SYMBOL_STR(__tracepoint_##name) " - .\n"\ > > + " .previous\n") > > + > > +struct tracepoint_entry_t { > > + int tp_offset; > > +}; > > + > > +static inline > > +struct tracepoint *tracepoint_from_entry(const struct tracepoint_entry_t *ent) > > +{ > > + return (struct tracepoint *)((unsigned long)ent + ent->tp_offset); > > +} > > +#else > > +#define __TRACEPOINT_ENTRY(name) \ > > + static struct tracepoint * const __tracepoint_ptr_##name __used \ > > + __attribute__((section("__tracepoints_ptrs"))) = \ > > + &__tracepoint_##name > > + > > +struct tracepoint_entry_t { > > + struct tracepoint *tp; > > +}; > > + > > +static inline > > +struct tracepoint *tracepoint_from_entry(const struct tracepoint_entry_t *ent) > > +{ > > + return ent->tp; > > +} > > +#endif > > + > > +extern struct tracepoint_entry_t const __start___tracepoints_ptrs[]; > > +extern struct tracepoint_entry_t const __stop___tracepoints_ptrs[]; > > + > > It appears the stuff above needs to be move inside the double-include > guard (which oddly enough does not cover the entire file) Why was this moved to the header file? To fulfill some checkpatch warning? -- Steve > > > /* > > * We have no guarantee that gcc and the linker won't up-align the tracepoint > > * structures, so we create an array of pointers that will be used for iteration > > @@ -237,11 +273,9 @@ extern void syscall_unregfunc(void); > > static const char __tpstrtab_##name[] \ > > __attribute__((section("__tracepoints_strings"))) = #name; \ > > struct tracepoint __tracepoint_##name \ > > - __attribute__((section("__tracepoints"))) = \ > > + __attribute__((section("__tracepoints"))) __used = \ > > { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\ > > - static struct tracepoint * const __tracepoint_ptr_##name __used \ > > - __attribute__((section("__tracepoints_ptrs"))) = \ > > - &__tracepoint_##name; > > + __TRACEPOINT_ENTRY(name); > > > > #define DEFINE_TRACE(name) \ > > DEFINE_TRACE_FN(name, NULL, NULL); > > diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c > > index 685c50ae6300..21bc41454fd6 100644 > > --- a/kernel/tracepoint.c > > +++ b/kernel/tracepoint.c > > @@ -28,9 +28,6 @@ > > #include > > #include > > > > -extern struct tracepoint * const __start___tracepoints_ptrs[]; > > -extern struct tracepoint * const __stop___tracepoints_ptrs[]; > > - > > /* Set to 1 to enable tracepoint debug output */ > > static const int tracepoint_debug; > > > > @@ -508,12 +505,12 @@ static void for_each_tracepoint_range(struct tracepoint * const *begin, > > void (*fct)(struct tracepoint *tp, void *priv), > > void *priv) > > { > > - struct tracepoint * const *iter; > > + struct tracepoint_entry_t const *iter; > > > > if (!begin) > > return; > > for (iter = begin; iter < end; iter++) > > - fct(*iter, priv); > > + fct(tracepoint_from_entry(iter), priv); > > } > > > > /** > > -- > > 2.11.0 > >