From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752393AbdHSSLY (ORCPT ); Sat, 19 Aug 2017 14:11:24 -0400 Received: from mail-wm0-f44.google.com ([74.125.82.44]:37099 "EHLO mail-wm0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752349AbdHSSLU (ORCPT ); Sat, 19 Aug 2017 14:11:20 -0400 From: Ard Biesheuvel To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Cc: Ard Biesheuvel , "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 , Nicolas Pitre , Steven Rostedt , Martin Schwidefsky , Sergey Senozhatsky , Linus Torvalds , Jessica Yu Subject: [PATCH v3 5/5] kernel: tracepoints: add support for relative references Date: Sat, 19 Aug 2017 19:10:35 +0100 Message-Id: <20170819181035.969-6-ard.biesheuvel@linaro.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170819181035.969-1-ard.biesheuvel@linaro.org> References: <20170819181035.969-1-ard.biesheuvel@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 | 19 +++++++++++++++---- kernel/tracepoint.c | 17 +++++++++++++---- 2 files changed, 28 insertions(+), 8 deletions(-) diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index a26ffbe09e71..d02bf1a695e8 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -228,6 +228,19 @@ 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") +#else +#define __TRACEPOINT_ENTRY(name) \ + static struct tracepoint * const __tracepoint_ptr_##name __used \ + __attribute__((section("__tracepoints_ptrs"))) = \ + &__tracepoint_##name +#endif + /* * 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 +250,9 @@ 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..68b0218ef66b 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -508,12 +508,21 @@ static void for_each_tracepoint_range(struct tracepoint * const *begin, void (*fct)(struct tracepoint *tp, void *priv), void *priv) { - struct tracepoint * const *iter; - if (!begin) return; - for (iter = begin; iter < end; iter++) - fct(*iter, priv); + + if (IS_ENABLED(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)) { + const int *iter; + + for (iter = (const int *)begin; iter < (const int *)end; iter++) + fct((struct tracepoint *)((unsigned long)iter + *iter), + priv); + } else { + struct tracepoint * const *iter; + + for (iter = begin; iter < end; iter++) + fct(*iter, priv); + } } /** -- 2.11.0