From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ard Biesheuvel Subject: [PATCH v2 6/6] kernel: tracepoints: add support for relative references Date: Fri, 18 Aug 2017 12:26:24 +0100 Message-ID: <20170818112624.24991-7-ard.biesheuvel@linaro.org> References: <20170818112624.24991-1-ard.biesheuvel@linaro.org> Return-path: In-Reply-To: <20170818112624.24991-1-ard.biesheuvel@linaro.org> Sender: linux-kernel-owner@vger.kernel.org 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 , Joe Perches , Nicolas Pitre , Steve List-Id: linux-arch.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 | 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[]; + /* * 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f178.google.com ([209.85.128.178]:33413 "EHLO mail-wr0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750920AbdHRL1O (ORCPT ); Fri, 18 Aug 2017 07:27:14 -0400 Received: by mail-wr0-f178.google.com with SMTP id b65so67589706wrd.0 for ; Fri, 18 Aug 2017 04:27:13 -0700 (PDT) From: Ard Biesheuvel Subject: [PATCH v2 6/6] kernel: tracepoints: add support for relative references Date: Fri, 18 Aug 2017 12:26:24 +0100 Message-ID: <20170818112624.24991-7-ard.biesheuvel@linaro.org> In-Reply-To: <20170818112624.24991-1-ard.biesheuvel@linaro.org> References: <20170818112624.24991-1-ard.biesheuvel@linaro.org> Sender: linux-arch-owner@vger.kernel.org List-ID: 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 , Joe Perches , Nicolas Pitre , Steven Rostedt , Martin Schwidefsky , Sergey Senozhatsky , Linus Torvalds , Andy Whitcroft , Jessica Yu Message-ID: <20170818112624.AVWksoECi1uCPB4CuQPRQcxZQrHA7SOOuJLOeyS6DU4@z> 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[]; + /* * 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