From patchwork Tue May 29 22:15:16 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Garnier X-Patchwork-Id: 10437307 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id A4D46601C7 for ; Tue, 29 May 2018 22:21:11 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8DBDE2891B for ; Tue, 29 May 2018 22:21:11 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 81AC928927; Tue, 29 May 2018 22:21:11 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED, USER_IN_DEF_DKIM_WL autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 3AD642891B for ; Tue, 29 May 2018 22:21:10 +0000 (UTC) Received: (qmail 18414 invoked by uid 550); 29 May 2018 22:17:45 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 18209 invoked from network); 29 May 2018 22:17:42 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=WEPPQRL0lo2GVz5s9Lpab+TBTjf13cI3VR/IEJ/DMdE=; b=MpJBfc662Ry9kOE5DY007l9K8fQjjEWCU6njLHglGF4QlVDYvLf79/mymaHOLu2Sgn OkILdnUqyPf3zbFPL796NuHbtCiUv3zBnq+O+iJb/1hnuZqx4x9Ty7f/znhQTSJKydJW O5bo4VvQfTTHK0tO3RoOKmiqA46Hy+lE3OfDtqxEaNkxcyeTxAuAoUJthsQaIyoq+4Ps zZAhTbnn/oK4Wg+uKjyDaadtIPwfL6uQ5DBLBox962uqlZ180wElo9mVVR89rJzHfwYG d4qQYaGqoO8M6Pvy4CnAwVX/tceaAG1PFQM0wG54Yye8GVvLygGMZ2XKvSxHVFku7EMu YI/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=WEPPQRL0lo2GVz5s9Lpab+TBTjf13cI3VR/IEJ/DMdE=; b=WPBnES0BPVUNo7iK00q2fZGkthnPyAOJzocoj6yPQW15e0zUN04INR59vq/FiN41d+ XGiTeI+efJprUuF8xh6pcMcxyW0IwdFuS+JPLwuoQUgtdvsX4w3ZwQiv+30yYmZTAB9R ikiDs/hI01566GnosU/4W1/RoG8x6hzdEIpI3MUYPuNRlgBm+hkn7ObpTgCe7vIJaVsY 8WD3ksRYVV0zPU/+6Kx0rVlpRdgcqvNycXOxQjg1VDlauxFIVnxn06c/bXck6c9sNzB+ +VmVDB2FPpI3gE6FsfIUhjMiCJf27byuwisUtjA3P9+5j6cNbyOeunOhbuOtuBEru8dY VTxQ== X-Gm-Message-State: ALKqPwdQ3MgL2YTyQV0+Ep91+zRvp0ZT3SCUhdjJsvGx7I/QVxktWoIS X53np4O4AAq49OjknlhXqKne3u3tFw4= X-Google-Smtp-Source: ADUXVKL6KiwVm6Abdk0SB2MKI2RN/wyNObHGm5vc/10PLGJ6pgtWL+2kxfX5C46O4KH2u8rJmZhZVg== X-Received: by 2002:a62:4086:: with SMTP id f6-v6mr212479pfd.194.1527632249687; Tue, 29 May 2018 15:17:29 -0700 (PDT) From: Thomas Garnier To: kernel-hardening@lists.openwall.com Cc: Thomas Garnier , Skip Mathieu Desnoyers , Skip Frederic Weisbecker , Skip Dominik Brodowski , Skip Nicholas Piggin , Skip Kees Cook , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Borislav Petkov , "Luis R. Rodriguez" , Greg Kroah-Hartman , Arnd Bergmann , Christopher Li , Steven Rostedt , Jason Baron , Dou Liyang , Lukas Wunner , "Paul E. McKenney" , Andrew Morton , Peter Zijlstra , Randy Dunlap , Sergey Senozhatsky , Petr Mladek , Masahiro Yamada , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-sparse@vger.kernel.org Subject: [PATCH v4 15/27] compiler: Option to default to hidden symbols Date: Tue, 29 May 2018 15:15:16 -0700 Message-Id: <20180529221625.33541-16-thgarnie@google.com> X-Mailer: git-send-email 2.17.0.921.gf22659ad46-goog In-Reply-To: <20180529221625.33541-1-thgarnie@google.com> References: <20180529221625.33541-1-thgarnie@google.com> X-Virus-Scanned: ClamAV using ClamSMTP Provide an option to default visibility to hidden except for key symbols. This option is disabled by default and will be used by x86_64 PIE support to remove errors between compilation units. The default visibility is also enabled for external symbols that are compared as they maybe equals (start/end of sections). In this case, older versions of GCC will remove the comparison if the symbols are hidden. This issue exists at least on gcc 4.9 and before. Signed-off-by: Thomas Garnier --- arch/x86/boot/boot.h | 2 +- arch/x86/include/asm/setup.h | 2 +- arch/x86/kernel/cpu/microcode/core.c | 4 ++-- drivers/base/firmware_loader/main.c | 4 ++-- include/asm-generic/sections.h | 6 ++++++ include/linux/compiler.h | 7 +++++++ init/Kconfig | 7 +++++++ kernel/kallsyms.c | 16 ++++++++-------- kernel/trace/trace.h | 4 ++-- lib/dynamic_debug.c | 4 ++-- 10 files changed, 38 insertions(+), 18 deletions(-) diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h index ef5a9cc66fb8..d726c35bdd96 100644 --- a/arch/x86/boot/boot.h +++ b/arch/x86/boot/boot.h @@ -193,7 +193,7 @@ static inline bool memcmp_gs(const void *s1, addr_t s2, size_t len) } /* Heap -- available for dynamic lists. */ -extern char _end[]; +extern char _end[] __default_visibility; extern char *HEAP; extern char *heap_end; #define RESET_HEAP() ((void *)( HEAP = _end )) diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h index ae13bc974416..083a6e99b884 100644 --- a/arch/x86/include/asm/setup.h +++ b/arch/x86/include/asm/setup.h @@ -68,7 +68,7 @@ static inline void x86_ce4100_early_setup(void) { } * This is set up by the setup-routine at boot-time */ extern struct boot_params boot_params; -extern char _text[]; +extern char _text[] __default_visibility; static inline bool kaslr_enabled(void) { diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index 77e201301528..6a4f5d9d7eb6 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -149,8 +149,8 @@ static bool __init check_loader_disabled_bsp(void) return *res; } -extern struct builtin_fw __start_builtin_fw[]; -extern struct builtin_fw __end_builtin_fw[]; +extern struct builtin_fw __start_builtin_fw[] __default_visibility; +extern struct builtin_fw __end_builtin_fw[] __default_visibility; bool get_builtin_firmware(struct cpio_data *cd, const char *name) { diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c index 0943e7065e0e..2ffd019af2d4 100644 --- a/drivers/base/firmware_loader/main.c +++ b/drivers/base/firmware_loader/main.c @@ -94,8 +94,8 @@ static struct firmware_cache fw_cache; #ifdef CONFIG_FW_LOADER -extern struct builtin_fw __start_builtin_fw[]; -extern struct builtin_fw __end_builtin_fw[]; +extern struct builtin_fw __start_builtin_fw[] __default_visibility; +extern struct builtin_fw __end_builtin_fw[] __default_visibility; static void fw_copy_to_prealloc_buf(struct firmware *fw, void *buf, size_t size) diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index 849cd8eb5ca0..0a0e23405ddd 100644 --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -32,6 +32,9 @@ * __softirqentry_text_start, __softirqentry_text_end * __start_opd, __end_opd */ +#ifdef CONFIG_DEFAULT_HIDDEN +#pragma GCC visibility push(default) +#endif extern char _text[], _stext[], _etext[]; extern char _data[], _sdata[], _edata[]; extern char __bss_start[], __bss_stop[]; @@ -49,6 +52,9 @@ extern char __start_once[], __end_once[]; /* Start and end of .ctors section - used for constructor calls. */ extern char __ctors_start[], __ctors_end[]; +#ifdef CONFIG_DEFAULT_HIDDEN +#pragma GCC visibility pop +#endif /* Start and end of .opd section - used for function descriptors. */ extern char __start_opd[], __end_opd[]; diff --git a/include/linux/compiler.h b/include/linux/compiler.h index ab4711c63601..a9ac84e37af9 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -278,6 +278,13 @@ unsigned long read_word_at_a_time(const void *addr) __u.__val; \ }) +#ifdef CONFIG_DEFAULT_HIDDEN +#pragma GCC visibility push(hidden) +#define __default_visibility __attribute__((visibility ("default"))) +#else +#define __default_visibility +#endif + #endif /* __KERNEL__ */ #endif /* __ASSEMBLY__ */ diff --git a/init/Kconfig b/init/Kconfig index e4acab9f9fd1..f16247675f84 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1694,6 +1694,13 @@ config PROFILING config TRACEPOINTS bool +# +# Default to hidden visibility for all symbols. +# Useful for Position Independent Code to reduce global references. +# +config DEFAULT_HIDDEN + bool + source "arch/Kconfig" endmenu # General setup diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index a23e21ada81b..f4e58b7a6daf 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -29,24 +29,24 @@ * These will be re-linked against their real values * during the second link stage. */ -extern const unsigned long kallsyms_addresses[] __weak; -extern const int kallsyms_offsets[] __weak; -extern const u8 kallsyms_names[] __weak; +extern const unsigned long kallsyms_addresses[] __weak __default_visibility; +extern const int kallsyms_offsets[] __weak __default_visibility; +extern const u8 kallsyms_names[] __weak __default_visibility; /* * Tell the compiler that the count isn't in the small data section if the arch * has one (eg: FRV). */ extern const unsigned long kallsyms_num_syms -__attribute__((weak, section(".rodata"))); +__attribute__((weak, section(".rodata"))) __default_visibility; extern const unsigned long kallsyms_relative_base -__attribute__((weak, section(".rodata"))); +__attribute__((weak, section(".rodata"))) __default_visibility; -extern const u8 kallsyms_token_table[] __weak; -extern const u16 kallsyms_token_index[] __weak; +extern const u8 kallsyms_token_table[] __weak __default_visibility; +extern const u16 kallsyms_token_index[] __weak __default_visibility; -extern const unsigned long kallsyms_markers[] __weak; +extern const unsigned long kallsyms_markers[] __weak __default_visibility; /* * Expand a compressed symbol data into the resulting uncompressed string, diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 6fb46a06c9dc..e659f452cf8c 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1746,8 +1746,8 @@ extern int trace_event_enable_disable(struct trace_event_file *file, int enable, int soft_disable); extern int tracing_alloc_snapshot(void); -extern const char *__start___trace_bprintk_fmt[]; -extern const char *__stop___trace_bprintk_fmt[]; +extern const char *__start___trace_bprintk_fmt[] __default_visibility; +extern const char *__stop___trace_bprintk_fmt[] __default_visibility; extern const char *__start___tracepoint_str[]; extern const char *__stop___tracepoint_str[]; diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c index c7c96bc7654a..40b752b53627 100644 --- a/lib/dynamic_debug.c +++ b/lib/dynamic_debug.c @@ -37,8 +37,8 @@ #include #include -extern struct _ddebug __start___verbose[]; -extern struct _ddebug __stop___verbose[]; +extern struct _ddebug __start___verbose[] __default_visibility; +extern struct _ddebug __stop___verbose[] __default_visibility; struct ddebug_table { struct list_head link;