From patchwork Mon Jun 25 22:39:03 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Garnier X-Patchwork-Id: 10488281 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 16CF7602B3 for ; Tue, 26 Jun 2018 08:42:44 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 03678287E1 for ; Tue, 26 Jun 2018 08:42:44 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id EA894287E5; Tue, 26 Jun 2018 08:42:43 +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 AABF6287E1 for ; Tue, 26 Jun 2018 08:42:42 +0000 (UTC) Received: (qmail 26390 invoked by uid 550); 26 Jun 2018 08:39:36 -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 Delivered-To: moderator for kernel-hardening@lists.openwall.com Received: (qmail 11755 invoked from network); 25 Jun 2018 22:42:06 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:date:in-reply-to:message-id:references:subject:from:to :cc; bh=YZtwxOCWQG9zzuB4MmeU+g0a2U4PhBZltez3EVA7Gyc=; b=QIqltt5xU3+HE/Lad39owEuAytloXCAyGHidtz/LtDDTbLj5Th0zZTPNRDk1EO/QHA L4ZgyO1TQ64shXJIUaKiUWHv+fdNYjTaVY4TEzdSC7xjVLIj1ult50Rv2GRL3XGus0Wt hah8ii23JRpI5vp5SXpiaJ/xDEKiFMGOW+P1XAmCbfeGAhEzI60QCEYSNISRLzcgwlZg HIm5+59z98BzBevLB5VRaokhA3KsYciV0wvPH6m+RclmBRdbFWbWOY2LvFfDbBKF3l7Y HuOSD2ukWbm3rokqaVaDmoasHKeos0z9LRFEegIdWVDy02O+hEghCQr5FINIcKMUkV5l aaLA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:date:in-reply-to:message-id :references:subject:from:to:cc; bh=YZtwxOCWQG9zzuB4MmeU+g0a2U4PhBZltez3EVA7Gyc=; b=V5v8CRa++jYCVIzgjxhobmn4DvDGkbo4E+FHt2SOC6nCy6lOLV6VUUBNHD9wDnRQl5 ZB08/raVMsDUhOHlme3akxnPaqC4MFF/F2vETtV9eRnb6MIm9rCYG8C967NTWdOqtJWg S9ajnogCg7ItEZfi1RG7JjX2gJzANvlruZmUUY78+bGerZfGb0G4fZcZJquUhehfxEOl RLtnpHPoGARKr335bjLZgBHUNyV3WSeBR3TbvsnJW0KI0obapmEne71/WYrhmaB7g5BD p8X57wgT//ZtjEmdn7PKMiXNZNrVSzTbjj+WIsAogUfCiZtg/EWmGVis5ADeZd0EnH8f CwAg== X-Gm-Message-State: APt69E2CME3iqL0zVAJEO0f4IKuPFyzpYu/AlAUhcWzoZ9dED6LWC4Ph tPQlt06Ybvjz8rDuSZs1MK8Uv1qv2JZfnHStsaNb2LAH/sUM659SStYvpNRSiyt6rMpSh6Y+zg4 xAlVvZFxYW+TttLA3PwGK4iPFD53Gr/AnU+o4OUPUJqEc9Ylm+F9jmk/HFvwsVNTKuGeQQDru1O EMq3Pk4608 X-Google-Smtp-Source: ADUXVKKArWleXolVizv3RP1IDn74c6KuG50B70SZ9jcW48mOsbqyKmkY/U1rmau7bq4bLirjGxlyVgXBv1MpXA== MIME-Version: 1.0 X-Received: by 2002:a1f:cf41:: with SMTP id f62-v6mr6657092vkg.29.1529966514067; Mon, 25 Jun 2018 15:41:54 -0700 (PDT) Date: Mon, 25 Jun 2018 15:39:03 -0700 In-Reply-To: <20180625224014.134829-1-thgarnie@google.com> Message-Id: <20180625224014.134829-16-thgarnie@google.com> References: <20180625224014.134829-1-thgarnie@google.com> X-Mailer: git-send-email 2.18.0.rc2.346.g013aa6912e-goog Subject: [PATCH v5 15/27] compiler: Option to default to hidden symbols From: Thomas Garnier To: kernel-hardening@lists.openwall.com Cc: Thomas Garnier , 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 , "Rafael J. Wysocki" , Kate Stewart , Mika Westerberg , Philippe Ombredanne , Lukas Wunner , Kees Cook , Masahiro Yamada , "Peter Zijlstra (Intel)" , Mathieu Desnoyers , Randy Dunlap , Sergey Senozhatsky , Petr Mladek , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-sparse@vger.kernel.org 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 08286269fd24..3ed2f9d54abb 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 42506e4d1f53..d9837a58906e 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 24b60536e26b..d4f90cc38ede 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1718,6 +1718,13 @@ 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 630c5a24b2b2..8dcfcf6961bc 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1751,8 +1751,8 @@ 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;