From patchwork Wed Oct 4 21:19:51 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Garnier X-Patchwork-Id: 9985599 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 1FD0B60586 for ; Wed, 4 Oct 2017 21:24:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1004B28B63 for ; Wed, 4 Oct 2017 21:24:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 0329328BCB; Wed, 4 Oct 2017 21:24:32 +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=-4.1 required=2.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, RCVD_IN_DNSWL_MED, T_DKIM_INVALID 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 8C03428B63 for ; Wed, 4 Oct 2017 21:24:30 +0000 (UTC) Received: (qmail 16057 invoked by uid 550); 4 Oct 2017 21:21:34 -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 15833 invoked from network); 4 Oct 2017 21:21:24 -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=PUA/5SnoSE2/Kn0/izvv2fE80joIJ7JYOYsBpDSK1hU=; b=RPwh3CtHwivgNo6Gtqxau0r6r4Eyr33QODJxIllSUoYB7SXUUDxAE8foKnHnRAohlH z4NniFutR2k0Q7ZKU6GKcsBfIvO5XBJzMz8k+KRIXFG4OUvqtwrCFJTYOBV3erT9T9I1 rOqtTGaqulogLJxc/rtk+7OdzK/HptDdkLsvQBmFUjHwD9uZOg9TPKqHw1i75i6/y1pQ 6POEH8iP573mfmAelF9w5KjfE3x7zkbTXFvI/Jo7iTrt1kvEt4g/4WTgYR4fTW5kMiO/ 8fcvEfgekMICjwrxZZPXD8X5MrPMn8MYG4CF0eAy/wd93b/zeTdT9ai7HD1uzxzfXgQu U0xw== 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=PUA/5SnoSE2/Kn0/izvv2fE80joIJ7JYOYsBpDSK1hU=; b=jQ5dbdgFqLGTSmtRbjaAL0DNqdTDrOHp+GFAnc9hPJdqMaoCRx0HVlt2ixqP0UUdi3 2IzfEuMso6yUD41GjGFRfT+j/5ypWvQ4lXrdiRZUgiq9T0eKleNSP/KLTaUBVrUJSA8n 5GApknZK74ikxJh+UEisikV2GZwTJkOiAc30plxCiM06KXBOxlBeqik6MQYeiIKTG6zT iEmvt1sJgfEE3RR8LwmUQxQ2w+HvJ4GOY9b0HoACESiu1onPEFhHJ2i3c8l63P/31e0K YEgY9DMAUglpuCOaFzOU+a+byVPmfRwiCZrNEIh6Jv8Xvu7cNMtea0RQFrgWk5MNB1Fu TVHw== X-Gm-Message-State: AHPjjUgDVOnO+hy6J9AC8S28p9bnfmCXZa5pVVy/SS4xsK1OoqQT7neA Vrbrw7TPI8CLOm4DU0LRB7CIYQ== X-Google-Smtp-Source: AOwi7QDZCCdujkF2bjy/G60Kxihcq2hC9Bx+eKA+Z8xbbDOed28e0HmI1w9o34iz2ouMxm5FMTYbdA== X-Received: by 10.159.204.147 with SMTP id t19mr20920822plo.7.1507152072492; Wed, 04 Oct 2017 14:21:12 -0700 (PDT) From: Thomas Garnier To: Herbert Xu , "David S . Miller" , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Peter Zijlstra , Josh Poimboeuf , Thomas Garnier , Arnd Bergmann , Kees Cook , Matthias Kaehlcke , Tom Lendacky , Andy Lutomirski , "Kirill A . Shutemov" , Borislav Petkov , "Rafael J . Wysocki" , Len Brown , Pavel Machek , Juergen Gross , Chris Wright , Alok Kataria , Rusty Russell , Tejun Heo , Christoph Lameter , Boris Ostrovsky , Alexey Dobriyan , Andrew Morton , Paul Gortmaker , Chris Metcalf , "Paul E . McKenney" , Nicolas Pitre , Borislav Petkov , "Luis R . Rodriguez" , Greg Kroah-Hartman , Christopher Li , Steven Rostedt , Jason Baron , Dou Liyang , "Rafael J . Wysocki" , Mika Westerberg , Lukas Wunner , Masahiro Yamada , Alexei Starovoitov , Daniel Borkmann , Markus Trippelsdorf , Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Joerg Roedel , Rik van Riel , David Howells , Ard Biesheuvel , Waiman Long , Kyle Huey , Andrey Ryabinin , Jonathan Corbet , Matthew Wilcox , Michal Hocko , Peter Foley , Paul Bolle , Jiri Kosina , Rob Landley , "H . J . Lu" , Baoquan He , =?UTF-8?q?Jan=20H=20=2E=20Sch=C3=B6nherr?= , Daniel Micay Cc: x86@kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, linux-arch@vger.kernel.org, linux-sparse@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, kernel-hardening@lists.openwall.com Date: Wed, 4 Oct 2017 14:19:51 -0700 Message-Id: <20171004212003.28296-16-thgarnie@google.com> X-Mailer: git-send-email 2.14.2.920.gcf0c67979c-goog In-Reply-To: <20171004212003.28296-1-thgarnie@google.com> References: <20171004212003.28296-1-thgarnie@google.com> Subject: [kernel-hardening] [RFC v3 15/27] compiler: Option to default to hidden symbols 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_class.c | 4 ++-- include/asm-generic/sections.h | 6 ++++++ include/linux/compiler.h | 8 ++++++++ init/Kconfig | 7 +++++++ kernel/kallsyms.c | 16 ++++++++-------- kernel/trace/trace.h | 4 ++-- lib/dynamic_debug.c | 4 ++-- 10 files changed, 39 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 a65cf544686a..7e0b54f605c6 100644 --- a/arch/x86/include/asm/setup.h +++ b/arch/x86/include/asm/setup.h @@ -67,7 +67,7 @@ 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 86e8f0b2537b..8f021783a929 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -144,8 +144,8 @@ 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_class.c b/drivers/base/firmware_class.c index 4b57cf5bc81d..77d4727f6594 100644 --- a/drivers/base/firmware_class.c +++ b/drivers/base/firmware_class.c @@ -45,8 +45,8 @@ MODULE_LICENSE("GPL"); #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 bool fw_get_builtin_firmware(struct firmware *fw, const char *name, void *buf, size_t size) diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index e5da44eddd2f..1aa5d6dac9e1 100644 --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -30,6 +30,9 @@ * __irqentry_text_start, __irqentry_text_end * __softirqentry_text_start, __softirqentry_text_end */ +#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[]; @@ -46,6 +49,9 @@ extern char __softirqentry_text_start[], __softirqentry_text_end[]; /* 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 extern __visible const void __nosave_begin, __nosave_end; diff --git a/include/linux/compiler.h b/include/linux/compiler.h index e95a2631e545..6997716f73bf 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -78,6 +78,14 @@ extern void __chk_io_ptr(const volatile void __iomem *); #include #endif +/* Useful for Position Independent Code to reduce global references */ +#ifdef CONFIG_DEFAULT_HIDDEN +#pragma GCC visibility push(hidden) +#define __default_visibility __attribute__((visibility ("default"))) +#else +#define __default_visibility +#endif + /* * Generic compiler-dependent macros required for kernel * build go below this comment. Actual compiler/compiler version diff --git a/init/Kconfig b/init/Kconfig index ccb1d8daf241..b640201fcff7 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1649,6 +1649,13 @@ 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 127e7cfafa55..252019c8c3a9 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -32,24 +32,24 @@ * 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; static inline int is_kernel_inittext(unsigned long addr) { diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 652c682707cd..31cb920039a2 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1742,8 +1742,8 @@ 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 da796e2dc4f5..10ed20177354 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;