From: Thomas Garnier <thgarnie@chromium.org>
To: kernel-hardening@lists.openwall.com
Cc: kristen@linux.intel.com, Thomas Garnier <thgarnie@chromium.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Luis Chamberlain <mcgrof@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Jason Baron <jbaron@akamai.com>,
Thomas Garnier <thgarnie@google.com>,
Jordan Borgner <mail@jordan-borgner.de>,
Masami Hiramatsu <mhiramat@kernel.org>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Kees Cook <keescook@chromium.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Andi Kleen <ak@linux.intel.com>, Jan Beulich <JBeulich@suse.com>,
Song Liu <songliubraving@fb.com>,
Adrian Hunter <adrian.hunter@intel.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
linux-sparse@vger.kernel.org
Subject: [PATCH v6 15/27] compiler: Option to default to hidden symbols
Date: Thu, 31 Jan 2019 11:24:22 -0800 [thread overview]
Message-ID: <20190131192533.34130-16-thgarnie@chromium.org> (raw)
In-Reply-To: <20190131192533.34130-1-thgarnie@chromium.org>
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 <thgarnie@chromium.org>
---
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 32a09eb5c101..c4afcfecc817 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 ed8ec011a9fd..74f0a8d87986 100644
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -71,7 +71,7 @@ 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 97f9ada9ceda..04ca89e65f79 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 8e9213b36e31..f04096161a52 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 d79abca81a52..94f072f3a48d 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_SYMS
+#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_SYMS
+#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 87692fdae97a..5c0723604a52 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -287,6 +287,13 @@ unsigned long read_word_at_a_time(const void *addr)
__u.__val; \
})
+#ifdef CONFIG_DEFAULT_HIDDEN_SYMS
+#pragma GCC visibility push(hidden)
+#define __default_visibility __attribute__((visibility ("default")))
+#else
+#define __default_visibility
+#endif
+
#endif /* __KERNEL__ */
/*
diff --git a/init/Kconfig b/init/Kconfig
index bb383615823a..116e0de4817f 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1848,6 +1848,13 @@ config CMDLINE_OVERRIDE
endif
+#
+# Default to hidden visibility for all symbols.
+# Useful for Position Independent Code to reduce global references.
+#
+config DEFAULT_HIDDEN_SYMS
+ bool
+
endmenu # General setup
source "arch/Kconfig"
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 14934afa9e68..547affc40b68 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 int 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 int kallsyms_markers[] __weak;
+extern const unsigned int 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 08900828d282..5246977a2db7 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1809,8 +1809,8 @@ 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 dbf2b457e47e..05482e65ae7d 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -37,8 +37,8 @@
#include <linux/device.h>
#include <linux/netdevice.h>
-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;
--
2.20.1.495.gaa96b0ce6b-goog
next prev parent reply other threads:[~2019-01-31 19:24 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-31 19:24 [PATCH v6 00/27] x86: PIE support and option to extend KASLR randomization Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 01/27] x86/crypto: Adapt assembly for PIE support Thomas Garnier
2019-02-07 11:48 ` Borislav Petkov
2019-02-07 17:01 ` Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 02/27] x86: Use symbol name in jump table " Thomas Garnier
2019-02-07 12:17 ` Borislav Petkov
2019-02-07 17:04 ` Thomas Garnier
2019-02-07 17:11 ` Borislav Petkov
2019-02-07 23:55 ` Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 03/27] x86: Add macro to get symbol address " Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 04/27] x86: relocate_kernel - Adapt assembly " Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 05/27] x86/entry/64: " Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 06/27] x86: pm-trace - " Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 07/27] x86/CPU: " Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 08/27] x86/acpi: " Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 09/27] x86/boot/64: " Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 10/27] x86/power/64: " Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 11/27] x86/paravirt: " Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 12/27] x86/alternatives: " Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 13/27] x86/boot/64: Build head64.c as mcmodel large when PIE is enabled Thomas Garnier
2019-02-01 11:15 ` Kirill A. Shutemov
2019-02-01 17:11 ` Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 14/27] x86/percpu: Adapt percpu for PIE support Thomas Garnier
2019-01-31 20:57 ` Christopher Lameter
2019-01-31 22:49 ` Thomas Garnier
2019-02-01 2:31 ` Christopher Lameter
2019-02-01 17:13 ` Thomas Garnier
2019-04-08 15:58 ` Thomas Garnier
2019-04-08 17:56 ` Christopher Lameter
2019-04-08 18:08 ` Thomas Garnier
2019-01-31 19:24 ` Thomas Garnier [this message]
2019-02-01 7:12 ` [PATCH v6 15/27] compiler: Option to default to hidden symbols Dan Carpenter
2019-02-01 17:00 ` Thomas Garnier
2019-02-01 8:22 ` Adrian Hunter
2019-02-01 17:35 ` Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 16/27] compiler: Option to add PROVIDE_HIDDEN replacement for weak symbols Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 17/27] x86/relocs: Handle PIE relocations Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 18/27] xen: Adapt assembly for PIE support Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 19/27] kvm: " Thomas Garnier
2019-02-06 19:56 ` Sean Christopherson
2019-02-06 21:23 ` Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 20/27] x86: Support global stack cookie Thomas Garnier
2019-02-01 19:27 ` Andy Lutomirski
2019-02-01 20:21 ` Thomas Garnier
2019-02-01 22:36 ` Andy Lutomirski
2019-02-01 23:56 ` Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 21/27] x86/ftrace: Adapt function tracing for PIE support Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 22/27] x86/modules: Add option to start module section after kernel Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 23/27] x86/modules: Adapt module loading for PIE support Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 24/27] x86/mm: Make the x86 GOT read-only Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 25/27] x86/pie: Add option to build the kernel as PIE Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 26/27] x86/relocs: Add option to generate 64-bit relocations Thomas Garnier
2019-01-31 19:24 ` [PATCH v6 27/27] x86/kaslr: Add option to extend KASLR range from 1GB to 3GB Thomas Garnier
2019-01-31 19:59 ` [PATCH v6 00/27] x86: PIE support and option to extend KASLR randomization Kees Cook
2019-01-31 21:40 ` Konrad Rzeszutek Wilk
2019-01-31 22:42 ` Thomas Garnier
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