From: Thomas Garnier <thgarnie@google.com>
To: Herbert Xu <herbert@gondor.apana.org.au>,
"David S . Miller" <davem@davemloft.net>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Arnd Bergmann <arnd@arndb.de>,
Thomas Garnier <thgarnie@google.com>,
Kees Cook <keescook@chromium.org>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Matthias Kaehlcke <mka@chromium.org>,
Tom Lendacky <thomas.lendacky@amd.com>,
Andy Lutomirski <luto@kernel.org>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Borislav Petkov <bp@suse.de>,
"Rafael J . Wysocki" <rjw@rjwysocki.net>,
Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
Juergen Gross <jgross@suse.com>,
Chris Wright <chrisw@sous-sol.org>,
Alok Kataria <akataria@vmware.com>,
Rusty Russell <rusty@rustcorp.com.au>, Tejun Heo <tj@kernel.>
Cc: linux-arch@vger.kernel.org, kvm@vger.kernel.org,
linux-pm@vger.kernel.org, x86@kernel.org,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
linux-sparse@vger.kernel.org, linux-crypto@vger.kernel.org,
kernel-hardening@lists.openwall.com,
xen-devel@lists.xenproject.org
Subject: [PATCH v1 15/27] compiler: Option to default to hidden symbols
Date: Wed, 11 Oct 2017 13:30:15 -0700 [thread overview]
Message-ID: <20171011203027.11248-16-thgarnie@google.com> (raw)
In-Reply-To: <20171011203027.11248-1-thgarnie@google.com>
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@google.com>
---
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 <linux/compiler-clang.h>
#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 <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;
--
2.15.0.rc0.271.g36b669edcc-goog
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next prev parent reply other threads:[~2017-10-11 20:30 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-11 20:30 [PATCH v1 00/27] x86: PIE support and option to extend KASLR randomization Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 01/27] x86/crypto: Adapt assembly for PIE support Thomas Garnier
2017-10-20 8:24 ` Ingo Molnar
2017-10-20 8:28 ` Ard Biesheuvel
2017-10-20 14:48 ` Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 02/27] x86: Use symbol name on bug table " Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 03/27] x86: Use symbol name in jump " Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 04/27] x86: Add macro to get symbol address " Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 05/27] x86: relocate_kernel - Adapt assembly " Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 06/27] x86/entry/64: " Thomas Garnier
2017-10-20 8:26 ` Ingo Molnar
2017-10-20 14:47 ` Thomas Garnier
2017-10-20 15:20 ` Ingo Molnar
2017-10-20 16:27 ` Andy Lutomirski
2017-10-20 17:52 ` Andy Lutomirski
2017-10-11 20:30 ` [PATCH v1 07/27] x86: pm-trace - " Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 08/27] x86/CPU: " Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 09/27] x86/acpi: " Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 10/27] x86/boot/64: " Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 11/27] x86/power/64: " Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 12/27] x86/paravirt: " Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 13/27] x86/boot/64: Use _text in a global " Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 14/27] x86/percpu: Adapt percpu " Thomas Garnier
2017-10-11 20:30 ` Thomas Garnier [this message]
2017-10-12 20:02 ` [PATCH v1 15/27] compiler: Option to default to hidden symbols Luis R. Rodriguez
2017-10-18 23:15 ` Thomas Garnier
2017-10-19 19:38 ` Luis R. Rodriguez
2017-10-11 20:30 ` [PATCH v1 16/27] x86/relocs: Handle PIE relocations Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 17/27] xen: Adapt assembly for PIE support Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 18/27] kvm: " Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 19/27] x86: Support global stack cookie Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 20/27] x86/ftrace: Adapt function tracing for PIE support Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 21/27] x86/mm/dump_pagetables: Fix address markers index on x86_64 Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 22/27] x86/modules: Add option to start module section after kernel Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 23/27] x86/modules: Adapt module loading for PIE support Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 24/27] x86/mm: Make the x86 GOT read-only Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 25/27] x86/pie: Add option to build the kernel as PIE Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 26/27] x86/relocs: Add option to generate 64-bit relocations Thomas Garnier
2017-10-11 20:30 ` [PATCH v1 27/27] x86/kaslr: Add option to extend KASLR range from 1GB to 3GB Thomas Garnier
2017-10-11 21:34 ` [PATCH v1 00/27] x86: PIE support and option to extend KASLR randomization Tom Lendacky
2017-10-12 15:34 ` Thomas Garnier
2017-10-12 15:51 ` Markus Trippelsdorf
2017-10-12 16:28 ` Tom Lendacky
2017-10-18 23:17 ` Thomas Garnier
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