Commit f922c4ab authored Aug 21, 2018 by Ard Biesheuvel Committed by Linus Torvalds Aug 22, 2018

module: allow symbol exports to be disabled

To allow existing C code to be incorporated into the decompressor or the
UEFI stub, introduce a CPP macro that turns all EXPORT_SYMBOL_xxx
declarations into nops, and #define it in places where such exports are
undesirable.  Note that this gets rid of a rather dodgy redefine of
linux/export.h's header guard.

Link: http://lkml.kernel.org/r/20180704083651.24360-3-ard.biesheuvel@linaro.org


Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morris <james.morris@microsoft.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 271ca788

arch/x86/boot/compressed/kaslr.c

+1 −4

Original line number	Diff line number	Diff line
		@@ -23,11 +23,8 @@
		* _ctype[] in lib/ctype.c is needed by isspace() of linux/ctype.h.
		* While both lib/ctype.c and lib/cmdline.c will bring EXPORT_SYMBOL
		* which is meaningless and will cause compiling error in some cases.
		* So do not include linux/export.h and define EXPORT_SYMBOL(sym)
		* as empty.
		*/
		#define _LINUX_EXPORT_H
		#define EXPORT_SYMBOL(sym)
		#define __DISABLE_EXPORTS

		#include "misc.h"
		#include "error.h"

drivers/firmware/efi/libstub/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -24,6 +24,7 @@ KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \
		-D__NO_FORTIFY \
		$(call cc-option,-ffreestanding) \
		$(call cc-option,-fno-stack-protector) \
		-D__DISABLE_EXPORTS

		GCOV_PROFILE := n
		KASAN_SANITIZE := n

include/linux/export.h

+10 −1

Original line number	Diff line number	Diff line
		@@ -66,7 +66,16 @@ extern struct module __this_module;
		__attribute__((section("___ksymtab" sec "+" #sym), used)) \
		= { (unsigned long)&sym, __kstrtab_##sym }

		#if defined(__KSYM_DEPS__)
		#if defined(__DISABLE_EXPORTS)

		/*
		* Allow symbol exports to be disabled completely so that C code may
		* be reused in other execution contexts such as the UEFI stub or the
		* decompressor.
		*/
		#define __EXPORT_SYMBOL(sym, sec)

		#elif defined(__KSYM_DEPS__)

		/*
		* For fine grained build dependencies, we want to tell the build system