[PATCH v7 02/10] module: allow symbol exports to be disabled
From: Ard Biesheuvel <hidden>
Date: 2018-01-02 20:06:30
Also in:
linux-arm-kernel, linux-mips, lkml, sparclinux
Subsystem:
extensible firmware interface (efi), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Ard Biesheuvel, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
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. Cc: matt@codeblueprint.co.uk Cc: keescook@chromium.org Cc: jeyu@kernel.org Signed-off-by: Ard Biesheuvel <redacted> --- arch/x86/boot/compressed/kaslr.c | 5 +---- drivers/firmware/efi/libstub/Makefile | 3 ++- include/linux/export.h | 9 +++++++++ 3 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 8199a6187251..3a2a6d7049e4 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c@@ -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"
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index adaa4a964f0c..312bd0b64a61 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile@@ -20,7 +20,8 @@ cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \ -D__NO_FORTIFY \ $(call cc-option,-ffreestanding) \ - $(call cc-option,-fno-stack-protector) + $(call cc-option,-fno-stack-protector) \ + -D__DISABLE_EXPORTS GCOV_PROFILE := n KASAN_SANITIZE := n
diff --git a/include/linux/export.h b/include/linux/export.h
index 1a1dfdb2a5c6..6dba2fb08f77 100644
--- a/include/linux/export.h
+++ b/include/linux/export.h@@ -83,6 +83,15 @@ extern struct module __this_module; */ #define __EXPORT_SYMBOL(sym, sec) === __KSYM_##sym === +#elif 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(CONFIG_TRIM_UNUSED_KSYMS) #include <generated/autoksyms.h>
--
2.11.0