export.h: allow for per-symbol configurable EXPORT_SYMBOL()

Similar to include/generated/autoconf.h, include/generated/autoksyms.h
will contain a list of defines for each EXPORT_SYMBOL() that we want
active. The format is:

  #define __KSYM_<symbol_name> 1

This list will be auto-generated with another patch.  For now we only
include the preprocessor magic to automatically create or omit the
corresponding struct kernel_symbol declaration.

Given the content of include/generated/autoksyms.h may not be known in
advance, an empty file is created early on to let the build proceed.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/Makefile b/Makefile
index 916b26e999d8f15190afd6136bf0b357eb658c28..451acbebee97ac1f1942b0378ee95f9b9afbd26d 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -998,6 +998,8 @@ prepare2: prepare3 outputmakefile asm-generic
 prepare1: prepare2 $(version_h) include/generated/utsrelease.h \
                    include/config/auto.conf
        $(cmd_crmodverdir)
+       $(Q)test -e include/generated/autoksyms.h || \
+           touch   include/generated/autoksyms.h
 
 archprepare: archheaders archscripts prepare1 scripts_basic
 

diff --git a/include/linux/export.h b/include/linux/export.h
index 96e45ea463e71e19575d1db97da22a0eb72d05c8..77afdb2a250653f77506ed5308649ae703163936 100644 (file)
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -38,7 +38,7 @@ extern struct module __this_module;
 
 #ifdef CONFIG_MODULES
 
-#ifndef __GENKSYMS__
+#if defined(__KERNEL__) && !defined(__GENKSYMS__)
 #ifdef CONFIG_MODVERSIONS
 /* Mark the CRC weak since genksyms apparently decides not to
  * generate a checksums for some symbols */
@@ -53,7 +53,7 @@ extern struct module __this_module;
 #endif
 
 /* For every exported symbol, place a struct in the __ksymtab section */
-#define __EXPORT_SYMBOL(sym, sec)                              \
+#define ___EXPORT_SYMBOL(sym, sec)                             \
        extern typeof(sym) sym;                                 \
        __CRC_SYMBOL(sym, sec)                                  \
        static const char __kstrtab_##sym[]                     \
@@ -65,6 +65,24 @@ extern struct module __this_module;
        __attribute__((section("___ksymtab" sec "+" #sym), unused))     \
        = { (unsigned long)&sym, __kstrtab_##sym }
 
+#ifdef CONFIG_TRIM_UNUSED_KSYMS
+
+#include <linux/kconfig.h>
+#include <generated/autoksyms.h>
+
+#define __EXPORT_SYMBOL(sym, sec)                              \
+       __cond_export_sym(sym, sec, config_enabled(__KSYM_##sym))
+#define __cond_export_sym(sym, sec, conf)                      \
+       ___cond_export_sym(sym, sec, conf)
+#define ___cond_export_sym(sym, sec, enabled)                  \
+       __cond_export_sym_##enabled(sym, sec)
+#define __cond_export_sym_1(sym, sec) ___EXPORT_SYMBOL(sym, sec)
+#define __cond_export_sym_0(sym, sec) /* nothing */
+
+#else
+#define __EXPORT_SYMBOL ___EXPORT_SYMBOL
+#endif
+
 #define EXPORT_SYMBOL(sym)                                     \
        __EXPORT_SYMBOL(sym, "")