target/linux/generic/hack-4.9/221-module_exports.patch

   1 From b14784e7883390c20ed3ff904892255404a5914b Mon Sep 17 00:00:00 2001
   2 From: Felix Fietkau <nbd@nbd.name>
   3 Date: Fri, 7 Jul 2017 17:05:53 +0200
   4 Subject: add an optional config option for stripping all unnecessary symbol exports from the kernel image
   5
   6 lede-commit: bb5a40c64b7c4f4848509fa0a6625055fc9e66cc
   7 Signed-off-by: Felix Fietkau <nbd@nbd.name>
   8 ---
   9  include/asm-generic/vmlinux.lds.h | 18 +++++++++++++++---
  10  include/linux/export.h            |  9 ++++++++-
  11  scripts/Makefile.build            |  2 +-
  12  3 files changed, 24 insertions(+), 5 deletions(-)
  13
  14 diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
  15 index 83784d9492b1..189b5c7a0758 100644
  16 --- a/include/asm-generic/vmlinux.lds.h
  17 +++ b/include/asm-generic/vmlinux.lds.h
  18 @@ -54,6 +54,16 @@
  19  #define LOAD_OFFSET 0
  20  #endif
  21
  22 +#ifndef SYMTAB_KEEP
  23 +#define SYMTAB_KEEP KEEP(*(SORT(___ksymtab+*)))
  24 +#define SYMTAB_KEEP_GPL KEEP(*(SORT(___ksymtab_gpl+*)))
  25 +#endif
  26 +
  27 +#ifndef SYMTAB_DISCARD
  28 +#define SYMTAB_DISCARD
  29 +#define SYMTAB_DISCARD_GPL
  30 +#endif
  31 +
  32  #include <linux/export.h>
  33
  34  /* Align . to a 8 byte boundary equals to maximum function alignment. */
  35 @@ -329,14 +339,14 @@
  36         /* Kernel symbol table: Normal symbols */                       \
  37         __ksymtab         : AT(ADDR(__ksymtab) - LOAD_OFFSET) {         \
  38                 VMLINUX_SYMBOL(__start___ksymtab) = .;                  \
  39 -               KEEP(*(SORT(___ksymtab+*)))                             \
  40 +               SYMTAB_KEEP                                             \
  41                 VMLINUX_SYMBOL(__stop___ksymtab) = .;                   \
  42         }                                                               \
  43                                                                         \
  44         /* Kernel symbol table: GPL-only symbols */                     \
  45         __ksymtab_gpl     : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) {     \
  46                 VMLINUX_SYMBOL(__start___ksymtab_gpl) = .;              \
  47 -               KEEP(*(SORT(___ksymtab_gpl+*)))                         \
  48 +               SYMTAB_KEEP_GPL                                         \
  49                 VMLINUX_SYMBOL(__stop___ksymtab_gpl) = .;               \
  50         }                                                               \
  51                                                                         \
  52 @@ -398,7 +408,7 @@
  53                                                                         \
  54         /* Kernel symbol table: strings */                              \
  55          __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) {        \
  56 -               *(__ksymtab_strings)                                    \
  57 +               *(__ksymtab_strings+*)                                  \
  58         }                                                               \
  59                                                                         \
  60         /* __*init sections */                                          \
  61 @@ -749,6 +759,8 @@
  62         EXIT_TEXT                                                       \
  63         EXIT_DATA                                                       \
  64         EXIT_CALL                                                       \
  65 +       SYMTAB_DISCARD                                                  \
  66 +       SYMTAB_DISCARD_GPL                                              \
  67         *(.discard)                                                     \
  68         *(.discard.*)                                                   \
  69         }
  70 diff --git a/include/linux/export.h b/include/linux/export.h
  71 index 2a0f61fbc731..889331d9643d 100644
  72 --- a/include/linux/export.h
  73 +++ b/include/linux/export.h
  74 @@ -53,12 +53,19 @@ extern struct module __this_module;
  75  #define __CRC_SYMBOL(sym, sec)
  76  #endif
  77
  78 +#ifdef MODULE
  79 +#define __EXPORT_SUFFIX(sym)
  80 +#else
  81 +#define __EXPORT_SUFFIX(sym) "+" #sym
  82 +#endif
  83 +
  84  /* For every exported symbol, place a struct in the __ksymtab section */
  85  #define ___EXPORT_SYMBOL(sym, sec)                                     \
  86         extern typeof(sym) sym;                                         \
  87         __CRC_SYMBOL(sym, sec)                                          \
  88         static const char __kstrtab_##sym[]                             \
  89 -       __attribute__((section("__ksymtab_strings"), aligned(1)))       \
  90 +       __attribute__((section("__ksymtab_strings"                      \
  91 +         __EXPORT_SUFFIX(sym)), aligned(1)))                           \
  92         = VMLINUX_SYMBOL_STR(sym);                                      \
  93         static const struct kernel_symbol __ksymtab_##sym               \
  94         __used                                                          \
  95 diff --git a/scripts/Makefile.build b/scripts/Makefile.build
  96 index 108d73273788..76a0e450123c 100644
  97 --- a/scripts/Makefile.build
  98 +++ b/scripts/Makefile.build
  99 @@ -398,7 +398,7 @@ targets += $(extra-y) $(MAKECMDGOALS) $(always)
 100  # Linker scripts preprocessor (.lds.S -> .lds)
 101  # ---------------------------------------------------------------------------
 102  quiet_cmd_cpp_lds_S = LDS     $@
 103 -      cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -C -U$(ARCH) \
 104 +      cmd_cpp_lds_S = $(CPP) $(EXTRA_LDSFLAGS) $(cpp_flags) -P -C -U$(ARCH) \
 105                              -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
 106
 107  $(obj)/%.lds: $(src)/%.lds.S FORCE
 108 --
 109 2.11.0
 110