target/linux/generic/hack-5.4/221-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 --- a/include/asm-generic/vmlinux.lds.h
  15 +++ b/include/asm-generic/vmlinux.lds.h
  16 @@ -54,6 +54,16 @@
  17  #define LOAD_OFFSET 0
  18  #endif
  19
  20 +#ifndef SYMTAB_KEEP
  21 +#define SYMTAB_KEEP KEEP(*(SORT(___ksymtab+*)))
  22 +#define SYMTAB_KEEP_GPL KEEP(*(SORT(___ksymtab_gpl+*)))
  23 +#endif
  24 +
  25 +#ifndef SYMTAB_DISCARD
  26 +#define SYMTAB_DISCARD
  27 +#define SYMTAB_DISCARD_GPL
  28 +#endif
  29 +
  30  /* Align . to a 8 byte boundary equals to maximum function alignment. */
  31  #define ALIGN_FUNCTION()  . = ALIGN(8)
  32
  33 @@ -407,14 +417,14 @@
  34         /* Kernel symbol table: Normal symbols */                       \
  35         __ksymtab         : AT(ADDR(__ksymtab) - LOAD_OFFSET) {         \
  36                 __start___ksymtab = .;                                  \
  37 -               KEEP(*(SORT(___ksymtab+*)))                             \
  38 +               SYMTAB_KEEP                                             \
  39                 __stop___ksymtab = .;                                   \
  40         }                                                               \
  41                                                                         \
  42         /* Kernel symbol table: GPL-only symbols */                     \
  43         __ksymtab_gpl     : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) {     \
  44                 __start___ksymtab_gpl = .;                              \
  45 -               KEEP(*(SORT(___ksymtab_gpl+*)))                         \
  46 +               SYMTAB_KEEP_GPL                                         \
  47                 __stop___ksymtab_gpl = .;                               \
  48         }                                                               \
  49                                                                         \
  50 @@ -476,7 +486,7 @@
  51                                                                         \
  52         /* Kernel symbol table: strings */                              \
  53          __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) {        \
  54 -               *(__ksymtab_strings)                                    \
  55 +               *(__ksymtab_strings+*)                                  \
  56         }                                                               \
  57                                                                         \
  58         /* __*init sections */                                          \
  59 @@ -885,6 +895,8 @@
  60         EXIT_TEXT                                                       \
  61         EXIT_DATA                                                       \
  62         EXIT_CALL                                                       \
  63 +       SYMTAB_DISCARD                                                  \
  64 +       SYMTAB_DISCARD_GPL                                              \
  65         *(.discard)                                                     \
  66         *(.discard.*)                                                   \
  67         *(.modinfo)                                                     \
  68 --- a/include/linux/export.h
  69 +++ b/include/linux/export.h
  70 @@ -98,18 +98,26 @@ struct kernel_symbol {
  71
  72  #else
  73
  74 +#ifdef MODULE
  75 +#define __EXPORT_SUFFIX(sym)
  76 +#else
  77 +#define __EXPORT_SUFFIX(sym) "+" #sym
  78 +#endif
  79 +
  80  #define ___export_symbol_common(sym, sec)                              \
  81         extern typeof(sym) sym;                                         \
  82         __CRC_SYMBOL(sym, sec);                                         \
  83         static const char __kstrtab_##sym[]                             \
  84 -       __attribute__((section("__ksymtab_strings"), used, aligned(1))) \
  85 +       __attribute__((section("__ksymtab_strings"                      \
  86 +         __EXPORT_SUFFIX(sym)), used, aligned(1)))                     \
  87         = #sym                                                          \
  88
  89  /* For every exported symbol, place a struct in the __ksymtab section */
  90  #define ___EXPORT_SYMBOL_NS(sym, sec, ns)                              \
  91         ___export_symbol_common(sym, sec);                              \
  92         static const char __kstrtabns_##sym[]                           \
  93 -       __attribute__((section("__ksymtab_strings"), used, aligned(1))) \
  94 +       __attribute__((section("__ksymtab_strings"                      \
  95 +         __EXPORT_SUFFIX(sym)), used, aligned(1)))                     \
  96         = #ns;                                                          \
  97         __KSYMTAB_ENTRY_NS(sym, sec)
  98
  99 --- a/scripts/Makefile.build
 100 +++ b/scripts/Makefile.build
 101 @@ -349,7 +349,7 @@ targets += $(extra-y) $(MAKECMDGOALS) $(
 102  # Linker scripts preprocessor (.lds.S -> .lds)
 103  # ---------------------------------------------------------------------------
 104  quiet_cmd_cpp_lds_S = LDS     $@
 105 -      cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -U$(ARCH) \
 106 +      cmd_cpp_lds_S = $(CPP) $(EXTRA_LDSFLAGS) $(cpp_flags) -P -U$(ARCH) \
 107                              -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
 108
 109  $(obj)/%.lds: $(src)/%.lds.S FORCE