target/linux/generic/hack-6.1/221-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 @@ -81,6 +81,16 @@
  17  #define RO_EXCEPTION_TABLE
  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 @@ -511,14 +521,14 @@
  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 @@ -538,7 +548,7 @@
  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 @@ -1042,6 +1052,8 @@
  60  #define COMMON_DISCARDS                                                        \
  61         SANITIZER_DISCARDS                                              \
  62         PATCHABLE_DISCARDS                                              \
  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 @@ -72,6 +72,12 @@ 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  /*
  81   * For every exported symbol, do the following:
  82   *
  83 @@ -87,7 +93,7 @@ struct kernel_symbol {
  84         extern typeof(sym) sym;                                                 \
  85         extern const char __kstrtab_##sym[];                                    \
  86         extern const char __kstrtabns_##sym[];                                  \
  87 -       asm("   .section \"__ksymtab_strings\",\"aMS\",%progbits,1      \n"     \
  88 +       asm("   .section \"__ksymtab_strings" __EXPORT_SUFFIX(sym) "\",\"aMS\",%progbits,1      \n"     \
  89             "__kstrtab_" #sym ":                                        \n"     \
  90             "   .asciz  \"" #sym "\"                                    \n"     \
  91             "__kstrtabns_" #sym ":                                      \n"     \
  92 --- a/include/asm-generic/export.h
  93 +++ b/include/asm-generic/export.h
  94 @@ -31,6 +31,12 @@
  95  #endif
  96  .endm
  97
  98 +#ifdef MODULE
  99 +#define __EXPORT_SUFFIX(name)
 100 +#else
 101 +#define __EXPORT_SUFFIX(name) + #name
 102 +#endif
 103 +
 104  /*
 105   * note on .section use: we specify progbits since usage of the "M" (SHF_MERGE)
 106   * section flag requires it. Use '%progbits' instead of '@progbits' since the
 107 @@ -44,7 +50,7 @@
 108  __ksymtab_\name:
 109         __put \val, __kstrtab_\name
 110         .previous
 111 -       .section __ksymtab_strings,"aMS",%progbits,1
 112 +       .section __ksymtab_strings __EXPORT_SUFFIX(name),"aMS",%progbits,1
 113  __kstrtab_\name:
 114         .asciz "\name"
 115         .previous
 116 --- a/scripts/Makefile.build
 117 +++ b/scripts/Makefile.build
 118 @@ -388,7 +388,7 @@ targets += $(real-dtb-y) $(lib-y) $(alwa
 119  # Linker scripts preprocessor (.lds.S -> .lds)
 120  # ---------------------------------------------------------------------------
 121  quiet_cmd_cpp_lds_S = LDS     $@
 122 -      cmd_cpp_lds_S = $(CPP) $(cpp_flags) -P -U$(ARCH) \
 123 +      cmd_cpp_lds_S = $(CPP) $(EXTRA_LDSFLAGS) $(cpp_flags) -P -U$(ARCH) \
 124                              -D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
 125
 126  $(obj)/%.lds: $(src)/%.lds.S FORCE