git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From cb87481ee89dbd6609e227afbf64900fb4e5c930 Mon Sep 17 00:00:00 2001
   2 From: Nicholas Piggin <npiggin@gmail.com>
   3 Date: Wed, 26 Jul 2017 22:46:27 +1000
   4 Subject: kbuild: linker script do not match C names unless LD_DEAD_CODE_DATA_ELIMINATION is configured
   5
   6 From: Nicholas Piggin <npiggin@gmail.com>
   7
   8 commit cb87481ee89dbd6609e227afbf64900fb4e5c930 upstream.
   9
  10 The .data and .bss sections were modified in the generic linker script to
  11 pull in sections named .data.<C identifier>, which are generated by gcc with
  12 -ffunction-sections and -fdata-sections options.
  13
  14 The problem with this pattern is it can also match section names that Linux
  15 defines explicitly, e.g., .data.unlikely. This can cause Linux sections to
  16 get moved into the wrong place.
  17
  18 The way to avoid this is to use ".." separators for explicit section names
  19 (the dot character is valid in a section name but not a C identifier).
  20 However currently there are sections which don't follow this rule, so for
  21 now just disable the wild card by default.
  22
  23 Example: http://marc.info/?l=linux-arm-kernel&m=150106824024221&w=2
  24
  25 Fixes: b67067f1176df ("kbuild: allow archs to select link dead code/data elimination")
  26 Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
  27 Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
  28 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  29
  30 ---
  31  include/asm-generic/vmlinux.lds.h |   38 ++++++++++++++++++++++++++------------
  32  1 file changed, 26 insertions(+), 12 deletions(-)
  33
  34 --- a/include/asm-generic/vmlinux.lds.h
  35 +++ b/include/asm-generic/vmlinux.lds.h
  36 @@ -60,6 +60,22 @@
  37  #define ALIGN_FUNCTION()  . = ALIGN(8)
  38
  39  /*
  40 + * LD_DEAD_CODE_DATA_ELIMINATION option enables -fdata-sections, which
  41 + * generates .data.identifier sections, which need to be pulled in with
  42 + * .data. We don't want to pull in .data..other sections, which Linux
  43 + * has defined. Same for text and bss.
  44 + */
  45 +#ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
  46 +#define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
  47 +#define DATA_MAIN .data .data.[0-9a-zA-Z_]*
  48 +#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]*
  49 +#else
  50 +#define TEXT_MAIN .text
  51 +#define DATA_MAIN .data
  52 +#define BSS_MAIN .bss
  53 +#endif
  54 +
  55 +/*
  56   * Align to a 32 byte boundary equal to the
  57   * alignment gcc 4.5 uses for a struct
  58   */
  59 @@ -198,12 +214,9 @@
  60
  61  /*
  62   * .data section
  63 - * LD_DEAD_CODE_DATA_ELIMINATION option enables -fdata-sections generates
  64 - * .data.identifier which needs to be pulled in with .data, but don't want to
  65 - * pull in .data..stuff which has its own requirements. Same for bss.
  66   */
  67  #define DATA_DATA                                                      \
  68 -       *(.data .data.[0-9a-zA-Z_]*)                                    \
  69 +       *(DATA_MAIN)                                                    \
  70         *(.ref.data)                                                    \
  71         *(.data..shared_aligned) /* percpu related */                   \
  72         MEM_KEEP(init.data)                                             \
  73 @@ -436,16 +449,17 @@
  74                 VMLINUX_SYMBOL(__security_initcall_end) = .;            \
  75         }
  76
  77 -/* .text section. Map to function alignment to avoid address changes
  78 +/*
  79 + * .text section. Map to function alignment to avoid address changes
  80   * during second ld run in second ld pass when generating System.map
  81 - * LD_DEAD_CODE_DATA_ELIMINATION option enables -ffunction-sections generates
  82 - * .text.identifier which needs to be pulled in with .text , but some
  83 - * architectures define .text.foo which is not intended to be pulled in here.
  84 - * Those enabling LD_DEAD_CODE_DATA_ELIMINATION must ensure they don't have
  85 - * conflicting section names, and must pull in .text.[0-9a-zA-Z_]* */
  86 + *
  87 + * TEXT_MAIN here will match .text.fixup and .text.unlikely if dead
  88 + * code elimination is enabled, so these sections should be converted
  89 + * to use ".." first.
  90 + */
  91  #define TEXT_TEXT                                                      \
  92                 ALIGN_FUNCTION();                                       \
  93 -               *(.text.hot .text .text.fixup .text.unlikely)           \
  94 +               *(.text.hot TEXT_MAIN .text.fixup .text.unlikely)       \
  95                 *(.ref.text)                                            \
  96         MEM_KEEP(init.text)                                             \
  97         MEM_KEEP(exit.text)                                             \
  98 @@ -613,7 +627,7 @@
  99                 BSS_FIRST_SECTIONS                                      \
 100                 *(.bss..page_aligned)                                   \
 101                 *(.dynbss)                                              \
 102 -               *(.bss .bss.[0-9a-zA-Z_]*)                              \
 103 +               *(BSS_MAIN)                                             \
 104                 *(COMMON)                                               \
 105         }
 106