package/gcc/6.3.0/892-libgcc-mkmap-symver-support-skip_underscore.patch

   1 From ae9c3e354440c4a0f105a9eabfb2f77be085ebc1 Mon Sep 17 00:00:00 2001
   2 From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
   3 Date: Thu, 18 Aug 2016 17:59:16 +0200
   4 Subject: [PATCH] libgcc/mkmap-symver: support skip_underscore
   5
   6 Some platforms, such as Blackfin, have a special prefix for assembly
   7 symbols as opposed to C symbols. For this reason, a function named
   8 "foo()" in C will in fact be visible as a symbol called "_foo" in the
   9 ELF binary.
  10
  11 The current linker version script logic in libgcc doesn't take into
  12 account this situation properly. The Blackfin specific
  13 libgcc/config/bfin/libgcc-glibc.ver has an additional "_" in front of
  14 every symbol so that it matches the output of "nm" (which gets parsed to
  15 produce the final linker version script). But due to this additional
  16 "_", ld no longer matches with the symbols since "ld" does the matching
  17 with the original symbol name, not the one prefixed with "_".
  18
  19 Due to this, none of the symbols in libgcc/config/bfin/libgcc-glibc.ver
  20 are actually matched with symbols in libgcc. This causes all libgcc
  21 symbols to be left as "LOCAL", which causes lots of "undefined
  22 reference" whenever some C or C++ code that calls a function of libgcc
  23 is compiled.
  24
  25 To address this, this commit introduces a "skip_underscore" variable to
  26 the mkmap-symver script. It tells mkmap-symver to ignore the leading
  27 underscore from the "nm" output.
  28
  29 Note that this new argument is different from the existing
  30 "leading_underscore" argument, which *adds* an additional underscore to
  31 the generated linker version script.
  32
  33 Having this functionality paves the way to using the generic linker
  34 version information for Blackfin, instead of using a custom one.
  35
  36 Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
  37 ---
  38  libgcc/mkmap-symver.awk | 6 +++++-
  39  1 file changed, 5 insertions(+), 1 deletion(-)
  40
  41 diff --git a/libgcc/mkmap-symver.awk b/libgcc/mkmap-symver.awk
  42 index 266832a..30bb179 100644
  43 --- a/libgcc/mkmap-symver.awk
  44 +++ b/libgcc/mkmap-symver.awk
  45 @@ -47,7 +47,11 @@ state == "nm" && ($1 == "U" || $2 == "U") {
  46
  47  state == "nm" && NF == 3 {
  48    split ($3, s, "@")
  49 -  def[s[1]] = 1;
  50 +  if (skip_underscore)
  51 +      symname = substr(s[1], 2);
  52 +  else
  53 +      symname = s[1];
  54 +  def[symname] = 1;
  55    sawsymbol = 1;
  56    next;
  57  }
  58 --
  59 2.7.4
  60