x86/boot: Mark global variables as static
authorArvind Sankar <nivedita@alum.mit.edu>
Mon, 11 May 2020 22:58:49 +0000 (18:58 -0400)
committerArd Biesheuvel <ardb@kernel.org>
Thu, 14 May 2020 09:11:20 +0000 (11:11 +0200)
commite78d334a5470ead861590ec83158f3b17bd6c807
tree588a4e9347d8c6f9e9b0a2662e3e20cb40235963
parent3d8c11efd528d56972d44ed0de51c4e11a9a4fa9
x86/boot: Mark global variables as static

Mike Lothian reports that after commit
  964124a97b97 ("efi/x86: Remove extra headroom for setup block")
gcc 10.1.0 fails with

  HOSTCC  arch/x86/boot/tools/build
  /usr/lib/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../x86_64-pc-linux-gnu/bin/ld:
  error: linker defined: multiple definition of '_end'
  /usr/lib/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../x86_64-pc-linux-gnu/bin/ld:
  /tmp/ccEkW0jM.o: previous definition here
  collect2: error: ld returned 1 exit status
  make[1]: *** [scripts/Makefile.host:103: arch/x86/boot/tools/build] Error 1
  make: *** [arch/x86/Makefile:303: bzImage] Error 2

The issue is with the _end variable that was added, to hold the end of
the compressed kernel from zoffsets.h (ZO__end). The name clashes with
the linker-defined _end symbol that indicates the end of the build
program itself.

Even when there is no compile-time error, this causes build to use
memory past the end of its .bss section.

To solve this, mark _end as static, and for symmetry, mark the rest of
the variables that keep track of symbols from the compressed kernel as
static as well.

Fixes: 964124a97b97 ("efi/x86: Remove extra headroom for setup block")
Reported-by: Mike Lothian <mike@fireburn.co.uk>
Tested-by: Mike Lothian <mike@fireburn.co.uk>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200511225849.1311869-1-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
arch/x86/boot/tools/build.c