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Subject[tip: efi/urgent] x86/boot: Mark global variables as static
The following commit has been merged into the efi/urgent branch of tip:

Commit-ID: e78d334a5470ead861590ec83158f3b17bd6c807
Gitweb: https://git.kernel.org/tip/e78d334a5470ead861590ec83158f3b17bd6c807
Author: Arvind Sankar <nivedita@alum.mit.edu>
AuthorDate: Mon, 11 May 2020 18:58:49 -04:00
Committer: Ard Biesheuvel <ardb@kernel.org>
CommitterDate: Thu, 14 May 2020 11:11:20 +02:00

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 | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c
index 8f8c8e3..c8b8c1a 100644
--- a/arch/x86/boot/tools/build.c
+++ b/arch/x86/boot/tools/build.c
@@ -59,14 +59,14 @@ u8 buf[SETUP_SECT_MAX*512];
#define PECOFF_COMPAT_RESERVE 0x0
#endif

-unsigned long efi32_stub_entry;
-unsigned long efi64_stub_entry;
-unsigned long efi_pe_entry;
-unsigned long efi32_pe_entry;
-unsigned long kernel_info;
-unsigned long startup_64;
-unsigned long _ehead;
-unsigned long _end;
+static unsigned long efi32_stub_entry;
+static unsigned long efi64_stub_entry;
+static unsigned long efi_pe_entry;
+static unsigned long efi32_pe_entry;
+static unsigned long kernel_info;
+static unsigned long startup_64;
+static unsigned long _ehead;
+static unsigned long _end;

/*----------------------------------------------------------------------*/

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