Re: [PATCH] x86/boot: Mark global variables as static

From: Ard Biesheuvel <ardb@kernel.org>
To: Mike Lothian <mike@fireburn.co.uk>
Cc: Arvind Sankar <nivedita@alum.mit.edu>,
	linux-efi <linux-efi@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	X86 ML <x86@kernel.org>
Subject: Re: [PATCH] x86/boot: Mark global variables as static
Date: Tue, 12 May 2020 13:05:21 +0200	[thread overview]
Message-ID: <CAMj1kXGbUg3g-s5qoHgrYoBnoJLR9Oc7YrCO1xMHx-+Ys6=Tfg@mail.gmail.com> (raw)
In-Reply-To: <CAHbf0-HLKiq_+erhHfV9XqMhfchN2975nAsuya4-oXEOUNdhiw@mail.gmail.com>

On Tue, 12 May 2020 at 01:12, Mike Lothian <mike@fireburn.co.uk> wrote:
>
> Feel free to add my tested by
>
>
> On Mon, 11 May 2020 at 23:58, Arvind Sankar <nivedita@alum.mit.edu> wrote:
> >
> > 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")
> > Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>

Thanks, I'll queue this as a fix.

> > ---
> >  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 8f8c8e386cea..c8b8c1a8d1fc 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;
> >
> >  /*----------------------------------------------------------------------*/
> >
> > --
> > 2.26.2
> >