On Tue, 14 Jul 2020 at 12:21, Sedat Dilek <sedat.di...@gmail.com> wrote: > > On Mon, Jun 29, 2020 at 4:09 PM Arvind Sankar <nived...@alum.mit.edu> wrote: > > > > From: Ard Biesheuvel <a...@kernel.org> > > > > Eliminate all GOT entries in the decompressor binary, by forcing hidden > > visibility for all symbol references, which informs the compiler that > > such references will be resolved at link time without the need for > > allocating GOT entries. > > > > To ensure that no GOT entries will creep back in, add an assertion to > > the decompressor linker script that will fire if the .got section has > > a non-zero size. > > > > [Arvind: fixup -include hidden.h to -include $(srctree)/$(src)/hidden.h] > > > > Thanks for your v3 patchset. > > I tried your initial patchset and informed you about the <hidden.h> > include file handling. > Dropped your patchset against Linux v5.7 as I got no (satisfying) replies.
Dropped from where? This series should be taken through the -tip tree. > For me this one is missing a Reported-by of mine. > We don't usually add reported-by lines for issues that were resolved before the series was merged, given that the reported issue never existed in mainline to begin with. > As I want to test the whole v3 series, I will report later. > A tested-by is always appreciated. > - Sedat - > > > Signed-off-by: Ard Biesheuvel <a...@kernel.org> > > Acked-by: Arvind Sankar <nived...@alum.mit.edu> > > Signed-off-by: Arvind Sankar <nived...@alum.mit.edu> > > From: Ard Biesheuvel <a...@kernel.org> > > Link: https://lore.kernel.org/r/20200523120021.34996-3-a...@kernel.org > > --- > > arch/x86/boot/compressed/Makefile | 1 + > > arch/x86/boot/compressed/hidden.h | 19 +++++++++++++++++++ > > arch/x86/boot/compressed/vmlinux.lds.S | 1 + > > 3 files changed, 21 insertions(+) > > create mode 100644 arch/x86/boot/compressed/hidden.h > > > > diff --git a/arch/x86/boot/compressed/Makefile > > b/arch/x86/boot/compressed/Makefile > > index 7619742f91c9..b01c8aed0f23 100644 > > --- a/arch/x86/boot/compressed/Makefile > > +++ b/arch/x86/boot/compressed/Makefile > > @@ -42,6 +42,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, gnu) > > KBUILD_CFLAGS += -Wno-pointer-sign > > KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) > > KBUILD_CFLAGS += -fno-asynchronous-unwind-tables > > +KBUILD_CFLAGS += -include $(srctree)/$(src)/hidden.h > > > > KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ > > GCOV_PROFILE := n > > diff --git a/arch/x86/boot/compressed/hidden.h > > b/arch/x86/boot/compressed/hidden.h > > new file mode 100644 > > index 000000000000..49a17b6b5962 > > --- /dev/null > > +++ b/arch/x86/boot/compressed/hidden.h > > @@ -0,0 +1,19 @@ > > +/* SPDX-License-Identifier: GPL-2.0 */ > > +/* > > + * When building position independent code with GCC using the -fPIC option, > > + * (or even the -fPIE one on older versions), it will assume that we are > > + * building a dynamic object (either a shared library or an executable) > > that > > + * may have symbol references that can only be resolved at load time. For a > > + * variety of reasons (ELF symbol preemption, the CoW footprint of the > > section > > + * that is modified by the loader), this results in all references to > > symbols > > + * with external linkage to go via entries in the Global Offset Table > > (GOT), > > + * which carries absolute addresses which need to be fixed up when the > > + * executable image is loaded at an offset which is different from its link > > + * time offset. > > + * > > + * Fortunately, there is a way to inform the compiler that such symbol > > + * references will be satisfied at link time rather than at load time, by > > + * giving them 'hidden' visibility. > > + */ > > + > > +#pragma GCC visibility push(hidden) > > diff --git a/arch/x86/boot/compressed/vmlinux.lds.S > > b/arch/x86/boot/compressed/vmlinux.lds.S > > index b17d218ccdf9..4bcc943842ab 100644 > > --- a/arch/x86/boot/compressed/vmlinux.lds.S > > +++ b/arch/x86/boot/compressed/vmlinux.lds.S > > @@ -81,6 +81,7 @@ SECTIONS > > DISCARDS > > } > > > > +ASSERT(SIZEOF(.got) == 0, "Unexpected GOT entries detected!") > > #ifdef CONFIG_X86_64 > > ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, "Unexpected > > GOT/PLT entries detected!") > > #else > > -- > > 2.26.2 > >
