From: Arvind Sankar <nivedita@alum.mit.edu>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Kees Cook <keescook@chromium.org>,
Arvind Sankar <nivedita@alum.mit.edu>,
Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>,
Fangrui Song <maskray@google.com>,
Sedat Dilek <sedat.dilek@gmail.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Peter Collingbourne <pcc@google.com>,
James Morse <james.morse@arm.com>, Borislav Petkov <bp@suse.de>,
Ingo Molnar <mingo@redhat.com>,
Russell King <linux@armlinux.org.uk>,
Masahiro Yamada <masahiroy@kernel.org>,
Nathan Chancellor <natechancellor@gmail.com>,
Arnd Bergmann <arnd@arndb.de>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
linux-arch <linux-arch@vger.kernel.org>,
linux-efi <linux-efi@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5 06/36] x86/boot: Remove run-time relocations from head_{32,64}.S
Date: Fri, 7 Aug 2020 16:20:56 -0400 [thread overview]
Message-ID: <20200807202056.GA1454138@rani.riverdale.lan> (raw)
In-Reply-To: <CAKwvOd=mY5=SWjGKA_KpvKnOPmJky_qMcyBYeFhskx6J=aJmNA@mail.gmail.com>
On Fri, Aug 07, 2020 at 11:12:29AM -0700, Nick Desaulniers wrote:
> On Fri, Jul 31, 2020 at 4:08 PM Kees Cook <keescook@chromium.org> wrote:
> >
> > From: Arvind Sankar <nivedita@alum.mit.edu>
> >
> > The BFD linker generates run-time relocations for z_input_len and
> > z_output_len, even though they are absolute symbols.
> >
> > This is fixed for binutils-2.35 [1]. Work around this for earlier
> > versions by defining two variables input_len and output_len in addition
> > to the symbols, and use them via position-independent references.
> >
> > This eliminates the last two run-time relocations in the head code and
> > allows us to drop the -z noreloc-overflow flag to the linker.
> >
> > Move the -pie and --no-dynamic-linker LDFLAGS to LDFLAGS_vmlinux instead
> > of KBUILD_LDFLAGS. There shouldn't be anything else getting linked, but
> > this is the more logical location for these flags, and modversions might
> > call the linker if an EXPORT_SYMBOL is left over accidentally in one of
> > the decompressors.
> >
> > [1] https://sourceware.org/bugzilla/show_bug.cgi?id=25754
> >
> > Tested-by: Nick Desaulniers <ndesaulniers@google.com>
> > Reviewed-by: Kees Cook <keescook@chromium.org>
> > Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
> > Reviewed-by: Fangrui Song <maskray@google.com>
> > Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
> > Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> > arch/x86/boot/compressed/Makefile | 12 ++----------
> > arch/x86/boot/compressed/head_32.S | 17 ++++++++---------
> > arch/x86/boot/compressed/head_64.S | 4 ++--
> > arch/x86/boot/compressed/mkpiggy.c | 6 ++++++
> > 4 files changed, 18 insertions(+), 21 deletions(-)
> >
> > diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> > index 489fea16bcfb..7db0102a573d 100644
> > --- a/arch/x86/boot/compressed/Makefile
> > +++ b/arch/x86/boot/compressed/Makefile
> > @@ -51,16 +51,8 @@ UBSAN_SANITIZE :=n
> > KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE)
> > # Compressed kernel should be built as PIE since it may be loaded at any
> > # address by the bootloader.
> > -ifeq ($(CONFIG_X86_32),y)
> > -KBUILD_LDFLAGS += $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker)
> > -else
> > -# To build 64-bit compressed kernel as PIE, we disable relocation
> > -# overflow check to avoid relocation overflow error with a new linker
> > -# command-line option, -z noreloc-overflow.
> > -KBUILD_LDFLAGS += $(shell $(LD) --help 2>&1 | grep -q "\-z noreloc-overflow" \
> > - && echo "-z noreloc-overflow -pie --no-dynamic-linker")
> > -endif
> > -LDFLAGS_vmlinux := -T
> > +LDFLAGS_vmlinux := $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker)
>
> Oh, do these still need ld-option? bfd and lld both support these
> flags. (Though in their --help, they mention single hyphen and double
> hyphen respectively. Also, if we don't build this as PIE because the
> linker doesn't support the option, we probably want to fail the build?
>
The check for pie doesn't, it's dropped in the next patch and pie is
used unconditionally.
no-dynamic-linker still needs the check as it was only supported from
binutils-2.26.
next prev parent reply other threads:[~2020-08-07 20:21 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-31 23:07 [PATCH v5 00/36] Warn on orphan section placement Kees Cook
2020-07-31 23:07 ` [PATCH v5 01/36] x86/boot/compressed: Move .got.plt entries out of the .got section Kees Cook
2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Ard Biesheuvel
2020-07-31 23:07 ` [PATCH v5 02/36] x86/boot/compressed: Force hidden visibility for all symbol references Kees Cook
2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Ard Biesheuvel
2020-07-31 23:07 ` [PATCH v5 03/36] x86/boot/compressed: Get rid of GOT fixup code Kees Cook
2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Ard Biesheuvel
2020-07-31 23:07 ` [PATCH v5 04/36] x86/boot: Add .text.* to setup.ld Kees Cook
2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Arvind Sankar
2020-07-31 23:07 ` [PATCH v5 05/36] x86/boot: Remove run-time relocations from .head.text code Kees Cook
2020-07-31 23:42 ` Nick Desaulniers
2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Arvind Sankar
2020-07-31 23:07 ` [PATCH v5 06/36] x86/boot: Remove run-time relocations from head_{32,64}.S Kees Cook
2020-08-07 18:12 ` Nick Desaulniers
2020-08-07 20:20 ` Arvind Sankar [this message]
2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Arvind Sankar
2020-07-31 23:07 ` [PATCH v5 07/36] x86/boot: Check that there are no run-time relocations Kees Cook
2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Arvind Sankar
2020-07-31 23:07 ` [PATCH v5 08/36] vmlinux.lds.h: Create COMMON_DISCARDS Kees Cook
2020-07-31 23:07 ` [PATCH v5 09/36] vmlinux.lds.h: Add .gnu.version* to COMMON_DISCARDS Kees Cook
2020-07-31 23:07 ` [PATCH v5 10/36] vmlinux.lds.h: Avoid KASAN and KCSAN's unwanted sections Kees Cook
2020-07-31 23:07 ` [PATCH v5 11/36] vmlinux.lds.h: Split ELF_DETAILS from STABS_DEBUG Kees Cook
2020-07-31 23:07 ` [PATCH v5 12/36] vmlinux.lds.h: Add .symtab, .strtab, and .shstrtab to ELF_DETAILS Kees Cook
2020-07-31 23:07 ` [PATCH v5 13/36] vmlinux.lds.h: add PGO and AutoFDO input sections Kees Cook
2020-08-01 3:51 ` Arvind Sankar
2020-08-01 6:18 ` Kees Cook
2020-08-01 17:27 ` Arvind Sankar
2020-08-03 19:05 ` Andi Kleen
2020-08-03 20:15 ` Arvind Sankar
2020-08-04 1:19 ` Fāng-ruì Sòng
2020-08-04 4:45 ` Andi Kleen
2020-08-04 5:32 ` Fāng-ruì Sòng
2020-08-04 16:06 ` Arvind Sankar
2020-08-21 19:18 ` Kees Cook
2020-07-31 23:07 ` [PATCH v5 14/36] efi/libstub: Disable -mbranch-protection Kees Cook
2020-07-31 23:07 ` [PATCH v5 15/36] arm64/mm: Remove needless section quotes Kees Cook
2020-07-31 23:08 ` [PATCH v5 16/36] arm64/kernel: Remove needless Call Frame Information annotations Kees Cook
2020-07-31 23:08 ` [PATCH v5 17/36] arm64/build: Remove .eh_frame* sections due to unwind tables Kees Cook
2020-07-31 23:08 ` [PATCH v5 18/36] arm64/build: Use common DISCARDS in linker script Kees Cook
2020-07-31 23:08 ` [PATCH v5 19/36] arm64/build: Add missing DWARF sections Kees Cook
2020-07-31 23:08 ` [PATCH v5 20/36] arm64/build: Assert for unwanted sections Kees Cook
2020-07-31 23:08 ` [PATCH v5 21/36] arm64/build: Warn on orphan section placement Kees Cook
2020-07-31 23:08 ` [PATCH v5 22/36] arm/build: Refactor linker script headers Kees Cook
2020-07-31 23:08 ` [PATCH v5 23/36] arm/build: Explicitly keep .ARM.attributes sections Kees Cook
2020-08-03 19:02 ` Nick Desaulniers
2020-08-17 22:06 ` Fangrui Song
2020-07-31 23:08 ` [PATCH v5 24/36] arm/build: Add missing sections Kees Cook
2020-07-31 23:08 ` [PATCH v5 25/36] arm/build: Warn on orphan section placement Kees Cook
2020-07-31 23:08 ` [PATCH v5 26/36] arm/boot: Handle all sections explicitly Kees Cook
2020-07-31 23:08 ` [PATCH v5 27/36] arm/boot: Warn on orphan section placement Kees Cook
2020-07-31 23:08 ` [PATCH v5 28/36] x86/asm: Avoid generating unused kprobe sections Kees Cook
2020-07-31 23:08 ` [PATCH v5 29/36] x86/build: Enforce an empty .got.plt section Kees Cook
2020-08-01 2:12 ` Arvind Sankar
2020-08-01 5:32 ` Kees Cook
2020-08-21 17:49 ` Kees Cook
2020-07-31 23:08 ` [PATCH v5 30/36] x86/build: Assert for unwanted sections Kees Cook
2020-07-31 23:08 ` [PATCH v5 31/36] x86/build: Warn on orphan section placement Kees Cook
2020-07-31 23:08 ` [PATCH v5 32/36] x86/boot/compressed: Reorganize zero-size section asserts Kees Cook
2020-08-01 1:47 ` Arvind Sankar
2020-08-01 2:53 ` Arvind Sankar
2020-08-01 5:36 ` Kees Cook
2020-08-01 17:12 ` Arvind Sankar
2020-08-21 18:24 ` Kees Cook
2020-08-01 5:35 ` Kees Cook
2020-08-01 17:00 ` Arvind Sankar
2020-08-21 18:19 ` Kees Cook
2020-07-31 23:08 ` [PATCH v5 33/36] x86/boot/compressed: Remove, discard, or assert for unwanted sections Kees Cook
2020-07-31 23:08 ` [PATCH v5 34/36] x86/boot/compressed: Add missing debugging sections to output Kees Cook
2020-07-31 23:08 ` [PATCH v5 35/36] x86/boot/compressed: Warn on orphan section placement Kees Cook
2020-07-31 23:08 ` [PATCH v5 36/36] arm/build: Assert for unwanted sections Kees Cook
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