[GIT PULL] urgent EFI fix for v4.9

[GIT PULL] urgent EFI fix for v4.9

[Ard Biesheuvel]

Please merge the single fix below: it addresses a build issue on ARM with
less recent toolchain versions, which surfaced now that EFI has been added
to multi_v7_defconfig, the de facto generic defconfig for the most recent
cores.

The following changes since commit b67be92feb486f800d80d72c67fd87b47b79b18e:

  Merge tag 'pwm/for-4.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/thierry.reding/linux-pwm (2016-10-12 11:11:05 -0700)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi.git tags/efi-urgent

for you to fetch changes up to 0d5b726f1009d05657ec71c716ba6529dcc98d2b:

  efi/arm: Fix absolute relocation detection for older toolchains (2016-10-14 10:57:59 +0100)

----------------------------------------------------------------
* Fix a build issue in the ARM version of libstub with slightly older
  toolchains

----------------------------------------------------------------
Ard Biesheuvel (1):
      efi/arm: Fix absolute relocation detection for older toolchains

 drivers/firmware/efi/libstub/Makefile | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

[PATCH] efi/arm: Fix absolute relocation detection for older toolchains

[Ard Biesheuvel]

When building the ARM kernel with CONFIG_EFI=y, the following build
error may occur when using a less recent version of binutils (2.23 or
older):

   STUBCPY drivers/firmware/efi/libstub/lib-sort.stub.o
 00000000 R_ARM_ABS32       sort
 00000004 R_ARM_ABS32       __ksymtab_strings
 drivers/firmware/efi/libstub/lib-sort.stub.o: absolute symbol references
 not allowed in the EFI stub

(and when building with debug symbols, the list above is much longer, and
contains all the internal references between the .debug sections and the
actual code)

This issue is caused by the fact that objcopy v2.23 or earlier does not
support wildcards in its -R and -j options, which means the following
line from the Makefile:

  STUBCOPY_FLAGS-y		:= -R .debug* -R *ksymtab* -R *kcrctab*

fails to take effect, leaving harmless absolute relocations in the binary
that are indistinguishable from relocations that may cause crashes at
runtime due to the fact that these relocations are resolved at link time
using the virtual address of the kernel, which is always different from
the address at which the EFI firmware loads and invokes the stub.

So, as a workaround, disable debug symbols explicitly when building the
stub for ARM, and strip the ksymtab and kcrctab symbols for the only
exported symbol we currently reuse in the stub, which is 'sort'.

Cc: Matt Fleming <matt@codeblueprint.co.uk>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 drivers/firmware/efi/libstub/Makefile | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index c06945160a41..5e23e2d305e7 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -11,7 +11,7 @@ cflags-$(CONFIG_X86)		+= -m$(BITS) -D__KERNEL__ $(LINUX_INCLUDE) -O2 \
 				   -mno-mmx -mno-sse
 
 cflags-$(CONFIG_ARM64)		:= $(subst -pg,,$(KBUILD_CFLAGS))
-cflags-$(CONFIG_ARM)		:= $(subst -pg,,$(KBUILD_CFLAGS)) \
+cflags-$(CONFIG_ARM)		:= $(subst -pg,,$(KBUILD_CFLAGS)) -g0 \
 				   -fno-builtin -fpic -mno-single-pic-base
 
 cflags-$(CONFIG_EFI_ARMSTUB)	+= -I$(srctree)/scripts/dtc/libfdt
@@ -79,5 +79,6 @@ quiet_cmd_stubcopy = STUBCPY $@
 # decompressor. So move our .data to .data.efistub, which is preserved
 # explicitly by the decompressor linker script.
 #
-STUBCOPY_FLAGS-$(CONFIG_ARM)	+= --rename-section .data=.data.efistub
+STUBCOPY_FLAGS-$(CONFIG_ARM)	+= --rename-section .data=.data.efistub \
+				   -R ___ksymtab+sort -R ___kcrctab+sort
 STUBCOPY_RELOC-$(CONFIG_ARM)	:= R_ARM_ABS
-- 
2.7.4

[tip:efi/urgent] efi/arm: Fix absolute relocation detection for older toolchains

[tip-bot for Ard Biesheuvel]

Commit-ID:  b0dddf6c147e6fe61374d625c4bb2b7c52018639
Gitweb:     http://git.kernel.org/tip/b0dddf6c147e6fe61374d625c4bb2b7c52018639
Author:     Ard Biesheuvel <ard.biesheuvel@linaro.org>
AuthorDate: Tue, 18 Oct 2016 16:53:11 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 19 Oct 2016 14:49:44 +0200

efi/arm: Fix absolute relocation detection for older toolchains

When building the ARM kernel with CONFIG_EFI=y, the following build
error may occur when using a less recent version of binutils (2.23 or
older):

   STUBCPY drivers/firmware/efi/libstub/lib-sort.stub.o
 00000000 R_ARM_ABS32       sort
 00000004 R_ARM_ABS32       __ksymtab_strings
 drivers/firmware/efi/libstub/lib-sort.stub.o: absolute symbol references not allowed in the EFI stub

(and when building with debug symbols, the list above is much longer, and
contains all the internal references between the .debug sections and the
actual code)

This issue is caused by the fact that objcopy v2.23 or earlier does not
support wildcards in its -R and -j options, which means the following
line from the Makefile:

  STUBCOPY_FLAGS-y		:= -R .debug* -R *ksymtab* -R *kcrctab*

fails to take effect, leaving harmless absolute relocations in the binary
that are indistinguishable from relocations that may cause crashes at
runtime due to the fact that these relocations are resolved at link time
using the virtual address of the kernel, which is always different from
the address at which the EFI firmware loads and invokes the stub.

So, as a workaround, disable debug symbols explicitly when building the
stub for ARM, and strip the ksymtab and kcrctab symbols for the only
exported symbol we currently reuse in the stub, which is 'sort'.

Tested-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/1476805991-7160-2-git-send-email-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 drivers/firmware/efi/libstub/Makefile | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index c069451..5e23e2d 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -11,7 +11,7 @@ cflags-$(CONFIG_X86)		+= -m$(BITS) -D__KERNEL__ $(LINUX_INCLUDE) -O2 \
 				   -mno-mmx -mno-sse
 
 cflags-$(CONFIG_ARM64)		:= $(subst -pg,,$(KBUILD_CFLAGS))
-cflags-$(CONFIG_ARM)		:= $(subst -pg,,$(KBUILD_CFLAGS)) \
+cflags-$(CONFIG_ARM)		:= $(subst -pg,,$(KBUILD_CFLAGS)) -g0 \
 				   -fno-builtin -fpic -mno-single-pic-base
 
 cflags-$(CONFIG_EFI_ARMSTUB)	+= -I$(srctree)/scripts/dtc/libfdt
@@ -79,5 +79,6 @@ quiet_cmd_stubcopy = STUBCPY $@
 # decompressor. So move our .data to .data.efistub, which is preserved
 # explicitly by the decompressor linker script.
 #
-STUBCOPY_FLAGS-$(CONFIG_ARM)	+= --rename-section .data=.data.efistub
+STUBCOPY_FLAGS-$(CONFIG_ARM)	+= --rename-section .data=.data.efistub \
+				   -R ___ksymtab+sort -R ___kcrctab+sort
 STUBCOPY_RELOC-$(CONFIG_ARM)	:= R_ARM_ABS

Re: [GIT PULL] urgent EFI fix for v4.9

[Ingo Molnar]

* Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:

> Please merge the single fix below: it addresses a build issue on ARM with
> less recent toolchain versions, which surfaced now that EFI has been added
> to multi_v7_defconfig, the de facto generic defconfig for the most recent
> cores.
> 
> The following changes since commit b67be92feb486f800d80d72c67fd87b47b79b18e:
> 
>   Merge tag 'pwm/for-4.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/thierry.reding/linux-pwm (2016-10-12 11:11:05 -0700)
> 
> are available in the git repository at:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi.git tags/efi-urgent
> 
> for you to fetch changes up to 0d5b726f1009d05657ec71c716ba6529dcc98d2b:
> 
>   efi/arm: Fix absolute relocation detection for older toolchains (2016-10-14 10:57:59 +0100)
> 
> ----------------------------------------------------------------
> * Fix a build issue in the ARM version of libstub with slightly older
>   toolchains
> 
> ----------------------------------------------------------------
> Ard Biesheuvel (1):
>       efi/arm: Fix absolute relocation detection for older toolchains
> 
>  drivers/firmware/efi/libstub/Makefile | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)

Applied, thanks Ard!

	Ingo