[U-Boot] [PATCH] efi_loader: Rename sections to allow for implicit data

[Bin Meng]

Hi Alex,

On Wed, Aug 8, 2018 at 1:16 AM, Alexander Graf <agraf at suse.de> wrote:
>
>
>> Am 07.08.2018 um 18:12 schrieb Simon Glass <sjg at chromium.org>:
>>
>> Hi Alex,
>>
>>> On 11 June 2018 at 23:48, Alexander Graf <agraf at suse.de> wrote:
>>> Some times gcc may generate data that is then used within code that may
>>> be part of an efi runtime section. That data could be jump tables,
>>> constants or strings.
>>>
>>> In order to make sure we catch these, we need to ensure that gcc emits
>>> them into a section that we can relocate together with all the other
>>> efi runtime bits. This only works if the -ffunction-sections and
>>> -fdata-sections flags are passed and the efi runtime functions are
>>> in a section that starts with ".text".
>>>
>>> Up to now we had all efi runtime bits in sections that did not
>>> interfere with the normal section naming scheme, but this forces
>>> us to do so. Hence we need to move the efi_loader text/data/rodata
>>> sections before the global *(.text*) catch-all section.
>>>
>>> With this patch in place, we should hopefully have an easier time
>>> to extend the efi runtime functionality in the future.
>>>
>>> Signed-off-by: Alexander Graf <agraf at suse.de>
>>> ---
>>> arch/arm/config.mk                        |  4 ++--
>>> arch/arm/cpu/armv8/u-boot.lds             | 24 +++++++++++++--------
>>> arch/arm/cpu/u-boot.lds                   | 36 ++++++++++++++++++-------------
>>> arch/arm/mach-zynq/u-boot.lds             | 36 ++++++++++++++++++-------------
>>> arch/riscv/cpu/ax25/u-boot.lds            | 26 +++++++++++++---------
>>> arch/sandbox/config.mk                    |  3 +++
>>> arch/sandbox/cpu/u-boot.lds               |  9 ++++----
>>> arch/x86/config.mk                        |  2 +-
>>> arch/x86/cpu/u-boot.lds                   | 32 ++++++++++++++-------------
>>> board/qualcomm/dragonboard410c/u-boot.lds | 17 +++++++++++++--
>>> board/qualcomm/dragonboard820c/u-boot.lds | 24 +++++++++++++--------
>>> board/ti/am335x/u-boot.lds                | 36 ++++++++++++++++++-------------
>>> include/efi_loader.h                      |  4 ++--
>>> 13 files changed, 154 insertions(+), 99 deletions(-)
>>>
>>
>> I missed this at the time, probably thinking the subject made it sound
>> innocuous. There is no 'sandbox:' tag.
>>
>> This seems to break sandbox in a pretty strange way:
>>
>> gdb --args /tmp/crosfw/sandbox/u-boot -D
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>> Reading symbols from /tmp/crosfw/sandbox/u-boot...done.
>> (gdb) r
>> Starting program: /tmp/crosfw/sandbox/u-boot -D
>> [Thread debugging using libthread_db enabled]
>> Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
>>
>> Program received signal SIGSEGV, Segmentation fault.
>> 0x0000555555571520 in open at plt ()
>> (gdb) up
>> #1  0x0000555555571e9a in sandbox_read_fdt_from_file ()
>>    at /home/sjg/c/src/third_party/u-boot/files/arch/sandbox/cpu/cpu.c:264
>> 264 fd = os_open(fname, OS_O_RDONLY);
>> (gdb) print fname
>> $1 = 0x7ffff7ff0000 "/tmp/crosfw/sandbox/u-boot.dtb"
>> (gdb) q
>>
>>
>> Also the commit message suggests that this patch changes sandbox to
>> use --gc-sections, which is not obvious from the subject. I think that
>> should be a separate commit and in fact it should really be separate
>> commits for each arch, I think. That might help people notice it...
>>
>> I only noticed now since the EFI pull request has landed.
>
> Can you try my bss patch really quick? Maybe we're just overwriting gd.
>
> Alex
>

This patch breaks efi-x86_app_defconfig. The EFI application no longer
boots. I was testing on top of u-boot/master.

If I do:

diff --git a/arch/x86/config.mk b/arch/x86/config.mk
index 586e11a..fc119ec 100644
--- a/arch/x86/config.mk
+++ b/arch/x86/config.mk
@@ -24,7 +24,6 @@ endif
 ifeq ($(IS_32BIT),y)
 PLATFORM_CPPFLAGS += -march=i386 -m32
 # TODO: These break on x86_64; need to debug further
-PLATFORM_RELFLAGS += -fdata-sections
 else
 PLATFORM_CPPFLAGS += $(if $(CONFIG_SPL_BUILD),,-fpic) -fno-common -m64
 endif

Then it boots again. Can you please take a look?

Regards,
Bin