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

[Alexander Graf]

> 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

> 
> Hopefully there is no impact on all the x86 builds.
> 
> Regards,
> Simon