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

[Simon Glass]

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.

Hopefully there is no impact on all the x86 builds.

Regards,
Simon