[PATCH 10/31] sandbox: Provide a linker script for MSYS2

[Simon Glass]

Hi Pali,

On Tue, 25 Apr 2023 at 12:11, Pali Rohár <pali at kernel.org> wrote:
>
> On Tuesday 25 April 2023 12:01:04 Simon Glass wrote:
> > Hi Pali,
> >
> > On Tue, 25 Apr 2023 at 10:21, Pali Rohár <pali at kernel.org> wrote:
> > >
> > > On Monday 24 April 2023 17:08:15 Simon Glass wrote:
> > > > Add a script to allow the U-Boot sandbox executable to be built for
> > > > Windows. Add a note as to why this seems to be necessary for now.
> > > >
> > > > Signed-off-by: Simon Glass <sjg at chromium.org>
> > > > ---
> > > >
> > > >  Makefile                       |  11 +-
> > > >  arch/sandbox/config.mk         |   4 +
> > > >  arch/sandbox/cpu/u-boot-pe.lds | 447 +++++++++++++++++++++++++++++++++
> > > >  3 files changed, 460 insertions(+), 2 deletions(-)
> > > >  create mode 100644 arch/sandbox/cpu/u-boot-pe.lds
> > > >
> > > > diff --git a/Makefile b/Makefile
> > > > index dd3fcd1782e5..0aa97a2c3b48 100644
> > > > --- a/Makefile
> > > > +++ b/Makefile
> > > > @@ -1730,6 +1730,13 @@ else
> > > >  u-boot-keep-syms-lto :=
> > > >  endif
> > > >
> > > > +ifeq ($(MSYS_VERSION),0)
> > > > +add_ld_script := -T u-boot.lds
> > > > +else
> > > > +add_ld_script := u-boot.lds
> > > > +$(warning msys)
> > > > +endif
> > > > +
> > > >  # Rule to link u-boot
> > > >  # May be overridden by arch/$(ARCH)/config.mk
> > > >  ifeq ($(LTO_ENABLE),y)
> > > > @@ -1738,7 +1745,7 @@ quiet_cmd_u-boot__ ?= LTO     $@
> > > >               $(CC) -nostdlib -nostartfiles                                   \
> > > >               $(LTO_FINAL_LDFLAGS) $(c_flags)                                 \
> > > >               $(KBUILD_LDFLAGS:%=-Wl,%) $(LDFLAGS_u-boot:%=-Wl,%) -o $@       \
> > > > -             -T u-boot.lds $(u-boot-init)                                    \
> > > > +             $(add_ld_script) $(u-boot-init)                                 \
> > > >               -Wl,--whole-archive                                             \
> > > >                       $(u-boot-main)                                          \
> > > >                       $(u-boot-keep-syms-lto)                                 \
> > > > @@ -1749,7 +1756,7 @@ quiet_cmd_u-boot__ ?= LTO     $@
> > > >  else
> > > >  quiet_cmd_u-boot__ ?= LD      $@
> > > >        cmd_u-boot__ ?= $(LD) $(KBUILD_LDFLAGS) $(LDFLAGS_u-boot) -o $@                \
> > > > -             -T u-boot.lds $(u-boot-init)                                    \
> > > > +             $(add_ld_script) $(u-boot-init)                                 \
> > > >               --whole-archive                                                 \
> > > >                       $(u-boot-main)                                          \
> > > >               --no-whole-archive                                              \
> > > > diff --git a/arch/sandbox/config.mk b/arch/sandbox/config.mk
> > > > index 2d184c5f652a..e05daf57ef8e 100644
> > > > --- a/arch/sandbox/config.mk
> > > > +++ b/arch/sandbox/config.mk
> > > > @@ -71,3 +71,7 @@ EFI_CRT0 := crt0_sandbox_efi.o
> > > >  EFI_RELOC := reloc_sandbox_efi.o
> > > >  AFLAGS_crt0_sandbox_efi.o += -DHOST_ARCH="$(HOST_ARCH)"
> > > >  CFLAGS_reloc_sandbox_efi.o += -DHOST_ARCH="$(HOST_ARCH)"
> > > > +
> > > > +ifneq ($(MSYS_VERSION),0)
> > > > +LDSCRIPT = $(srctree)/arch/sandbox/cpu/u-boot-pe.lds
> > > > +endif
> > > > diff --git a/arch/sandbox/cpu/u-boot-pe.lds b/arch/sandbox/cpu/u-boot-pe.lds
> > > > new file mode 100644
> > > > index 000000000000..031e70fafd03
> > > > --- /dev/null
> > > > +++ b/arch/sandbox/cpu/u-boot-pe.lds
> > > > @@ -0,0 +1,447 @@
> > > > +/* SPDX-License-Identifier: GPL-2.0+ */
> > > > +/*
> > > > + * U-Boot note: This was obtained by using the -verbose linker option. The
> > > > + * U-Boot additions are marked below.
> > > > + *
> > > > + * Ideally we would add sections to the executable, as is done with the Linux
> > > > + * build. But PE executables do not appear to work correctly if unexpected
> > > > + * sections are present:
> > > > + *
> > > > + *   $ /tmp/b/sandbox/u-boot.exe
> > > > + *   -bash: /tmp/b/sandbox/u-boot.exe: cannot execute binary file: Exec format error
> > > > + *
> > > > + * So we take a approach of rewriting the whole file, for now. This will likely
> > > > + * break in the future when a toolchain change is made.
> > >
> > > Why not rather provide "layer" linker script which does this "rewriting"
> > > on top of the default linker script? With this way it is not needed to
> > > update linker script when a toolchain change it.
> > >
> >
> > How can we reliably do that, though? We don't really know the format
> > of the script and where to insert stuff.
> >
> > Regards,
> > Simon
>
> Well, I do not know what is the current issue. The proposed script in

See the comment at the top of the script:

+ * Ideally we would add sections to the executable, as is done with the Linux
+ * build. But PE executables do not appear to work correctly if unexpected
+ * sections are present:
+ *
+ *   $ /tmp/b/sandbox/u-boot.exe
+ *   -bash: /tmp/b/sandbox/u-boot.exe: cannot execute binary file:
Exec format error
+ *
+ * So we take a approach of rewriting the whole file, for now. This will likely
+ * break in the future when a toolchain change is made.

> your patch looks like it is copied from some binutils version and then
> modified.

Yes, exactly.

> Also I do not know from which binutils you have copied and
> what modification you have done in it.

But I have marked this clearly in the script. See  /* U-Boot additions
from here on */

> So I cannot react or comment
> anymore more here.
>
> My idea is that to write those modifications into new layer script.

So I think you are suggesting that I get binutils to emit the default
script, then have a script which detects the end of the .rdata section
and emits its own stuff in there? That may be more robust, since it is
unlikely that the .rdata section will be removed.

But I was rather hoping that someone could help with the core problem,
i.e. why I cannot just insert another section into the image, like we
do with ELF?

Regards,
Simon