[PATCH v2 1/1] sandbox: eliminate unused functions from binaries

[Simon Glass]

Hi,

On Mon, 23 Oct 2023 at 10:03, Tom Rini <trini at konsulko.com> wrote:
>
> On Mon, Oct 23, 2023 at 01:37:27AM +0200, Heinrich Schuchardt wrote:
> > The sandbox should closely mimic other architectures.
> >
> > Place each function or data in a separate section and let the linker
> > eliminate unused ones. This will reduce the binary size.
> >
> > In the linker script mark that u_boot_sandbox_getopt are to be kept.
> >
> > Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> > ---
> > v2:
> >       mark _u_boot_sandbox_getopt secitons a KEEP()
> > ---
> >  arch/sandbox/config.mk      | 4 +++-
> >  arch/sandbox/cpu/u-boot.lds | 6 +++---
> >  2 files changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/sandbox/config.mk b/arch/sandbox/config.mk
> > index 2d184c5f65..c02f0229c2 100644
> > --- a/arch/sandbox/config.mk
> > +++ b/arch/sandbox/config.mk
> > @@ -2,7 +2,7 @@
> >  # Copyright (c) 2011 The Chromium OS Authors.
> >
> >  PLATFORM_CPPFLAGS += -D__SANDBOX__ -U_FORTIFY_SOURCE
> > -PLATFORM_CPPFLAGS += -fPIC
> > +PLATFORM_CPPFLAGS += -fPIC -ffunction-sections -fdata-sections
> >  PLATFORM_LIBS += -lrt
> >  SDL_CONFIG ?= sdl2-config
> >
> > @@ -26,6 +26,7 @@ cmd_u-boot__ = $(CC) -o $@ -Wl,-T u-boot.lds $(u-boot-init) \
> >       $(KBUILD_LDFLAGS:%=-Wl,%) \
> >       $(SANITIZERS) \
> >       $(LTO_FINAL_LDFLAGS) \
> > +     -Wl,--gc-section \
> >       -Wl,--whole-archive \
> >               $(u-boot-main) \
> >               $(u-boot-keep-syms-lto) \
> > @@ -37,6 +38,7 @@ cmd_u-boot-spl = (cd $(obj) && $(CC) -o $(SPL_BIN) -Wl,-T u-boot-spl.lds \
> >       $(SANITIZERS) \
> >       $(LTO_FINAL_LDFLAGS) \
> >       $(patsubst $(obj)/%,%,$(u-boot-spl-init)) \
> > +     -Wl,--gc-section \
> >       -Wl,--whole-archive \
> >               $(patsubst $(obj)/%,%,$(u-boot-spl-main)) \
> >               $(patsubst $(obj)/%,%,$(u-boot-spl-platdata)) \
>
> There's already a call to --gc-sections for u-boot-spl on sandbox (in
> the last line of the link command).  We should probably move the main
> u-boot call there too, for consistency.
>

For the moment I really don't want this in sandbox. I think I explain
that there is very little benefit in terms of size and it takes us
away from how native apps are normally built. It also seems to mask
problems in your CMDLINE series

Regards,
Simon