[RFC PATCH 0/6] Clean up arm linker scripts

[Tom Rini]

On Thu, Feb 29, 2024 at 02:07:39PM -0700, Sam Edwards wrote:
> 
> 
> On 2/28/24 04:15, Ilias Apalodimas wrote:
> > On Wed, 28 Feb 2024 at 13:11, Peter Robinson <pbrobinson at gmail.com> wrote:
> > > 
> > > On Wed, 28 Feb 2024 at 10:58, Ilias Apalodimas
> > > <ilias.apalodimas at linaro.org> wrote:
> > > > 
> > > > The arm linker scripts had a mix of symbols and C defined variables in an
> > > > effort to emit relative references instead of absolute ones e.g [0].
> > > > This has led to confusion over the years, ending up with mixed section
> > > > definitions. Some sections being defined with overlays and different
> > > > definitions between v7 and v8 architectures.
> > > > For example __efi_runtime_rel_start/end is defined as a linker symbol for
> > > > armv8 and a C variable in armv7.
> > > > 
> > > > I am not sure if this used to be a compiler bug, but linker scripts nowadays
> > > > can emit relative references, as long as the symbol definition is contained
> > > > within the section definition. So let's switch most of the C defined variables
> > > 
> > > Should we be setting/upping the minimum version of the linker version
> > > as part of this?
> > 
> > The patch that added those as C-defined variables, was in 2013. So any
> > linker that's not ancient history should emit those correctly.
> > 
> 
> GNU ld fixed the problem on 2016-02-23, with this entry in the bfd
> changelog:
> 
> 	* elflink.c (bfd_elf_record_link_assignment): Check for shared
> 	library, instead of PIC, and don't check PDE when making linker
> 	assigned symbol dynamic.
> 
> It looks like the change was first included in binutils 2.27, released
> 2016-08-03. I don't know where the minimum linker version requirement is
> memorialized but there's a good chance that U-Boot already requires a
> version more recent than that. (Someone who knows where that is will have to
> check.)
> 
> In either case, I strongly agree: sections.c is an unnecessary workaround
> with any reasonably recent linker version, it's fickle/incompatible with
> non-GNU linkers such as LLD, and the marker symbols belong in the linker
> script. This patchset is a big step in the right direction!

We have the ld-version check logic same as the kernel but do not today
enforce any minimum version. On ARM we only enforce gcc 6.0.0 being a
minimum version, and that's likely too old too, in reality. So adding a
check would be nice, but not required I think, given the age of the fix.
Thanks for digging in to this!

-- 
Tom
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