Re: [PATCH v3 01/13] objtool/klp: honor SHF_MERGE entry alignment in elf_add_data()

[Josh Poimboeuf]

On Tue, Feb 17, 2026 at 11:14:17AM -0500, Joe Lawrence wrote:
> On Tue, Feb 17, 2026 at 11:06:32AM -0500, Joe Lawrence wrote:
> > When adding data to an SHF_MERGE section, set the Elf_Data d_align to
> > the section's sh_addralign so libelf aligns entries within the section.
> > This ensures that entry offsets are consistent with previously calculated
> > relocation addends.
> > 
> > Fixes: 431dbabf2d9d ("objtool: Add elf_create_data()")
> > Signed-off-by: Joe Lawrence <joe.lawre...@redhat.com>
> > ---
> >  tools/objtool/elf.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
> > index 2c02c7b49265..bd6502e7bdc0 100644
> > --- a/tools/objtool/elf.c
> > +++ b/tools/objtool/elf.c
> > @@ -1375,7 +1375,7 @@ void *elf_add_data(struct elf *elf, struct section 
> > *sec, const void *data, size_
> >             memcpy(sec->data->d_buf, data, size);
> >  
> >     sec->data->d_size = size;
> > -   sec->data->d_align = 1;
> > +   sec->data->d_align = (sec->sh.sh_flags & SHF_MERGE) ? 
> > sec->sh.sh_addralign : 1;
> >  
> >     offset = ALIGN(sec->sh.sh_size, sec->sh.sh_addralign);
> >     sec->sh.sh_size = offset + size;
> > -- 
> > 2.53.0
> > 
> > 
> 
> This one stretches my ELF internals knowledge a bit, is ^^ true or
> should we rely on the section ".str1.8" suffix to indicate internal
> alignment?

I hit the same issue in my testing for the klp-build arm64 port, I think
it can be simplified to the below?

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
@@ -1375,7 +1382,7 @@ void *elf_add_data(struct elf *elf, struct section *sec, 
const void *data, size_
                memcpy(sec->data->d_buf, data, size);
 
        sec->data->d_size = size;
-       sec->data->d_align = 1;
+       sec->data->d_align = sec->sh.sh_addralign;
 
        offset = ALIGN(sec->sh.sh_size, sec->sh.sh_addralign);
        sec->sh.sh_size = offset + size;