Re: [PATCH] x86/boot/compressed: Fix compressed kernel linking with lld

[Fangrui Song]

On 2020-02-22, Nathan Chancellor wrote:
> On Sat, Feb 22, 2020 at 12:18:59PM -0500, Arvind Sankar wrote:
> > Commit TBD ("x86/boot/compressed: Remove unnecessary sections from
> > bzImage") discarded unnecessary sections with *(*). While this works
> > fine with the bfd linker, lld tries to also discard essential sections
> > like .shstrtab, .symtab and .strtab, which results in the link failing
> > since .shstrtab is required by the ELF specification. .symtab and
> > .strtab are also necessary to generate the zoffset.h file for the
> > bzImage header.
> >
> > Since the only sizeable section that can be discarded is .eh_frame,
> > restrict the discard to only .eh_frame to be safe.
> >
> > Signed-off-by: Arvind Sankar <nivedita@xxxxxxxxxxxx>
> > ---
> > Sending as a fix on top of tip/x86/boot.
> >
> >  arch/x86/boot/compressed/vmlinux.lds.S | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
> > index 12a20603d92e..469dcf800a2c 100644
> > --- a/arch/x86/boot/compressed/vmlinux.lds.S
> > +++ b/arch/x86/boot/compressed/vmlinux.lds.S
> > @@ -74,8 +74,8 @@ SECTIONS
> >  	. = ALIGN(PAGE_SIZE);	/* keep ZO size page aligned */
> >  	_end = .;
> >
> > -	/* Discard all remaining sections */
> > +	/* Discard .eh_frame to save some space */
> >  	/DISCARD/ : {
> > -		*(*)
> > +		*(.eh_frame)
> >  	}
> >  }
> > --
> > 2.24.1
>
> FWIW:
>
> Tested-by: Nathan Chancellor <natechancellor@xxxxxxxxx>

I am puzzled. Doesn't -fno-asynchronous-unwind-tables suppress
.eh_frame in the object files? Why are there still .eh_frame?

Though, there is prior art: arch/s390/boot/compressed/vmlinux.lds.S also discards .eh_frame