Re: [PATCH 3/3] livepatch: correctly handle altinstruction sections

["Roger Pau Monné" <roger.pau@citrix.com>]

On Fri, Mar 11, 2022 at 08:35:18AM +0100, Jan Beulich wrote:
> On 10.03.2022 16:08, Roger Pau Monne wrote:
> > --- a/common.c
> > +++ b/common.c
> > @@ -249,19 +249,22 @@ int is_text_section(struct section *sec)
> >  		(sec->sh.sh_flags & SHF_EXECINSTR));
> >  }
> >  
> > +#define SEC_MATCH(n) !strncmp(sec->name, n, strlen(n) - 1)
> >  int is_rodata_section(struct section *sec)
> >  {
> >  	return sec->sh.sh_type == SHT_PROGBITS &&
> >  	       !(sec->sh.sh_flags & (SHF_EXECINSTR | SHF_WRITE)) &&
> > -	       !strncmp(sec->name, ".rodata", 7);
> > +	       (SEC_MATCH(".rodata") || SEC_MATCH(".data.ro_after_init"));
> >  }
> >  
> >  int is_init_section(struct section *sec)
> >  {
> >  	return sec->sh.sh_type == SHT_PROGBITS &&
> >  	       (sec->sh.sh_flags & SHF_ALLOC) &&
> > -	       !strncmp(sec->name, ".init", 5);
> > +	       (SEC_MATCH(".init") || SEC_MATCH(".text.startup") ||
> > +	        SEC_MATCH(".altinstr") || SEC_MATCH(".ctors"));
> 
> Having dealt with this recently - what about .init_array? Modern gcc
> prefers that over .ctors. Of course the question is whether either
> really needs dealing with here - these sections, to my knowledge,
> appear only with gcov support enabled. Not sure that's a case where
> livepatching is actually expected to be used.

.init_array will match the .init comparison, and thus is already
handled.

Regarding .ctors, it's certainly an .init section, so it doesn't hurt
to get added here in any case? (regardless of us only knowing it being
used for code coverage so far)

Thanks, Roger.