Re: [Xen-devel] [PATCH LP-BUILD-TOOLS] Allow patching files compiled multiple times

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Mar 05, 2018 at 10:32:51AM +0000, Ross Lagerwall wrote:
> On 02/23/2018 05:08 PM, Ross Lagerwall wrote:
> > gas prior to binutils commit fbdf9406b0 (appears in 2.27) outputs symbol
> > table entries resulting from .file in reverse order. If we get two
> > consecutive file symbols, prefer the first one if that names an object
> > file or has a directory component (to cover multiply compiled files).
> > 
> > This is the same workaround that was applied in Xen commit d37d63d4b548
> > ("symbols: prefix static symbols with their source file names") for
> > Xen's internal symbol table.
> > 
> > This fixes building a livepatch for XSA-243.
> > ---
> >   lookup.c | 18 ++++++++++++++++++
> >   1 file changed, 18 insertions(+)
> > 
> > diff --git a/lookup.c b/lookup.c
> > index 39125c6..645b91a 100644
> > --- a/lookup.c
> > +++ b/lookup.c
> > @@ -149,16 +149,34 @@ int lookup_local_symbol(struct lookup_table *table, 
> > char *name, char *hint,
> >     struct symbol *sym, *match = NULL;
> >     int i;
> >     char *curfile = NULL;
> > +   enum { other, multi_source } last_type = other;
> >     memset(result, 0, sizeof(*result));
> >     for_each_symbol(i, sym, table) {
> >             if (sym->type == STT_FILE) {
> > +                   const char *ext = strrchr(sym->name, '.');
> > +                   int multi = strchr(sym->name, '/') ||
> > +                               (ext && ext[1] == 'o');
> > +
> > +                   /*
> > +                    * gas prior to binutils commit fbdf9406b0 (appears in
> > +                    * 2.27) outputs symbol table entries resulting from
> > +                    * .file in reverse order. If we get two consecutive
> > +                    * file symbols, prefer the first one if that names an
> > +                    * object file or has a directory component (to cover
> > +                    * multiply compiled files).
> > +                    */
> > +                   if (last_type == multi_source)
> > +                           continue;
> > +
> >                     if (!strcmp(sym->name, hint)) {
> >                             curfile = sym->name;
> > +                           last_type = multi ? multi_source : other;
> >                             continue; /* begin hint file symbols */

Perhaps add some logging as well?
> >                     } else if (curfile)
> >                             curfile = NULL; /* end hint file symbols */
> >             }
> > +           last_type = other;
> >             if (!curfile)
> >                     continue;
> >             if (sym->bind == STB_LOCAL && !strcmp(sym->name, name)) {
> > 
> 
> Ping, Konrad?

This looks familiar, but how come it has no SoB?

> 
> -- 
> Ross Lagerwall

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