Re: [Xen-devel] [PATCH v2 3/3] livepatch: Sync cache of build-id before using it first time.

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

On Fri, Aug 05, 2016 at 09:40:43AM -0600, Jan Beulich wrote:
> >>> On 04.08.16 at 17:49, <konrad.wilk@xxxxxxxxxx> wrote:
> > --- a/xen/include/xen/livepatch.h
> > +++ b/xen/include/xen/livepatch.h
> > @@ -44,7 +44,7 @@ unsigned long livepatch_symbols_lookup_by_name(const char 
> > *symname);
> >  bool_t is_patch(const void *addr);
> >  int xen_build_id_check(const Elf_Note *n, unsigned int n_sz,
> >                         const void **p, unsigned int *len);
> > -
> > +void xen_build_init(void);
> >  /* Arch hooks. */
> 
> Please don't ditch a blank line like this. But this is the wrong header
> anyway, or else you'd have to make version.c include it (which would
> again seem odd). And as I now realize that same aspect applies to
> xen_build_id_check() too - this needs to move into xen/version.h.

Back in April (feels like eons ago) with
"xsplice: Stacking build-id dependency checking."

I have this comment (on v7 of it) - 
https://lists.xen.org/archives/html/xen-devel/2016-04/msg01492.html:
" Moved xen_build_id_check definition to xsplice.h from version.h
        (and dropping the #include's in version.h)"

on that patch.

Digging in the archive, the reason is outlined in:
https://lists.xen.org/archives/html/xen-devel/2016-04/msg00407.html
where:

         @@ -17,4 +17,7 @@ const char *xen_deny(void);
        >  #include <xen/types.h>
        >  int xen_build_id(const void **p, unsigned int *len);
        >  
        > +#include <xen/elfstructs.h>
        > +int xen_build_id_check(const Elf_Note *n, const void **p, unsigned 
int *len);

        The #include is misplaced again, and I'm rather hesitant to see
        version.h gain this dependency. Couldn't this go into xen/elf.h?

And I somehow made it go in version.h not elf.h (I believe that was due
to the Elf_Note being a macro - that is dependent on ELF_SIZE - which
was not set in elf.h - and would cause compilation issues).

Anyhow if I move those two in version.h:

In file included from console.c:13:0:
/home/konrad/ssd/konrad/xtt-x86_64/bootstrap/xen.git/xen/include/xen/version.h:19:30:
 error: unknown type name ‘Elf_Note’
 int xen_build_id_check(const Elf_Note *n, unsigned int n_sz,
                              ^~~~~~~~
make[4]: *** [console.o] Error 1
make[3]: *** [char/built_in.o] Error 2
make[3]: *** Waiting for unfinished jobs....
In file included from kernel.c:10:0:
/home/konrad/ssd/konrad/xtt-x86_64/bootstrap/xen.git/xen/include/xen/version.h:19:30:
 error: unknown type name ‘Elf_Note’
 int xen_build_id_check(const Elf_Note *n, unsigned int n_sz,
                              ^~~~~~~~
make[3]: *** [kernel.o] Error 1
make[2]: *** 
[/home/konrad/ssd/konrad/xtt-x86_64/bootstrap/xen.git/xen/common/built_in.o] Err


I belive I have to include the #include <xen/elfstructs.h> to deal with 
Elf_Note macro.

P.S.
This is the patch (copy-n-paste):

diff --git a/xen/include/xen/livepatch.h b/xen/include/xen/livepatch.h
index cfc9601..c297056 100644
--- a/xen/include/xen/livepatch.h
+++ b/xen/include/xen/livepatch.h
@@ -42,9 +42,6 @@ int livepatch_op(struct xen_sysctl_livepatch_op *);
 void check_for_livepatch_work(void);
 unsigned long livepatch_symbols_lookup_by_name(const char *symname);
 bool_t is_patch(const void *addr);
-int xen_build_id_check(const Elf_Note *n, unsigned int n_sz,
-                       const void **p, unsigned int *len);
-void xen_build_init(void);
 /* Arch hooks. */
 int arch_livepatch_verify_elf(const struct livepatch_elf *elf);
 int arch_livepatch_perform_rel(struct livepatch_elf *elf,
diff --git a/xen/include/xen/version.h b/xen/include/xen/version.h
index 400160f..19a3aaa 100644
--- a/xen/include/xen/version.h
+++ b/xen/include/xen/version.h
@@ -15,4 +15,10 @@ const char *xen_banner(void);
 const char *xen_deny(void);
 int xen_build_id(const void **p, unsigned int *len);
 
+#ifdef BUILD_ID
+int xen_build_id_check(const Elf_Note *n, unsigned int n_sz,
+                       const void **p, unsigned int *len);
+void xen_build_init(void);
+#endif
+
 #endif /* __XEN_VERSION_H__ */


> 
> Jan
> 

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