[v6,54/57] dyndbg: add .gnu.linkonce. & __dyndbg* sections in module.lds.h

Commit Message

Jim Cromie Sept. 4, 2022, 9:41 p.m. UTC

For a long time now, loadable modules have tacitly linked the __dyndbg
section into the .ko, as is observable in dmesg by enabling module.c's
pr_debugs and loading a module.  Recently, __dyndbg_sites was added,
following the original model.

But now, we need to explicitly name those (__dyndbg, __dyndbg_sites)
sections in order to place new .gnu.linkonce.dyndbg* sections in front
of them.

This gives us the properties we need for _ddebug_map_site() to drop
the _ddebug.site pointer:

   fixed offset from &__dyndbg[N] to &__dyndbg[0]
   container_of gets &header
   header has ptr to __dyndbg_sites[]
   __dyndbg_sites[_map] gives de-duplicated site recs

NOTE

HEAD~1 took headers off front of descs,sites and saved them into
_ddebug_info, this puts the gnu.linkonce.* records into those vectors.

Signed-off-by: Jim Cromie <[e-mail]>
---
 include/asm-generic/module.lds.h | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Patch

diff --git a/include/asm-generic/module.lds.h b/include/asm-generic/module.lds.h
index f210d5c1b78b..328c48dfc88c 100644
--- a/include/asm-generic/module.lds.h
+++ b/include/asm-generic/module.lds.h
@@ -4,7 +4,17 @@ 
 
 /*
  * <asm/module.lds.h> can specify arch-specific sections for linking modules.
- * Empty for the asm-generic header.
+ *
+ * For loadable modules with CONFIG_DYNAMIC_DEBUG, we need to keep the
+ * 2 __dyndbg* ELF sections, which are loaded by module.c
+ *
+ * Pack the 2 __dyndbg* input sections with their respective
+ * .gnu.linkonce. header records into 2 output sections, with those
+ * header records in the 0th element.
  */
+SECTIONS {
+__dyndbg_sites	: ALIGN(8) { *(.gnu.linkonce.dyndbg_site) *(__dyndbg_sites) }
+__dyndbg	: ALIGN(8) { *(.gnu.linkonce.dyndbg)	  *(__dyndbg) }
+}
 
 #endif /* __ASM_GENERIC_MODULE_LDS_H */