[PATCH v6 2/5] elf: Properly handle zero DT_RELA/DT_REL values

["H.J. Lu" <hjl.tools@gmail.com>]

With DT_RELR, there may be no relocations in DT_RELA/DT_REL and their
entry values are zero.  Don't relocate DT_RELA/DT_REL and update the
combined relocation start address if their entry values are zero.
---
 elf/dynamic-link.h     |  6 +++++-
 elf/get-dynamic-info.h | 18 ++++++++++++++----
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/elf/dynamic-link.h b/elf/dynamic-link.h
index d04c457e55..252f407a12 100644
--- a/elf/dynamic-link.h
+++ b/elf/dynamic-link.h
@@ -84,7 +84,9 @@ elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
 	     __typeof (((ElfW(Dyn) *) 0)->d_un.d_val) nrelative; int lazy; }  \
       ranges[2] = { { 0, 0, 0, 0 }, { 0, 0, 0, 0 } };			      \
 									      \
-    if ((map)->l_info[DT_##RELOC])					      \
+    /* With DT_RELR, DT_RELA/DT_REL can have zero value.  */		      \
+    if ((map)->l_info[DT_##RELOC]					      \
+	&& (map)->l_info[DT_##RELOC]->d_un.d_ptr != 0)			      \
       {									      \
 	ranges[0].start = D_PTR ((map), l_info[DT_##RELOC]);		      \
 	ranges[0].size = (map)->l_info[DT_##RELOC##SZ]->d_un.d_val;	      \
@@ -98,6 +100,8 @@ elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
 	ElfW(Addr) start = D_PTR ((map), l_info[DT_JMPREL]);		      \
 	ElfW(Addr) size = (map)->l_info[DT_PLTRELSZ]->d_un.d_val;	      \
 									      \
+	if (ranges[0].start == 0)					      \
+	  ranges[0].start = start;					      \
 	if (ranges[0].start + ranges[0].size == (start + size))		      \
 	  ranges[0].size -= size;					      \
 	if (!(do_lazy)							      \
diff --git a/elf/get-dynamic-info.h b/elf/get-dynamic-info.h
index 6c2a3a12b1..f4b957684b 100644
--- a/elf/get-dynamic-info.h
+++ b/elf/get-dynamic-info.h
@@ -83,16 +83,26 @@ elf_get_dynamic_info (struct link_map *l, bool bootstrap,
       ADJUST_DYN_INFO (DT_PLTGOT);
       ADJUST_DYN_INFO (DT_STRTAB);
       ADJUST_DYN_INFO (DT_SYMTAB);
+      ADJUST_DYN_INFO (DT_RELR);
+      ADJUST_DYN_INFO (DT_JMPREL);
+      ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
+      ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
+# undef ADJUST_DYN_INFO
+
+      /* DT_RELA/DT_REL are mandatory.  But they may have zero value if
+	 there is DT_RELR.  Don't relocate them if they are zero.  */
+# define ADJUST_DYN_INFO(tag) \
+      do								      \
+	if (info[tag] != NULL && info[tag]->d_un.d_ptr != 0)		      \
+         info[tag]->d_un.d_ptr += l_addr;				      \
+      while (0)
+
 # if ! ELF_MACHINE_NO_RELA
       ADJUST_DYN_INFO (DT_RELA);
 # endif
 # if ! ELF_MACHINE_NO_REL
       ADJUST_DYN_INFO (DT_REL);
 # endif
-      ADJUST_DYN_INFO (DT_RELR);
-      ADJUST_DYN_INFO (DT_JMPREL);
-      ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
-      ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
 # undef ADJUST_DYN_INFO
     }
   if (info[DT_PLTREL] != NULL)
-- 
2.35.1