strip: Handle mixed allocated/non-allocated sections.

Normally in non-ET_REL files all allocated sections come before
all non-allocated sections. eu-strip relies on this when stripping
a file and calculating the file offsets. But recently on Fedora
there are non-allocated .gnu.build.attributes NOTE sections in
the middle of the allocated sections, with a sh_offset field that
is larger then the next section. This confuses eu-strip so much that
it might corrupt the stripped file.

Work around this by calculating the sh_offset fields in two phases
when detecting mixed allocated/non-allocated sections. First handle
the allocated ones, then use the offset after the last allocated
section to calculate the offsets of the non-allocated sections left
in the stripped file.

Signed-off-by: Mark Wielaard <mark@klomp.org>

diff --git a/src/ChangeLog b/src/ChangeLog
index 2f9f774..29d3644 100644 (file)
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2018-07-30  Mark Wielaard  <mark@klomp.org>
+
+       * strip.c (handle_elf): Track allocated/unallocated sections seen. Set
+       section offset of unallocated sections after handling all allocated
+       sections.
+
 2018-08-18  Mark Wielaard  <mark@klomp.org>
 
        * readelf.c (print_debug_aranges_section): Make sure there is enough

diff --git a/src/strip.c b/src/strip.c
index 791347c..1367de7 100644 (file)
--- a/src/strip.c
+++ b/src/strip.c
@@ -661,6 +661,11 @@ handle_elf (int fd, Elf *elf, const char *prefix, const char *fname,
       memset (shdr_info, '\0', (shnum + 2) * sizeof (struct shdr_info));
     }
 
+  /* Track whether allocated sections all come before non-allocated ones.  */
+  bool seen_allocated = false;
+  bool seen_unallocated = false;
+  bool mixed_allocated_unallocated = false;
+
   /* Prepare section information data structure.  */
   scn = NULL;
   cnt = 1;
@@ -676,6 +681,17 @@ handle_elf (int fd, Elf *elf, const char *prefix, const char *fname,
       if (gelf_getshdr (scn, &shdr_info[cnt].shdr) == NULL)
        INTERNAL_ERROR (fname);
 
+      /* Normally (in non-ET_REL files) we see all allocated sections first,
+        then all non-allocated.  */
+      if ((shdr_info[cnt].shdr.sh_flags & SHF_ALLOC) == 0)
+       seen_unallocated = true;
+      else
+       {
+         if (seen_unallocated && seen_allocated)
+           mixed_allocated_unallocated = true;
+         seen_allocated = true;
+       }
+
       /* Get the name of the section.  */
       shdr_info[cnt].name = elf_strptr (elf, shstrndx,
                                        shdr_info[cnt].shdr.sh_name);
@@ -1535,24 +1551,58 @@ handle_elf (int fd, Elf *elf, const char *prefix, const char *fname,
              }
          }
 
-       /* If we have to, compute the offset of the section.  */
-       if (shdr_info[cnt].shdr.sh_offset == 0)
-         shdr_info[cnt].shdr.sh_offset
-           = ((lastoffset + shdr_info[cnt].shdr.sh_addralign - 1)
-              & ~((GElf_Off) (shdr_info[cnt].shdr.sh_addralign - 1)));
-
-       /* Set the section header in the new file.  */
-       if (unlikely (gelf_update_shdr (scn, &shdr_info[cnt].shdr) == 0))
-         /* There cannot be any overflows.  */
-         INTERNAL_ERROR (fname);
+       /* If we have to, compute the offset of the section.
+          If allocate and unallocated sections are mixed, we only update
+          the allocated ones now.  The unallocated ones come second.  */
+       if (! mixed_allocated_unallocated
+           || (shdr_info[cnt].shdr.sh_flags & SHF_ALLOC) != 0)
+         {
+           if (shdr_info[cnt].shdr.sh_offset == 0)
+             shdr_info[cnt].shdr.sh_offset
+               = ((lastoffset + shdr_info[cnt].shdr.sh_addralign - 1)
+                  & ~((GElf_Off) (shdr_info[cnt].shdr.sh_addralign - 1)));
+
+           /* Set the section header in the new file.  */
+           if (unlikely (gelf_update_shdr (scn, &shdr_info[cnt].shdr) == 0))
+             /* There cannot be any overflows.  */
+             INTERNAL_ERROR (fname);
 
-       /* Remember the last section written so far.  */
-       GElf_Off filesz = (shdr_info[cnt].shdr.sh_type != SHT_NOBITS
-                          ? shdr_info[cnt].shdr.sh_size : 0);
-       if (lastoffset < shdr_info[cnt].shdr.sh_offset + filesz)
-         lastoffset = shdr_info[cnt].shdr.sh_offset + filesz;
+           /* Remember the last section written so far.  */
+           GElf_Off filesz = (shdr_info[cnt].shdr.sh_type != SHT_NOBITS
+                              ? shdr_info[cnt].shdr.sh_size : 0);
+           if (lastoffset < shdr_info[cnt].shdr.sh_offset + filesz)
+             lastoffset = shdr_info[cnt].shdr.sh_offset + filesz;
+         }
       }
 
+  /* We might have to update the unallocated sections after we done the
+     allocated ones.  lastoffset is set to right after the last allocated
+     section.  */
+  if (mixed_allocated_unallocated)
+    for (cnt = 1; cnt <= shdridx; ++cnt)
+      if (shdr_info[cnt].idx > 0)
+       {
+         scn = elf_getscn (newelf, shdr_info[cnt].idx);
+         if ((shdr_info[cnt].shdr.sh_flags & SHF_ALLOC) == 0)
+           {
+             if (shdr_info[cnt].shdr.sh_offset == 0)
+               shdr_info[cnt].shdr.sh_offset
+                 = ((lastoffset + shdr_info[cnt].shdr.sh_addralign - 1)
+                    & ~((GElf_Off) (shdr_info[cnt].shdr.sh_addralign - 1)));
+
+             /* Set the section header in the new file.  */
+             if (unlikely (gelf_update_shdr (scn, &shdr_info[cnt].shdr) == 0))
+               /* There cannot be any overflows.  */
+               INTERNAL_ERROR (fname);
+
+             /* Remember the last section written so far.  */
+             GElf_Off filesz = (shdr_info[cnt].shdr.sh_type != SHT_NOBITS
+                                ? shdr_info[cnt].shdr.sh_size : 0);
+             if (lastoffset < shdr_info[cnt].shdr.sh_offset + filesz)
+               lastoffset = shdr_info[cnt].shdr.sh_offset + filesz;
+           }
+       }
+
   /* Adjust symbol references if symbol tables changed.  */
   if (any_symtab_changes)
     /* Find all relocation sections which use this symbol table.  */