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.
---
src/strip.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 65 insertions(+), 15 deletions(-)
diff --git a/src/strip.c b/src/strip.c
index 791347c..1367de7 100644
--- 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. */
--
1.8.3.1
