libelf: Fix some 32bit offset/size issues that break updating 4G+ files.

Some years ago, in commit b1d0b0fc "libelf: Use int64_t for offsets in
libelf.h", we changed the public interface to use 64bit offsets/sizes.
This wasn't really a API change, before we relied on loff_t always
being 64bits on all platforms.

We didn't change the implementation to use the int64_t type though.
That was a little confusing, since the function definitions used a
different type, int64_t, from the function implementations, off_t.
Since we always build with _FILE_OFFSET_BITS=64 this should be fine.
But it was a bit sloppy and confusing.

Worse is that we got the translation of offset/sizes wrong in a
couple of places when translating to ELF types. In various places
we would use Elf32_Word or Elf64_Word. But both are 32bit (unsigned)
types! As is GElf_Word. Elf32_Off is 32bits and Elf64_Off is 64bits.
But we were not using those consistently.

This patch introduces comments for the usage of [G]Elf(32|64)Word in
libelf that are correct. And introduces Elf(32|64)_SizeWord in
elf32_updatenull.c where we want to make a difference between sizes
and offsets (the ELF variants are both unsigned, while int64_t/loff_t
is signed).

It also includes a new run-large-elf-file.sh test that creates a
large ELF files (one 64bit, little endian, rel and another big endian,
non-rel) and runs eu-strip, eu-elflint, eu-unstrip and eu-elfcmp.
Before this patch, that test case fails and creates corrupt ELF files.

The test is guarded by some checks that try to make sure there is
enough disk space and memory available on the machine. The test is
skipped otherwise.

Signed-off-by: Mark Wielaard <[email protected]>

1 files changed, 4 insertions, 4 deletions

diff --git a/libelf/elf32_updatefile.c b/libelf/elf32_updatefile.c
index eea51a7f..f67e6261 100644
--- a/libelf/elf32_updatefile.c
+++ b/libelf/elf32_updatefile.c
@@ -498,7 +498,7 @@ __elfw2(LIBELFBITS,updatemmap) (Elf *elf, int change_bo, size_t shnum)
 
 /* Helper function to write out fill bytes.  */
 static int
-fill (int fd, off_t pos, size_t len, char *fillbuf, size_t *filledp)
+fill (int fd, int64_t pos, size_t len, char *fillbuf, size_t *filledp)
 {
   size_t filled = *filledp;
   size_t fill_len = MIN (len, FILLBUFSIZE);
@@ -651,7 +651,7 @@ __elfw2(LIBELFBITS,updatefile) (Elf *elf, int change_bo, size_t shnum)
 
   /* From now on we have to keep track of the last position to eventually
      fill the gaps with the prescribed fill byte.  */
-  off_t last_offset;
+  int64_t last_offset;
   if (elf->state.ELFW(elf,LIBELFBITS).phdr == NULL)
     last_offset = elf_typesize (LIBELFBITS, ELF_T_EHDR, 1);
   else
@@ -664,7 +664,7 @@ __elfw2(LIBELFBITS,updatefile) (Elf *elf, int change_bo, size_t shnum)
 					+ sizeof (ElfW2(LIBELFBITS,Shdr)))))
 	return 1;
 
-      off_t shdr_offset = elf->start_offset + ehdr->e_shoff;
+      int64_t shdr_offset = elf->start_offset + ehdr->e_shoff;
 #undef shdr_fctp
 #define shdr_fctp __elf_xfctstom[ELFW(ELFCLASS, LIBELFBITS) - 1][ELF_T_SHDR]
 
@@ -712,7 +712,7 @@ __elfw2(LIBELFBITS,updatefile) (Elf *elf, int change_bo, size_t shnum)
 	  if (shdr->sh_type == SHT_NOBITS)
 	    goto next;
 
-	  off_t scn_start = elf->start_offset + shdr->sh_offset;
+	  int64_t scn_start = elf->start_offset + shdr->sh_offset;
 	  Elf_Data_List *dl = &scn->data_list;
 	  bool scn_changed = false;