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 <mark@klomp.org>

15 files changed, 239 insertions, 52 deletions

diff --git a/libelf/ChangeLog b/libelf/ChangeLog
index 82e18ebc..dde6c81d 100644
--- a/libelf/ChangeLog
+++ b/libelf/ChangeLog
@@ -1,3 +1,35 @@
+2019-06-18  Mark Wielaard  <mark@klomp.org>
+
+	* common.h (allocate_elf): Use int64_t instead of off_t for offset.
+	* elf32_newphdr.c (newphdr): Document why Elf32/64_Word is correct.
+	* elf32_updatefile.c (fill): Use int64_t instead of off_t for pos.
+	(updatefile): Define last_offset, shdr_offset and scn_start as
+	int64_t instead of off_t.
+	* elf32_updatenull.c: Define Elf32_SizeWord and Elf64_SizeWord.
+	(updatenull_wrlock): Return int64_t instead of off_t. Define size,
+	sh_entsize, sh_align and sh_size as SizeWords. Define offset as
+	int64_t.  Cast data->d_off to SizeWord instead of GElf_Word. Drop
+	size GElf_Word cast. Cast offset to SizeWord instead of GElf_Word
+	when comparing with sh_size.
+	* elf_begin.c (get_shnum): Define offset as int64_t instead of
+	off_t. Document why use GElf_Word is correct.
+	(file_read_elf): Define offset as int64_t instead of off_t.
+	(__libelf_read_mmaped_file): Likewise.
+	(read_unmmaped_file): Likewise.
+	(read_file): Likewise.
+	* elf_getaroff.c (elf_getaroff): Return int64_t.
+	* elf_getbase.c (elf_getbase): Likewise.
+	* elf_getdata_rawchunk.c (elf_getdata_rawchunk): Define offset as
+	int64_t instead of off_t.
+	* elf_update.c (write_file): Return int64_t instead of off_t,
+	define size as int64_t instead of off_t.
+	(elf_update): Likewise.
+	* libelfP.h (struct Elf): Define start_offset, sizestr_offset and
+	offset as int64_t.
+	(__libelf_read_mmaped_file): Define offset as int64_t.
+	(__elf32_updatenull_wrlock): Return int64_t.
+	(__elf64_updatenull_wrlock): Return int64_t.
+
 2019-05-12  Mark Wielaard  <mark@klomp.org>
 
 	* elf32_updatenull.c (updatenull_wrlock): Mark shdr_flags dirty if
diff --git a/libelf/common.h b/libelf/common.h
index 62486903..b0175f60 100644
--- a/libelf/common.h
+++ b/libelf/common.h
@@ -68,7 +68,7 @@ determine_kind (void *buf, size_t len)
 /* Allocate an Elf descriptor and fill in the generic information.  */
 static inline Elf *
 __attribute__ ((unused))
-allocate_elf (int fildes, void *map_address, off_t offset, size_t maxsize,
+allocate_elf (int fildes, void *map_address, int64_t offset, size_t maxsize,
               Elf_Cmd cmd, Elf *parent, Elf_Kind kind, size_t extra)
 {
   Elf *result = (Elf *) calloc (1, sizeof (Elf) + extra);
diff --git a/libelf/elf32_newphdr.c b/libelf/elf32_newphdr.c
index 4aa72137..7dd78ca9 100644
--- a/libelf/elf32_newphdr.c
+++ b/libelf/elf32_newphdr.c
@@ -56,6 +56,9 @@ elfw2(LIBELFBITS,newphdr) (Elf *elf, size_t count)
       return NULL;
     }
 
+  /* This check is correct, it is for sh_info, which is either
+     Elf32_Word or Elf64_Word, both being 32 bits.  But count is size_t
+     so might not fit on 32bit ELF files.  */
   if (unlikely ((ElfW2(LIBELFBITS,Word)) count != count))
     {
       __libelf_seterrno (ELF_E_INVALID_OPERAND);
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;
 
diff --git a/libelf/elf32_updatenull.c b/libelf/elf32_updatenull.c
index 303055a0..5f3cdbf6 100644
--- a/libelf/elf32_updatenull.c
+++ b/libelf/elf32_updatenull.c
@@ -45,6 +45,10 @@
 # define LIBELFBITS 32
 #endif
 
+/* Some fields contain 32/64 sizes.  We cannot use Elf32/64_Word for those,
+   since those are both 32bits.  Elf32/64_Xword is always 64bits.  */
+#define Elf32_SizeWord Elf32_Word
+#define Elf64_SizeWord Elf64_Xword
 
 
 static int
@@ -122,7 +126,7 @@ ELFW(default_ehdr,LIBELFBITS) (Elf *elf, ElfW2(LIBELFBITS,Ehdr) *ehdr,
 }
 
 
-off_t
+int64_t
 internal_function
 __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
 {
@@ -137,7 +141,7 @@ __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
     return -1;
 
   /* At least the ELF header is there.  */
-  off_t size = elf_typesize (LIBELFBITS, ELF_T_EHDR, 1);
+  ElfW2(LIBELFBITS,SizeWord) size = elf_typesize (LIBELFBITS, ELF_T_EHDR, 1);
 
   /* Set the program header position.  */
   if (elf->state.ELFW(elf,LIBELFBITS).phdr == NULL)
@@ -152,7 +156,7 @@ __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
 	{
 	  /* The user is supposed to fill out e_phoff.  Use it and
 	     e_phnum to determine the maximum extend.  */
-	  size = MAX ((size_t) size,
+	  size = MAX (size,
 		      ehdr->e_phoff
 		      + elf_typesize (LIBELFBITS, ELF_T_PHDR, phnum));
 	}
@@ -205,11 +209,11 @@ __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
 	    {
 	      Elf_Scn *scn = &list->data[cnt];
 	      ElfW2(LIBELFBITS,Shdr) *shdr = scn->shdr.ELFW(e,LIBELFBITS);
-	      off_t offset = 0;
+	      int64_t offset = 0;
 
 	      assert (shdr != NULL);
-	      ElfW2(LIBELFBITS,Word) sh_entsize = shdr->sh_entsize;
-	      ElfW2(LIBELFBITS,Word) sh_align = shdr->sh_addralign ?: 1;
+	      ElfW2(LIBELFBITS,SizeWord) sh_entsize = shdr->sh_entsize;
+	      ElfW2(LIBELFBITS,SizeWord) sh_align = shdr->sh_addralign ?: 1;
 	      if (unlikely (! powerof2 (sh_align)))
 		{
 		  __libelf_seterrno (ELF_E_INVALID_ALIGN);
@@ -299,8 +303,8 @@ __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
 			  /* The user specified the offset and the size.
 			     All we have to do is check whether this block
 			     fits in the size specified for the section.  */
-			  if (unlikely ((GElf_Word) (data->d_off
-						     + data->d_size)
+			  if (unlikely ((ElfW2(LIBELFBITS,SizeWord))
+					(data->d_off + data->d_size)
 					> shdr->sh_size))
 			    {
 			      __libelf_seterrno (ELF_E_SECTION_TOO_SMALL);
@@ -329,7 +333,7 @@ __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
 
 	      if (elf->flags & ELF_F_LAYOUT)
 		{
-		  size = MAX ((GElf_Word) size,
+		  size = MAX (size,
 			      (shdr->sh_type != SHT_NOBITS
 			       ? shdr->sh_offset + shdr->sh_size : 0));
 
@@ -353,8 +357,7 @@ __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
 
 		  size = (size + sh_align - 1) & ~(sh_align - 1);
 		  int offset_changed = 0;
-		  update_if_changed (shdr->sh_offset, (GElf_Word) size,
-				     offset_changed);
+		  update_if_changed (shdr->sh_offset, size, offset_changed);
 		  changed |= offset_changed;
 
 		  if (offset_changed && scn->data_list_rear == NULL)
@@ -367,7 +370,8 @@ __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
 
 		  /* See whether the section size is correct.  */
 		  int size_changed = 0;
-		  update_if_changed (shdr->sh_size, (GElf_Word) offset,
+		  update_if_changed (shdr->sh_size,
+				     (ElfW2(LIBELFBITS,SizeWord)) offset,
 				     size_changed);
 		  changed |= size_changed;
 
@@ -384,7 +388,7 @@ __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
 		  && (elf->flags & ELF_F_PERMISSIVE) == 0)
 		{
 		  /* For compressed sections check the uncompressed size.  */
-		  ElfW2(LIBELFBITS,Word) sh_size;
+		  ElfW2(LIBELFBITS,SizeWord) sh_size;
 		  if ((shdr->sh_flags & SHF_COMPRESSED) == 0)
 		    sh_size = shdr->sh_size;
 		  else
@@ -418,7 +422,7 @@ __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
 	  /* The user is supposed to fill out e_shoff.  Use it and
 	     e_shnum (or sh_size of the dummy, first section header)
 	     to determine the maximum extend.  */
-	  size = MAX ((GElf_Word) size,
+	  size = MAX (size,
 		      (ehdr->e_shoff
 		       + (elf_typesize (LIBELFBITS, ELF_T_SHDR, shnum))));
 	}
@@ -432,7 +436,7 @@ __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
 #define SHDR_ALIGN sizeof (ElfW2(LIBELFBITS,Off))
 	  size = (size + SHDR_ALIGN - 1) & ~(SHDR_ALIGN - 1);
 
-	  update_if_changed (ehdr->e_shoff, (GElf_Word) size, elf->flags);
+	  update_if_changed (ehdr->e_shoff, size, elf->flags);
 
 	  /* Account for the section header size.  */
 	  size += elf_typesize (LIBELFBITS, ELF_T_SHDR, shnum);
diff --git a/libelf/elf_begin.c b/libelf/elf_begin.c
index 5d095ff0..8107a103 100644
--- a/libelf/elf_begin.c
+++ b/libelf/elf_begin.c
@@ -71,8 +71,8 @@ file_read_ar (int fildes, void *map_address, off_t offset, size_t maxsize,
 
 
 static size_t
-get_shnum (void *map_address, unsigned char *e_ident, int fildes, off_t offset,
-	   size_t maxsize)
+get_shnum (void *map_address, unsigned char *e_ident, int fildes,
+	   int64_t offset, size_t maxsize)
 {
   size_t result;
   union
@@ -243,6 +243,9 @@ get_shnum (void *map_address, unsigned char *e_ident, int fildes, off_t offset,
 		CONVERT (size);
 	    }
 
+	  /* Although sh_size is an Elf64_Xword and can contain a 64bit
+	     value, we only expect an 32bit value max.  GElf_Word is
+	     32bit unsigned.  */
 	  if (size > ~((GElf_Word) 0))
 	    {
 	      /* Invalid value, it is too large.  */
@@ -266,7 +269,7 @@ get_shnum (void *map_address, unsigned char *e_ident, int fildes, off_t offset,
 /* Create descriptor for ELF file in memory.  */
 static Elf *
 file_read_elf (int fildes, void *map_address, unsigned char *e_ident,
-	       off_t offset, size_t maxsize, Elf_Cmd cmd, Elf *parent)
+	       int64_t offset, size_t maxsize, Elf_Cmd cmd, Elf *parent)
 {
   /* Verify the binary is of the class we can handle.  */
   if (unlikely ((e_ident[EI_CLASS] != ELFCLASS32
@@ -531,7 +534,7 @@ file_read_elf (int fildes, void *map_address, unsigned char *e_ident,
 
 Elf *
 internal_function
-__libelf_read_mmaped_file (int fildes, void *map_address,  off_t offset,
+__libelf_read_mmaped_file (int fildes, void *map_address,  int64_t offset,
 			   size_t maxsize, Elf_Cmd cmd, Elf *parent)
 {
   /* We have to find out what kind of file this is.  We handle ELF
@@ -564,7 +567,7 @@ __libelf_read_mmaped_file (int fildes, void *map_address,  off_t offset,
 
 
 static Elf *
-read_unmmaped_file (int fildes, off_t offset, size_t maxsize, Elf_Cmd cmd,
+read_unmmaped_file (int fildes, int64_t offset, size_t maxsize, Elf_Cmd cmd,
 		    Elf *parent)
 {
   /* We have to find out what kind of file this is.  We handle ELF
@@ -626,7 +629,7 @@ read_unmmaped_file (int fildes, off_t offset, size_t maxsize, Elf_Cmd cmd,
 
 /* Open a file for reading.  If possible we will try to mmap() the file.  */
 static struct Elf *
-read_file (int fildes, off_t offset, size_t maxsize,
+read_file (int fildes, int64_t offset, size_t maxsize,
 	   Elf_Cmd cmd, Elf *parent)
 {
   void *map_address = NULL;
diff --git a/libelf/elf_getaroff.c b/libelf/elf_getaroff.c
index 5b59203f..5c102ad6 100644
--- a/libelf/elf_getaroff.c
+++ b/libelf/elf_getaroff.c
@@ -38,7 +38,7 @@
 #include "libelfP.h"
 
 
-off_t
+int64_t
 elf_getaroff (Elf *elf)
 {
   /* Be gratious, the specs demand it.  */
diff --git a/libelf/elf_getbase.c b/libelf/elf_getbase.c
index 8ec5f87e..4890d336 100644
--- a/libelf/elf_getbase.c
+++ b/libelf/elf_getbase.c
@@ -37,8 +37,8 @@
 #include "libelfP.h"
 
 
-off_t
+int64_t
 elf_getbase (Elf *elf)
 {
-  return elf == NULL ? (off_t) -1 : elf->start_offset;
+  return elf == NULL ? (int64_t) -1 : elf->start_offset;
 }
diff --git a/libelf/elf_getdata_rawchunk.c b/libelf/elf_getdata_rawchunk.c
index 6a130737..1072f7de 100644
--- a/libelf/elf_getdata_rawchunk.c
+++ b/libelf/elf_getdata_rawchunk.c
@@ -41,7 +41,7 @@
 #include "common.h"
 
 Elf_Data *
-elf_getdata_rawchunk (Elf *elf, off_t offset, size_t size, Elf_Type type)
+elf_getdata_rawchunk (Elf *elf, int64_t offset, size_t size, Elf_Type type)
 {
   if (unlikely (elf == NULL))
     return NULL;
diff --git a/libelf/elf_update.c b/libelf/elf_update.c
index 36997c2b..9b8867ce 100644
--- a/libelf/elf_update.c
+++ b/libelf/elf_update.c
@@ -40,8 +40,8 @@
 #include "libelfP.h"
 
 
-static off_t
-write_file (Elf *elf, off_t size, int change_bo, size_t shnum)
+static int64_t
+write_file (Elf *elf, int64_t size, int change_bo, size_t shnum)
 {
   int class = elf->class;
 
@@ -164,11 +164,11 @@ write_file (Elf *elf, off_t size, int change_bo, size_t shnum)
 }
 
 
-off_t
+int64_t
 elf_update (Elf *elf, Elf_Cmd cmd)
 {
   size_t shnum;
-  off_t size;
+  int64_t size;
   int change_bo = 0;
 
   if (cmd != ELF_C_NULL
diff --git a/libelf/libelfP.h b/libelf/libelfP.h
index 51344142..b55d5c48 100644
--- a/libelf/libelfP.h
+++ b/libelf/libelfP.h
@@ -296,7 +296,7 @@ struct Elf
   int fildes;
 
   /* Offset in the archive this file starts or zero.  */
-  off_t start_offset;
+  int64_t start_offset;
 
   /* Size of the file in the archive or the entire file size, or ~0
      for an (yet) unknown size.  */
@@ -350,7 +350,7 @@ struct Elf
       int ehdr_flags;		/* Flags (dirty) for ELF header.  */
       int phdr_flags;		/* Flags (dirty|malloc) for program header.  */
       int shdr_malloced;	/* Nonzero if shdr array was allocated.  */
-      off_t sizestr_offset;	/* Offset of the size string in the parent
+      int64_t sizestr_offset;	/* Offset of the size string in the parent
 				   if this is an archive member.  */
       Elf32_Ehdr ehdr_mem;	/* Memory used for ELF header when not
 				   mmaped.  */
@@ -375,7 +375,7 @@ struct Elf
       int ehdr_flags;		/* Flags (dirty) for ELF header.  */
       int phdr_flags;		/* Flags (dirty|malloc) for program header.  */
       int shdr_malloced;	/* Nonzero if shdr array was allocated.  */
-      off_t sizestr_offset;	/* Offset of the size string in the parent
+      int64_t sizestr_offset;	/* Offset of the size string in the parent
 				   if this is an archive member.  */
       Elf64_Ehdr ehdr_mem;	/* Memory used for ELF header when not
 				   mmaped.  */
@@ -392,7 +392,7 @@ struct Elf
       char *long_names;		/* If no index is available but long names
 				   are used this elements points to the data.*/
       size_t long_names_len;	/* Length of the long name table.  */
-      off_t offset;		/* Offset in file we are currently at.
+      int64_t offset;		/* Offset in file we are currently at.
 				   elf_next() advances this to the next
 				   member of the archive.  */
       Elf_Arhdr elf_ar_hdr;	/* Structure returned by 'elf_getarhdr'.  */
@@ -445,7 +445,7 @@ extern Elf_Type __libelf_data_type (Elf *elf, int sh_type, GElf_Xword align)
 
 /* Create Elf descriptor from memory image.  */
 extern Elf *__libelf_read_mmaped_file (int fildes, void *map_address,
-				       off_t offset, size_t maxsize,
+				       int64_t offset, size_t maxsize,
 				       Elf_Cmd cmd, Elf *parent)
      internal_function;
 
@@ -467,10 +467,10 @@ extern int __libelf_set_rawdata_wrlock (Elf_Scn *scn) internal_function;
 
 
 /* Helper functions for elf_update.  */
-extern off_t __elf32_updatenull_wrlock (Elf *elf, int *change_bop,
-					size_t shnum) internal_function;
-extern off_t __elf64_updatenull_wrlock (Elf *elf, int *change_bop,
-					size_t shnum) internal_function;
+extern int64_t __elf32_updatenull_wrlock (Elf *elf, int *change_bop,
+					  size_t shnum) internal_function;
+extern int64_t __elf64_updatenull_wrlock (Elf *elf, int *change_bop,
+					  size_t shnum) internal_function;
 
 extern int __elf32_updatemmap (Elf *elf, int change_bo, size_t shnum)
      internal_function;
diff --git a/tests/ChangeLog b/tests/ChangeLog
index e0387939..9d15f8fa 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,3 +1,12 @@
+2019-06-18  Mark Wielaard  <mark@klomp.org>
+
+	* Makefile.am (TESTS): Add run-large-elf-file.sh.
+	(EXTRA_DIST): Likewise.
+	* addsections.c (add_sections): Add sec_size argument, use it
+	as the size of the section data.
+	(main): Handle extra sec_size argument. Pass to add_sections.
+	* run-large-elf-file.sh: New test.
+
 2019-06-03  Mark Wielaard  <mark@klomp.org>
 
 	* elfcopy.c (copy_elf): When swapping the sh_offsets of two sections,
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 87428aa7..3d95cf68 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -83,6 +83,7 @@ TESTS = run-arextract.sh run-arsymtest.sh run-ar.sh newfile test-nlist \
 	run-next-files.sh run-next-lines.sh \
 	run-get-pubnames.sh run-get-aranges.sh run-allfcts.sh \
 	run-show-abbrev.sh run-line2addr.sh hash \
+	run-large-elf-file.sh \
 	newscn run-strip-test.sh run-strip-test2.sh \
 	run-strip-test3.sh run-strip-test4.sh run-strip-test5.sh \
 	run-strip-test6.sh run-strip-test7.sh run-strip-test8.sh \
@@ -422,6 +423,7 @@ EXTRA_DIST = run-arextract.sh run-arsymtest.sh run-ar.sh \
 	     testfile-riscv64-core.bz2 \
 	     run-reverse-sections.sh run-reverse-sections-self.sh \
 	     run-copyadd-sections.sh run-copymany-sections.sh \
+	     run-large-elf-file.sh \
 	     run-typeiter-many.sh run-strip-test-many.sh \
 	     testfile-debug-rel-ppc64-g.o.bz2 \
 	     testfile-debug-rel-ppc64-z.o.bz2 \
diff --git a/tests/addsections.c b/tests/addsections.c
index cc8d0655..c1b0fa81 100644
--- a/tests/addsections.c
+++ b/tests/addsections.c
@@ -70,9 +70,9 @@ setshstrndx (Elf *elf, size_t ndx)
 /* Will add nr new '.extra' sections and a new '.new_shstrtab' section
    at the end.  */
 static void
-add_sections (const char *name, size_t nr, int use_mmap)
+add_sections (const char *name, size_t nr, int use_mmap, size_t sec_size)
 {
-  printf ("add_sections '%s': %zd\n", name, nr);
+  printf ("add_sections '%s': %zd (sec_size: %zd)\n", name, nr, sec_size);
 
   int fd = open (name, O_RDWR);
   if (fd < 0)
@@ -149,6 +149,25 @@ add_sections (const char *name, size_t nr, int use_mmap)
       exit (1);
     }
 
+  void *buf;
+  size_t bufsz;
+  if (sec_size == 0)
+    {
+      buf = strdup ("extra");
+      bufsz = strlen ("extra") + 1;
+    }
+  else
+    {
+      buf = malloc (sec_size);
+      if (buf == NULL)
+	{
+	  printf ("cannot allocate buffer data of %zd bytes\n", sec_size);
+	  exit (1);
+	}
+      memset (buf, 0xAA, sec_size);
+      bufsz = sec_size;
+    }
+
   // Add lots of .extra sections...
   size_t cnt = 0;
   while (cnt++ < nr)
@@ -169,8 +188,8 @@ add_sections (const char *name, size_t nr, int use_mmap)
 	  exit (1);
 	}
 
-      data->d_size = strlen ("extra") + 1;
-      data->d_buf = "extra";
+      data->d_size = bufsz;
+      data->d_buf = buf;
       data->d_type = ELF_T_BYTE;
       data->d_align = 1;
 
@@ -274,6 +293,7 @@ add_sections (const char *name, size_t nr, int use_mmap)
       exit (1);
     }
 
+  free (buf);
   free (new_shstrtab_buf);
 }
 
@@ -282,10 +302,11 @@ main (int argc, char *argv[])
 {
   elf_version (EV_CURRENT);
 
-  /* Takes the given file, and adds the given number of sections.  */
-  if (argc < 3 || argc > 4)
+  /* Takes the given file, and adds the given number of sections.
+     Optionally using mmap and optionally using a given section size.  */
+  if (argc < 3 || argc > 5)
     {
-      fprintf (stderr, "addsections [--mmap] nr elf.file\n");
+      fprintf (stderr, "addsections [--mmap] nr elf.file [sec_size]\n");
       exit (1);
     }
 
@@ -298,8 +319,13 @@ main (int argc, char *argv[])
     }
 
   size_t nr = atoi (argv[argn++]);
-  const char *file = argv[argn];
-  add_sections (file, nr, use_mmap);
+  const char *file = argv[argn++];
+
+  size_t sec_size = 0;
+  if (argn < argc)
+    sec_size = atol (argv[argn++]);
+
+  add_sections (file, nr, use_mmap, sec_size);
 
   return 0;
 }
diff --git a/tests/run-large-elf-file.sh b/tests/run-large-elf-file.sh
new file mode 100755
index 00000000..c244c602
--- /dev/null
+++ b/tests/run-large-elf-file.sh
@@ -0,0 +1,108 @@
+#! /bin/bash
+# Copyright (C) 2019 Red Hat, Inc.
+# This file is part of elfutils.
+#
+# This file is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# elfutils is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. $srcdir/test-subr.sh
+
+# Only run on 64bit systems, 32bit systems don't support > 4GB
+# ELF files.
+long_bit=$(getconf LONG_BIT)
+echo "long_bit: $long_bit"
+if test $long_bit -ne 64; then
+  echo "Only 64bit systems can create > 4GB ELF files"
+  exit 77
+fi
+
+# These tests need lots of disk space since they test files > 4GB.
+# Skip if there just isn't enough (2.5 * 4 = 10GB).
+space_available=$[$(stat -f --format="%a*%S" .)/(1024 * 1024 * 1024)]
+echo "space_available: $space_available"
+if test $space_available -lt 10; then
+  echo "Not enough disk space, need at least 10GB available"
+  exit 77
+fi
+
+# Make sure the files fit into memory, assume 6GB needed (2.5 * 2 + 1 extra).
+mem_available=$(free -g | grep ^Mem: | awk -F ' +' '{print $7}')
+echo "mem_available: $mem_available"
+if test $mem_available -lt 6; then
+  echo "Need at least 6GB free available memory"
+  exit 77
+fi
+
+# Make sure the disk is reasonably fast, should be able to write 100MB/s
+fast_disk=1
+timeout -s9 10s dd conv=fsync if=/dev/zero of=tempfile bs=1M count=1K \
+  || fast_disk=0; rm tempfile
+if test $fast_disk -eq 0; then
+  echo "File system not fast enough, need at least 100MB/s"
+  exit 77
+fi
+
+# NOTE: test file will be mangled and removed!
+test_file ()
+{
+  in_file="$1"
+  readelf_out="${in_file}.readelf.out"
+  out_file_strip="${in_file}.strip"
+  out_file_debug="${in_file}.debug"
+
+  testfiles ${in_file}
+  tempfiles ${readelf_out} ${out_file_mmap} ${out_file_strip} ${out_file_debug}
+
+  # Add two 2GB sections to the file.
+  echo "addsections 2 ${in_file} 2147483648"
+  testrun ${abs_builddir}/addsections 2 ${in_file} 2147483648
+  testrun ${abs_top_builddir}/src/readelf -S ${in_file} > ${readelf_out}
+  nr=$(grep '.extra' ${readelf_out} | wc -l)
+  if test ${nr} != 2; then
+    # Show what went wrong
+    cat ${readelf_out}
+    exit 1
+  fi
+
+  echo "strip -o ${out_file_strip} -f ${out_file_debug} ${in_file}"
+  testrun ${abs_top_builddir}/src/strip -o ${out_file_strip} \
+                                        -f ${out_file_debug} ${in_file}
+
+  echo "elflint --gnu ${out_file_strip}"
+  testrun ${abs_top_builddir}/src/elflint --gnu ${out_file_strip}
+
+  echo "elflint --gnu -d ${out_file_debug}"
+  testrun ${abs_top_builddir}/src/elflint --gnu -d ${out_file_debug}
+
+  # Now test unstrip recombining those files.
+  echo "unstrip ${out_file_strip} ${out_file_debug}"
+  testrun ${abs_top_builddir}/src/unstrip ${out_file_strip} ${out_file_debug}
+
+  echo "elfcmp ${out_file} ${out_file_strip}"
+  testrun ${abs_top_builddir}/src/elfcmp ${in_file} ${out_file_debug}
+
+  # Remove the temp files immediately, they are big...
+  rm -f ${in_file} ${out_file_strip} ${out_file_debug}
+}
+
+# A collection of random testfiles to test 64bit, little/big endian
+# and non-ET_REL (with phdrs)/ET_REL (without phdrs).
+# Don't test 32bit, they cannot go beyond 4GB.
+
+# 64bit, little endian, rel
+test_file testfile38
+
+# 64bit, big endian, non-rel
+test_file testfile27
+
+exit 0