* Don't write zeros to a gap in the output file
@ 2023-03-02 12:01 Alan Modra
0 siblings, 0 replies; only message in thread
From: Alan Modra @ 2023-03-02 12:01 UTC (permalink / raw)
To: binutils
Writing out zeros is counterproductive if a file system supports
sparse files. A very large gap need not take much actual disk space,
but it usually will if zeros are written.
memory_bseek also supports not writing out zeros in a gap.
* elf.c (write_zeros): Delete.
(assign_file_positions_for_load_sections): Don't call write_zeros.
Comment.
diff --git a/bfd/elf.c b/bfd/elf.c
index 37f331b98cd..409be7068ec 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -5402,22 +5402,6 @@ print_segment_map (const struct elf_segment_map *m)
fflush (stderr);
}
-static bool
-write_zeros (bfd *abfd, file_ptr pos, bfd_size_type len)
-{
- void *buf;
- bool ret;
-
- if (bfd_seek (abfd, pos, SEEK_SET) != 0)
- return false;
- buf = bfd_zmalloc (len);
- if (buf == NULL)
- return false;
- ret = bfd_bwrite (buf, len, abfd) == len;
- free (buf);
- return ret;
-}
-
/* Assign file positions to the sections based on the mapping from
sections to segments. This function also sets up some fields in
the file header. */
@@ -5866,11 +5850,13 @@ assign_file_positions_for_load_sections (bfd *abfd,
if (p->p_filesz + adjust < p->p_memsz)
{
/* We have a PROGBITS section following NOBITS ones.
- Allocate file space for the NOBITS section(s) and
- zero it. */
+ Allocate file space for the NOBITS section(s).
+ We don't need to write out the zeros, posix
+ fseek past the end of data already written
+ followed by a write at that location is
+ guaranteed to result in zeros being read
+ from the gap. */
adjust = p->p_memsz - p->p_filesz;
- if (!write_zeros (abfd, off, adjust))
- return false;
}
}
/* We only adjust sh_offset in SHT_NOBITS sections
--
Alan Modra
Australia Development Lab, IBM
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