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[PATCH 0/8] ELF unexec (bug#20614)

From: Alan Modra
Subject: [PATCH 0/8] ELF unexec (bug#20614)
Date: Mon, 2 Nov 2015 12:23:34 +1030
User-agent: Mutt/1.5.23 (2014-03-12)

This series of patches addresses bug #20614 by rewriting the bss
handling code rather than adding yet more hacks.  Finding bss sections
by name as we do currently results in complicated code that
- does not account for all names of possible bss sections,
- assumes specific ordering of bss sections,
- can wrongly choose a SHT_NOBITS section not in the bss segment,
- incorrectly calculates bss size (no accounting for alignment gaps),
- assumes .data and .bss are in the same segment.

All of these problems and more are solved by finding the bss segment
in PT_LOAD headers, ie. the address range included in p_memsz but not
p_filesz of the last PT_LOAD header, then matching SHT_NOBITS sections
in that address range.

I've split the patch into a series as there are multiple problems of
varying severity in this code, and it might be a little easier to
review this way.  The series was tested indiviually on x86_64-linux
and on powerpc64-linux and powerpc64le-linux after fixing bug #20614
with patch 7/8.

Patch 8/8 goes further and removes the added .data2 section.  I don't
see any need for a new SHT_PROGBITS section to cover the old bss
section(s) plus dumped data.  Not adding a section means there is no
need to patch symbol st_shndx or section sh_info and sh_link fields,
which is fragile code.  At least, sh_info shouldn't really be patched
unless SHF_INFO_LINK is set in sh_flags, but not all linkers set the
flag properly.

Alan Modra (8):
  ELF unexec: Correct section header index
  ELF unexec: Tidy code
  ELF unexec: Merge Alpha and MIPS COFF debug handling
  ELF unexec: Symbol table patching
  ELF unexec: _OBJC_ symbols in bss sections
  ELF unexec: R_*_NONE relocs
  ELF unexec: Drive from PT_LOAD header rather than sections
  ELF unexec: Don't insert a new section

 src/unexelf.c | 1022 ++++++++++++---------------------------------------------
 1 file changed, 206 insertions(+), 816 deletions(-)

Alan Modra
Australia Development Lab, IBM

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