It turns out the startup code in csu/elf-init.c has a perfect pair of
ROP gadgets (see Marco-Gisbert and Ripoll-Ripoll, "return-to-csu: A
New Method to Bypass 64-bit Linux ASLR"). These functions are not
needed in dynamically-linked binaries because DT_INIT/DT_INIT_ARRAY
are already processed by the dynamic linker. However, the dynamic
linker skipped the main program for some reason. For maximum
backwards compatibility, this is not changed, and instead, the main
map is consulted from __libc_start_main if the init function argument
is a NULL pointer.
For statically linked binaries, the old approach based on linker
symbols is still used because there is nothing else available.
A new symbol version __libc_start_main@@GLIBC_2.34 is introduced because
new binaries running on an old libc would not run their ELF
constructors, leading to difficult-to-debug issues.
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master
Since __libc_start_main may not be in the same 256MB-aligned region as
the function __start, replace use of jal instruction with la/jalr.
This fixes linker issue reported in:
https://sourceware.org/bugzilla/show_bug.cgi?id=17601
[BZ #17601]
* sysdeps/mips/start.S (__start): Use indirect jump to call
__libc_start_main.
I've moved the MIPS port from ports to the main sysdeps hierarchy.
Beyond the README update, the move of the files was simply
git mv ports/sysdeps/mips sysdeps/mips
git mv ports/sysdeps/unix/mips sysdeps/unix/mips
git mv ports/sysdeps/unix/sysv/linux/mips sysdeps/unix/sysv/linux/mips
and in addition to the ChangeLog entries here, I put a note at the top
of ports/ChangeLog.mips similar to those in other files.
Tested that disassembly of installed shared libraries for mips is the
same before and after this patch (except for ld.so where paths in
assertions are involved, as for arm).
* sysdeps/mips: Move directory from ports/sysdeps/mips.
* sysdeps/unix/mips: Move directory from ports/sysdeps/unix/mips.
* sysdeps/unix/sysv/linux/mips: Move directory from
ports/sysdeps/unix/sysv/linux/mips.
* README: Update listing for mips-*-linux-gnu and
mips64-*-linux-gnu.
* sysdeps/mips: Move directory to ../sysdeps/mips.
* sysdeps/unix/mips: Move directory to ../sysdeps/unix/mips.
* sysdeps/unix/sysv/linux/mips: Move directory to
../sysdeps/unix/sysv/linux/mips.
