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
* sysdeps/hppa/start.S (_start): Check PIC instead of SHARED. Load
address of $global$ into %dp register earlier. Use pc-relative
instruction sequence for PIC case.
The patched change fixes a regression for executables compiled with the
-p option and linked with gcrt1.o. The executables crash on startup.
This regression was introduced in 2.22 and was noticed in the gcc testsuite.
The definition of SHARED is tested with #ifdef pretty much everywhere
apart from these few places. The tlsdesc.c code seems to be copy and
pasted to a few architectures and there is one instance in the hppa
startup code.
ChangeLog:
2014-07-09 Will Newton <will.newton@linaro.org>
* sysdeps/aarch64/tlsdesc.c (_dl_unmap): Test SHARED with #ifdef.
* sysdeps/arm/tlsdesc.c (_dl_unmap): Likewise.
* sysdeps/i386/tlsdesc.c (_dl_unmap): Likewise.
* sysdeps/x86_64/tlsdesc.c (_dl_unmap): Likewise.
* sysdeps/hppa/start.S (_start): Likewise.
