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When an executable is invoked as ./ld.so [ld.so-args] ./exe [exe-args] then the argv is adujusted in ld.so before calling the entry point of the executable so ld.so args are not visible to it. On most targets this requires moving argv, env and auxv on the stack to ensure correct stack alignment at the entry point. This had several issues: - The code for this adjustment on the stack is written in asm as part of the target specific ld.so _start code which is hard to maintain. - The adjustment is done after _dl_start returns, where it's too late to update GLRO(dl_auxv), as it is already readonly, so it points to memory that was clobbered by the adjustment. This is bug 23293. - _environ is also wrong in ld.so after the adjustment, but it is likely not used after _dl_start returns so this is not user visible. - _dl_argv was updated, but for this it was moved out of relro, which changes security properties across targets unnecessarily. This patch introduces a generic _dl_start_args_adjust function that handles the argument adjustments after ld.so processed its own args and before relro protection is applied. The same algorithm is used on all targets, _dl_skip_args is now 0, so existing target specific adjustment code is no longer used. The bug affects aarch64, alpha, arc, arm, csky, ia64, nios2, s390-32 and sparc, other targets don't need the change in principle, only for consistency. The GNU Hurd start code relied on _dl_skip_args after dl_main returned, now it checks directly if args were adjusted and fixes the Hurd startup data accordingly. Follow up patches can remove _dl_skip_args and DL_ARGV_NOT_RELRO. Tested on aarch64-linux-gnu and cross tested on i686-gnu. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This directory contains the sources of the GNU C Library. See the file "version.h" for what release version you have. The GNU C Library is the standard system C library for all GNU systems, and is an important part of what makes up a GNU system. It provides the system API for all programs written in C and C-compatible languages such as C++ and Objective C; the runtime facilities of other programming languages use the C library to access the underlying operating system. In GNU/Linux systems, the C library works with the Linux kernel to implement the operating system behavior seen by user applications. In GNU/Hurd systems, it works with a microkernel and Hurd servers. The GNU C Library implements much of the POSIX.1 functionality in the GNU/Hurd system, using configurations i[4567]86-*-gnu. When working with Linux kernels, this version of the GNU C Library requires Linux kernel version 3.2 or later. Also note that the shared version of the libgcc_s library must be installed for the pthread library to work correctly. The GNU C Library supports these configurations for using Linux kernels: aarch64*-*-linux-gnu alpha*-*-linux-gnu arc*-*-linux-gnu arm-*-linux-gnueabi csky-*-linux-gnuabiv2 hppa-*-linux-gnu i[4567]86-*-linux-gnu x86_64-*-linux-gnu Can build either x86_64 or x32 ia64-*-linux-gnu m68k-*-linux-gnu microblaze*-*-linux-gnu mips-*-linux-gnu mips64-*-linux-gnu or1k-*-linux-gnu powerpc-*-linux-gnu Hardware or software floating point, BE only. powerpc64*-*-linux-gnu Big-endian and little-endian. s390-*-linux-gnu s390x-*-linux-gnu riscv32-*-linux-gnu riscv64-*-linux-gnu sh[34]-*-linux-gnu sparc*-*-linux-gnu sparc64*-*-linux-gnu If you are interested in doing a port, please contact the glibc maintainers; see https://www.gnu.org/software/libc/ for more information. See the file INSTALL to find out how to configure, build, and install the GNU C Library. You might also consider reading the WWW pages for the C library at https://www.gnu.org/software/libc/. The GNU C Library is (almost) completely documented by the Texinfo manual found in the `manual/' subdirectory. The manual is still being updated and contains some known errors and omissions; we regret that we do not have the resources to work on the manual as much as we would like. For corrections to the manual, please file a bug in the `manual' component, following the bug-reporting instructions below. Please be sure to check the manual in the current development sources to see if your problem has already been corrected. Please see https://www.gnu.org/software/libc/bugs.html for bug reporting information. We are now using the Bugzilla system to track all bug reports. This web page gives detailed information on how to report bugs properly. The GNU C Library is free software. See the file COPYING.LIB for copying conditions, and LICENSES for notices about a few contributions that require these additional notices to be distributed. License copyright years may be listed using range notation, e.g., 1996-2015, indicating that every year in the range, inclusive, is a copyrightable year that would otherwise be listed individually.