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GNU C Library master sources
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The target specific internal __longjmp is called with a __jmp_buf argument which has its size exposed in the ABI. On aarch64 this has no space left, so GCSPR cannot be restored in longjmp in the usual way, which is needed for the Guarded Control Stack (GCS) extension. setjmp is implemented via __sigsetjmp which has a jmp_buf argument however it is also called with __pthread_unwind_buf_t argument cast to jmp_buf (in cancellation cleanup code built with -fno-exception). The two types, jmp_buf and __pthread_unwind_buf_t, have common bits beyond the __jmp_buf field and there is unused space there which we can use for saving GCSPR. For this to work some bits of those two generic types have to be reserved for target specific use and the generic code in glibc has to ensure that __longjmp is always called with a __jmp_buf that is embedded into one of those two types. Morally __longjmp should be changed to take jmp_buf as argument, but that is an intrusive change across targets. Note: longjmp is never called with __pthread_unwind_buf_t from user code, only the internal __libc_longjmp is called with that type and thus the two types could have separate longjmp implementations on a target. We don't rely on this now (but might in the future given that cancellation unwind does not need to restore GCSPR). Given the above this patch finds an unused slot for GCSPR. This placement is not exposed in the ABI so it may change in the future. This is also very target ABI specific so the generic types cannot be easily changed to clearly mark the reserved fields. Reviewed-by: Carlos O'Donell <carlos@redhat.com> Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com> |
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| configure | ||
| configure.ac | ||
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| extra-lib.mk | ||
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| version.h | ||
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 and x86_64-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 loongarch64-*-linux-gnu Hardware floating point, LE only. 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.