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this branch contains experimental GCS support (not ABI stable)
source and branches
-------------------
binutils-gdb: upstream-git users/ARM/gcs-binutils-gdb-master
gcc (trunk): upstream-git vendors/ARM/gcs
gcc (gcc-13): upstream-git vendors/ARM/gcs-13
note: gcc vendor branches need setup https://gcc.gnu.org/gitwrite.html#vendor
glibc: upstream-git arm/gcs
linux: https://git.kernel.org/pub/scm/linux/kernel/git/broonie/misc.git arm64-gcs
fvp fast model can be used for testing.
toolchain build
---------------
two options:
(1) branch-protect by default
configure gcc with --enable-standard-branch-protection
and build glibc normally
(2) do not branch-protect by default, require explicit cflags
configure gcc with
CFLAGS_FOR_TARGET='-O2 -mbranch-protection=standard'
CXXFLAGS_FOR_TARGET='-O2 -mbranch-protection=standard'
and configure glibc with
CFLAGS='-g -O2 -mbranch-protection=standard'
build user code with
CFLAGS+=-mbranch-protection=standard
(equivalent to -mbranch-protection=bti+pac+gcs)
linking
-------
use ldflags:
-z experimental-gcs={always,never,implicit}
always: force GCS marking on
never: force GCS marking off
implicit: mark output if all inputs are marked (default)
-z experimental-gcs-report={none,warning,error}
none: silent (default)
warning: when output is marked, unmarked input is a warning
error: when output is marked, unmarked input is an error
runtime
-------
run with environment var
GLIBC_TUNABLES=glibc.cpu.aarch64_gcs=1:glibc.cpu.aarch64_gcs_policy=2
by default both tunables are 0, the meaning is
glibc.cpu.aarch64_gcs_policy=0:
GCS is enabled if glibc.cpu.aarch64_gcs is set
glibc.cpu.aarch64_gcs_policy=1:
GCS is enabled if glibc.cpu.aarch64_gcs is set and binary is marked
if GCS is enabled an incompatible dlopen is an error
glibc.cpu.aarch64_gcs_policy=2:
GCS is enabled if glibc.cpu.aarch64_gcs is set
if GCS is enabled any incompatible binary is an error
original readme
---------------
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.
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