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| -rw-r--r-- | README | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/README b/README index 2e360eb70a..061818d51b 100644 --- a/README +++ b/README @@ -1,3 +1,72 @@ +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. |