Planning to update to supporting GCC 9 as found in GNU Tools for Arm
Embedded Processors 9-2019q4-major.
Newer GCC in particular supports ARMv8-M security extensions, and
link-time optimisation - two areas of interest.
Should be no code changes required, but need to change the warning in
the toolchain script.
Change the heuristic for selection of CMSE in the tools python, so that
a non-TrustZone ARMv8 build can happen.
Ideally we would have more direct flagging in the targets, but this
refines the heuristic so the necessary behaviour can be easily
achieved.
* DOMAIN_NS=1 is based purely on the `-NS` suffix on the core name.
* Enabling CMSE in the compiler and outputting a secure import library
is now enabled when the core doesn't have an `-NS` suffix by either
the target label `TFM` being present or the flag `trustzone` being set.
This covers the existing ARMv8-M behaviour - TF-M builds have the TFM
label, as per its documentation; M2351 secure builds have no explicit
flagging, so we ensure that the M2351_NS target has the trustzone flag
set, and the out-of-tree secure target inherits that.
* For ARMC6, core types `Cortex-M4` and `Cortex-M7` did not explicitly
add `--fpu=none`, so it defaulted to assuming FPU present. This would
cause a compilation error if the target's cmsis.h had `__FPU_PRESENT`
defined to 0.
* For GCC, `Cortex-M33FE` did not include `+dsp` in the architecture
selection.
* For ARMC5 and ARMC6, `Cortex-M0+` did not pass `M0plus` to the
non-Clang tools.
The "hook tools" were capable of hooking into many commands run by the build system.
To my knowlage, the only hook is the "post-build-hook". The post build hook could be
easier to reason about if the implementation is specialized for just post-build
hooking.
This commit make it much easier to point out where post build hooks are called by
making the call explicit.
Cortex v8 architecture based devices support secure/non-secure builds.
Secure build should generate the object file/library from elf during link
process which is used by non-secure binary during linking.
--out-implib=file specifies output library in which symbols are exported
--cmse-implib requests libraries mentioned above are secure gateway
libraries
Creation of secure library is done as part of linking process in GCC/ARMC6/IAR
Non-Secure project should add this secure object file as part of the
linking process.
Secure library is named as cmse_lib.o.