hujun260 opened a new pull request, #21748:
URL: https://github.com/apache/nuttx/pull/21748
# NuttX PR Description
## Title
arm64: optimize startup by skipping zero-BSS initialization
## Description
This PR contains the following two commits:
1. **ARM64: Add `ARCH_SKIP_ZERO_BSS` option**
- Add the generic `ARCH_SKIP_ZERO_BSS` Kconfig option.
- Allow architectures and startup code to skip explicit zeroing of the BSS
section when the boot environment already guarantees the required memory
state.
- Add the startup guard to ARM, ARMv7-A, ARMv7-R, ARMv8-R, ARM64, MPS,
RISC-V QEMU, x86_64 Intel64, ESP32, ESP32-S2, and ESP32-S3 startup
paths.
- Reduce boot time by avoiding unnecessary BSS initialization.
2. **arm64: Remove `arm64_earlyprintinit`**
- Remove the obsolete `arm64_earlyprintinit` path.
- Clean up the ARM64 common startup code and platform-specific low-level
UART
initialization code.
- Update A64, FVP-v8R, Goldfish, i.MX8, i.MX9, QEMU, RK3399, and Zynq
MPSoC startup paths.
- Preserve the existing early-console behavior through the remaining
platform initialization paths.
## Motivation
Reduce ARM64 and multi-architecture boot overhead by avoiding redundant BSS
zeroing and remove an obsolete ARM64 early-print initialization mechanism.
The
changes simplify startup code while preserving normal console and application
startup behavior.
## Runtime and Build Testing
The ARM64 QEMU `nsh` configuration was built with CMake and Ninja using the
GNU Arm Embedded toolchain.
### Build log
```text
-- Board: qemu-armv8a
-- Config: nsh
-- The C compiler identification is GNU 13.2.1
-- Found assembler: arm-none-eabi-gcc
-- Configuring done
-- Generating done
-- Build files have been written to: build
[1328/1328] Linking CXX executable final_nuttx
Memory region Used Size Region Size %age Used
ROM: 373960 B 1 MB 35.66%
RAM: 28 KB 16 MB 0.17%
```
The build completed successfully. The linker emitted only the existing RWX
LOAD segment warning.
### QEMU startup log
```text
qemu-system-arm -cpu cortex-a7 -semihosting \
-M virt,virtualization=off,gic-version=2 -m 1024 -nographic \
-kernel ./build/nuttx
nsh>
```
### ARMv7-A `ostest`
```text
nsh> ostest
stdio_test: Standard I/O Check: printf
ostest_main: Started user_main at PID=6
user_main: vfork() test
vfork_test: Child 7 ran and exited before the parent resumed
user_main: FPU test
FPU#1: Succeeded
FPU#2: Succeeded
user_main: wqueue test
wqueue_test: backend = flat
wqueue_test: HPWORK done
wqueue_test: custom queue, threads = 1 done
wqueue_test: custom queue, threads = 2 done
wqueue_test: multiple custom queues done
wqueue_test: teardown done
user_main: mutex test
mutex_test: PASSED
user_main: signal handler test
sighand_test: SUCCESS
user_main: nested signal handler test
signest_test: done
user_main: priority inheritance test
priority_inheritance: PASSED Priority were correctly restored.
priority_inheritance: Finished
user_main: scheduler lock test
sched_lock: PASSED No pre-emption occurred while scheduler was locked.
sched_lock: Finished
Final memory usage:
VARIABLE BEFORE AFTER
======== ======== ========
arena ff3ffc ff3ffc
ordblks 2 7
mxordblk fec130 fd5460
uordblks 7d94 7ed4
fordblks fec268 fec128
user_main: Exiting
ostest_main: Exiting with status 0
nsh>
```
## Testing Status
- [x] Built with the ARM64 QEMU `nsh` configuration.
- [x] Booted the resulting image under QEMU.
- [x] ARMv7-A `ostest` completed with status 0.
- [x] FPU, vfork, work queue, mutex, signal, priority inheritance, and
scheduler-lock tests completed successfully.
- [ ] Measured boot-time improvement across all affected architectures.
- [ ] Tested all secure and non-secure ARM64 platform variants.
## Commits
- `2c768c4c098a8a73a996ce67e4fa093446652a09` ARM64: add ARCH_SKIP_ZERO_BSS
option
- `3d4aea9413b1d82e7c746c8ff522fb195f207892` arm64: remove
arm64_earlyprintinit
## Change Summary
The two commits modify 21 files with 68 insertions and 97 deletions.
Signed-off-by: sunjikun <[email protected]>
Signed-off-by: hujun5 <[email protected]>
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