cjj66619 opened a new pull request, #18888:
URL: https://github.com/apache/nuttx/pull/18888
… host
boards/sim: skip -no-pie on HOST_ARM64 to fix sim:nsh link on aarch64 host
boards/sim/sim/sim/scripts/Make.defs adds `-no-pie` to ARCHCFLAGS /
ARCHPICFLAGS / LDFLAGS for every 64-bit non-Mac sim build. The original
comment ("To compile 64-bit Sim, adding no-pie is necessary to prevent linking
errors but this may cause other issues on Ubuntu 20.") already flagged the
workaround as fragile.
On HOST_ARM64 the option is in fact actively harmful. When gcc is asked to
produce a non-PIE executable on aarch64 it switches the libgcc resolution path
from the dynamic library
`libgcc_s.so.1` to the static archive `libgcc_s.a`. Ubuntu's arm64
toolchain (and Debian / Raspbian arm64) **does not ship** `libgcc_s.a` (only
`libgcc_s.so.1`), so the link aborts with:
/usr/bin/ld: cannot find -lgcc_s
/usr/bin/ld: cannot find -lgcc_s (push-state / as-needed both fail)
collect2: error: ld returned 1 exit status
`ld --verbose` shows ld searching 20+ paths for `libgcc_s.a`, finding only
`libgcc_s.so` (a linker script pointing at `libgcc_s.so.1`) which is invalid in
non-PIE mode.
x86_64 Linux is unaffected because Ubuntu ships the static `libgcc_s.a` (or
a compatible static-fallback library) in its amd64 libgcc-N-dev packaging.
macOS, Windows and Cygwin go through completely different code paths and never
reach this branch.
Gate the existing `-no-pie` block with `ifneq ($(CONFIG_HOST_ARM64),y)` so
aarch64 hosts fall through to gcc's default PIE-aware link path, which works
correctly. The default text-segment placement `-Ttext-segment=0x40000000` and
`-Wl,--gc-sections` (set in the common LDFLAGS just above this block) are
honored regardless of PIE / non-PIE.
Verified on NVIDIA Jetson Orin (Ubuntu 20.04 L4T, GCC 9.4) and Raspberry Pi
4B (Debian 13 trixie, GCC 14.2):
$ ./build.sh sim:nsh -j$(nproc)
$ ./nuttx
NuttShell (NSH)
nsh> ostest
... [38 user_main stages, 14 PASS, 0 FAIL] ...
ostest_main: Exiting with status 0
x86_64 Linux behaviour is unchanged (the `ifneq` is false there, so the
block is taken exactly as before).
Companion patch: arch/sim: rename nuttx libc memchr to avoid host glibc
collision (independent fix needed on the same aarch64 hosts).
# Summary
`boards/sim/sim/sim/scripts/Make.defs` unconditionally adds `-no-pie` /
`-Wl,-no-pie` to every 64-bit non-macOS sim build (line 322-328). The block's
own comment already flags it as fragile: _"To compile 64-bit Sim, adding no-pie
is necessary to prevent linking errors but **this may cause other issues on
Ubuntu 20.**"_ On **Ubuntu / Debian aarch64 hosts** this workaround is in fact
actively broken — the build cannot link because gcc switches to looking for the
static `libgcc_s.a` library which the Ubuntu/Debian arm64 toolchain does not
ship.
This PR gates the existing `-no-pie` block on `!CONFIG_HOST_ARM64`,
restoring sim:nsh build / run capability on aarch64 Linux hosts. x86_64
behaviour is byte-identical.
## Impact
- Affects every sim defconfig (`sim:nsh`, `sim:nsh2`, `sim:smp`,
`sim:bluetooth`, `sim:binder`, `sim:matter`, ...) on a Linux **aarch64** host.
- Concrete environments reproduced: Ubuntu 20.04 L4T (NVIDIA Jetson Orin)
and Debian 13 trixie (Raspberry Pi 4B).
- ARM64-based developer workstations (Apple M1/M2 running Linux VMs, Ampere
Altra, AWS Graviton, etc.) are also affected.
## Root Cause
1. `Make.defs:322-328` adds `ARCHCFLAGS += -no-pie`, `ARCHPICFLAGS +=
-no-pie`, `LDFLAGS += -Wl,-no-pie` whenever (a) sim is 64-bit, (b) host is not
macOS.
2. `-no-pie` causes gcc's collect2 spec to inject the libgcc resolution from
the **non-PIE** branch of the spec — which on aarch64 attempts to link against
the **static** `libgcc_s.a`.
3. Ubuntu / Debian arm64 packaging ships **only** the dynamic library
(`libgcc_s.so.1`) and a linker-script alias
(`/usr/lib/gcc/aarch64-linux-gnu/9/libgcc_s.so` → `GROUP ( libgcc_s.so.1 -lgcc
)`). There is no `libgcc_s.a`.
4. The link fails with `cannot find -lgcc_s` after ld searches 20+ standard
paths.
```
$ cc -v -fno-pic -mcmodel=large -Wl,-no-pie -o dummy dummy.c
... (collect2 invocation includes -lgcc_s but ld can't find static .a)
/usr/bin/ld: cannot find -lgcc_s
/usr/bin/ld: cannot find -lgcc_s
collect2: error: ld returned 1 exit status
```
Same `cc` command without `-Wl,-no-pie` succeeds and produces a valid PIE
executable.
## Fix
Wrap the existing 3-line block in `ifneq ($(CONFIG_HOST_ARM64),y)`, with a
comment explaining the aarch64-host packaging mismatch:
```
else ifeq ($(CONFIG_HOST_MACOS),)
+ifneq ($(CONFIG_HOST_ARM64),y)
# To compile 64-bit Sim, adding no-pie is necessary to prevent linking
errors
# but this may cause other issues on Ubuntu 20.
+ # NOTE: On HOST_ARM64 (Ubuntu aarch64), -no-pie forces ld to look for the
+ # static libgcc_s.a which is not packaged on Ubuntu's arm64 toolchain
+ # (only the shared libgcc_s.so.1 ships). Skipping -no-pie lets gcc use
+ # the default PIE link path which works correctly on aarch64.
ARCHCFLAGS += -no-pie
ARCHPICFLAGS += -no-pie
LDFLAGS += -Wl,-no-pie
endif
+endif
```
After the patch aarch64 hosts fall through to gcc's default PIE link path,
which works correctly. The default text-segment placement
`-Ttext-segment=0x40000000` and `-Wl,--gc-sections` (set in the common LDFLAGS
above) are honored regardless of PIE / non-PIE.
## Test results
| Platform | Status |
|---|---|
| NVIDIA Jetson Orin (Ubuntu 20.04 L4T aarch64, GCC 9.4) | `sim:nsh` clean
build, NSH prompt, 18.2 ms median boot, `ostest` 38 stages PASS |
| Raspberry Pi 4B (Debian 13 trixie aarch64, GCC 14.2) | Jetson binary
cross-runs ✅, `ostest` 38 stages PASS |
| x86_64 Linux | `ifneq` is false → block taken unchanged → behaviour
byte-identical |
Detailed reproduction log + ld trace + bytecount diff in
[`test-report.md`](test-report.md).
## Companion patch
This patch alone is not sufficient to build `sim:nsh` on Ubuntu aarch64
hosts; the `nuttx.rel` link also collides on the unrenamed nuttx-libc `memchr`.
See companion PR: **`arch/sim: rename nuttx libc memchr to avoid host glibc
collision`** (single-line addition to `arch/sim/src/nuttx-names.in`).
The two PRs are independently mergeable — each fix is a strict subset
narrowing of an existing failure mode — but on aarch64 hosts you need both to
get a working sim binary.
## checkpatch
`tools/checkpatch.sh -f boards/sim/sim/sim/scripts/Make.defs` → ✔️ All
checks pass.
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