[springmin]

Summary

OpenHarmony's seccomp policy traps close_range() with SIGSYS, so
Process.Start with handle-inheritance restrictions dies before a fallback can
run. Skip the libc function and the raw-syscall paths on TARGET_OPENHARMONY
and set FD_CLOEXEC on the open descriptors by listing /proc/self/fd.

Changes

• src/native/libs/System.Native/pal_process.c: add !defined(TARGET_OPENHARMONY)
  to both close_range branches of RestrictHandleInheritance; on OpenHarmony
  the function calls SetCloexecForAllFdsFallback() instead.
• The fallback reads /proc/self/fd with getdents64 into a stack buffer (it
  runs in the forked child, where malloc is not safe) and sets FD_CLOEXEC on
  the descriptors it finds. The already-existing bounded RLIMIT_NOFILE scan
  remains the fallback for when the listing cannot be read completely.
• One file, 171 insertions and 8 deletions.

Impact

• OpenHarmony only. Every other target keeps the upstream close_range paths
  and upstream's ENOTSUP result when neither close_range nor fdwalk is
  available.
• Shared helpers are factored so the fdwalk callback and the /proc/self/fd
  walk use the same per-descriptor routine; behavior on Illumos/Solaris is
  unchanged.

Validation

• pal_process.c compiles for openharmony-arm64 with the OHOS NDK clang
  (--target=aarch64-linux-ohos, -Weverything), no warnings.

Test

1. Build System.Native for openharmony-arm64 (this defines
   TARGET_OPENHARMONY).
2. On the device, start a child process with ProcessStartInfo.InheritedHandles
   configured; the child should exec, the inherited handles should survive, and
   the other descriptors should be close-on-exec.

Note

This PR was authored with AI assistance (agent tooling) under the author's direction.

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[springmin]

Superseded by #136194, which consolidates the remaining native-libs fixes and includes device validation (hello world, child process start, network interfaces, RSA/TLS through the OpenSSL shim).

Note

This comment was drafted with AI assistance (agent tooling) under the author's direction.