f015be63ec
Build #10 failed with: ld.lld: error: duplicate symbol: pthread_create >>> defined at pthread_shim.c:30 >>> ... in archive libpthread_shim.a (the other definition coming from libstd's bundled libc.a stub) The raw-symbol-override approach was naive: when two static archives both define the same symbol the linker refuses instead of picking one. Switch to GNU-ld's `--wrap=pthread_create` mechanism: - All `pthread_create` references get rewritten to `__wrap_pthread_create` - Our shim now defines `__wrap_pthread_create` (no symbol clash) - Inside the shim we `dlopen("libc.so")` + `dlsym("pthread_create")` to get the real runtime symbol directly, bypassing BOTH the broken static stub (libstd's libc.a copy) AND libstd's own pthread_create path - `--real_pthread_create` is deliberately NOT used — it would alias the same broken stub the wrap exists to avoid The wrap flag is emitted via `cargo:rustc-link-arg` in build.rs so it only affects the Android target (the Android-branch of build.rs is the only place that emits it). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
55 lines
2.1 KiB
C
55 lines
2.1 KiB
C
/* pthread_shim.c
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*
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* Interpose pthread_create via linker --wrap to bypass Rust libstd's broken
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* static pthread_create stub (pulled in from an old NDK libc.a), which
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* transitively calls __init_tcb+4 and SIGSEGVs in any .so loaded via dlopen.
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*
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* Link flags (see build.rs):
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* -Wl,--wrap=pthread_create
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*
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* The wrap flag makes the linker redirect every unresolved reference to
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* `pthread_create` → `__wrap_pthread_create` (below). Inside the shim we
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* explicitly open libc.so and look up the real, fully working runtime
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* pthread_create, bypassing libstd's bundled archive entirely.
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*
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* We deliberately do NOT call `__real_pthread_create` — that alias is the
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* SAME broken stub the wrap is designed to get around.
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*/
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#ifdef __ANDROID__
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#define _GNU_SOURCE
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#include <dlfcn.h>
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#include <pthread.h>
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#include <stddef.h>
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typedef int (*pthread_create_fn)(pthread_t *, const pthread_attr_t *,
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void *(*)(void *), void *);
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int __wrap_pthread_create(pthread_t *thread, const pthread_attr_t *attr,
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void *(*start_routine)(void *), void *arg) {
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static pthread_create_fn real = NULL;
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if (real == NULL) {
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/* Explicitly open libc.so and fetch the runtime pthread_create.
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* RTLD_NOLOAD would be wrong here — we want the mapping even if
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* bionic already loaded libc. The standard filename "libc.so" is
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* safe on Android; bionic's dynamic linker resolves it to
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* /apex/com.android.runtime/lib64/bionic/libc.so at runtime. */
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void *libc = dlopen("libc.so", RTLD_LAZY | RTLD_GLOBAL);
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if (libc != NULL) {
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real = (pthread_create_fn)dlsym(libc, "pthread_create");
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}
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if (real == NULL) {
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/* Fallback: try RTLD_DEFAULT — may or may not work depending on
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* link order but it's better than segfaulting. */
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real = (pthread_create_fn)dlsym(RTLD_DEFAULT, "pthread_create");
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}
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if (real == NULL) {
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return -1;
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}
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}
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return real(thread, attr, start_routine, arg);
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}
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#endif /* __ANDROID__ */
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