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vdso: emit unwind tables and check PT_GNU_EH_FRAME / DT_NEEDED - #17627
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Some C++ toolchains pass `-fno-asynchronous-unwind-tables` in non-optimized or sanitizer builds. When `.eh_frame` is omitted, the linker leaves the `PT_GNU_EH_FRAME` segment declared in the vDSO linker script at virtual address 0 with size 0. On arm64, `libgcc_s` (`_Unwind_Find_FDE`) dereferences `dlpi_addr + p_vaddr` when unwinding across `__kernel_rt_sigreturn` (e.g. during `pthread_cancel` in `EpollTest.UnblockWithSignal`), causing a `SIGSEGV`. Pass `-fasynchronous-unwind-tables` in `copts` on `vdso.so` so `.eh_frame` and `.eh_frame_hdr` are always emitted, and teach `check_vdso.py` to verify both that `PT_GNU_EH_FRAME` is non-empty and mapped inside a `PT_LOAD` segment and that the vDSO carries no `DT_NEEDED` dynamic dependencies. PiperOrigin-RevId: 1020815689
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vdso: emit unwind tables and check PT_GNU_EH_FRAME / DT_NEEDED
Some C++ toolchains pass
-fno-asynchronous-unwind-tablesin non-optimized orsanitizer builds. When
.eh_frameis omitted, the linker leaves thePT_GNU_EH_FRAMEsegment declared in the vDSO linker script at virtual address0 with size 0. On arm64,
libgcc_s(_Unwind_Find_FDE) dereferencesdlpi_addr + p_vaddrwhen unwinding across__kernel_rt_sigreturn(e.g.during
pthread_cancelinEpollTest.UnblockWithSignal), causing aSIGSEGV.Pass
-fasynchronous-unwind-tablesincoptsonvdso.soso.eh_frameand.eh_frame_hdrare always emitted, and teachcheck_vdso.pyto verify boththat
PT_GNU_EH_FRAMEis non-empty and mapped inside aPT_LOADsegment andthat the vDSO carries no
DT_NEEDEDdynamic dependencies.