pthread: zero-fill .tbss when initializing thread TLS#78
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pthread_create_common() copied the whole TLS image with memcpy, but the .tbss portion is NOBITS and has no valid source bytes -- it must be zeroed, not copied. As a result a new thread's .tbss inherited garbage. Initialize TLS per the ELF spec: memcpy .tdata, then memset .tbss to zero, using the weak linker symbols __tdata_source/__tdata_size/ __tbss_size (they resolve to 0 on legacy non-picolibc links, making the change a no-op there). Signed-off-by: Kushal Pal <kushpal@qti.qualcomm.com>
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Bryan Bayerdorffer (bryanb-h2)
July 15, 2026 09:51
Bryan Bayerdorffer (bryanb-h2)
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Jul 22, 2026
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pthread_create_common() copied the whole TLS image with memcpy, but the .tbss portion is NOBITS and has no valid source bytes -- it must be zeroed, not copied. As a result a new thread's .tbss inherited garbage.
Initialize TLS per the ELF spec: memcpy .tdata, then memset .tbss to zero, using the weak linker symbols __tdata_source/__tdata_size/ __tbss_size (they resolve to 0 on legacy non-picolibc links, making the change a no-op there).