runtime: extract out allocate_stack_0 to work around a "Local Exec" TLS model issue and prevent segfaulting
#458
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… TLS model issue and prevent segfaulting `allocate_stack_0` writes the allocated stack to `ia2_stackptr_0`. Previously, this was done inline in `init_stacks_and_setup_tls`, which is defined in the main compartment with `INIT_RUNTIME`, and thus may sometimes use the "Local Exec" TLS model and thus use a different thread-local address. Moving this to `allocate_stack_0` in `libia2` forces it to use the correct GOT thread local. This is a workaround to #457, but doesn't actually fix the root issue. It does successfully prevent compartmentalized `dav1d` from segfaulting, though.
ayrtonm
approved these changes
Nov 18, 2024
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allocate_stack_0writes the allocated stack toia2_stackptr_0. Previously, this was done inline ininit_stacks_and_setup_tls, which is defined in the main compartment withINIT_RUNTIME, and thus may sometimes use the "Local Exec" TLS model and thus use a different thread-local address. Moving this toallocate_stack_0inlibia2forces it to use the correct GOT thread local.This is a workaround to #457, but doesn't actually fix the root issue, so I'm not sure if we should merge it instead of fixing #457 properly. But it does successfully prevent compartmentalized
dav1dfrom segfaulting, and thus is included in #454.