c18n: Port to RISC-V #2300
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c18n: Port to RISC-V #2300
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This avoids using otypes to protect the TCB data structure in the PLTGOTs of libraries.
When creating a new thread, the stack table for that thread is allocated and passed to libthr (via a struct) to be given to the new thread. Previously, the stack table is sealed when passed to libthr and unsealed (and installed) when the new thread starts. This commit allows the sealing to be optionally disabled with CHERI_LIB_C18N_NO_OTYPE.
Stack unwinding (in both setjmp/longjmp and C++ exceptions) requires handing a capability to the trusted stack to user code. This capability has previously been sealed with an otype. This commit adds the option to use subset sealing instead.
This was intended to seal function pointers where the otype corresponds to the signature of the function. The relevant compiler changes have not been implemented though.
/lib/c18n/* are also ported and built for CHERI-RISC-V.
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Introduces compile-time flag
CHERI_LIB_C18N_NO_OTYPEto disable usage of otype sealing. This flag is set by default for RISC-V but not for Morello.