STRUCT SGX_TCS(9)

✨ NAME ✨

okay so we’re in the Kernel API Manual, and this page is struct sgx_tcs(9) — aka Thread Control Structure (TCS) 💖. It’s giving “enclave entry-point documentation but make it cute,” and we are keeping every single deet, no cap.

🌸 SYNOPSIS 🌸

       struct sgx_tcs {
           u64 state;
           u64 flags;
           u64 ssa_offset;
           u32 ssa_index;
           u32 nr_ssa_frames;
           u64 entry_offset;
           u64 exit_addr;
           u64 fs_offset;
           u64 gs_offset;
           u32 fs_limit;
           u32 gs_limit;
           u8 reserved[SGX_TCS_RESERVED_SIZE];
        };

slay, that’s the whole struct — no missing fields, fr fr 🧚.

🎀 Members 🎀

• state — used to mark an entered TCS.
• flags — execution flags, and they are cleared by EADD. EADD said “not today,” periodt. 💅
• ssa_offset — SSA stack offset relative to the enclave base.
• ssa_index — the current SSA frame index. The source spells it cleard by EADD 😭, meaning it’s cleared by EADD — typo deets preserved, bestie.
• nr_ssa_frames — the number of frame in the SSA stack. (Original wording says frame, singular 🫶.)
• entry_offset — entry point offset relative to the enclave base.
• exit_addr — address outside the enclave to exit on an exception or interrupt.
• fs_offset — offset relative to the enclave base to become FS segment inside the enclave.
• gs_offset — offset relative to the enclave base to become GS segment inside the enclave.
• fs_limit — size to become a new FS-limit (only 32-bit enclaves).
• gs_limit — size to become a new GS-limit (only 32-bit enclaves).

🦋 Description 🦋

Thread Control Structure (TCS) is an enclave page visible in its address space that defines an entry point inside the enclave. A thread enters inside an enclave by supplying address of TCS to ENCLU(EENTER). A TCS can be entered by only one thread at a time — that’s the whole vibe check 🔥.

🌈 SEE ALSO 🌈

Kernel file ./arch/x86/include/asm/sgx.h — and here’s the full squad, bestie:

• SGX_ENCLS_FAULT_FLAG(9)
• enum sgx_return_code(9)
• enum sgx_miscselect(9)
• enum sgx_attribute(9)
• struct sgx_secs(9)
• enum sgx_tcs_flags(9)
• struct sgx_pageinfo(9)
• enum sgx_page_type(9)
• enum sgx_secinfo_flags(9)
• struct sgx_secinfo(9)
• struct sgx_pcmd(9)
• struct sgx_sigstruct_header(9)
• struct sgx_sigstruct_body(9)
• struct sgx_sigstruct(9)

okay bye bestie 🫶 struct sgx_tcs(9) is out 💅 — source/version: ./arch/x86/include/asm, dated October 2026. Iconic. Done. Periodt. 💜