EPA (ENCLS leaf 0AH)

Leaf functions of ENCLS

ENCLS performs the leaf function whose number is in EAX. Only the operating system (CPL 0) may run ENCLS. The Linux kernel's headers give every number but ELDB's, which Linux does not use, and Intel's SGX SDK the first seven; ELDB's number is the one the manual gives.

EAX	Leaf function	Summary	Requires
`00H`	`ECREATE`	Starts building an enclave by copying its control structure, the SECS, from ordinary memory into a page of the EPC.	SGX1
`01H`	`EADD`	Copies a page from ordinary memory into the EPC for an enclave being built, and adds its offset and attributes to the enclave's measurement.	SGX1
`02H`	`EINIT`	Completes the build of an enclave: checks its signed SIGSTRUCT and launch token, fixes its measurement and makes it ready for EENTER.	SGX1
`03H`	`EREMOVE`	Removes a page from the EPC, detaching it from its enclave and marking it unused.	SGX1
`04H`	`EDBGRD`	Reads eight bytes (four outside 64-bit mode) of a debug enclave's memory, at the address in RCX, into RBX.	SGX1
`05H`	`EDBGWR`	Writes RBX (EBX outside 64-bit mode) to a debug enclave's memory at the address in RCX.	SGX1
`06H`	`EEXTEND`	Adds 256 bytes of a page of an enclave being built to the enclave's measurement, MRENCLAVE.	SGX1
`07H`	`ELDB`	Loads a page that EWB wrote out back into the EPC, checking and decrypting it, and marks it blocked.	SGX1
`08H`	`ELDU`	Loads a page that EWB wrote out back into the EPC, checking and decrypting it, and leaves it unblocked.	SGX1
`09H`	`EBLOCK`	Marks an EPC page as blocked, the first step of evicting it from the EPC.	SGX1
`0AH`	`EPA`	Turns an EPC page into a version array, which holds the versions of pages evicted from the EPC.	SGX1
`0BH`	`EWB`	Evicts a blocked EPC page: encrypts it, writes it to ordinary memory and keeps its version in a version array.	SGX1
`0CH`	`ETRACK`	Starts tracking the TLB flushes that must follow EBLOCK before the blocked pages of an enclave can be evicted.	SGX1
`0DH`	`EAUG`	Adds a zeroed page to an enclave that is already running; the enclave must accept it with EACCEPT or EACCEPTCOPY.	SGX2
`0EH`	`EMODPR`	Restricts the access rights of a page of a running enclave, which then accepts the change with EACCEPT.	SGX2
`0FH`	`EMODT`	Changes the type of a page of a running enclave, to trim it for example, which then accepts the change with EACCEPT.	SGX2
`18H`	`EUPDATESVN`	Updates the SGX security version of the processor to that of the loaded microcode update, when the EPC holds no valid page.	EUPDATESVN

CPUID and processors

EPA needs what ENCLS needs: the processor must report one of the alternatives of its ISA set, and the SGX1 bit, CPUID.(EAX=12H,ECX=0):EAX[0], as well.

CPUID requirements and processors of the XED ISA sets above. Alternatives are separated by “or”; processors follow XED’s chip model, whose AMD processors end with Zen 2, and the CPU data of this site for Zen 3 to Zen 6.

ISA set	CPUID	Processors
`SGX` SGX	SGX `CPUID.(EAX=07H,ECX=0):EBX[2]` SGX	Skylake, Comet Lake, Cannon Lake, Ice Lake (client), Tiger Lake, Skylake-SP, Cascade Lake, Cooper Lake, Ice Lake (server), Sapphire Rapids, Emerald Rapids, Granite Rapids, Diamond Rapids, Goldmont Plus

Leaf functions of ENCLS

CPUID and processors

Sources