Vol. 3D 41-41

SGX INSTRUCTION REFERENCES

ELDB/ELDU—Load an EPC page and Marked its State 

Instruction Operand Encoding

Description

This leaf function copies a page from regular main memory to the EPC. As part of the copying process, the page is 
cryptographically authenticated and decrypted. This instruction can only be executed when current privilege level 
is 0.
The ELDB leaf function sets the BLOCK bit in the EPCM entry for the destination page in the EPC after copying. The 
ELDU leaf function clears the BLOCK bit in the EPCM entry for the destination page in the EPC after copying.
RBX contains the effective address of a PAGEINFO structure; RCX contains the effective address of the destination 
EPC page; RDX holds the effective address of the version array slot that holds the version of the page.
The table below provides additional information on the memory parameter of ELDB/ELDU leaf functions.

EBLDB/ELDBU Memory Parameter Semantics

The error codes are: 

Concurrency Restrictions

Opcode/

Instruction

Op/En

64/32 

bit Mode 

Support

CPUID 

Feature 

Flag

Description

 EAX = 07H

IR

V/V

SGX1

This leaf function loads, verifies an EPC page and marks the page 

as blocked.

ENCLS[ELDB]
 EAX = 08H

IR

V/V

SGX1

This leaf function loads, verifies an EPC page and marks the page 

as unblocked.

ENCLS[ELDU]

Op/En

EAX

RBX

RCX

RDX

IR

ELDB/ELDU 

(In)

Return error 

code (Out)

Address of the PAGEINFO 

(In)

Address of the EPC page 

(In)

Address of the version-

array slot (In)

PAGEINFO

PAGEINFO.SRCPGE

PAGEINFO.PCMD

PAGEINFO.SECS

EPCPAGE

Version-Array Slot

Non-enclave 

read access

Non-enclave read 

access

Non-enclave read 

access

Enclave read/write 

access

Read/Write access 

permitted by Enclave

Read/Write access per-

mitted by Enclave

Table 41-25.  ELDB/ELDU Return Value in RAX

 Error Code (see Table 41-3)

Description

No Error

ELDB/ELDU successful

SGX_MAC_COMPARE_FAIL

If the MAC check fails

Table 41-26.  Concurrency Restrictions of ELDB/ELDU with Intel® SGX Instructions - 1of 2

Operation

EEXIT

EADD

EBLOCK

ECRE

ATE

EDBGRD/

WR

EENTER/

ERESUME

EEXTEND

EGETKEY

EINIT

ELDB/ELDU

EPA

Param Targ VA

SECS Targ SECS Targ SECS SECS

Targ SECS TCS SSA SECS Targ SECS Param SECS SECS Targ VA

SECS VA

ELDB/E

LDU

Targ

N

N

N

N

N

N

N

N

N

N

N

VA

N

N

Y

N

Y

N

SECS

Y

N

Y

Y

N

Y

Y

Y

Y

Y

N

Y