EADD — Add a Page to an Uninitialized Enclave

Instruction Operand Encoding ¶

Description ¶

This leaf function copies a source page from non-enclave memory into the EPC, associates the EPC page with an SECS page residing in the EPC, and stores the linear address and security attributes in EPCM. As part of the association, the enclave offset and the security attributes are measured and extended into the SECS.MRENCLAVE. This instruction can only be executed when current privilege level is 0.

RBX contains the effective address of a PAGEINFO structure while RCX contains the effective address of an EPC page. The table below provides additional information on the memory parameter of EADD leaf function.

EADD Memory Parameter Semantics ¶

The instruction faults if any of the following:

EADD Faulting Conditions ¶

Concurrency Restrictions ¶

Operation ¶

Temp Variables in EADD Operational Flow ¶

IF (DS:RBX is not 32Byte Aligned)

THEN #GP(0); FI;

IF (DS:RCX is not 4KByte Aligned)

THEN #GP(0); FI;

IF (DS:RCX does not resolve within an EPC)

THEN #PF(DS:RCX); FI;

TMP_SRCPGE := DS:RBX.SRCPGE;

TMP_SECS := DS:RBX.SECS;

TMP_SECINFO := DS:RBX.SECINFO;

TMP_LINADDR := DS:RBX.LINADDR;

IF (DS:TMP_SRCPGE is not 4KByte aligned or DS:TMP_SECS is not 4KByte aligned or

DS:TMP_SECINFO is not 64Byte aligned or TMP_LINADDR is not 4KByte aligned)

THEN #GP(0); FI;

IF (DS:TMP_SECS does not resolve within an EPC)

THEN #PF(DS:TMP_SECS); FI;

SCRATCH_SECINFO := DS:TMP_SECINFO;

(* Check for misconfigured SECINFO flags*)

IF (SCRATCH_SECINFO reserved fields are not zero or

! (SCRATCH_SECINFO.FLAGS.PT is PT_REG or SCRATCH_SECINFO.FLAGS.PT is PT_TCS or

(SCRATCH_SECINFO.FLAGS.PT is PT_SS_FIRST and CPUID.(EAX=12H, ECX=1):EAX[6] = 1) or

(SCRATCH_SECINFO.FLAGS.PT is PT_SS_REST and CPUID.(EAX=12H, ECX=1):EAX[6] = 1)) )

THEN #GP(0); FI;

(* If PT_SS_FIRST/PT_SS_REST page types are requested then CR4.CET must be 1 *)

IF ( (SCRATCH_SECINFO.FLAGS.PT is PT_SS_FIRST OR

SCRATCH_SECINFO.FLAGS.PT is PT_SS_REST) AND CR4.CET == 0)

THEN #GP(0); FI;

(* Check the EPC page for concurrency *)

IF (EPC page is not available for EADD)

THEN

IF (<<VMX non-root operation>> AND <<ENABLE_EPC_VIRTUALIZATION_EXTENSIONS>>)

THEN

VMCS.Exit_reason := SGX_CONFLICT;

VMCS.Exit_qualification.code := EPC_PAGE_CONFLICT_EXCEPTION;

VMCS.Exit_qualification.error := 0;

VMCS.Guest-physical_address := << translation of DS:RCX produced by paging >>;

VMCS.Guest-linear_address := DS:RCX;

Deliver VMEXIT;

ELSE

#GP(0);

FI;

FI;

IF (EPCM(DS:RCX).VALID ≠ 0)

THEN #PF(DS:RCX); FI;

(* Check the SECS for concurrency *)

IF (SECS is not available for EADD)

THEN #GP(0); FI;

IF (EPCM(DS:TMP_SECS).VALID = 0 or EPCM(DS:TMP_SECS).PT ≠ PT_SECS)

THEN #PF(DS:TMP_SECS); FI;

(* Copy 4KBytes from source page to EPC page*)

DS:RCX[32767:0] := DS:TMP_SRCPGE[32767:0];

CASE (SCRATCH_SECINFO.FLAGS.PT)

PT_TCS:

IF (DS:RCX.RESERVED ≠ 0) #GP(0); FI;

IF ( (DS:TMP_SECS.ATTRIBUTES.MODE64BIT = 0) and

((DS:TCS.FSLIMIT & 0FFFH ≠ 0FFFH) or (DS:TCS.GSLIMIT & 0FFFH ≠ 0FFFH) )) #GP(0); FI;

(* Ensure TCS.PREVSSP is zero *)

IF (CPUID.(EAX=07H, ECX=00h):ECX[CET_SS] = 1) and (DS:RCX.PREVSSP != 0) #GP(0); FI;

BREAK;

PT_REG:

IF (SCRATCH_SECINFO.FLAGS.W = 1 and SCRATCH_SECINFO.FLAGS.R = 0) #GP(0); FI;

BREAK;

PT_SS_FIRST:

PT_SS_REST:

(* SS pages cannot be created on first or last page of ELRANGE *)

IF ( TMP_LINADDR = DS:TMP_SECS.BASEADDR or TMP_LINADDR = (DS:TMP_SECS.BASEADDR + DS:TMP_SECS.SIZE - 0x1000) )

THEN #GP(0); FI;

IF ( DS:RCX[4087:0] != 0 ) #GP(0); FI;

IF (SCRATCH_SECINFO.FLAGS.PT == PT_SS_FIRST)

THEN

(* Check that valid RSTORSSP token exists *)

IF ( DS:RCX[4095:4088] != ((TMP_LINADDR + 0x1000) | DS:TMP_SECS.ATTRIBUTES.MODE64BIT) ) #GP(0); FI;

ELSE

(* Check the 8 bytes are zero *)

IF ( DS:RCX[4095:4088] != 0 ) #GP(0); FI;

FI;

IF (SCRATCH_SECINFO.FLAGS.W = 0 OR SCRATCH_SECINFO.FLAGS.R = 0 OR

SCRATCH_SECINFO.FLAGS.X = 1) #GP(0); FI;

BREAK;

ESAC;

(* Check the enclave offset is within the enclave linear address space *) IF (TMP_LINADDR < DS:TMP_SECS.BASEADDR or TMP_LINADDR ≥ DS:TMP_SECS.BASEADDR + DS:TMP_SECS.SIZE) THEN #GP(0); FI;

(* Check concurrency of measurement resource*)

IF (Measurement being updated)

THEN #GP(0); FI;

(* Check if the enclave to which the page will be added is already in Initialized state *)

IF (DS:TMP_SECS already initialized)

THEN #GP(0); FI;

(* For TCS pages, force EPCM.rwx bits to 0 and no debug access *)

IF (SCRATCH_SECINFO.FLAGS.PT = PT_TCS)

THEN

SCRATCH_SECINFO.FLAGS.R := 0;

SCRATCH_SECINFO.FLAGS.W := 0;

SCRATCH_SECINFO.FLAGS.X := 0;

(DS:RCX).FLAGS.DBGOPTIN := 0; // force TCS.FLAGS.DBGOPTIN off

DS:RCX.CSSA := 0;

DS:RCX.AEP := 0;

DS:RCX.STATE := 0;

FI;

(* Add enclave offset and security attributes to MRENCLAVE *)

TMP_ENCLAVEOFFSET := TMP_LINADDR - DS:TMP_SECS.BASEADDR;

TMPUPDATEFIELD[63:0] := 0000000044444145H; // “EADD”

TMPUPDATEFIELD[127:64] := TMP_ENCLAVEOFFSET;

TMPUPDATEFIELD[511:128] := SCRATCH_SECINFO[375:0]; // 48 bytes

DS:TMP_SECS.MRENCLAVE := SHA256UPDATE(DS:TMP_SECS.MRENCLAVE, TMPUPDATEFIELD)

INC enclave’s MRENCLAVE update counter;

(* Add enclave offset and security attributes to MRENCLAVE *)

EPCM(DS:RCX).R := SCRATCH_SECINFO.FLAGS.R;

EPCM(DS:RCX).W := SCRATCH_SECINFO.FLAGS.W;

EPCM(DS:RCX).X := SCRATCH_SECINFO.FLAGS.X;

EPCM(DS:RCX).PT := SCRATCH_SECINFO.FLAGS.PT;

EPCM(DS:RCX).ENCLAVEADDRESS := TMP_LINADDR;

(* associate the EPCPAGE with the SECS by storing the SECS identifier of DS:TMP_SECS *)

Update EPCM(DS:RCX) SECS identifier to reference DS:TMP_SECS identifier;

(* Set EPCM entry fields *)

EPCM(DS:RCX).BLOCKED := 0;

EPCM(DS:RCX).PENDING := 0;

EPCM(DS:RCX).MODIFIED := 0;

EPCM(DS:RCX).VALID := 1;

Flags Affected ¶

None

Protected Mode Exceptions ¶

64-Bit Mode Exceptions ¶