EACCEPT — Accept Changes to an EPC Page

Instruction Operand Encoding ¶

Description ¶

This leaf function accepts changes to a page in the running enclave by verifying that the security attributes specified in the SECINFO match the security attributes of the page in the EPCM. This instruction leaf can only be executed when inside the enclave.

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

EACCEPT Memory Parameter Semantics ¶

The instruction faults if any of the following:

EACCEPT Faulting Conditions ¶

The error codes are:

Concurrency Restrictions ¶

Operation ¶

Temp Variables in EACCEPT Operational Flow ¶

IF (DS:RBX is not 64Byte Aligned)

THEN #GP(0); FI;

IF (DS:RBX is not within CR_ELRANGE)

THEN #GP(0); FI;

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

THEN #PF(DS:RBX); FI;

IF ( (EPCM(DS:RBX &~FFFH).VALID = 0) or (EPCM(DS:RBX &~FFFH).R = 0) or (EPCM(DS:RBX &~FFFH).PENDING ≠ 0) or

(EPCM(DS:RBX &~FFFH).MODIFIED ≠ 0) or (EPCM(DS:RBX &~FFFH).BLOCKED ≠ 0) or

(EPCM(DS:RBX &~FFFH).PT ≠ PT_REG) or (EPCM(DS:RBX &~FFFH).ENCLAVESECS ≠ CR_ACTIVE_SECS) or

(EPCM(DS:RBX &~FFFH).ENCLAVEADDRESS ≠ (DS:RBX & FFFH)) )

THEN #PF(DS:RBX); FI;

(* Copy 64 bytes of contents *)

SCRATCH_SECINFO := DS:RBX;

(* Check for misconfigured SECINFO flags*)

IF (SCRATCH_SECINFO reserved fields are not zero )

THEN #GP(0); FI;

IF (DS:RCX is not 4KByte Aligned)

THEN #GP(0); FI;

IF (DS:RCX is not within CR_ELRANGE)

THEN #GP(0); FI;

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

THEN #PF(DS:RCX); FI;

(* Check that the combination of requested PT, PENDING, and MODIFIED is legal *)

IF (CPUID.(EAX=12H, ECX=1):EAX[6] = 0 )

THEN

IF (NOT (((SCRATCH_SECINFO.FLAGS.PT is PT_REG) and

((SCRATCH_SECINFO.FLAGS.PR is 1) or

(SCRATCH_SECINFO.FLAGS.PENDING is 1)) and

(SCRATCH_SECINFO.FLAGS.MODIFIED is 0)) or

((SCRATCH_SECINFO.FLAGS.PT is PT_TCS or PT_TRIM) and

(SCRATCH_SECINFO.FLAGS.PR is 0) and

(SCRATCH_SECINFO.FLAGS.PENDING is 0) and

(SCRATCH_SECINFO.FLAGS.MODIFIED is 1) )))

THEN #GP(0); FI

ELSE

IF (NOT (((SCRATCH_SECINFO.FLAGS.PT is PT_REG) AND

((SCRATCH_SECINFO.FLAGS.PR is 1) OR

(SCRATCH_SECINFO.FLAGS.PENDING is 1)) AND

(SCRATCH_SECINFO.FLAGS.MODIFIED is 0)) OR

((SCRATCH_SECINFO.FLAGS.PT is PT_TCS OR PT_TRIM) AND

(SCRATCH_SECINFO.FLAGS.PENDING is 0) AND

(SCRATCH_SECINFO.FLAGS.MODIFIED is 1) AND

(SCRATCH_SECINFO.FLAGS.PR is 0)) OR

((SCRATCH_SECINFO.FLAGS.PT is PT_SS_FIRST or PT_SS_REST) AND

(SCRATCH_SECINFO.FLAGS.PENDING is 1) AND

(SCRATCH_SECINFO.FLAGS.MODIFIED is 0) AND

(SCRATCH_SECINFO.FLAGS.PR is 0))))

THEN #GP(0); FI;

FI;

(* Check security attributes of the destination EPC page *)

IF ( (EPCM(DS:RCX).VALID is 0) or (EPCM(DS:RCX).BLOCKED is not 0) or

((EPCM(DS:RCX).PT is not PT_REG) and (EPCM(DS:RCX).PT is not PT_TCS) and (EPCM(DS:RCX).PT is not PT_TRIM)

and (EPCM(DS:RCX).PT is not PT_SS_FIRST) and (EPCM(DS:RCX).PT is not PT_SS_REST)) or

(EPCM(DS:RCX).ENCLAVESECS ≠ CR_ACTIVE_SECS))

THEN #PF((DS:RCX); FI;

(* Check the destination EPC page for concurrency *)

IF ( EPC page in use )

THEN #GP(0); FI;

(* Re-Check security attributes of the destination EPC page *)

IF ( (EPCM(DS:RCX).VALID is 0) or (EPCM(DS:RCX).ENCLAVESECS ≠ CR_ACTIVE_SECS) )

THEN #PF(DS:RCX); FI;

(* Verify that accept request matches current EPC page settings *)

IF ( (EPCM(DS:RCX).ENCLAVEADDRESS ≠ DS:RCX) or (EPCM(DS:RCX).PENDING ≠ SCRATCH_SECINFO.FLAGS.PENDING) or

(EPCM(DS:RCX).MODIFIED ≠ SCRATCH_SECINFO.FLAGS.MODIFIED) or (EPCM(DS:RCX).R ≠ SCRATCH_SECINFO.FLAGS.R) or

(EPCM(DS:RCX).W ≠ SCRATCH_SECINFO.FLAGS.W) or (EPCM(DS:RCX).X ≠ SCRATCH_SECINFO.FLAGS.X) or

(EPCM(DS:RCX).PT ≠ SCRATCH_SECINFO.FLAGS.PT) )

THEN

RFLAGS.ZF := 1;

RAX := SGX_PAGE_ATTRIBUTES_MISMATCH;

GOTO DONE;

FI;

(* Check that all required threads have left enclave *)

IF (Tracking not correct)

THEN

RFLAGS.ZF := 1;

RAX := SGX_NOT_TRACKED;

GOTO DONE;

FI;

(* Get pointer to the SECS to which the EPC page belongs *)

TMP_SECS = << Obtain physical address of SECS through EPCM(DS:RCX)>>

(* For TCS pages, perform additional checks *)

IF (SCRATCH_SECINFO.FLAGS.PT = PT_TCS)

THEN

IF (DS:RCX.RESERVED ≠ 0) #GP(0); FI;

(* Check that TCS.FLAGS.DBGOPTIN, TCS stack, and TCS status are correctly initialized *)

(* check that TCS.PREVSSP is 0 *) IF ( ((DS:RCX).FLAGS.DBGOPTIN is not 0) or ((DS:RCX).CSSA ≥ (DS:RCX).NSSA) or ((DS:RCX).AEP is not 0) or ((DS:RCX).STATE is not 0) or ((CPUID.(EAX=07H, ECX=0H):ECX[CET_SS] = 1) AND ((DS:RCX).PREVSSP != 0)))

THEN #GP(0); FI;

(* Check consistency of FS & GS Limit *)

IF ( (TMP_SECS.ATTRIBUTES.MODE64BIT is 0) and ((DS:RCX.FSLIMIT & FFFH ≠ FFFH) or (DS:RCX.GSLIMIT & FFFH ≠ FFFH)) )

THEN #GP(0); FI;

FI;

(* Clear PENDING/MODIFIED flags to mark accept operation complete *)

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

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

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

(* Clear EAX and ZF to indicate successful completion *)

RFLAGS.ZF := 0;

RAX := 0;

DONE:

RFLAGS.CF,PF,AF,OF,SF := 0;

Flags Affected ¶

Sets ZF if page cannot be accepted, otherwise cleared. Clears CF, PF, AF, OF, SF

Protected Mode Exceptions ¶

64-Bit Mode Exceptions ¶