Vol. 3D 38-9

ENCLAVE ACCESS CONTROL AND DATA STRUCTURES

38.9.1.2   VECTOR Field Definition

Table 38-10 contains the VECTOR field. This field contains information about some exceptions which occur inside 
the enclave. These vector values are the same as the values that would be used when vectoring into regular excep-
tion handlers. All values not shown are not reported inside an enclave. 

38.9.2 MISC 

Region

The layout of the MISC region is shown in Table 38-11. The number of components that the processor supports in 
the MISC region corresponds to the set bits of CPUID.(EAX=12H, ECX=0):EBX[31:0] set to 1. Each set bit in 
CPUID.(EAX=12H, ECX=0):EBX[31:0] has a defined size for the corresponding component, as shown in Table 
38-11. Enclave writers needs to do the following:

•

Decide which MISC region components will be supported for the enclave.

•

Allocate an SSA frame large enough to hold the components chosen above.

•

Instruct each enclave builder software to set the appropriate bits in SECS.MISCSELECT.

The first component, EXINFO, starts next to the GPRSGX region. Additional components in the MISC region grow 
in ascending order within the MISC region towards the XSAVE region.
The size of the MISC region is calculated as follows:

•

If CPUID.(EAX=12H, ECX=0):EBX[31:0] = 0, MISC region is not supported. 

•

If CPUID.(EAX=12H, ECX=0):EBX[31:0] != 0, the size of MISC region is derived from sum of the highest bit set 
in SECS.MISCSELECT and the size of the MISC component corresponding to that bit. Offset and size 

Table 38-9.  Layout of EXITINFO Field

Field

Bit Position

Description

VECTOR

7:0

Exception number of exceptions reported inside enclave.

EXIT_TYPE

10:8

011b: Hardware exceptions.

110b: Software exceptions.

Other values: Reserved.

RESERVED

30:11

Reserved as zero.

VALID

31

0: unsupported exceptions.

1: Supported exceptions. Includes two categories:

•

Unconditionally supported exceptions: #DE, #DB, #BP, #BR, #UD, #MF, #AC, #XM.

•

Conditionally supported exception: 
— #PF, #GP if SECS.MISCSELECT.EXINFO = 1.

Table 38-10.  Exception Vectors

Name

Vector #

Description

#DE

0

Divider exception.

#DB

1

Debug exception.

#BP

3

Breakpoint exception.

#BR

5

Bound range exceeded exception.

#UD

6

Invalid opcode exception.

#GP

13

General protection exception. Only reported if SECS.MISCSELECT.EXINFO = 1.

#PF

14

Page fault exception. Only reported if SECS.MISCSELECT.EXINFO = 1.

#MF

16

x87 FPU floating-point error.

#AC

17

Alignment check exceptions.

#XM

19

SIMD floating-point exceptions.