Intel IA-32 - Manual (Page 172)

4-42 Vol. 3A
PROTECTION
tures. Execute-disable bit protection can be activated using the execute-disable bit at any level
of the paging structure, irrespective of the corresponding entry in other levels. When execute-
disable-bit protection is not activated, the page can be used as code or data.
In legacy PAE-enabled mode, Table 4-7 and Table 4-8 show the effect of setting the execute-
disable bit for code and data pages.
Table 4-6. IA-32e Mode Page Level Protection Matrix
with Execute-Disable Bit Capability
Execute Disable Bit Value (Bit 63) Valid Usage
PML4 PDP PDE PTE
Bit 63 = 1 * * * Data
* Bit 63 = 1 * * Data
* * Bit 63 = 1 * Data
* * * Bit 63 = 1 Data
Bit 63 = 0 Bit 63 = 0 Bit 63 = 0 Bit 63 = 0 Data/Code
NOTE:
* Value not checked.
Table 4-7. Legacy PAE-Enabled 4-KByte Page Level Protection Matrix
with Execute-Disable Bit Capability
Execute Disable Bit Value (Bit 63) Valid Usage
PDE PTE
Bit 63 = 1 * Data
* Bit 63 = 1 Data
Bit 63 = 0 Bit 63 = 0 Data/Code
NOTE:
* Value not checked.
Table 4-8. Legacy PAE-Enabled 2-MByte Page Level Protection
with Execute-Disable Bit Capability
Execute Disable Bit Value (Bit 63) Valid Usage
PDE
Bit 63 = 1 Data
Bit 63 = 0 Data/Code