Intel IA-32 Manuale Utente
2-24 Vol. 3A
SYSTEM ARCHITECTURE OVERVIEW
2.5.1
CPUID Qualification of Control Register Flags
The VME, PVI, TSD, DE, PSE, PAE, MCE, PGE, PCE, OSFXSR, and OSXMMEXCPT flags
in control register CR4 are model specific. All of these flags (except the PCE flag) can be qual-
ified with the CPUID instruction to determine if they are implemented on the processor before
they are used.
in control register CR4 are model specific. All of these flags (except the PCE flag) can be qual-
ified with the CPUID instruction to determine if they are implemented on the processor before
they are used.
The CR8 register is available on processors that support Intel EM64T. Support for Intel EM64T
can determined using CPUID.
can determined using CPUID.
2.6
SYSTEM INSTRUCTION SUMMARY
System instructions handle system-level functions such as loading system registers, managing
the cache, managing interrupts, or setting up the debug registers. Many of these instructions can
be executed only by operating-system or executive procedures (that is, procedures running at
privilege level 0). Others can be executed at any privilege level and are thus available to appli-
cation programs.
the cache, managing interrupts, or setting up the debug registers. Many of these instructions can
be executed only by operating-system or executive procedures (that is, procedures running at
privilege level 0). Others can be executed at any privilege level and are thus available to appli-
cation programs.
Table 2-2 lists the system instructions and indicates whether they are available and useful for
application programs. These instructions are described in Chapter 3 and Chapter 4 of the IA-32
Intel® Architecture Software Developer’s Manual, Volumes 2A & 2B.
application programs. These instructions are described in Chapter 3 and Chapter 4 of the IA-32
Intel® Architecture Software Developer’s Manual, Volumes 2A & 2B.
Table 2-2. Summary of System Instructions
Instruction
Description
Useful to
Application?
Application?
Protected from
Application?
Application?
LLDT
Load LDT Register
No
Yes
SLDT
Store LDT Register
No
No
LGDT
Load GDT Register
No
Yes
SGDT
Store GDT Register
No
No
LTR
Load Task Register
No
Yes
STR
Store Task Register
No
No
LIDT
Load IDT Register
No
Yes
SIDT
Store IDT Register
No
No
MOV CRn
Load and store control registers
No
Yes
SMSW
Store MSW
Yes
No
LMSW
Load MSW
No
Yes
CLTS
Clear TS flag in CR0
No
Yes
ARPL
Adjust RPL
Yes
1, 5
No
LAR
Load Access Rights
Yes
No
LSL
Load Segment Limit
Yes
No
VERR
Verify for Reading
Yes
No
VERW
Verify for Writing
Yes
No