This preview shows page 1. Sign up to view the full content.
Unformatted text preview: /3 CALL m16:32 Valid Valid REX.W + FF /3 CALL m16:64 Valid N.E. Description
Saves procedure linking information on the stack and branches to the called procedure specified using the target operand. The target operand specifies the address of the first instruction in the called procedure. The operand can be an immediate value, a general-purpose register, or a memory location. 3-86 Vol. 2 INSTRUCTION SET REFERENCE, A-M This instruction can be used to execute four types of calls: Near Call -- A call to a procedure in the current code segment (the segment currently pointed to by the CS register), sometimes referred to as an intrasegment call. Far Call -- A call to a procedure located in a different segment than the current code segment, sometimes referred to as an inter-segment call. Inter-privilege-level far call -- A far call to a procedure in a segment at a different privilege level than that of the currently executing program or procedure. Task switch -- A call to a procedure located in a different task. The latter two call types (inter-privilege-level call and task switch) can only be executed in protected mode. See "Calling Procedures Using Call and RET" in Chapter 6 of the Intel 64 and IA-32 Architectures Software Developer's Manual, Volume 1, for additional information on near, far, and inter-privilege-level calls. See Chapter 6, "Task Management," in the Intel 64 and IA-32 Architectures Software Developer's Manual, Volume 3A, for information on performing task switches with the CALL instruction. Near Call. When executing a near call, the processor pushes the value of the EIP register (which contains the offset of the instruction following the CALL instruction) on the stack (for use later as a return-instruction pointer). The processor then branches to the address in the current code segment specified by the target operand. The target operand specifies either an absolute offset in the code segment (an offset from the base of the code segment) or a relative offset (a signed displacement relative to the current value of the instruction pointer in the EIP register; this value points to the instruction following the CALL instruction). The CS register is not changed on near calls. For a near call absolute, an absolute offset is specified indirectly in a general-purpose register or a memory location (r/m16, r/m32, or r/m64). The operand-size attribute determines the size of the target operand (16, 32 or 64 bits). When in 64-bit mode, the operand size for near call (and all near branches) is forced to 64-bits. Absolute offsets are loaded directly into the EIP(RIP) register. If the operand size attribute is 16, the upper two bytes of the EIP register are cleared, resulting in a maximum instruction pointer size of 16 bits. When accessing an absolute offset indirectly using the stack pointer [ESP] as the base register, the base value used is the value of the ESP before the instruction executes. A relative offset (rel16 or rel32) is ge...
View Full Document
This note was uploaded on 10/01/2013 for the course CPE 103 taught by Professor Watlins during the Winter '11 term at Mississippi State.
- Winter '11