System Call
Transfer control to the operating system at a higher privilege level.
System
Semantics
Raises privilege and vectors to a kernel entry point defined by the architecture's exception model.
| Architecture | Instructions | Expressed as | How this architecture does it |
|---|---|---|---|
| x86 | one instruction | SYSCALL is the fast 64-bit path; the older INT 0x80 software interrupt still exists for compatibility. | |
| ARM | one instruction | SVC takes an immediate and traps to EL1; HVC and SMC target the hypervisor and secure monitor. | |
| RISC-V | one instruction | One instruction for every privilege transition: where it traps depends on the current mode, not on the encoding. | |
| PowerISA | one instruction | sc traps to the supervisor, with the LEV field selecting hypervisor entry. |
Other operations
Add With Carry Atomic Compare and Swap Atomic Fetch and Add Breakpoint Trap Byte Swap (Endianness Reversal) Cache Line Flush Cache Prefetch Hint Compare and Branch Conditional Select (Branchless Move) Count Leading Zeros Count Trailing Zeros Floating-Point Square Root Fused Multiply-Add Integer Addition Integer Divide Integer Multiply Load-Acquire Memory Barrier / Fence No Operation Population Count Rotate Left Sign Extend Byte