<!-- Instructions here described in PowerISA Version 3.0 B Book 1 -->

<!-- 3.3.1 System Linkage Instructions Page 952 - 956 -->

<!-- These instructions provide the means by which a program can call upon the system to perform a service. -->

# System Call

SC-Form

* sc LEV

Pseudo-code:

    SRR0 <-iea CIA + 4
    SRR1[33:36] <- 0
    SRR1[42:47] <- 0
    SRR1[0:32]  <- MSR[0:32]
    SRR1[37:41] <- MSR[37:41]
    SRR1[48:63] <- MSR[48:63]
    TRAP(0xC00, None)

Special Registers Altered:

    SRR0 SRR1 MSR

# System Call Vectored

SC-Form

* scv LEV

Pseudo-code:

    LR <- CIA + 4
    SRR1[33:36] <- undefined([0]*4)
    SRR1[42:47] <- undefined([0]*6)
    SRR1[0:32]  <- MSR[0:32]
    SRR1[37:41] <- MSR[37:41]
    SRR1[48:63] <- MSR[48:63]
    MSR <- new_value
    NIA <- vectored

Special Registers Altered:

    LR CTR MSR

# Return From System Call Vectored

XL-Form

* rfscv

Pseudo-code:

    if (MSR[29:31] != 0b010) | (CTR[29:31] != 0b000) then
        MSR[29:31] <- CTR[29:31]
    MSR[48] <- CTR[49]
    MSR[58] <- CTR[49]
    MSR[59] <- CTR[49]
    MSR[0:2] <- CTR[0:2]
    MSR[4:28] <- CTR[4:28]
    MSR[32] <- CTR[32]
    MSR[37:41] <- CTR[37:41]
    MSR[49:50] <- CTR[49:50]
    MSR[52:57] <- CTR[52:57]
    MSR[60:63] <- CTR[60:63]
    NIA <-iea LR[0:61] || 0b00

Special Registers Altered:

    MSR

# Return From Interrupt Doubleword

XL-Form

* rfid

Pseudo-code:

    MSR[51] <- (MSR[3] & SRR1[51]) | ((¬MSR[3] & MSR[51]))
    MSR[3] <- (MSR[3] & SRR1[3])
    if (MSR[29:31] != 0b010) | (SRR1[29:31] != 0b000) then
        MSR[29:31] <- SRR1[29:31]
    MSR[48] <- SRR1[48] | SRR1[49]
    MSR[58] <- SRR1[58] | SRR1[49]
    MSR[59] <- SRR1[59] | SRR1[49]
    MSR[0:2] <- SRR1[0:2]
    MSR[4:28] <- SRR1[4:28]
    MSR[32] <- SRR1[32]
    MSR[37:41] <- SRR1[37:41]
    MSR[49:50] <- SRR1[49:50]
    MSR[52:57] <- SRR1[52:57]
    MSR[60:63] <- SRR1[60:63]
    NIA <-iea SRR0[0:61] || 0b00

Special Registers Altered:

    MSR

# Hypervisor Return From Interrupt Doubleword

XL-Form

* hrfid

Pseudo-code:

    if (MSR[29:31] != 0b010) | (HSRR1[29:31] != 0b000) then
        MSR[29:31] <- HSRR1[29:31]
    MSR[48] <- HSRR1[48] | HSRR1[49]
    MSR[58] <- HSRR1[58] | HSRR1[49]
    MSR[59] <- HSRR1[59] | HSRR1[49]
    MSR[0:28] <- HSRR1[0:28]
    MSR[32] <- HSRR1[32]
    MSR[37:41] <- HSRR1[37:41]
    MSR[49:57] <- HSRR1[49:57]
    MSR[60:63] <- HSRR1[60:63]
    NIA <-iea HSRR0[0:61] || 0b00

Special Registers Altered:

    MSR

<!-- Checked March 2021 -->