how does bluepill Trigger sigill?

[Kobe Kobe]

I know  sigill handler will call  bluepillHandler, but how does bluepill Trigger sigill?

// sighandler: see bluepill.go for documentation.

//

// The arguments are the following:

//

//      R0 - The signal number.

//      R1 - Pointer to siginfo_t structure.

//      R2 - Pointer to ucontext structure.

//

TEXT ·sighandler(SB),NOSPLIT,$0

        // si_signo should be sigill.

        MOVD    SIGINFO_SIGNO(R1), R7

        CMPW    $4, R7

        BNE     fallback

        MOVD    CONTEXT_PC(R2), R7

        CMPW    $0, R7

        BEQ     fallback

        MOVD    R2, 8(RSP)

        BL      ·bluepillHandler(SB)   // Call the handler.

        RET

fallback:

        // Jump to the previous signal handler.

        MOVD    ·savedHandler(SB), R7

        B       (R7)

// See bluepill.go.

TEXT ·bluepill(SB),NOSPLIT,$0

begin:

        MOVD    vcpu+0(FP), R8

        MOVD    $VCPU_CPU(R8), R9

        ORR     $0xffff000000000000, R9, R9

        // Trigger sigill.

        // In ring0.Start(), the value of R8 will be stored into tpidr_el1.

        // When the context was loaded into vcpu successfully,

        // we will check if the value of R10 and R9 are the same.

        WORD    $0xd538d08a // MRS TPIDR_EL1, R10

check_vcpu:

        CMP     R10, R9

        BEQ     right_vCPU

wrong_vcpu:

        CALL    ·redpill(SB)

        B       begin

right_vCPU:

        RET