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Shared Debug.Authentication Pseudocode

Library pseudocode for shared/debug/authentication/AllowExternalDebugAccess

// AllowExternalDebugAccess()
// ==========================
// Returns TRUE if an external debug interface access to the External debug registers
// is allowed, FALSE otherwise.

boolean AllowExternalDebugAccess()
    // The access may also be subject to OS Lock, power-down, etc.
    if HaveSecureExtDebugView() then
        return AllowExternalDebugAccess(IsAccessSecure());
    else
        return AllowExternalDebugAccess(ExternalSecureInvasiveDebugEnabled());

// AllowExternalDebugAccess()
// ==========================
// Returns TRUE if an external debug interface access to the External debug registers
// is allowed for the given Security state, FALSE otherwise.

boolean AllowExternalDebugAccess(boolean allow_secure)
    // The access may also be subject to OS Lock, power-down, etc.
    if HaveSecureExtDebugView() || ExternalInvasiveDebugEnabled() then
        if allow_secure then
            return TRUE;
        elsif HaveEL(EL3) then
            if ELUsingAArch32(EL3) then
                return SDCR.EDAD == '0';
            else
                return MDCR_EL3.EDAD == '0';
        else
            return !IsSecure();
    else
        return FALSE;

Library pseudocode for shared/debug/authentication/AllowExternalPMUAccess

// AllowExternalPMUAccess()
// ========================
// Returns TRUE if an external debug interface access to the PMU registers is allowed, FALSE otherwise.

boolean AllowExternalPMUAccess()
    // The access may also be subject to OS Lock, power-down, etc.
    if HaveSecureExtDebugView() then
        return AllowExternalPMUAccess(IsAccessSecure());
    else
        return AllowExternalPMUAccess(ExternalSecureNoninvasiveDebugEnabled());

// AllowExternalPMUAccess()
// ========================
// Returns TRUE if an external debug interface access to the PMU registers is allowed for the given
// Security state, FALSE otherwise.

boolean AllowExternalPMUAccess(boolean allow_secure)
    // The access may also be subject to OS Lock, power-down, etc.
    if HaveSecureExtDebugView() || ExternalNoninvasiveDebugEnabled() then
        if allow_secure then
            return TRUE;
        elsif HaveEL(EL3) then
            if ELUsingAArch32(EL3) then
                return SDCR.EPMAD == '0';
            else
                return MDCR_EL3.EPMAD == '0';
        else
            return !IsSecure();
    else
        return FALSE;

Library pseudocode for shared/debug/authentication/Debug_authentication

signal DBGEN;
signal NIDEN;
signal SPIDEN;
signal SPNIDEN;

Library pseudocode for shared/debug/authentication/ExternalInvasiveDebugEnabled

// ExternalInvasiveDebugEnabled()
// ==============================
// The definition of this function is IMPLEMENTATION DEFINED.
// In the recommended interface, this function returns the state of the DBGEN signal.

boolean ExternalInvasiveDebugEnabled()
    return DBGEN == HIGH;

Library pseudocode for shared/debug/authentication/ExternalNoninvasiveDebugAllowed

// ExternalNoninvasiveDebugAllowed()
// =================================
// Returns TRUE if Trace and PC Sample-based Profiling are allowed

boolean ExternalNoninvasiveDebugAllowed()
    return (ExternalNoninvasiveDebugEnabled() &&
            (!IsSecure() || ExternalSecureNoninvasiveDebugEnabled() ||
             (ELUsingAArch32(EL1) && PSTATE.EL == EL0 && SDER.SUNIDEN == '1')));

Library pseudocode for shared/debug/authentication/ExternalNoninvasiveDebugEnabled

// ExternalNoninvasiveDebugEnabled()
// =================================
// This function returns TRUE if the ARMv8.4-Debug is implemented, otherwise this
// function is IMPLEMENTATION DEFINED.
// In the recommended interface, ExternalNoninvasiveDebugEnabled returns the state of the (DBGEN
// OR NIDEN) signal.

boolean ExternalNoninvasiveDebugEnabled()
    return !HaveNoninvasiveDebugAuth() || ExternalInvasiveDebugEnabled() || NIDEN == HIGH;

Library pseudocode for shared/debug/authentication/ExternalSecureInvasiveDebugEnabled

// ExternalSecureInvasiveDebugEnabled()
// ====================================
// The definition of this function is IMPLEMENTATION DEFINED.
// In the recommended interface, this function returns the state of the (DBGEN AND SPIDEN) signal.
// CoreSight allows asserting SPIDEN without also asserting DBGEN, but this is not recommended.

boolean ExternalSecureInvasiveDebugEnabled()
    if !HaveEL(EL3) && !IsSecure() then return FALSE;
    return ExternalInvasiveDebugEnabled() && SPIDEN == HIGH;

Library pseudocode for shared/debug/authentication/ExternalSecureNoninvasiveDebugEnabled

// ExternalSecureNoninvasiveDebugEnabled()
// =======================================
// This function returns the value of ExternalSecureInvasiveDebugEnabled() when ARMv8.4-Debug
// is implemented. Otherwise, the definition of this function is IMPLEMENTATION DEFINED.
// In the recommended interface, this function returns the state of the (DBGEN OR NIDEN) AND
// (SPIDEN OR SPNIDEN) signal.

boolean ExternalSecureNoninvasiveDebugEnabled()
    if !HaveEL(EL3) && !IsSecure() then return FALSE;
    if HaveNoninvasiveDebugAuth() then
        return ExternalNoninvasiveDebugEnabled() && (SPIDEN == HIGH || SPNIDEN == HIGH);
    else
        return ExternalSecureInvasiveDebugEnabled();

Library pseudocode for shared/debug/authentication/IsAccessSecure

// Returns TRUE when an access is Secure
boolean IsAccessSecure();
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