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Upgrading Privileged-Code Applications on OpenVMS Alpha and OpenVMS I64 Systems

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4.6.1 Example: Declaring 64-Bit Functions

Original: 


ini_fdt_act(...,IO$_WRITELBLK,lr$write,BUFFERED); ... ini_fdt_act(...,IO$_SENSECHAR,exe_std$sensemode,                                        BUFFERED);

64-Bit Version: 


ini_fdt_act(...,IO$_WRITELBLK,lr$write,BUFFERED_64); (1)ini_fdt_act(...,IO$_WRITEPBLK,lr$write,BUFFERED_64); ini_fdt_act(...,IO$_WRITEVBLK,lr$write,BUFFERED_64); ini_fdt_act(...,IO$_SETMODE,lr$setmode,BUFFERED_64); (2)ini_fdt_act(...,IO$_SETCHAR,lr$setmode,BUFFERED_64); ini_fdt_act(...,IO$_SENSEMODE,exe_std$sensemode,                                        BUFFERED_64); (3)ini_fdt_act(...,IO$_SENSECHAR,exe_std$sensemode,                                        BUFFERED_64);

  1. Source changes required to LR$WRITE routine
  2. Source changes required to LR$SETMODE routine
  3. No user buffer, no $QIO parameters

4.6.2 Example: Declaring 64-Bit Buffered I/O Packet

Original: 


typedef struct _sysbuf_hdr {       (1)    char *pkt_datap;     char *usr_bufp;     short pkt_size;     short :16; SYSBUF_HDR;

64-Bit Version: 


#include <bufiodef.h>     (2)

  1. Locally defined type, SYSBUF_HDR, for a buffered I/O packet header was necessary.
  2. The new bufiodef.h header file defines the BUFIO type, which includes both the 32-bit and 64-bit buffered I/O packet header cells.

4.6.3 Example: Changes to LR$WRITE

Original: 


char *qio_bufp;         (1)SYSBUF_HDR *sys_bufp;  qio_bufp = (char *) irp->irp$l_qio_p1;  (2)sys_buflen = qio_buflen + sizeof(SYSBUF_HDR);  (3) status = exe_std$debit_bytcnt_alo(sys_buflen,  (4)                                  pcb,                                   &sys_buflen,                                   (void **) &sys_bufp);  irp->irp$l_svapte = (void *) sys_bufp;  (5)irp->irp$l_boff = sys_buflen; sys_datap = (char *) sys_bufp + sizeof(SYSBUF_HDR); (6)

  1. Define 32-bit pointer to caller's buffer
  2. Pointer is initialized using the 32-bit $QIO P1 value
  3. Size of buffered I/O packet includes header size
  4. Allocate pool for buffered I/O packet
  5. Connect the buffered I/O packet to IRP
  6. Compute pointer to data region within packet

64-Bit Version: 


CHAR_PQ qio_bufp;       (1)BUFIO *sys_bufp;  qio_bufp   = (CHAR_PQ) irp->irp$q_qio_p1;    (2)sys_buflen = qio_buflen + BUFIO$K_HDRLEN64;  (3)status = exe_std$alloc_bufio_64(irp,         (4)                                pcb,                                 (VOID_PQ) qio_bufp,                                 sys_buflen); sys_bufp  = irp->irp$ps_bufio_pkt;           (5)sys_datap = sys_bufp->bufio$ps_pktdata;      (6)
  1. Define a 64-bit pointer to caller's buffer.
  2. Pointer is initialized using the 64-bit $QIO P1 value. No source changes on references, for example: 


    exe_std$writechk(irp,pcb,ucb,qio_bufp,qio_buflen); memcpy (sys_datap, qio_bufp, qio_buflen);

  3. Size of buffered I/O packet includes 64-bit header size.
  4. Allocate pool for a 64-bit buffered I/O packet and connect it to the IRP.
  5. Get pointer to the buffered I/O packet.
  6. Get pointer to data region within packet.

4.6.4 Example: Changes to LR$SETMODE

Original: 


SETMODE_BUF *setmode_bufp;  (1)setmode_bufp = (SETMODE_BUF *) irp->irp$l_qio_p1; (2)

64-Bit Version: 


#pragma __required_pointer_size __save #pragma __required_pointer_size __long (3)typedef SETMODE_BUF *SETMODE_BUF_PQ; (4)#pragma __required_pointer_size __restore (5) SETMODE_BUF_PQ setmode_bufp; (6)setmode_bufp = (SETMODE_BUF_PQ) irp->irp$q_qio_p1; (7)

  1. 32-bit pointer to a SETMODE_BUF.
  2. Pointer is initialized using the 32-bit $QIO P1 value.
  3. Change pointer size to 64-bits.
  4. Define a type for a 64-bit pointer to a SETMODE_BUF structure.
  5. Restore saved pointer size, 32-bits.
  6. Define a 64-bit pointer to a SETMODE_BUF structure.
  7. Pointer is initialized using the 64-bit $QIO P1 value.

4.6.5 Example: Changes to LR$STARTIO

Original: 


ucb->ucb$r_ucb.ucb$l_svapte =                (char *) ucb->ucb$r_ucb.ucb$l_svapte +                sizeof(SYSBUF_HDR);           (1)

64-Bit Version: 


ucb->ucb$r_ucb.ucb$l_svapte =                (char *) ucb->ucb$r_ucb.ucb$l_svapte +                BUFIO$K_HDRLEN64;             (2)

  1. Skip 32-bit buffered I/O packet header.
  2. Skip 64-bit buffered I/O packet header.

Chapter 5
Modifying User-Written System Services

An application can contain certain routines that perform privileged functions, called user-written system services. This chapter describes the OpenVMS Alpha Version 7.0 changes that can affect user-written system services.

For more information about how to create user-written system services, see the OpenVMS Programming Concepts Manual.

As part of the 64-bit virtual addressing support, the Alpha system service dispatcher automatically performs a sign-extension check on service arguments to ensure that only 32-bit sign extended virtual addresses are passed. This sign-extension check prevents an application from passing a 64-bit virtual address to system services that are not equipped to handle 64-bit virtual addresses. This sign-extension check occurs for the system services (regardless of mode) provided by Compaq as well as for user-written system services.

Although the sign-extension check occurs by default, it is possible to disable the check for services that can properly handle 64-bit virtual addresses. A new flag, PLV$M_64_BIT_ARGS (see Table 5-2), can be specified when creating a user-written system service that is designed to accept 64-bit virtual addresses. The system service dispatcher purposely omits the sign-extension check when this flag is set for a particular service. Table 5-1 shows the components of the Alpha Privileged Library Vector that are new or changed as of OpenVMS Alpha Version 7.0.

Table 5-1 Components of the Alpha Privileged Library Vector
Component Symbol Description
User-supplied rundown routine for executive mode services PLV$PS_EXEC_RUNDOWN_HANDLER May contain the address of a user-supplied rundown routine that performs image-specific cleanup and resource deallocation. When the image linked against the user-written system service is run down by the system, this run-time routine is invoked. Unlike exit handlers, the routine is always called when a process or image exits. (Image rundown code calls this routine with a JSB instruction; it returns with an RSB instruction called in executive mode at IPL 0.)
Kernel Routine Flags Vector PLV$PS_KERNEL_ROUTINE_FLAGS Contains either the address of an array of longwords which contain the defined flags associated with each kernel system service, or a zero. Table 5-2 contains a description of the available flags.
Executive Routine Flags Vector PLV$PS_EXEC_ROUTINE_FLAGS Contains either the address of an array of longwords which contain the defined flags associated with each executive mode system service, or a zero. Table 5-2 contains a description of the available flags.

Table 5-2 Flags for 64-Bit User-Written Services
Flag Description
PLV$M_WAIT_CALLERS_MODE Informs the system service dispatcher that the service can return the status SS$_WAIT_CALLERS_MODE. This flag can only be specified for kernel mode services.
PLV$M_WAIT_CALLERS_NO_REEXEC Informs the system service dispatcher that the service can return the status SS$_WAIT_CALLERS_MODE but should not reexecute the service. This flag can only be specified for kernel mode services.
PLV$M_CLRREG Informs the system service dispatcher to clear the scratch integer registers before returning to the system service requestor. A security-related service may set this flag to ensure that sensitive information is not left in scratch registers. This flag can be specified for both kernel and executive mode system services.
PLV$M_RETURN_ANY Flags the system service dispatcher that the service can return arbitrary values in R0. This flag can only be specified for kernel mode system services.
PLV$M_WCM_NO_SAVE Informs the system service dispatcher that the service has taken steps to save the contents of the scratch integer registers. In this case, the dispatcher will not take the extra steps to save and restore these registers. This flag can only be specified for kernel mode system services.
PLV$M_STACK_ARGS Use of this flag is reserved to Compaq.
PLV$M_THREAD_SAFE Informs the system service dispatcher that the service requires no explicit synchronization. It is assumed by the dispatcher that the service provides its own internal data synchronization and that muliple kernel threads can safely execute other inner mode code in parallel. This flag can be specified for both kernel and executive mode system services.
PLV$M_64_BIT_ARGS Informs the system service dispatcher that the service can accept 64-bit virtual addresses. When set, the dispatcher will not perform the sign-extension check on the service arguments. The sign-extension check is the method used to guarantee that only 32-bit, sign-extended virtual addreses are passed to system services. This check is enabled by default. This flag can be specified for both kernel and executive mode system services.
PLV$M_CHECK_UPCALL Use of this flag is reserved to Compaq.
Example 5-1 illustrates how to create a PLV on Alpha systems using C.

Example 5-1 Creating a Privileged Library Vector (PLV) for C on Alpha Systems 

 /* "Forward routine" declarations */ int     first_service(),         second_service(),         third_service(),         fourth_service(); int     rundown_handler();  /* Kernel and exec routine lists: */ int (*(kernel_table[]))() = {         first_service,         second_service,         fourth_service};  int (*(exec_table[]))() = {         third_service};  /* ** Kernel and exec flags.  The flag settings below enable second_service ** and fourth_service to be 64-bit capable.  First_service and third_service ** cannot accept a 64-bit pointer.  Attempts to pass 64-bit pointers to ** these services will result in a return status of SS$_ARG_GTR_32_BITS. ** The PLV$M_64_BIT_ARGS flag instructs the system service dispatcher to ** bypass sign-extension checking of the service arguments for a particular ** service. */ int     kernel_flags [] = {         0,         PLV$M_64_BIT_ARGS,         0},      exec_flags [] = {         PLV$M_64_BIT_ARGS};  /* ** The next two defines allow the kernel and executive routine counts ** to be filled in automatically after lists have been declared for ** kernel and exec mode.  They must be placed before the PLV ** declaration and initialization, and for this module will be ** functionally equivalent to: ** ** #define KERNEL_ROUTINE_COUNT 3 ** #define EXEC_ROUTINE_COUNT 1 ** */  #define EXEC_ROUTINE_COUNT sizeof(exec_table)/sizeof(int *) #define KERNEL_ROUTINE_COUNT sizeof(kernel_table)/sizeof(int *)  /* ** Now build and initialize the PLV structure.  Since the PLV must have ** the VEC psect attribute, and must be the first thing in that psect, ** we use the strict external ref-def model which allows us to put the ** PLV structure in its own psect.  This is like the globaldef ** extension in VAX C, where you can specify in what psect a global ** symbol may be found; unlike globaldef, it allows the declaration ** itself to be ANSI-compliant.  Note that the initialization here ** relies on the change-mode-specific portion (plv$r_cmod_data) of the ** PLV being declared before the portions of the PLV which are specific ** to message vector PLVs (plv$r_msg_data) and system service intercept ** PLVs (plv$r_ssi_data). ** */  #ifdef __ALPHA #pragma extern_model save #pragma extern_model strict_refdef "USER_SERVICES" #endif extern const PLV user_services = {         PLV$C_TYP_CMOD,         /* type */         0,                      /* version */         {         {KERNEL_ROUTINE_COUNT,  /* # of kernel routines */         EXEC_ROUTINE_COUNT,     /* # of exec routines */         kernel_table,           /* kernel routine list */         exec_table,             /* exec routine list */         rundown_handler,        /* kernel rundown handler */         rundown_handler,        /* exec rundown handler */         0,                      /* no RMS dispatcher */         kernel_flags,           /* kernel routine flags */         exec_flags}             /* exec routine flags */         }         }; #ifdef __ALPHA #pragma extern_model restore #endif

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