1 Symbols An SDA symbol can represent several value types. It can represent a constant, a data address, a procedure or function descriptor address, or a routine address. Constants are usually offsets of a particular field in a data structure; however, they can also represent constant values such as the BUG$_xxx symbols. Symbols are composed of up to 31 letters and numbers, and can include the dollar sign ($) and underscore (_) characters. When you invoke SDA, it reads in the global symbols from the symbols table section of SYS$BASE_IMAGE.EXE, and from REQSYSDEF.STB, a required subset of the symbols in the file SYSDEF.STB. You can add other symbols to SDA's symbol table by using the DEFINE and READ commands. All address symbols identify memory locations. SDA generally does not distinguish among different types of address symbols. However, for a symbol identified as the name of a procedure descriptor, SDA takes an additional step of creating an associated symbol to name the code entry point address of the procedure. It forms the code entry point symbol name by appending _C to the name of the procedure descriptor. Also, SDA substitutes the code entry point symbol name for the procedure descriptor symbol when you enter the following command: SDA> EXAMINE/INSTRUCTION procedure-descriptor For example, enter the following command: SDA> EXAMINE/INSTRUCTION SCH$QAST SDA displays the following information: SCH$QAST_C: SUBQ SP,#X40,SP Now enter the EXAMINE command but do not specify the /INSTRUCTION qualifier, as follows: SDA> EXAMINE SCH$QAST SDA displays the following information: SCH$QAST: 0000002C.00003009 ".0..,..." This display shows the contents of the first two longwords of the procedure descriptor. Note that there are no routine address symbols on Alpha systems, except for those in MACRO-64 assembly language modules. Therefore, SDA creates a routine address symbol for every procedure descriptor it has in its symbol table. The new symbol name is the same as for the procedure descriptor except that it has an _C appended to the end of the name. 2 Sources_of_Symbols SDA obtains its information from the following: o Images (.EXE files) o Image symbol table files (.STB files) o Object files SDA also defines symbols to access registers and to access common data structures. The only images with symbols are shareable images and executive images. These images contain only universal symbols, such as constants and addresses. The image symbol table files are produced by the linker with the /SYMBOLS qualifier. These files normally contain only universal symbols, as do the executable images. However, if the SYMBOL_ TABLE=GLOBALS linker option is specified, the .STB file also contains all global symbols defined in the image. See the OpenVMS Linker Utility Manual for more information. Symbols can include lowercase letters. Commands that manipulate symbols (such as DEFINE, SHOW SYMBOL, and UNDEFINE) require these symbols to be enclosed within quotation marks ("symbol" ). Some SDA commands predefine additional symbols. This includes SET CPU and SET PROCESS (as shown in the following subtopics) and also SHOW DEVICE and SHOW CLUSTER. 3 Modules_Containing_Symbols Object files can contain global constant values. An object file used with SDA typically contains symbol definitions for data structure fields. Such an object file can be generated by compiling a MACRO-32 source module that invokes specific macros. The macros, which are typically defined in SYS$LIBRARY:LIB.MLB or STARLET.MLB, define symbols that correspond to data structure field offsets. The macro $UCBDEF, for example, defines offsets for fields within a unit control block (UCB). OpenVMS Alpha and Integrity servers provide several such object modules in SDA$READ_DIR, as listed in the following table. For compatibility with OpenVMS VAX, the modules' file types have been renamed to .STB. File Contents DCLDEF.STB Symbols for the DCL interpreter DECDTMDEF.STB Symbols for transaction processing GLXDEF.STB Symbols for OpenVMS Galaxy data structures IMGDEF.STB Symbols for the image activator IODEF.STB I/O database structure symbols NETDEF.STB Symbols for DECnet data structures REQSYSDEF.STB Required symbols for SDA RMSDEF.STB Symbols that define RMS internal and user data structures and RMS$_xxx completion codes SCSDEF.STB Symbols that define data structures for system communications services SYSDEF.STB Symbols that define system data structures, including the I/O database TCPIP$NET_GLOBALS.STB* Data structure definitions for TCP/IP internet driver, execlet, and ACP data structures TCPIP$NFS_GLOBALS.STB* Data structure definitions for TCP/IP NFS server TCPIP$PROXY_GLOBALS.STB* Data structure definitions for TCP/IP proxy execlet TCPIP$PWIP_GLOBALS.STB* Data structure definitions for TCP/IP PWIP driver, and ACP data structures TCPIP$TN_GLOBALS.STB* Data structure definitions for TCP/IP TELNET/RLOGIN server driver data structures * The TCPIP$*.STB files are available only if TCP/IP has been installed. These files are found in SYS$SYSTEM, so that all files are not automatically read in when you issue a READ/EXEC command. 3 Symbols_Defined_on_Initialization The following table lists symbols that SDA defines automatically on initialization. ASN Address space number AST Both the asynchronous system trap status and enable registers: AST<3:0> = AST enable; AST<7:4> = AST status BR0 through BR7 Branch registers (Integrity servers only) CYCLE_COUNTER Process cycle counter ESP Executive stack pointer EBSP Executive register stack pointer (Integrity servers only) FEN Floating-point enable FP Frame pointer (R29) FP0 through FP31 Floating-point registers (Alpha only) FP0 through FP127 Floating point registers (Integrity servers only) FPCR Floating-point control register (Alpha only) FPSR Floating-point status register (Integrity servers only) GP Global pointer (R1) (Integrity servers only) G FFFFFFFF.80000000(16), the base address of system space H 00000000.7FFE0000(16), a base address in P1 space I FFFFFFFF.FFFFFFFF(16), also fills the leading digits of a hexadecimal number with the value of F KSP Kernel stack pointer KBSP Kernel register stack pointer (Integrity servers only) PAL_RSVD PAL reserved area in process HWPCB PC Program counter PCC Process cycle counter PS Processor status PTBR Page table base register R0 through R31 Integer registers (Alpha only) R0 through R127 Integer registers (Integrity servers only) SCC System cycle counter SP Current stack pointer of a process SSP Supervisor stack pointer SBSP Supervisor register stack pointer (Integrity servers only) SYSPTBR Page table base register for system space USP User stack pointer UBSP User register stack pointer (Integrity servers only) VIRBND Virtual Address Boundary for RADs (Alpha only) 3 Symbols_Defined_by_SET_CPU After a SET CPU command is issued (for analyzing a crash dump only), the symbols defined in the following table are set for that CPU. CPUDB Address of CPU database IPL Interrupt priority level register MCES Machine check error summary register PCBB Process context block base register PRBR Processor base register (CPU database address) RAD Address of RAD database SCBB System control block base register SISR Software interrupt status register VPTB Virtual Page Table Base register 3 Symbols_Defined_by_SET_PROCESS After a SET PROCESS command is issued, the symbols listed in the following table are defined for that process. ARB Address of access rights block FRED Address of floating-point register and execution data block JIB Address of job information block KTB Address of the kernel thread block ORB Address of object rights block PCB Address of process control block PHD Address of process header PSB Address of persona security block 2 Initialization_of_Symbols On initialization, SDA reads the universal symbols defined by SYS$BASE_IMAGE.EXE. For every procedure descriptor address symbol found, a routine address symbol is created (with _C appended to the symbol name). SDA then reads the object file REQSYSDEF.STB. This file contains data structure definitions that are required for SDA to run correctly. It uses these symbols to access some of the data structures in the crash dump file or on the running system. Finally, SDA initializes the process registers defined in the SET PROCESS command and executes a SET CPU command, defining the symbols as well. 2 Using_Symbols There are two major uses of the address type symbols. First, the EXAMINE command employs them to find the value of a known symbol. For example, EXAMINE CTL$GL_PCB finds the PCB for the current process. Then, certain SDA commands (such as EXAMINE, SHOW STACK, and FORMAT) use them to symbolize addresses when generating output. When the code for one of these commands needs a symbol for an address, it calls the SDA symbolize routine. The symbolize routine tries to find the symbol in the symbol table whose address is closest to, but not greater than the requested address. This means, for any given address, the routine may return a symbol of the form symbol_name+offset. If, however, the offset is greater than 0FFF(16), it fails to find a symbol for the address. As a last resort, the symbolize routine checks to see if this address falls within a known memory range. Currently, the only known memory ranges are those used by the OpenVMS executive images and those used by active images in a process. SDA searches through the executive loaded image list (LDRIMG data structure) and activated image list (IMCB data structures) to see if the address falls within any of the image sections. If SDA does find a match, it returns one of the following types of symbols: executive_image_name+offset activated_image_name+offset The offset is the same as the image offset as defined in the map file. The constants in the SDA symbol table are usually used to display a data structure with the FORMAT command. For example, the PHD offsets are defined in SYSDEF.STB; you can display all the fields of the PHD by entering the following commands: SDA> READ SDA$READ_DIR:SYSDEF.STB SDA> FORMAT/TYPE=PHD phd_address 2 Address_Resolution_with_Symbols In OpenVMS, executive and user images are loaded into dynamically assigned address space. To help you associate a particular virtual address with the image whose code has been loaded at that address, SDA provides several features: o The SHOW EXECUTIVE command o The symbolization of addresses, described in the Using_Symbols help topic o The READ command o The SHOW PROCESS command with the /IMAGES qualifier o The MAP command The OpenVMS executive consists of two base images, SYS$BASE_ IMAGE.EXE and SYS$PUBLIC_VECTORS.EXE, and a number of other separately loadable images. Some of these images are loaded on all systems, while others support features unique to particular system configurations. Executive images are mapped into system space during system initialization. By default, a typical executive image is not mapped at contiguous virtual addresses. Instead, its nonpageable image sections are loaded into a reserved set of pages with other executive images' nonpageable sections. The pageable sections of a typical executive image are mapped contiguously into a different part of system space. An image mapped in this manner is said to be sliced. A particular system may have system parameters defined that disable executive image slicing altogether. Each executive image is described by a data structure called a loadable image data block (LDRIMG). The LDRIMG specifies whether the image has been sliced. If the image is sliced, the LDRIMG indicates the beginning of each image section and the size of each section. All the LDRIMGs are linked together in a list that SDA scans to determine what images have been loaded and into what addresses they have been mapped. The SHOW EXECUTIVE command displays a list of all images that are included in the OpenVMS executive. Each executive image is a shareable image whose universal symbols are defined in the SYS$BASE_IMAGE.EXE symbol vector. On initialization, SDA reads this symbol vector and adds its universal symbols to the SDA symbol table. Executive image .STB files define additional symbols within an executive image that are not defined as universal symbols and thus are not in the SYS$BASE_IMAGE.EXE symbol vector. You can enter a READ/EXECUTIVE command to read symbols defined in all executive image .STB files into the SDA symbol table, or a READ/IMAGE filespec command to read the .STB for a specified image only. To obtain a display of all images mapped within a process, execute a SHOW PROCESS/IMAGE command. See the description of the SHOW PROCESS command for additional information about displaying the hardware and software context of a process. You can also identify the image name and offset that correspond to a specified address with the MAP command. With the information obtained from the MAP command, you can then examine the image map to locate the source module and program section offset corresponding to an address.