ref: 02ac617541ca1a7bf82b1615fb5a58235469b5d3
dir: /man/2/dis/
.TH DIS 2 .SH NAME dis \- read Dis object files .SH SYNOPSIS .EX include "dis.m"; dis := load Dis Dis->PATH; Inst: adt { op: int; addr: int; mid: int; src: int; dst: int; }; Type: adt { size: int; map: array of byte; }; Data: adt { op: int; # encoded op n: int; # number of elements off: int; # byte offset in data space pick { Zero => # DEFZ Bytes => # DEFB bytes: array of byte; Words => # DEFW words: array of int; String => # DEFS str: string; Reals => # DEFF reals: array of real; Array => # DEFA typex: int; length: int; Aindex => # DIND index: int; Arestore => # DAPOP Bigs => # DEFL bigs: array of big; } }; Link: adt { pc: int; desc: int; sig: int; name: string; }; Import: adt { sig: int; name: string; }; Except: adt { s: string; pc: int; }; Handler: adt { pc1: int; pc2: int; eoff: int; ne: int; t: ref Type; etab: array of ref Except; }; Mod: adt { name: string; srcpath: string; magic: int; rt: int; ssize: int; isize: int; dsize: int; tsize: int; lsize: int; entry: int; entryt: int; inst: array of ref Inst; types: array of ref Type; data: list of ref Data; links: array of ref Link; imports: array of array of ref Import; handlers: array of ref Handler; sign: array of byte; }; init: fn(); loadobj: fn(file: string): (ref Mod, string); op2s: fn(op: int): string; inst2s: fn(i: ref Inst): string; .EE .SH DESCRIPTION The .B Dis module decodes the contents of a Dis object file containing a single module, of the format defined by .IR dis (6). The module defines many constants, giving symbolic names to Dis instruction codes, addressing mode masks, magic numbers, and other bits of the object code. .PP .B Init must be called before any other function, to initialise the module. .PP .B Loadobj reads a Dis object file from .IR file , and returns a reference to a .B Mod adt that represents the module's contents, as the first element of the tuple; the string element of the tuple is nil. On error, the string element contains a diagnostic, and the reference is nil. .PP .B Op2s returns the assembly-language representation, as used by .IR asm (1), of the Dis operation code .IR op . It returns the string .IB ` OP op' if .I op does not correspond to a known operation code. .PP .B Inst2s returns a string corresponding to a disassembly of Dis instruction .IR i , including addressing modes. .PP The module defines integer constants giving symbolic names to the Dis instruction codes, all of the form .BI I name where .I name is the name of the instruction, all in upper case: .IP .BR INOP , .BR IALT , .BR INBALT , \&... .BR INEWZ , .BR INEWAZ , .BR IRAISE .PP The name .B MAXDIS is also defined; it has the value of the first unassigned Dis operation code. .PP Most of the members of the adt types have an obvious interpretation on reference to .IR dis (6). .PP The adt .B Mod represents a single module. It contains values extracted from the module's header, and references to structures representing the contents of the Dis file's code, data, type and external linkage sections: .TF entryt .PD .TP .B magic The constant .B XMAGIC (unsigned Dis module) or the constant .B SMAGIC (signed Dis module). .TP .B sign If .B magic is .BR SMAGIC , the .B sign field contains the bytes in the signature section of the module header. Otherwise, there is no signature and .B sign is .BR nil . .TP .B name The name of the implementation module. .TP .B srcpath The source of the dis file relative to the inferno root. .TP .B rt Run-time options: a bit mask of the constants .BR MUSTCOMPILE , .B DONTCOMPILE and .BR SHAREMP . .TP .B ssize Stack extent .TP .B isize Number of instructions .TP .B dsize Size in bytes of the module's global data area .TP .B tsize Number of type descriptors .TP .B lsize Number of external linkage descriptors .TP .B entry PC (instruction offset) of the default entry point for the module .TP .B entryt Index of the type descriptor for the module's entry point .TP .B inst Array representing the contents of the code segment; length .IB m .isize .TP .B types Array of the module's type descriptors; length .IB m .tsize .TP .B data list of data descriptors representing instructions for creating the module's data segment .TP .B links array of the module's external linkage descriptors (for exported functions); length .IB m .lsize .TP .B imports an array of import descriptor tables, one table for each module imported by this module. Each table is an array of pairs giving the signature and name of each function imported. .TP .B handlers an array of exception handlers used in this module. Each handler consists of the range of pc's it covers, the exception structure offset within the frame, the number of declared exceptions (as opposed to strings) in the handler, the type (if any) of any memory to clear when the exception occurs and a table of exceptions. The latter is an array containing pairs of exceptions and pc values. The final entry gives the pc to jump to in the '*' case or -1 if not applicable. .PP The .B Type adt represents the value of a type descriptor: .TF entryt .PD .TP .B size Size in bytes of the object represented by this descriptor .TP .B map Bitmap describing the location of pointers in the object (see .IR dis (6)) .PP The .B Link adt represents the value of a link descriptor: .TF entryt .PD .TP .B name Name of the exported function .TP .B pc Instruction index in .B Mod.code of the function's entry point .TP .B desc Index in .B Mod.types of the type describing the function's stack frame .TP .B sig Integer hash of the function's type signature .PP The .B Inst adt represents a single Dis instruction in the instruction stream. The member .B op is the Dis instruction code. The member .B addr contains the addressing mode flags for middle, source and destination operands. Constants are defined to help unpack it. .PP The middle operand description is selected by the constant mask .BR ARM : .IP .IB i ".addr & ARM" .PP The valid results and interpretation are as follows: .IP .RS .TF AXNON .TP .B AXNON No middle operand. .TP .B AXIMM .BI $ n .TP .B AXINF .IB n (fp) .TP .B AXINM .IB n (mp) .PD .RE .PP The source operand's addressing mode is extracted as follows: .IP .BI ( i ".addr>>3)&AMASK" .PP The following combinations are valid, where .I n is the value in .IB i .src : .IP .RS .TF AIND|AMP .TP .B AXXX No operand .TP .B AFP The operand is .IB n (fp) .TP .B AMP The operand is .IB n (mp) .TP .B AIMM The operand is .BI $ n (ie, immediate literal .IR n ) .TP .B AIND|AFP The operand is .IB si ( fi (fp)) .TP .B AIND|AMP The operand is .IB si ( fi (mp)) .RE .PD .PP where .I fi is the offset for the first indirection, extracted from .IR n : .IP .BI ( n ">>16)&16rFFFF)" , .PP and .I si is the offset for the second indirection, also extracted from .IR n: .IP .BI ( n "&16rFFFF)" . .PP The destination addressing mode is interpreted in a similar way, except that the addressing mode is extracted as follows: .IP .BI ( i ".addr&AMASK)" .PP and the value of the offset .I n is found in .IB i .dst . .I Fi and .I si are extracted from .I n as before. .PP Finally, .B Data adt represents a data item, which tells the system's module loader how to initialise part of the module's global data segment. It has the following members: .TP .B op the encoded type and length; usually ignored: the .B pick tag and .BR n , below, usually suffice .TP .B n the number of data values .TP .B off the byte offset of the first data value to initialise, relative to the current loading base .PP The alternatives of the .B pick select the correct variant to see the data values encoded in the object file as Limbo values of the correct type. The interpretation is straightforward for the tags .BR Bytes , .BR Words , .B Bigs and .BR Reals : the corresponding array members are arrays of .B n elements of the appropriate type. The remaining cases are as follows: .TF Arestore .PD .TP .B String The member .B str has the decoded representation of the corresponding .I n data bytes from the object file. .TP .B Array The member .B typex is the index in .B Mod.types of the array's type, and member .B length is its length. .TP .B Aindex This alternative can appear only following a value of .BR Data.Array . The member .B index is an index into the corresponding array as represented in the global data space, which determines a new loading base address for subsequent .B Data items. The previous base address is stacked on an internal stack. .TP .B Arestore Pop the address from the internal address stack and make that the current loading address. The request marks the end of a sequence of .B Data items initialising an array. .SH SOURCE .B /appl/lib/dis.b .SH SEE ALSO .IR disdep (1), .B wm/rt in .IR wm-misc (1), .IR dis (6) .br "The Dis Virtual Machine", in Volume 2.