Understanding map files

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This topic describes map files and their formats.

The binder map file is a symbol map in address order format. Each symbol listed in the map file has a storage class (CL) and a type (TY) associated with it.

Storage classes correspond to the XMC_TY variables defined in the syms.h file. Each storage class belongs to one of the following section types:

.text
Contains read-only data (instructions). Addresses listed in this section use the beginning of the .text section as origin. The .text section can contain one of the following storage class (CL) values:
DB
Debug Table. Identifies a class of sections that has the same characteristics as read only data.
GL
Glue Code. Identifies a section that has the same characteristics as a program code. This type of section has code to interface with a routine in another module. Part of the interface code requirement is to maintain the table of contents data structure (TOC) addressability across the call.
PR
Program Code. Identifies the sections that provide executable instructions for the module.
R0
Read Only Data. Identifies the sections that contain constants that are not modified while the program is running.
TB
Reserved for future use.
TI
Reserved for future use.
XO
Extended Operations code. Identifies a section of code that is to be treated as a pseudo-machine instruction.
.data
Contains read-write initialized data. Addresses listed in this section use the beginning of the .data section as the origin. The .data section can contain one of the following storage class (CL) value types:
DS
Descriptor. Identifies a function descriptor. This information is used to describe function pointers in languages such as C and Fortran.
RW
Read Write Data. Identifies a section that contains data that is known to require change while the program is running.
SV
SVC. Identifies a section of code that is to be treated as a supervisory call.
T0
TOC Anchor. Used only by the predefined TOC symbol. Identifies the TOC special symbol that is used only by the TOC header.
TC
TOC Entry. Identifies address data that will reside in the TOC.
TD
TOC Data Entry. Identifies data that will reside in the TOC.
UA
Unclassified. Identifies data that contains data of an unknown storage class.
.bss
Contains read-write data that is not initialized. Addresses listed in this section use the beginning of the .data section as origin. The .bss section contains one of the following storage class (CL) values:
BS
BSS class. Identifies a section that contains data that is not initialized.
UC
Unnamed Fortran Common. Identifies a section that contains read/write data.

Types correspond to the XTY_TY variables defined in the syms.h file. The type (TY) can be one of the following values:

Item Description
ER External Reference
LD Label Definition
SD Section Definition
CM BSS Common Definition

The following is the map file for the demonstration kernel extension. This file was created because of the -bmap:demokext.map option of the ld command.

 1   ADDRESS MAP FOR demokext                                 SOURCE-FILE(OBJECT) or
 2   *IE ADDRESS  LENGTH AL CL TY Sym#  NAME                  IMPORT-FILE{SHARED-OBJECT}
 3   --- -------- ------ -- -- -- ----- --------------------- ---------------------------
 4    I                        ER S1    _system_configuration /lib/syscalls.exp{/unix}
 5    I                        ER S2    fp_open               /lib/kernex.exp{/unix}
 6    I                        ER S3    fp_close              /lib/kernex.exp{/unix}
 7    I                        ER S4    fp_write              /lib/kernex.exp{/unix}
 8    I                        ER S5    sprintf               /lib/kernex.exp{/unix}
 9       00000000 000360  2 PR SD S6    <>                    demokext.c(demokext.o)
10       00000000           PR LD S7    .demokext
11       00000210           PR LD S8    .close_log
12       00000264           PR LD S9    .write_log
13       000002F4           PR LD S10   .open_log
14       00000360 000108  5 PR SD S11   .strcpy               strcpy.s(/usr/lib/libcsys.a[strcpy.o])
15       00000468 000028  2 GL SD S12   <.sprintf>            glink.s(/usr/lib/glink.o)
16       00000468           GL LD S13   .sprintf
17       00000490 000028  2 GL SD S14   <.fp_close>           glink.s(/usr/lib/glink.o)
18       00000490           GL LD S15   .fp_close
19       000004C0 0000F8  5 PR SD S16   .strlen               strlen.s(/usr/lib/libcsys.a[strlen.o])
20       000005B8 000028  2 GL SD S17   <.fp_write>           glink.s(/usr/lib/glink.o)
21       000005B8           GL LD S18   .fp_write
22       000005E0 000028  2 GL SD S19   <.fp_open>            glink.s(/usr/lib/glink.o)
23       000005E0           GL LD S20   .fp_open
24       00000000 0000F9  3 RW SD S21   <_$STATIC>            demokext.c(demokext.o)
25     E 000000FC 000004  2 RW SD S22   demokext_j            demokext.c(demokext.o)
26   *   00000100 00000C  2 DS SD S23   demokext              demokext.c(demokext.o)
27       0000010C 000000  2 T0 SD S24   <TOC>
28       0000010C 000004  2 TC SD S25   <_$STATIC>
29       00000110 000004  2 TC SD S26   <_system_configuration>
30       00000114 000004  2 TC SD S27   <demokext_j>
31       00000118 000004  2 TC SD S28   <sprintf>
32       0000011C 000004  2 TC SD S29   <fp_close>
33       00000120 000004  2 TC SD S30   <fp_write>
34       00000124 000004  2 TC SD S31   <fp_open>

In the above map file, the .data section begins at the statement for line 24:

24       00000000 0000F9  3 RW SD S21   <_$STATIC>          demokext.c(demokext.o)

The TOC (Table Of Contents) starts at the statement for line 27:

27       0000010C 000000  2 T0 SD S24   <TOC>