4 objdump

objdump [-a|--archive-headers]
        [-b bfdname|--target=bfdname]
        [-C|--demangle[=style] ]
        [-d|--disassemble]
        [-D|--disassemble-all]
        [-z|--disassemble-zeroes]
        [-EB|-EL|--endian={big | little }]
        [-f|--file-headers]
        [-F|--file-offsets]
        [--file-start-context]
        [-g|--debugging]
        [-e|--debugging-tags]
        [-h|--section-headers|--headers]
        [-i|--info]
        [-j section|--section=section]
        [-l|--line-numbers]
        [-S|--source]
        [-m machine|--architecture=machine]
        [-M options|--disassembler-options=options]
        [-p|--private-headers]
        [-P options|--private=options]
        [-r|--reloc]
        [-R|--dynamic-reloc]
        [-s|--full-contents]
        [-W[lLiaprmfFsoRt]|
         --dwarf[=rawline,=decodedline,=info,=abbrev,=pubnames]
                 [=aranges,=macro,=frames,=frames-interp,=str,=loc]
                 [=Ranges,=pubtypes,=trace_info,=trace_abbrev]
                 [=trace_aranges,=gdb_index]
        [-G|--stabs]
        [-t|--syms]
        [-T|--dynamic-syms]
        [-x|--all-headers]
        [-w|--wide]
        [--start-address=address]
        [--stop-address=address]
        [--prefix-addresses]
        [--[no-]show-raw-insn]
        [--adjust-vma=offset]
        [--dwarf-depth=n]
        [--dwarf-start=n]
        [--special-syms]
        [--prefix=prefix]
        [--prefix-strip=level]
        [--insn-width=width]
        [-V|--version]
        [-H|--help]
        objfile…

objdump displays information about one or more object files. The options control what particular information to display. This information is mostly useful to programmers who are working on the compilation tools, as opposed to programmers who just want their program to compile and work.

objfile… are the object files to be examined. When you specify archives, objdump shows information on each of the member object files.

The long and short forms of options, shown here as alternatives, are equivalent. At least one option from the list -a,-d,-D,-e,-f,-g,-G,-h,-H,-p,-P,-r,-R,-s,-S,-t,-T,-V,-x must be given.

-a

--archive-header

If any of the objfile files are archives, display the archive header information (in a format similar to ‘ls -l’). Besides the information you could list with ‘ar tv’, ‘objdump -a’ shows the object file format of each archive member.

--adjust-vma=offset

When dumping information, first add offset to all the section addresses. This is useful if the section addresses do not correspond to the symbol table, which can happen when putting sections at particular addresses when using a format which can not represent section addresses, such as a.out.

-b bfdname

--target=bfdname

Specify that the object-code format for the object files is bfdname. This option may not be necessary; objdump can automatically recognize many formats.

For example,

objdump -b oasys -m vax -h fu.o

displays summary information from the section headers (-h) of fu.o, which is explicitly identified (-m) as a VAX object file in the format produced by Oasys compilers. You can list the formats available with the -i option. See Target Selection, for more information.

-C

--demangle[=style]

Decode (demangle) low-level symbol names into user-level names. Besides removing any initial underscore prepended by the system, this makes C++ function names readable. Different compilers have different mangling styles. The optional demangling style argument can be used to choose an appropriate demangling style for your compiler. See c++filt, for more information on demangling.

-g

--debugging

Display debugging information. This attempts to parse STABS and IEEE debugging format information stored in the file and print it out using a C like syntax. If neither of these formats are found this option falls back on the -W option to print any DWARF information in the file.

-e

--debugging-tags

Like -g, but the information is generated in a format compatible with ctags tool.

-d

--disassemble

Display the assembler mnemonics for the machine instructions from objfile. This option only disassembles those sections which are expected to contain instructions.

-D

--disassemble-all

Like -d, but disassemble the contents of all sections, not just those expected to contain instructions.

This option also has a subtle effect on the disassembly of instructions in code sections. When option -d is in effect objdump will assume that any symbols present in a code section occur on the boundary between instructions and it will refuse to disassemble across such a boundary. When option -D is in effect however this assumption is supressed. This means that it is possible for the output of -d and -D to differ if, for example, data is stored in code sections.

If the target is an ARM architecture this switch also has the effect of forcing the disassembler to decode pieces of data found in code sections as if they were instructions.

--prefix-addresses

When disassembling, print the complete address on each line. This is the older disassembly format.

-EB

-EL

--endian={big|little}

Specify the endianness of the object files. This only affects disassembly. This can be useful when disassembling a file format which does not describe endianness information, such as S-records.

-f

--file-headers

Display summary information from the overall header of each of the objfile files.

-F

--file-offsets

When disassembling sections, whenever a symbol is displayed, also display the file offset of the region of data that is about to be dumped. If zeroes are being skipped, then when disassembly resumes, tell the user how many zeroes were skipped and the file offset of the location from where the disassembly resumes. When dumping sections, display the file offset of the location from where the dump starts.

--file-start-context

Specify that when displaying interlisted source code/disassembly (assumes -S) from a file that has not yet been displayed, extend the context to the start of the file.

-h

--section-headers

--headers

Display summary information from the section headers of the object file.

File segments may be relocated to nonstandard addresses, for example by using the -Ttext, -Tdata, or -Tbss options to ld. However, some object file formats, such as a.out, do not store the starting address of the file segments. In those situations, although ld relocates the sections correctly, using ‘objdump -h’ to list the file section headers cannot show the correct addresses. Instead, it shows the usual addresses, which are implicit for the target.

Note, in some cases it is possible for a section to have both the READONLY and the NOREAD attributes set. In such cases the NOREAD attribute takes precedence, but objdump will report both since the exact setting of the flag bits might be important.

-H

--help

Print a summary of the options to objdump and exit.

-i

--info

Display a list showing all architectures and object formats available for specification with -b or -m.

-j name

--section=name

Display information only for section name.

-l

--line-numbers

Label the display (using debugging information) with the filename and source line numbers corresponding to the object code or relocs shown. Only useful with -d, -D, or -r.

-m machine

--architecture=machine

Specify the architecture to use when disassembling object files. This can be useful when disassembling object files which do not describe architecture information, such as S-records. You can list the available architectures with the -i option.

If the target is an ARM architecture then this switch has an additional effect. It restricts the disassembly to only those instructions supported by the architecture specified by machine. If it is necessary to use this switch because the input file does not contain any architecture information, but it is also desired to disassemble all the instructions use -marm.

-M options

--disassembler-options=options

Pass target specific information to the disassembler. Only supported on some targets. If it is necessary to specify more than one disassembler option then multiple -M options can be used or can be placed together into a comma separated list.

If the target is an ARM architecture then this switch can be used to select which register name set is used during disassembler. Specifying -M reg-names-std (the default) will select the register names as used in ARM’s instruction set documentation, but with register 13 called ’sp’, register 14 called ’lr’ and register 15 called ’pc’. Specifying -M reg-names-apcs will select the name set used by the ARM Procedure Call Standard, whilst specifying -M reg-names-raw will just use ‘r’ followed by the register number.

There are also two variants on the APCS register naming scheme enabled by -M reg-names-atpcs and -M reg-names-special-atpcs which use the ARM/Thumb Procedure Call Standard naming conventions. (Either with the normal register names or the special register names).

This option can also be used for ARM architectures to force the disassembler to interpret all instructions as Thumb instructions by using the switch --disassembler-options=force-thumb. This can be useful when attempting to disassemble thumb code produced by other compilers.

For the x86, some of the options duplicate functions of the -m switch, but allow finer grained control. Multiple selections from the following may be specified as a comma separated string.

x86-64

i386

i8086

Select disassembly for the given architecture.

intel

att

Select between intel syntax mode and AT&T syntax mode.

amd64

intel64

Select between AMD64 ISA and Intel64 ISA.

intel-mnemonic

att-mnemonic

Select between intel mnemonic mode and AT&T mnemonic mode. Note: intel-mnemonic implies intel and att-mnemonic implies att.

addr64

addr32

addr16

data32

data16

Specify the default address size and operand size. These four options will be overridden if x86-64, i386 or i8086 appear later in the option string.

suffix

When in AT&T mode, instructs the disassembler to print a mnemonic suffix even when the suffix could be inferred by the operands.

For PowerPC, booke controls the disassembly of BookE instructions. 32 and 64 select PowerPC and PowerPC64 disassembly, respectively. e300 selects disassembly for the e300 family. 440 selects disassembly for the PowerPC 440. ppcps selects disassembly for the paired single instructions of the PPC750CL.

For MIPS, this option controls the printing of instruction mnemonic names and register names in disassembled instructions. Multiple selections from the following may be specified as a comma separated string, and invalid options are ignored:

no-aliases

Print the ’raw’ instruction mnemonic instead of some pseudo instruction mnemonic. I.e., print ’daddu’ or ’or’ instead of ’move’, ’sll’ instead of ’nop’, etc.

msa

Disassemble MSA instructions.

virt

Disassemble the virtualization ASE instructions.

xpa

Disassemble the eXtended Physical Address (XPA) ASE instructions.

gpr-names=ABI

Print GPR (general-purpose register) names as appropriate for the specified ABI. By default, GPR names are selected according to the ABI of the binary being disassembled.

fpr-names=ABI

Print FPR (floating-point register) names as appropriate for the specified ABI. By default, FPR numbers are printed rather than names.

cp0-names=ARCH

Print CP0 (system control coprocessor; coprocessor 0) register names as appropriate for the CPU or architecture specified by ARCH. By default, CP0 register names are selected according to the architecture and CPU of the binary being disassembled.

hwr-names=ARCH

Print HWR (hardware register, used by the rdhwr instruction) names as appropriate for the CPU or architecture specified by ARCH. By default, HWR names are selected according to the architecture and CPU of the binary being disassembled.

reg-names=ABI

Print GPR and FPR names as appropriate for the selected ABI.

reg-names=ARCH

Print CPU-specific register names (CP0 register and HWR names) as appropriate for the selected CPU or architecture.

For any of the options listed above, ABI or ARCH may be specified as ‘numeric’ to have numbers printed rather than names, for the selected types of registers. You can list the available values of ABI and ARCH using the --help option.

For VAX, you can specify function entry addresses with -M entry:0xf00ba. You can use this multiple times to properly disassemble VAX binary files that don’t contain symbol tables (like ROM dumps). In these cases, the function entry mask would otherwise be decoded as VAX instructions, which would probably lead the rest of the function being wrongly disassembled.

-p

--private-headers

Print information that is specific to the object file format. The exact information printed depends upon the object file format. For some object file formats, no additional information is printed.

-P options

--private=options

Print information that is specific to the object file format. The argument options is a comma separated list that depends on the format (the lists of options is displayed with the help).

For XCOFF, the available options are:

header

aout

sections

syms

relocs

lineno,

loader

except

typchk

traceback

toc

ldinfo

Not all object formats support this option. In particular the ELF format does not use it.

-r

--reloc

Print the relocation entries of the file. If used with -d or -D, the relocations are printed interspersed with the disassembly.

-R

--dynamic-reloc

Print the dynamic relocation entries of the file. This is only meaningful for dynamic objects, such as certain types of shared libraries. As for -r, if used with -d or -D, the relocations are printed interspersed with the disassembly.

-s

--full-contents

Display the full contents of any sections requested. By default all non-empty sections are displayed.

-S

--source

Display source code intermixed with disassembly, if possible. Implies -d.

--prefix=prefix

Specify prefix to add to the absolute paths when used with -S.

--prefix-strip=level

Indicate how many initial directory names to strip off the hardwired absolute paths. It has no effect without --prefix=prefix.

--show-raw-insn

When disassembling instructions, print the instruction in hex as well as in symbolic form. This is the default except when --prefix-addresses is used.

--no-show-raw-insn

When disassembling instructions, do not print the instruction bytes. This is the default when --prefix-addresses is used.

--insn-width=width

Display width bytes on a single line when disassembling instructions.

-W[lLiaprmfFsoRt]

--dwarf[=rawline,=decodedline,=info,=abbrev,=pubnames]

--dwarf[=aranges,=macro,=frames,=frames-interp,=str,=loc]

--dwarf[=Ranges,=pubtypes,=trace_info,=trace_abbrev]

--dwarf[=trace_aranges,=gdb_index]

Displays the contents of the debug sections in the file, if any are present. If one of the optional letters or words follows the switch then only data found in those specific sections will be dumped.

Note that there is no single letter option to display the content of trace sections or .gdb_index.

Note: the output from the =info option can also be affected by the options --dwarf-depth, the --dwarf-start and the --dwarf-check.

--dwarf-depth=n

Limit the dump of the .debug_info section to n children. This is only useful with --dwarf=info. The default is to print all DIEs; the special value 0 for n will also have this effect.

With a non-zero value for n, DIEs at or deeper than n levels will not be printed. The range for n is zero-based.

--dwarf-start=n

Print only DIEs beginning with the DIE numbered n. This is only useful with --dwarf=info.

If specified, this option will suppress printing of any header information and all DIEs before the DIE numbered n. Only siblings and children of the specified DIE will be printed.

This can be used in conjunction with --dwarf-depth.

--dwarf-check

Enable additional checks for consistency of Dwarf information.

-G

--stabs

Display the full contents of any sections requested. Display the contents of the .stab and .stab.index and .stab.excl sections from an ELF file. This is only useful on systems (such as Solaris 2.0) in which .stab debugging symbol-table entries are carried in an ELF section. In most other file formats, debugging symbol-table entries are interleaved with linkage symbols, and are visible in the --syms output.

--start-address=address

Start displaying data at the specified address. This affects the output of the -d, -r and -s options.

--stop-address=address

Stop displaying data at the specified address. This affects the output of the -d, -r and -s options.

-t

--syms

Print the symbol table entries of the file. This is similar to the information provided by the ‘nm’ program, although the display format is different. The format of the output depends upon the format of the file being dumped, but there are two main types. One looks like this:

[  4](sec  3)(fl 0x00)(ty   0)(scl   3) (nx 1) 0x00000000 .bss
[  6](sec  1)(fl 0x00)(ty   0)(scl   2) (nx 0) 0x00000000 fred

where the number inside the square brackets is the number of the entry in the symbol table, the sec number is the section number, the fl value are the symbol’s flag bits, the ty number is the symbol’s type, the scl number is the symbol’s storage class and the nx value is the number of auxilary entries associated with the symbol. The last two fields are the symbol’s value and its name.

The other common output format, usually seen with ELF based files, looks like this:

00000000 l    d  .bss   00000000 .bss
00000000 g       .text  00000000 fred

Here the first number is the symbol’s value (sometimes refered to as its address). The next field is actually a set of characters and spaces indicating the flag bits that are set on the symbol. These characters are described below. Next is the section with which the symbol is associated or *ABS* if the section is absolute (ie not connected with any section), or *UND* if the section is referenced in the file being dumped, but not defined there.

After the section name comes another field, a number, which for common symbols is the alignment and for other symbol is the size. Finally the symbol’s name is displayed.

The flag characters are divided into 7 groups as follows:

l

g

u

!

The symbol is a local (l), global (g), unique global (u), neither global nor local (a space) or both global and local (!). A symbol can be neither local or global for a variety of reasons, e.g., because it is used for debugging, but it is probably an indication of a bug if it is ever both local and global. Unique global symbols are a GNU extension to the standard set of ELF symbol bindings. For such a symbol the dynamic linker will make sure that in the entire process there is just one symbol with this name and type in use.

w

The symbol is weak (w) or strong (a space).

C

The symbol denotes a constructor (C) or an ordinary symbol (a space).

W

The symbol is a warning (W) or a normal symbol (a space). A warning symbol’s name is a message to be displayed if the symbol following the warning symbol is ever referenced.

I

i

The symbol is an indirect reference to another symbol (I), a function to be evaluated during reloc processing (i) or a normal symbol (a space).

d

D

The symbol is a debugging symbol (d) or a dynamic symbol (D) or a normal symbol (a space).

F

f

O

The symbol is the name of a function (F) or a file (f) or an object (O) or just a normal symbol (a space).

-T

--dynamic-syms

Print the dynamic symbol table entries of the file. This is only meaningful for dynamic objects, such as certain types of shared libraries. This is similar to the information provided by the ‘nm’ program when given the -D (--dynamic) option.

--special-syms

When displaying symbols include those which the target considers to be special in some way and which would not normally be of interest to the user.

-V

--version

Print the version number of objdump and exit.

-x

--all-headers

Display all available header information, including the symbol table and relocation entries. Using -x is equivalent to specifying all of -a -f -h -p -r -t.

-w

--wide

Format some lines for output devices that have more than 80 columns. Also do not truncate symbol names when they are displayed.

-z

--disassemble-zeroes

Normally the disassembly output will skip blocks of zeroes. This option directs the disassembler to disassemble those blocks, just like any other data.