dwarfdump - Online in the Cloud

PROGRAM:

NAME

dwarfdump - dumps DWARF debug information of an ELF object

SYNOPSIS

dwarfdump [options] objectfilename

DESCRIPTION

The dwarfdump command prints or checks DWARF sections as requested by specific options.
With no options (but with the required objectfilename ) all sections print (but some
sections cannot be printed independently safely, so those are only printed at offsets
where the .debug_info section refers to those sections).

As of June 2011 the printing options and the checking options are mutually exclusive (if
checking options are selected the section details are not printed). When errors are
encountered dwarfdump does attempt to print sufficient context so that one can understand
exactly where the error is in the DWARF. This change makes checking really large object
files much easier.

The format is intended to be human readable. If a script is to parse the output, the -d
option is useful.

Not all sections actually exist in any given object file.

The format may change from release to release, so it is unwise to depend too heavily on
the format.

Frame information (.debug_frame and .eh_frame) is heavily dependent on the ABI/ISA of the
object file. By default we use a generic set of register names handling up to 100
registers named r0-100. The '-R' option uses a built-in generic register name set
handling up to 1200 registers named r0-r1199. The '-x abi=<abi>' description below shows
how to name an abi and use that to guide the -f or -F processing. Unless the cpu for the
object file being dumped has many registers, do not use -R or -x abi=generic as those can
be needlessly slow dumping frame sections. Instead, use the correct abi (if it exists in
dwarfdump.conf) or a generic such as -x abi=generic100 or -x abi=generic500. To get
MIPS/IRIX register names names and call the old version 2 libdwarf frame interface use the
option '-x abi=mips'. Without '-R' or '-x abi=<abi>' dwarfdump ignores the dwarfdump.conf
file and uses compiled-in generic set of register names. If no '-x name=<path>' is given,
dwarfdump looks for "./dwarfdump.conf", "$HOME/.dwarfdump.conf", "<install-
prefix>/lib/dwarfdump.conf" and takes the first it finds. If one or more '-x name=<path>'
is given the last of these is used and all other such files are ignored.

Some -k (checking) options print so-called harmless errors. These are compiler errors
that do not cause any known problem and are only detected inside libdwarf itself. These
are difficult to properly report in dwarfdump and any error strings may not appear close
to the time the error was encountered.

URI STYLE INPUT STRINGS

The <objectfilename> and the options taking name strings look for URIs and translate the
URI strings to characters by default (see -x, -c<compiler name>, -S, -u). So any single %
character is treated as if the following two characters are hex digits representing the
underlying true character. Various characters are meaningful to shells (such as bash or
sh) and to getopt (such as the space character) If the URI translation does anything it
prints the before and after of the URI translation on standard output, so inspection of
the first lines of output will show if URI did anything. The actual options themselves
are assumed to be non-URI. So in the option '-cS&T' the -c portion must be non-URI, but
the & character might cause input issues so '-cS%26T' could be used instead. To actually
input a single % character (in a name, for example), double it to %% on the command line.

Options -U (turning off URI interpretation) and -q (making finding URI sequences silent)
give finer control of URI interpretation. PP As an example, to get a string'a b' make the
string 'a%20b' (here the quote (') is for exposition not part of the string, though quote
is certainly problematic in a name). Instead of escaping " quotes in the string, type
%25, as in
'a "b' should be typed 'a%20%25b' Any characters can be typed in URI style, not just
characters which are problematic to the shell or getopt. We strongly suggest you not type
URI-style characters where such are not needed or use the % character itself in command
line strings unless you must.

PRINTING OPTIONS

-a Print each section as independently as possible. Sections that can safely be
printed independently (like .debug_abbrev) have relevant info printed in the report
(sometimes dependent on -v).

-b Print the .debug_abbrev section. Because the DWARF specfications do not rule out
garbage data areas in .debug_abbrev (if they are not referenced from .debug_info)
any garbage bytes can result in this print failing.

-c Print locations lists.

-f Print the .debug_frame section.

-F Print the .eh_frame section.

-i Print the .debug_info section.

-l Print the .debug_info section and the associated line section data.

-m Print the .debug_macinfo section.

-N Print .debug_ranges section. Because the DWARF specfications do not rule out
garbage data areas in .debug_ranges (if they are not referenced from .debug_info)
any garbage bytes can result in this print failing.

-p Print the .debug_pubnames section.

-r Print the .debug_aranges section.

-s Print .debug_string section.

-ta Print the IRIX only sections .debug_static_funcs and .debug_static_vars.

-tf Print the IRIX only section .debug_static_funcs.

-tv Print the IRIX only section .debug_static_vars.

-w Print the IRIX-only .debug_weaknames section.

-y Print the .debug_pubtypes section (and .debug_typenames, an SGI IRIX-only section).

Having dwarfdump print relocations may help establish whether dwarfdump understands any
relocations that might exist.

-o Print all relocation records as well as we can manage.

-oi Print .rel*debug_info relocations.

-ol Print .rel*debug_line relocation.

-op Print .rel*debug_pubnames relocation.

-oa Has no effect.

-or Print .rel*debug_aranges relocations.

-of Print .rel*debug_frame relocations.

-oo Print .rel*debug_loc relocations.

-oR Print .rel*debug_ranges relocations.

-g Normally used only for testing libdwarf, this tells dwarfdump to print .debug_info
and use an older dwarf_loclist() interface function (a function that cannot handle
all current location lists).

-V Print a dwarfdump date/version string and stop.

CHECKING OPTIONS

-cg Restricts checking to compilers whose producer string starts with 'GNU' and turns
off -cs .

-cs Restricts checking to compilers whose producer string starts with 'SN' and turns
off -cg .

-cname Restricts checking to compilers whose producer string contains 'name' (not case
sensitive). The 'name' is read as a URI string.

-ka : Turns on all checking options except -kxe (-kxe might
be slow enough one mignt not want to use it routinely.)

-kb : Checks for certain abbreviations section errors when reading
DIEs.

-kc Checks for errors in constants in debug_info.

-kd Turns on full reporting of error totals per producer. (the default shows less
detail).

-ke Turns on reading pubnames and checking for fde errors.

-kf Turns on checking for FDE errors.

-kF Turns on checking for line table errors.

-kg Turns on checking for unused gaps in .debug_info (these gaps are not an error, just
a waste of space).

-ki Causes a summary of checking results per compiler (producer) to be printed at the
end.

-kl Turns on locations list checking.

-km Turns on checking of ranges.

-kM Turns on checking of aranges.

-kr Turns on DIE tag-attr combinations checking.

-kR Turns on reading DIEs and checking for forward declarations rom DW_AT_specification
attributes. (which are not an error but can be a source of inefficiency for
debuggers).

-ks Turns on extra reporting for some DIE errors checking detects .

-kS Turns on checking DIE references for circular references.

-kt Turns on tag-tag combinations checking.

-kx Turns on check_frames.

-kxe Turns off basic check_frames and turns on extended frame checking.

-ky Turns on type_offset, decl_file checking,

OPTION MODIFIERS

-C Normally when checking for tag-tag or tag-attribute combinations both the standard
combinations and some common extensions are allowed. With -C the extensions are
taken out of the allowed class of combinations.

-d When printing DIEs, put all the attributes for each DIE on the same (long) line as
the TAG. This makes searching for DIE information (as with grep) much simpler as
the entire DIE is on one line.

-D Turns off the display of section offsets and attribute values in printed output.
So the .debug_info output isjust TAGs and Attributes. For pubnames (and the like)
it removes offsets from the output. For locations lists it removes offsets from
the output, but that is useless since the attribute values don't show so neither
does the location data.

-e Turns on truncation of attribute and tag names. For example DW_TAG_foo becomes
foo . Not compatible with checking, only useful for printing DIEs.

-G When printing, add global offsets to the offsets printed.

-H number
When printing or checking .debug_info, this terminates the search after 'number'
compilation units. When printing frame information this terminates the FDE
reporting after 'number' FDEs and the CIE reporting (which occurs if one adds -v)
after 'number' CIEs. Example '-H 1'

-M When printing, this means one want to have the FORM show for each attribute. If a
-v is also added (or more than one) then details of any form indirection are also
shown.

-n When printing frames, this turns off the search for function names. In a really
large object the search can take more time than one wants to wait, so this avoids
the search.

-Q Suppresses section data printing (set automatically with a checking option).

-R When printing frames for ABIs with lots of registers, this allows up to 1200
registers to be named (like R999) without choosing an ABI with, for example '-x
abi=ppc'

-v Increases the detail shown when printing. In some sections, using more -v options
will increase the detail (one to three are useful) or may change the report to
show, for example, the actual line-data-commands instead of the resultant line-
table.

SELECTIVE ENTRY PRINTING

These -S options stand alone and basic print information about the compilation unit and
DIE where the string(s) appear. At most one of each of the following is effective (so for
example one can only have one 'match', but one can have a 'match', an 'any', and a
'regex'). Any -S causes the .debug_info section to be inspected. No checking options or
printing options should be supplied with -S.

-S match=string
When printing DIEs for each tag value or attribute name that matches 'string'
exactly print the compilation unit information and its section offset. Any CU with
no match is not printed. The 'string' is read as a URI string.

-S any=string
When printing DIEs for each tag value or attribute name that contains 'string'
somewhere in the tag or attribute (case insensitive) print the compilation unit
information and its section offset. Any CU with no match is not printed. The
'string' is read as a URI string.

-S regex=string
When printing DIEs for each tag value or attribute name where the 'string' reqular
expression matches print the compilation unit information and its section offset.
Any CU with no match is not printed. The 'string' is read as a URI string.

The string cannot have spaces or other characters which are meaningful to getopt(3) and
the shell will strip off quotes and other characters. So the string is assumed to be in
URI style and is translated. In other words, to match 'a b' make the -S string 'a%20b'
Instead of escaping " quotes in the string, type %25, as in
'a "b' should be typed 'a%20%25b' (the ' are for exposition here, not part of the
strings). Any characters can be typed in URI style, not just characters which are
problematic to the shell or getopt.

The -S any= and -S regex= options are only usable if the library functions required are
found at configure time.

The -W option is a modifier to the -S option, and increases the amount of output -W
prints. Now we show the -W in context with a -S option.

-S match=string1 -W
Prints the parent tree and the children tree for the DIEs that -S matches.

-S match=string2 -Wp
Prints the parent tree for the DIEs that -S matches.

-S match=string3 -Wc
Prints the parent tree for the DIEs that -S matches.

OTHER OPTIONS

-# number
This option controls internal debugging output, higher numbers mean more debug
actions. See the source code.

-x name=/p/a/t/h.conf
The file path given is the name of a file assumed to be a dwarfdump.conf-like file.
The file path is read as a URI string.

-x abi=ppc
Selects the abi (from a dwarfdump.conf file) to be used in printing frame
information (here using ppc as an example). The abi is read as a URI string.

-P When checking this adds the list of compilation-unit names seen for each producer-
compiler to the printed checking results.

-q When a URI is found and translated while reading the command line, be quiet about
the URI translation. That is, don't print the original and translated option
strings.

-E Turns on printing object-internal header data for some systems (for Unix/Linux does
nothing).

-u cuname
Turns on selective printing of DIEs (printing like -i). Only the DIEs for a
compilation unit that match the name provided are printed. If the compilation unit
is ./a/b/c.c the 'cuname' you provide should be c.c as the characters through the
final path-separating / are ignored. If 'cuname' begins with a / then the entire
name string of a compilation unit must match 'cuname'. The 'cuname' is read as a
URI string.

-U Turn off the URI interpretation of the command line strings entirely. Must be be
on the command line before any URI strings encountered to be fully effective.

-z No longer suported.

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