dwarfdump - Man Page

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).

For split-dwarf (DWARF5) object files see Split Object Files, DWARF5 section 7.3.

Nearly all options are available in the traditional (single-letter) form and in a long-options form with meaningful names. New options are only in the long-options form.

With no options dwarfdump prints a basic set of DWARF section information.  If any option is given on the command line the basic set is ignored and one must tell dwarfdump what to print or check (for example by adding the -a option).

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 --format-dense (-d) option is useful.

As of December 2020 DWARF expressions are broken out to print each expression (DW_OP_plus for example) in a block on a separate line.  To restore the previous behavior, sort of like --format-dense but only applying to blocks of DWARF expression operators (DW_OP*). the --format-expr-ops-joined is useful. If the option is placed in the dwarfdump.conf file (see the file itself for the format) it will apply without needing to put it on the command line.

Not all sections actually exist in any given object file.

The output 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-r99.

As of 2020 there are three different ways compiler writers separate the DWARF information from an executable/shared-object. One is DWARF5 Split Dwarf (the --file-tied option is useful for these). Another is GNU debuglink (libdwarf automatically finds the DWARF when given the name of the executable, use --no-follow-debuglink to suppress this and make possible printing the backtrace data in section .eh_frame). The third way is on MacOS: the debug DWARF is in a separate object (dwarfdump/libdwarf automatically find it if it is present, --no-follow-debuglink suppresses this finding).

In many cases one can get additional detail by specifying -v (sometimes -v -v gets even more, see the --verbose discussion below). When printing DIEs (Debugging Information Entries) the options -G (showing global offsets) and -M (naming the DW_FORM* of attributes) (or their -- counterparts) can be a great aid to understanding DWARF..

The --format-registers (-R) option uses a built-in generic register name set handling up to 1200 registers named r0-r1199.

The --file-abi=<abi> (-x abi=<abi>) description below shows how to name an abi and use that to guide the --print-frame (-f) or --print-eh-frame (-F) processing.

One of --print-frame (-f) or --print-eh-frame (-F) implies lots of abi (register names,  register counts) in the output, but sections other than frame sections may also need register names.

Unless the cpu for the object file being dumped has many registers, do not use --format-registers or -file-abi=<abi> 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 --file-abi=abi=generic100 or --file-abi=abi=generic500
.

The most useful abi choices are likely mips or x86 or x86_64 or ppc or arm
. Without --format-registers (-R) or -file-abi=<abi> (-x abi=<abi>) dwarfdump uses a compiled-in generic set of register names. If no --file-name=<path> (-x name=<path>) is given, dwarfdump looks for "./dwarfdump.conf",  "$HOME/dwarfdump.conf",  "$HOME/.dwarfdump.conf",  "<install-prefix>/lib/dwarfdump.conf"  and takes the first it finds. Use the --show-dwarfdump-conf option  to see what dwarfdump finds. If one or more --file-name=<path> (-x name=<path>) is given the last of these is used and all other such files are ignored.

Some checking ( -k) options  (See "Check DWARF Integrity" in the help output) 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.

If zlib compression was used on the DWARF sections in the object file being read the real section names such as .zdebug_info etc will be reported by dwarfdump.   When dwarfdump says something is at offset 55  of .zdebug_info (or the like) keep in mind that  the offset applies to the uncompressed section (in memory),  not the .zdebug_ compressed section in objectfilename.

URI-Style Input Strings

The <objectfilename> and all the options taking name strings look for URIs and translate the URI strings to characters by default. 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 --format-producer=S&T (-cS&T) the & character might cause input issues so --format-producer=S%26T should be used instead. To actually input a single % character (in a name, for example),  double it to %% on the command line (or use %25).

Options --format-suppress-uri (-U) (turning off URI interpretation) and --format-suppress-uri-msg (-q) (making finding URI sequences silent) give finer control of URI interpretation.

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.

URI-STYLE OUTPUT (printing)

Dwarfdump translates any characters in strings which are not ordinary printable ASCII (and some which are ASCII) in the reverse of the previous section. It prints into a uri-style output in the form %xx, where xx are hex digits in the form of ASCII 0-9a-0f. The percent character(%) is printed as '%25'

This is a clumsy way to deal with UTF-8 strings and sensible way to deal with the low ASCII values that on many systems cause one's terminal to behave oddly. Such translations are not idempotent so dwarfdump avoids doing the translation more than once on any string. See option --format-suppress-sanitize below to eliminate the output transformation.

Printing Options

--print-all (-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).

--print-abbrev (-b)

Print the .debug_abbrev section. Because the DWARF specifications 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.

--print-loc (-c)

Print locations lists.

--print-debug-gnu

Print  the .debug_gnu_pubnames and .debug_gnu_typenames sections.

--print-fission

Print  the .gdb_index, .debug_cu_index,
.debug_tu_index, .gnu.debuglink,
 and .note.gnu.build-id sections.

--print-gnu-debuglink

Print .gnu_debuglink and .note.gnu.build-id sections

--elf (-E)

prints, for Elf objects, object file details. See the "Print ELF Section Headers" section of the help file for additional choices on elf printing. If libdwarf or dwarfdump is built without libelf this and related options are not available.

--print-frame (-f)

Print the .debug_frame section.

--print-eh-frame (-F)

Print the GNU .eh_frame section.

--print-info (-i)

Print the .debug_info section.

--print-fission (-I)

Print any .gdb_index, .debug_cu_index, and .debug_tu_index sections that exist in the object.

--print-gnu-debuglink

If the .gnu_debuglink section is present its content is printed. If the .note.gnu.build-id section is present its content is printed. If a DWARF containing file named by the content of the .gnu_debuglink section exists the name will be printed.

--print-lines (-l)

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

--print-lines-short (-ls)

Print the .debug_info section and  the associated line section data, but omit the <pc> address.  Useful when a comparison of line sections from objects with slight differences is required.

--print-macinfo (-m)

Print the .debug_macinfo (DWARF 2,3,4) and .debug_macro (DWARF5) sections. The .debug_macro reporting may show output labeled MACRONOTES, mentioning macro content that might be questionable.   See also --check-macros (-kw).

--print-ranges (-N)

Print .debug_ranges section.  Because the DWARF specifications 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.

--print-pubnames (-p)

Print the .debug_pubnames section.

--print-str-offsets

Print the .debug_str_offsets section.

--print-aranges (-r)

Print the .debug_aranges section.

--print-strings (-s)

Print .debug_string section.

--print-static (-ta)

Print the IRIX only sections .debug_static_funcs and .debug_static_vars.

--print-type (-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. Other tools may be more useful than dwarfdump for printing object-file details. If dwarfdump or libelf is built without libelf the relocation options are not available. See "Print Elf Relocation Data" in the help output for additional relocation printing choices.

--reloc (-o)

Print all relocation records as well as we can manage. If libdwarf or dwarfdump were built without libelf this option is unavailable.

--version (-V)

Print a dwarfdump date/version string and stop.

Checking Options

--check-all (-ka)

Turns on all checking options except --check-frame-extended (-kxe) (which might be slow enough one  might not want to use it routinely.)

--check-abbrev (-kb)

Checks for certain abbreviations section errors when reading DIEs.

--check-macros (-kw)

Checks for issues in DWARF5 .debug_macro and identifies issues that might be questionable but not necessarily errors with the string MACRONOTES (and reports some MACRONOTES that --print-macinfo will not show). It also checks .debug_macinfo, but less thoroughly and never emits MACRONOTES for .debug_macinfo. See also --print-macinfo (-m). (regrettably inconsistent spelling...).

--check-constants (-kc)

Checks for errors in constants in debug_info.

-check-show (-kd)

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

--check-silent-ks

Turns off some verbose checking detection.

--check-attr-dup (-kD)

Turns on reporting of duplicated attributes. Duplicated attributes on a single DW_TAG are improper DWARF, but at least one compiler emitted such.

--check-pubnames (-ke)

Turns on reading pubnames and checking for fde errors.

--check-frame-info (-kf)

Turns on checking for FDE errors (.debug_frame  and .eh_frame).

--check-files-lines (-kF)

Turns on checking for line table errors.

--check-gaps (-kg)

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

--check-unique (-kG)

Print only unique errors. Error lines are simplified (hex numbers removed, for example) and when a given message string would otherwise appear  again it is suppressed.

--check-summary (-ki)

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

--check-loc (-kl)

Turns on locations list checking.

--check-ranges (-km)

Turns on checking of ranges.

--check-aranges (-kM)

Turns on checking of aranges.

--check-tag-attr (-kr)

Turns on DIE tag-attr combinations checking, looking for surprising attributes for DIE tags.  Prints a DWARF-CHECK message for each such found. It does not report common extensions as errors. A summary of usage is printed at the end. Common extensions to the standard are allowed as if standard. See the -C (--format-extensions) option to show common extensions as DWARF-CHECK messages. See -kuf (--check-usage-extended) to add additional details to the summary report.

--check-usage (-ku)

The same as -kr except only the summary is printed at the end,  the detailed DWARF-CHECK messages per instance are not printed.

--check-attr-encodings (-kE)

Checks the integer encoding representation of constant FORMs in debug_info, computing whether these integer values could fit in fewer bytes if represented in LEB128 and reports the space saving that would achieve.

--check-forward-refs (-kR)

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

--check-self-refs (-kS)

Turns on checking DIE references for circular references.

--check-tag-tag (-kt)

Turns on tag-tag combinations checking, looking for surprising parent-child DIE relationships. It does not report common extensions as errors. Common extensions to the standard are allowed as if standard. See the -C (--format-extensions) option to show common extensions as errors.

--check-frame-basic (-kx)

Turns on basic frames checking for .debug_frame and .eh_frame).

--check-frame-extended (-kxe)

Turns off basic check_frames and  turns on extended frame checking for .debug_frame and .eh_frame. This option can be slow.

--check-type (-ky)

Turns on type_offset checking (ensuring local attribute  offsets refer to what they should) and that DW_AT_decl_file and some other offsets refer to appropriate locations.

Option Modifiers

--format-extensions (-C)

This is a secondary option  after --check-tag-tag (-kt) or --check-tag-attr (-kr) or  Normally when checking for tag-tag  or tag-attribute combinations both the standard combinations and  some common extensions are allowed (not reported). With this option the extensions are taken out of the class of allowed combinations.

-kuf (--check-usage-extended)

This modifies --check-tag-attr (-kr) or --check-usage (-ku) to print additional details in the summary. Add the -kuf (--check-usage-extended) before or after the option it modifies.

--format-dense (-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.

--format-suppress-offsets (-D)

Turns off the display of section offsets and attribute values in printed output. So the .debug_info output is just 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.

--format-ellipsis (-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.

--format-global-offsets (-G)

When printing, add global offsets to the offsets printed.

--format-limit=<num> (-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 '--format-limit=1'

--format-attr-name (-M)

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

--format-suppress-lookup (-n)

When printing frames, this turns off the search for function names in inner scopes. Unless the language used to build the object file supports function definitions in inner scopes there is no point in looking for function names in inner scopes. And a really large object the search can take more time than one wants to wait. This option suppresses the inner scope search.

--file-output=<path> (-Ofile=<path>)

The <path> will be used as the file name for output instead  of writing to stdout (stdout is the default).

--format-suppress-data (-Q)

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

--format-suppress-sanitize

Suppresses the default string-printing  translations so non-ascii and non-printable characters from the object file are printed as-is. See "URI-STYLE OUTPUT" above.

--format-suppress-uri (-U)

Suppresses the default URI translation of following options on the command line. See "URI-Style Input Strings" above.

--format-registers (-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' or, equivalently, '--file-abi=ppc'

--verbose (-v)

Increases the detail shown when printing. In some sections, using more -v options will increase the detail (one to four are useful) or may change the report to show, for example, the actual line-data-commands instead of the resultant line-table. Two to four -v options make a difference when printing DIEs and rnglists (-i),  lines (-l), frames (-f,-F), gdb_index(-I). Additional -v beyond four do not currently add-to or change the output.

--show-dwarfdump-conf

Shows what files are checked to find a dwarfdump.conf and its register naming tables.

Limiting Output

The simplest limiting option is to stop the examination/printing after <num> compilation units. See -H and  --format-limit above. This option also limits the number of FDEs and CIEs printed from any .debug_frame or .eh_frame section.

The --search (-S) options  print information about the compilation unit and DIE where the string(s) appear. These cannot be combined with other options. 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 --search (-S) causes the .debug_info section to be inspected. No checking options or printing options should be supplied  with --search(-S) options. The strings should use URI-style to avoid any conflicts with the command-line parser applicable (bash, sh, ...) or getopt(), as well as using URI to deal with searching for strings in non-ASCII such as French, (etc) or the now-nearly-universal UTF8.

These are particularly useful when the amount of DWARF information output by -i is multiple gigabytes of data.

If -Sv used instead of -S , the number of occurrences is printed. (see below for an example).

--search-match=<string> (-Smatch=string)
--search-match-count=<string> (-Svmatch=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. The count (Sv) form reports the count of occurrences.

--search-any=<string> (-Sany=string)
--search-any-count=<string> (-Svany=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. The count (Sv) form reports the count of occurrences.

--search-regex=string (-Sregex=string)
--search-regex-count=string (-Svregex=string)

When printing DIEs for each tag value or attribute name where the 'string' regular 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 count (Sv) form reports the count of occurrences.

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 --search-any (-Sany) and --regex-any (-Sregex) options are only usable if regular-expression library functions required are found at configure time.

The --search-print (-W) option is a modifier to the -S option, and increases the amount of output -S prints. An example v modifier to the -S option is shown below. And we show the -W in context with a -S option.

--search-match-count=string

Prints information about the DIEs that -S matches and prints the count of occurrences.

-S match=string1 -W
--search-match=string1 --search-print-tree

Prints the parent tree and the children tree for the DIEs that --search-match  matches.

-S match=string2 -Wp
--search-match=string2 --search-print-parent

Prints the parent tree for the DIEs that -S matches.

-S match=string3 -Wc
--search-match=string3 --search-print-children

Prints the children tree for the DIEs that -S matches.

--format-gcc (-cg)

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

--format-snc (-cs)

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

--format-producer=<name> (-c<name>)

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

Other Options

-x name=<path>
--file-name=/p/a/t/h.conf (-xname=/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
--file-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.

--format-group-number=<n> (-x groupnumber=<n>)

For an object file with both DWARF5 split  dwarf (.debug_info.dwo for example)  and ordinary DWARF sections (.debug_info for example) in the single object file one must use --format-group-number=2 to print the dwo sections. Adding --file-tied=<path> naming the object file ties in the non-dwo skeleton sections (the <path> is to the skeleton object file when the main object file is dwo/dwp).

-x tied=/t/i/depath
--file-tied=/t/i/depath

Used when opening a main object that is a .dwo or .dwp file. For example if /path/to/myapp.dwp is the split-dwarf object and /path/to/myapp is the executable, do "dwarfdump --file-tied=/path/to/myapp /path/to/myapp.dwp"  .  The tied file path names the executable which has the .debug_addr section that may be referred to from the main object. See Split Objects (aka Debug Fission) in the DWARF5 standard. This cannot be used with MacOS debug or GNU debuglink, such files do not have a Split Dwarf object file.

-x line5=s2l
--file-line5=s2l

Normally used only to test libdwarf interfaces. There are 4 different interface function sets and to ensure they all work this option lets us choose which to use.  The options are 's2l' (default, Allows standard and two-level line tables using the latest interface functions), 'std' (Allows standard single level line tables using the latest interface functions), 'orig' (allows DWARF2,3,4 original line tables using an older interface function set), 'orig2l' (allows original line tables and some two-level line tables using an older interface set).

--print-producers

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

-q
--format-suppress-uri-msg

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.

-u cuname
--format-file=<file>

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 'file' is read as a URI string.

-U
--format-suppress-uri

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. Likely something no one needs to do.

-h
--help

Show this man page.

Split Dwarf

With Split Dwarf (DWARF5) the main body of the DWARF is in a separate file, often having the name suffix .dwp or .dwo .

For example if /path/to/myapp.dwp is the split-dwarf object and /path/to/myapp is the executable, do "dwarfdump --file-tied=/path/to/myapp /path/to/myapp.dwp"  . The tied file path names the executable which has the .debug_addr section and other sections that may be referred to from the .dwo/.dwp object.

See Split Object Files (sometimes called Debug Fission) in the DWARF5 standard, section 7.3.

Files

dwarfdump

./dwarfdump.conf

$(HOME)/.dwarfdump.conf

$(HOME)/dwarfdump.conf

<install-prefix>/lib/dwarfdump.conf

Notes

In some cases compilers use DW_FORM_data1 (for example) and in such cases the signedness of the value must be taken from context.  Rather than attempt to determine the context, dwarfdump prints the value with both signedness whenever there is ambiguity about the correct interpretation. For example,  "DW_AT_const_value           176(as signed = -80)". For normal DWARF consumers that correctly and fully evaluate all attributes there is no ambiguity of signedness: the ambiguity for dwarfdump is due to dwarfdump evaluating DIEs in a simple order and not keeping track of much context.

Bugs

Support for printing certain DWARF5 location expressions is incomplete. Report problems to libdwarf-list -at- linuxmail -dot- org