path: root/usr/src/man/man1/lari.1

'\" te
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.TH LARI 1 "December 28, 2020"
.SH NAME
lari \- link analysis of runtime interfaces
.SH SYNOPSIS
.nf
\fBlari\fR [\fB-bCDsVv\fR] [\fB-a\fR | \fB-i\fR | \fB-o\fR] \fIfile\fR | \fIdirectory\fR...
.fi

.LP
.nf
\fBlari\fR [\fB-CDosv\fR] [\fB-m\fR [\fB-d\fR \fImapdir\fR]] \fIfile\fR
.fi

.SH DESCRIPTION
The \fBlari\fR utility analyzes the interface requirements of dynamic \fBELF\fR
objects. Two basic modes of operation are available. The first mode displays
runtime interface information. The second mode generates interface definitions.
.sp
.LP
Dynamic objects offer symbolic definitions that represent the interface that
the object provides for external consumers. At runtime, bindings are
established from the symbolic references of one object to the symbolic
definitions of another object. \fBlari\fR analyzes both the interface
definitions and runtime bindings of the specified objects.
.sp
.LP
When displaying runtime interface information, \fBlari\fR can analyze a number
of files and/or directories. \fBlari\fR analyzes each \fIfile\fR that is
specified on the command line. \fBlari\fR recursively descends into each
\fIdirectory\fR that is specified on the command line, processing each file
that is found.
.sp
.LP
When generating interface definitions, \fBlari\fR can only process a single
\fIfile\fR specified on the command line.
.sp
.LP
Without the \fB-D\fR option, \fBlari\fR processes files as dynamic \fBELF\fR
objects by using \fBldd\fR(1). This processing uses the following options:
.sp
.in +2
.nf
\fB-r\fR and \fB-e\fR \fBLD_DEBUG=files,bindings,detail\fR
.fi
.in -2
.sp

.sp
.LP
These options provide information on all bindings that are established as part
of loading the object. Notice that by using \fBldd\fR, the specified object is
not executed, and hence no user controlled loading of objects, by
\fBdlopen\fR(3C) for example, occurs. To capture all binding information from
an executing process, the following environment variables can be passed
directly to the runtime linker, \fBld.so.1\fR(1):
.sp
.in +2
.nf
\fBLD_DEBUG=files,bindings,detail LD_DEBUG_OUTPUT=lari.dbg \
LD_BIND_NOW=yes\fR
.fi
.in -2
.sp

.sp
.LP
The resulting debug output, \fBlari.dbg.\fIpid\fR\fR, can be processed by
\fBlari\fR using the \fB-D\fR option. \fBNote:\fR \fBlari\fR attempts to
analyze each object that has been processed using the path name defined in the
debug output. Each object must therefore be accessible to \fBlari\fR for a
complete, accurate analysis to be provided. The debug output file must be
generated in the \fBC\fR locale.
.sp
.LP
When displaying interface information, \fBlari\fR analyzes the interfaces of
the processed dynamic objects and, by default, displays any interesting
information. See \fBInteresting Information\fR under EXTENDED DESCRIPTION. The
information that is displayed is also suitable for piping to other tools. This
capability can aid developers in analyzing process bindings or debugging
complex binding scenarios.
.sp
.LP
The generation of interface definitions by \fBlari\fR can be used to refine the
interface requirements of the dynamic objects that are processed. When creating
a dynamic object, you should define an explicit, versioned interface. This
definition controls the symbol definitions that are available to external
users. In addition, this definition frequently reduces the overall runtime
execution cost of the object. Interface definitions can be assigned to an
object during its creation by the link-editor using the \fB-M\fR option and the
associated \fImapfile\fR directives. See the \fILinker and Libraries Guide\fR
for more details on using \fImapfiles\fR to version objects. An initial version
of these \fImapfiles\fR can be created by \fBlari\fR.
.SH OPTIONS
The following options are supported.
.sp
.ne 2
.na
\fB\fB-a\fR\fR
.ad
.RS 13n
Displays all interface information for the objects analyzed. \fBNote:\fR The
output from this option can be substantial, but is often useful for piping to
other analysis tools.
.RE

.sp
.ne 2
.na
\fB\fB-b\fR\fR
.ad
.RS 13n
Limits the interface information to those symbols that have been explicitly
bound to. \fBNote:\fR Symbols defined as protected might have been bound to
from within the defining object. This binding is satisfied at link-edit time
and is therefore not visible to the runtime environment. Protected symbols are
displayed with this option.
.RE

.sp
.ne 2
.na
\fB\fB-C\fR\fR
.ad
.RS 13n
Demangles C++ symbol names. This option is useful for augmenting runtime
interface information. When generating interface definitions, demangled names
are added to the \fImapfiles\fR as comments.
.RE

.sp
.ne 2
.na
\fB\fB-d\fR \fImapdir\fR\fR
.ad
.RS 13n
Defines the directory, \fImapdir\fR, in which \fImapfiles\fR are created. By
default, the current working directory is used.
.RE

.sp
.ne 2
.na
\fB\fB-D\fR\fR
.ad
.RS 13n
Interprets any input \fIfiles\fR as debugging information rather than as
dynamic objects.
.RE

.sp
.ne 2
.na
\fB\fB-i\fR\fR
.ad
.RS 13n
Displays interesting interface binding information. This mode is the default if
no other output controlling option is supplied. See \fBInteresting
Information\fR under EXTENDED DESCRIPTION.
.RE

.sp
.ne 2
.na
\fB\fB-m\fR\fR
.ad
.RS 13n
Creates \fImapfiles\fR for each dynamic object that is processed. These
\fImapfiles\fR reflect the interface requirements of each object as required by
the input file being processed.
.RE

.sp
.ne 2
.na
\fB\fB-o\fR\fR
.ad
.RS 13n
Limits the interface information to those symbols that are deemed an overhead.
When creating \fImapfiles\fR, any overhead symbols are itemized as local
symbols. See \fBOverhead Information\fR under EXTENDED DESCRIPTION.
.RE

.sp
.ne 2
.na
\fB\fB-s\fR\fR
.ad
.RS 13n
Saves the bindings information produced from \fBldd\fR(1) for further analysis.
See FILES.
.RE

.sp
.ne 2
.na
\fB\fB-V\fR\fR
.ad
.RS 13n
Appends interesting symbol visibilities. Symbols that are defined as
\fBsingleton\fR or are defined \fBprotected\fR are identified with this option.
.RE

.sp
.ne 2
.na
\fB\fB-v\fR\fR
.ad
.RS 13n
Ignores any objects that are already versioned. Versioned objects have had
their interfaces defined, but can contribute to the interface information
displayed. For example, a versioned shared object might reveal overhead symbols
for a particular process. Shared objects are frequently designed for use by
multiple processes, and thus the interfaces these objects provide can extend
beyond the requirements of any one process. The \fB-v\fR option therefore, can
reduce noise when displaying interface information.
.RE

.sp
.LP
The runtime interface information produced from \fBlari\fR has the following
format:
.sp
.in +2
.nf
[information]: \fIsymbol-name\fR [demangled-name]: \fIobject-name\fR
.fi
.in -2
.sp

.sp
.LP
Each line describes the interface symbol, \fBsymbol-name\fR, together with the
object, \fBobject-name\fR, in which the symbol is defined. If the symbol
represents a function, the symbol name is followed by \fB()\fR. If the symbol
represents a data object, the symbol name is followed by the symbols size,
enclosed within \fB[]\fR. If the \fB-C\fR option is used, the symbol name is
accompanied by the symbols demangled name, \fBdemangled-name\fR. The
information field provides one or more of the following tokens that describe
the symbol's use:
.sp
.ne 2
.na
\fB\fIcnt\fR:\fIbnd\fR\fR
.ad
.RS 11n
Two decimal values indicate the symbol count, \fBcnt\fR, and the number of
bindings to this object, \fBbnd\fR. The symbol count is the number of
occurrences of this symbol definition that have been found in the objects that
are analyzed. A count that is greater than \fB1\fR indicates multiple instances
of a symbol definition. The number of bindings indicate the number of objects
that have been bound to this symbol definition by the runtime linker.
.RE

.sp
.ne 2
.na
\fB\fBE\fR\fR
.ad
.RS 11n
This symbol definition has been bound to from an external object.
.RE

.sp
.ne 2
.na
\fB\fBS\fR\fR
.ad
.RS 11n
This symbol definition has been bound to from the same object.
.RE

.sp
.ne 2
.na
\fB\fBD\fR\fR
.ad
.RS 11n
This symbol definition has been directly bound to.
.RE

.sp
.ne 2
.na
\fB\fBI\fR\fR
.ad
.RS 11n
This symbol definition provides for an interposer.  An object that explicitly
identifies itself as an interposer defines all global symbols as interposers.
See the \fB-z\fR \fBinterpose\fR option of \fBld\fR(1), and the
\fBLD_PRELOAD\fR variable of \fBld.so.1\fR(1). Individual symbols within a
dynamic executable can be defined as interposers by using the \fBINTERPOSE\fR
\fBmapfile\fR directive.
.RE

.sp
.ne 2
.na
\fB\fBC\fR\fR
.ad
.RS 11n
This symbol definition is the reference data of a copy-relocation.
.RE

.sp
.ne 2
.na
\fB\fBF\fR\fR
.ad
.RS 11n
This symbol definition resides in a filtee.
.RE

.sp
.ne 2
.na
\fB\fBP\fR\fR
.ad
.RS 11n
This symbol is defined as protected. This symbol might have an internal binding
from the object in which the symbol is declared. Any internal bindings with
this attribute can not be interposed upon by another symbol definition.
.RE

.sp
.ne 2
.na
\fB\fBA\fR\fR
.ad
.RS 11n
This symbol definition is the address of a procedure linkage table entry within
a dynamic executable.
.RE

.sp
.ne 2
.na
\fB\fBU\fR\fR
.ad
.RS 11n
This symbol lookup originated from a user request, for example,
\fBdlsym\fR(3C).
.RE

.sp
.ne 2
.na
\fB\fBR\fR\fR
.ad
.RS 11n
This symbol definition is acting as a filter, and provides for redirection to a
filtee.
.RE

.sp
.ne 2
.na
\fB\fBr\fR\fR
.ad
.RS 11n
A binding to this symbol was rejected at some point during a symbol search. A
rejection can occur when a direct binding request finds a symbol that has been
tagged to prevent direct binding. In this scenario, the symbol search is
repeated using a default search model. The binding can still resolve to the
original, rejected symbol. A rejection can also occur when a non-default symbol
search finds a symbol identified as a \fBsingleton\fR. Again, the symbol search
is repeated using a default search model.
.RE

.sp
.ne 2
.na
\fB\fBN\fR\fR
.ad
.RS 11n
This symbol definition explicitly prohibits directly binding to the definition.
.RE

.sp
.LP
See the \fILinker and Libraries Guide\fR for more details of these symbol
classifications.
.SH EXTENDED DESCRIPTION
.SS "Interesting Information"
By default, or specifically using the \fB-i\fR option, \fBlari\fR filters any
runtime interface information to present interesting events. This filtering is
carried out mainly to reduce the amount of information that can be generated
from large applications. In addition, this information is intended to be the
focus in debugging complex binding scenarios, and often highlights problem
areas. However, classifying what information is interesting for any particular
application is an inexact science. You are still free to use the \fB-a\fR
option and to search the binding information for events that are unique to the
application being investigated.
.sp
.LP
When an interesting symbol definition is discovered, all other definitions of
the same symbol are output.
.sp
.LP
The focus of interesting interface information is the existence of multiple
definitions of a symbol. In this case, one symbol typically interposes on one
or more other symbol definitions. This interposition is seen when the binding
count, \fBbnd\fR, of one definition is non-zero, while the binding count of all
other definitions is zero. Interposition that results from the compilation
environment, or the linking environment, is not characterized as interesting.
Examples of these interposition occurrences include copy relocations
(\fB[C]\fR) and the binding to procedure linkage addresses (\fB[A]\fR).
.sp
.LP
Interposition is often desirable. The intent is to overload, or replace, the
symbolic definition from a shared object. Interpositioning objects can be
explicitly tagged (\fB[I]\fR), using the \fB-z interpose\fR option of
\fBld\fR(1). These objects can safely interpose on symbols, no matter what
order the objects are loaded in a process. However, be cautious when
non-explicit interposition is employed, as this interposition is a consequence
of the load-order of the objects that make up the process.
.sp
.LP
User-created, multiply-defined symbols are output from \fBlari\fR as
interesting. In this example, two definitions of \fBinterpose1()\fR exist, but
only the definition in \fBmain\fR is referenced:
.sp
.in +2
.nf
[2:1E]: interpose1(): ./main
[2:0]: interpose1(): ./libA.so
.fi
.in -2
.sp

.sp
.LP
Interposition can also be an undesirable and surprising event, caused by an
unexpected symbol name clash. A symptom of this interposition might be that a
function is never called although you know a reference to the function exists.
This scenario can be identified as a multiply defined symbol, as covered in the
previous example. However, a more surprising scenario is often encountered when
an object both defines and references a specific symbol.
.sp
.LP
An example of this scenario is if two dynamic objects define and reference the
same function, \fBinterpose2()\fR. Any reference to this symbol binds to the
first dynamic object loaded with the process. In this case, the definition of
\fBinterpose2()\fR in object \fBlibA.so\fR interposes on, and hides, the
definition of \fBinterpose2()\fR in object \fBlibB.so\fR. The output from
\fBlari\fR might be:
.sp
.in +2
.nf
[2:2ES]: interpose2(): ./libA.so
[2:0]: interpose2(): ./libB.so
.fi
.in -2
.sp

.sp
.LP
Multiply defined symbols can also be bound to separately. Separate bindings can
be the case when direct bindings are in effect (\fB[D]\fR), or because a symbol
has protected visibility (\fB[P]\fR). Although separate bindings can be
explicitly established, instances can exist that are unexpected and surprising.
Directly bound symbols, and symbols with protected visibility, are output as
interesting information.
.SS "Overhead Information"
When using the \fB-o\fR option, \fBlari\fR displays symbol definitions that
might be considered overhead.
.sp
.LP
Global symbols that are not referenced are considered an overhead. The symbol
information that is provided within the object unnecessarily adds to the size
of the object's text segment. In addition, the symbol information can increase
the processing required to search for other symbolic references within the
object at runtime.
.sp
.LP
Global symbols that are only referenced from the same object have the same
characteristics. The runtime search for a symbolic reference, that results in
binding to the same object that made the reference, is an additional overhead.
.sp
.LP
Both of these symbol definitions are candidates for reduction to local scope by
defining the object's interface. Interface definitions can be assigned to a
file during its creation by the link-editor using the \fB-M\fR option and the
associated \fImapfile\fR directives. See the \fILinker and Libraries Guide\fR
for more details on \fImapfiles\fR. Use \fBlari\fR with the \fB-m\fR option to
create initial versions of these \fImapfiles\fR.
.sp
.LP
If \fBlari\fR is used to generate \fImapfiles\fR, versioned shared objects will
have \fImapfiles\fR created indicating that their overhead symbols should be
reduced to locals. This model allows \fBlari\fR to generate \fImapfiles\fR for
comparison with existing interface definitions. Use the \fB-v\fR option to
ignore versioned shared objects when creating \fImapfiles\fR.
.sp
.LP
Copy-relocations are also viewed as an overhead and generally should be
avoided. The size of the copied data is a definition of its interface. This
definition restricts the ability to change the data size in newer versions of
the shared object in which the data is defined. This restriction, plus the cost
of processing a copy relocation, can be avoided by referencing data using a
functional interface. The output from \fBlari\fR for a copy relocation might
be:
.sp
.in +2
.nf
[2:1EC]: __iob[0x140]: ./main
[2:0]: __iob[0x140]: ./libA.so.1
.fi
.in -2
.sp

.sp
.LP
Notice that a number of small copy relocations, such as \fB__iob\fR used in the
previous example, exist because of historic programming interactions with
system libraries.
.sp
.LP
Another example of overhead information is the binding of a dynamic object to
the procedure linkage table entry of a dynamic executable. If a dynamic
executable references an external function, a procedure linkage table entry is
created. This structure allows the reference binding to be deferred until the
function call is actually made. If a dynamic object takes the address of the
same referenced function, the dynamic object binds to the dynamic executables
procedure linkage table entry. An example of this type of event reveals the
following:
.sp
.in +2
.nf
[2:1EA]: foo(): ./main
[2:1E]: foo(): ./libA.so
.fi
.in -2
.sp

.sp
.LP
A small number of bindings of this type are typically not cause for concern.
However, a large number of these bindings, perhaps from a jump-table
programming technique, can contribute to start up overhead. Address relocation
bindings of this type require relocation processing at application start up,
rather than the deferred relocation processing used when calling functions
directly. Use of this address also requires an indirection at runtime.
.SH EXAMPLES
\fBExample 1 \fRAnalyzing a case of multiple bindings
.sp
.LP
The following example shows the analysis of a process in which multiple symbol
definitions exist. The shared objects \fBlibX.so\fR and \fBlibY.so\fR both call
the function \fBinterpose()\fR. This function exists in both the application
\fBmain\fR, and the shared object \fBlibA.so\fR. Because of interposition, both
references bind to the definition of \fBinterpose()\fR in \fBmain\fR.

.sp
.LP
The shared objects \fBlibX.so\fR and \fBlibY.so\fR also both call the function
\fBfoo()\fR. This function exists in the application \fBmain\fR, and the shared
objects \fBlibA.so\fR, \fBlibX.so\fR, and \fBlibY.so\fR. Because both
\fBlibX.so\fR and \fBlibY.so\fR were built with direct bindings enabled, each
object binds to its own definition.

.sp
.in +2
.nf
example% \fBlari ./main\fR
[3:0]: foo(): ./libA.so
[3:1SD]: foo(): ./libX.so
[3:1SD]: foo(): ./libY.so
[2:0]: interpose(): ./libA.so
[2:2EP]: interpose(): ./main
.fi
.in -2
.sp

.sp
.LP
To analyze binding information more thoroughly, the bindings data can be saved
for further inspection. For example, the previous output indicates that the
function \fBinterpose()\fR was called from two objects external to \fBmain\fR.
Inspection of the binding output reveals where the references to this function
originated.

.sp
.in +2
.nf
example% \fBlari -s ./main\fR
lari: ./main: bindings information saved as: /usr/tmp/lari.dbg.main
\&.....
example% \fBfgrep foo /usr/tmp/lari.dbg.main\fR
binding file=./libX.so to file=./main: symbol `interpose'
binding file=./libY.so to file=./main: symbol `interpose'
.fi
.in -2
.sp

.sp
.LP
\fBNote:\fR The bindings output is typically more extensive than shown here, as
the output is accompanied with process identifier, address and other bindings
information.

.LP
\fBExample 2 \fRGenerating an interface definition
.sp
.LP
The following example creates interface definitions for an application and its
dependency, while ignoring any versioned system libraries. The application
\fBmain\fR makes reference to the interfaces \fBone()\fR, \fBtwo()\fR, and
\fBthree()\fR in \fBfoo.so\fR:

.sp
.in +2
.nf
example% \fBlari -omv ./main\fR
example% \fBcat mapfile-foo.so\fR
#
# Interface Definition mapfile for:
#       Dynamic Object: ./foo.so
#       Process:        ./main
#

foo.so {
        global:
                one;
                three;
                two;
        local:
                _one;
                _three;
                _two;
                *;
};
.fi
.in -2
.sp

.SH FILES
.ne 2
.na
\fB\fB$TMPDIR/lari.dbg.\fIfile\fR\fR\fR
.ad
.RS 25n
Binding output produced by \fBldd\fR(1).
.RE

.SH ATTRIBUTES
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	See below.
.TE

.sp
.LP
The human readable output is Uncommitted. The options are Committed.
.SH SEE ALSO
\fBld\fR(1), \fBldd\fR(1), \fBld.so.1\fR(1), \fBdlopen\fR(3C), \fBdlsym\fR(3C),
\fBattributes\fR(5)
.sp
.LP
\fILinker and Libraries Guide\fR