NAME

check_rtime - check ELF runtime attributes

SYNOPSIS

check_rtime [-imosv] [-D depfile | -d depdir] [-E errfile] [-e exfile] [-f listfile] [-I infofile] [-w outdir] file | dir, ...

DESCRIPTION

check_rtime attempts to check a number of ELF runtime attributes for consistency with common build rules. These checks involve running ldd(1) and elfdump(1) against a family of dynamic objects. A dynamic object can be defined explicitly as a file or multiple dynamic objects can be located under the directory dir.

check_rtime is typically called from nightly(1ONBLD) when the -r option is in effect. In this case the dynamic objects under the associated proto area ($ROOT) are checked. check_rtime can also be run standalone against any set of dynamic objects.

check_rtime uses ldd(1) to verify dependencies. This implies that by default any object inspected will bind to its dependencies as they are found in the underlying system. Use of the -D, -d option, or the existence of the environment variables $CODEMGR_WS/$ROOT instruct check_rtime to establish an alternative dependency mapping using runtime configuration files generated with crle(1).

check_rtime uses ldd(1) to completely relocate any dynamic object and thus detect missing dependencies, unsatisfied symbol relocations, unused and unreferenced dependencies. These checks are carried out for the following reasons:

•

An object that cannot find its dependencies may fail to load at runtime. This error condition often goes unnoticed because the existing use of the object is as a dependency itself, and the objects' dependencies are already satisfied by the caller. However, if the object itself is unable to satisfy its dependencies, its use in new environments may be compromised.

 

A missing or erroneous runpath is the typical reason why an object can not locate its dependencies. Use of the link-editors -zdefs option when building a shared object ensures required dependencies are established. This flag is inherited from $(DYNFLAGS) in lib/Makefile.lib. Missing dependencies are displayed as:

 

•

Unsatisfied symbol relocations indicate that some thread of execution through the object will fail when it is unable to locate a referenced symbol.

 

A missing, or mismatched version of a dependency is the typical reason for unsatisfied symbol relocations (see missing dependency discussion above). Unsatisfied symbol relocations are displayed as:

 

•

Unused dependencies are wasteful at runtime, as they take time to load and relocate, but will not be used by the calling object. They also result in unnecessary processing at link-edit time.

 

Dependency lists (typically defined via $(LDLIBS)) that have been yanked-and-put between Makefiles without verifying their need, are a typical reason why unused dependencies exist. Unused dependencies are displayed as:

 

•

Unreferenced dependencies are also wasteful at runtime, although not to the extent of unused dependencies. They also result in unnecessary processing at link-edit time.

 

Unreferenced dependency removal guards against a dependency becoming unused when combined with different objects, or as the other object dependencies evolve. Unreferenced dependencies are displayed as:

 

•

Unused search paths are wasteful at runtime. Unused search paths are displayed as:

 

check_rtime uses elfdump(1) to look for a concatenated relocation section in shared objects, the existence of text relocations, whether debugging or symbol table information exists, whether applications have a non-executable stack defined, duplicate entries in the symbol sorting sections, and for direct bindings. These checks are carried out for the following reasons:

•

A concatenated relocation section (.SUNW_reloc) provides optimal symbol table access at runtime, and thus reduces the overhead of relocating the shared object. In past releases, the link-edit of a dynamic object with the -z combreloc option was required to generate a combined relocation section. However, with the integration of 6642769, this section combination is a default behavior of the link-editor.

 

In past releases, not inheriting $(DYNFLAGS) from lib/Makefile.lib was the typical reason for not having a concatenated relocation section. The misguided use of the -z nocombreloc option will also prevent the creation of a concatenated relocation section. A missing concatenated relocation section is displayed as:

 

•

Text relocations result in impure text segments. As text segments are typically read-only, they can be shared between numerous processes. If they must be updated as part of the relocation then the updated pages become unsharable and swap space must be allocated to back these pages. These events consume unnecessary system resources and reduce overall system performance.

 

Not inheriting the $(PICS) rules from lib/Makefile.lib is the typical reason for having non-pic code in shared objects. Text relocations are displayed as:

 

•

Debugging information is unnecessary in released objects. Although extensive when compiled -g, small quantities of debugging information are stored in .stabs sections under normal compilations. This debugging information is geared towards aiding debuggers locate relocatable objects associated with the dynamic objects being debugged. As relocatable objects aren't made available as part of a software release this information has no use.

 

Not inheriting the correct $(LDFLAGS) from cmd/Makefile.cmd (which asserts -s), or $(POST_PROCESS_SO) (which asserts strip -x) are typical reasons for not removing debugging information. Note, removal of debugging information is only enabled for release builds. The existence of debugging information is displayed as:

 

•

All objects should retain their full .symtab symbol table. Although this consumes disk space, it provides for more extensive stack tracing when debugging user applications.

 

Hard coding a -s flag with $(LDFLAGS) or $(DYNFLAGS) is the typical reason for symbol tables being removed. Objects that do not contain a symbol table are displayed as:

 

•

Applications should have a non-executable stack defined to make them less vulnerable to buffer overflow attacks.

 

Not inheriting the $(LDFLAGS) macro in cmd/Makefile.cmd is the typical reason for not having a non-executable stack definition. Applications without this definition are displayed as:

 

•

x86 applications should have a non-executable data segment defined to make them less vulnerable to buffer overflow attacks.

 

Not inheriting the $(LDFLAGS) macro in cmd/Makefile.cmd is the typical reason for not having a non-executable data definition. Applications without this definition are displayed as:

 

•

Solaris ELF files contain symbol sort sections used by DTrace to map addresses in memory to the related function or variable symbols. There are two such sections, .SUNW_dynsymsort for regular symbols, and .SUNW_dyntlssort for thread-local symbols. To ensure that the best names are shown for each such address, and that the same name is given across Solaris releases, check_rtime enforces the rule that only one symbol can appear in the sort sections for any given address. There are two common ways in which multiple symbols or a given address occur in the ON distribution. The first is from code written in assembly language. The second is as a result of using #pragma weak in C to create weak symbols. The best solution to this situation is to modify the code to avoid symbol aliasing. Alternatively, the NODYNSORT mapfile attribute can be used to eliminate the unwanted symbol.

 

Duplicate entries in a symbol sort section are displayed in one of the following ways, depending on whether the section is for regular or thread-local symbols:

 

•

OSNet dynamic ELF objects are expected to employ direct bindings whenever feasible. This runtime binding technique helps to avoid accidental interposition problems, and provides a more optimal runtime symbol search model.

 

Not inheriting the correct $(LDFLAGS) from cmd/Makefile.cmd, or the correct $(DYNFLAGS) from lib/Makefile.lib, are the typical reasons for not enabling direct bindings. Dynamic objects that do not contain direct binding information are displayed as:

 

check_rtime also uses elfdump(1) to display useful dynamic entry information under the -i option. This doesn't necessarily indicate an error condition, but provides information that is often useful for gatekeepers to track changes in a release. Presently the information listed is:

•

Runpaths are printed for any dynamic object. This is a historic sanity check to insure compiler supplied runpaths (typically from CC) are not recorded in any objects. Runpaths are displayed as:

 

•

Needed dependencies are printed for any dynamic object. In the freeware world this often helps the introducer of a new shared object discover that an existing binary has become its consumer, and thus that binaries package dependencies may require updating. Dependencies are printed as:

 

check_rtime uses mcs(1) to inspect an object's .comment section. During development, this section contains numerous file identifiers marked with the tag " @(#)". For release builds these sections are deleted and rewritten under control of the $(POST_PROCESS) macro to produce a common release identifier. This identifier typically consists of three lines including a single comment starting with the string " @(#) SunOS". If this common identifier isn't found the following diagnostic is generated:

check_rtime uses pvs(1) to display version definitions under the -v option. Each symbol defined by the object is shown along with the version it belongs to. Changes to the symbols defined by an object, or the versions they belong to, do not necessarily indicate an error condition, but provides information that is often useful for gatekeepers to track changes in a release.

OPTIONS

The following options are supported:

-D depfile

Use depfile to generate an alternative dependency mapping. depfile must be created by 'find_elf -r'. The -D and -d options are mutually exclusive.

-d depdir

Use depdir to generate an alternative dependency mapping. find_elf(1ONBLD) is used to locate the ELF sharable objects for which alternative mappings are required. The -D and -d options are mutually exclusive.

-E errfile

Direct error messages for the analyzed objects to errfile instead of stdout.

-e exfile

An exception file is used to exclude objects from the usual rules. See EXCEPTION FILE FORMAT.

-f listfile

Normally, interface_check runs find_elf to locate the ELF objects to analyze. The -f option can be used to instead provide a file containing the list of objects to analyze, in the format produced by ' find_elf -r'.

-I infofile

Direct informational messages (-i, and -v options) for the analyzed objects to infofile instead of stdout.

-i

Provide dynamic entry information. Presently only dependencies and runpaths are printed.

-m

Enable mcs(1) checking.

-o

Produce a one-line output for each condition discovered, prefixed by the objects name. This output style is more terse, but is more appropriate for sorting and diffing with previous build results.

-s

Determine whether .stabs sections exist.

-v

Provide version definition information. Each symbol defined by the object is printed along with the version it is assigned to.

-w outdir

Interpret the paths of all input and output files relative to outdir.

EXCEPTION FILE FORMAT

Exceptions to the rules enforced by check_rtime are specified using an exception file. The -e option is used to specify an explicit exception file. Otherwise, if used in an activated workspace, the default exception file is $CODEMGR_WS/exception_list/check_rtime if that file exists. If not used in an activated workspace, or if $CODEMGR_WS/exception_list/check_rtime does not exist, check_rtime will use /opt/onbld/etc/exception_list/check_rtime as a fallback default exception file. To run check_rtime without applying exceptions, specify -e with a value of /dev/null.

A '#' character at the beginning of a line, or at any point in a line when preceded by whitespace, introduces a comment. Empty lines, and lines containing only comments, are ignored by check_rtime. Exceptions are specified as space separated keyword, and perl(1) regular expression:

keyword perl-regex

Since whitespace is used as a separator, the regular expression cannot itself contain whitespace. Use of the \s character class to represent whitespace within the regular expression is recommended. Before the perl regular expression is used, constructs of the form MACH(dir) are expanded into a regular expression that matches the directory given, as well as any 64-bit architecture subdirectory that might be present (i.e. amd64, sparcv9). For instance, MACH(lib) will match any of the following:

lib
lib/amd64
lib/sparcv9

The exceptions understood by check_rtime are: EXEC_DATA EXEC_STACK NOCRLEALT NODIRECT NOSYMSORT OLDDEP SKIP STAB TEXTREL UNDEF_OBJ UNDEF_REF UNUSED_DEPS UNUSED_OBJ UNUSED_RPATH

ALTERNATIVE DEPENDENCY MAPPING

check_rtime was primarily designed to process a nightly builds $ROOT hierarchy. It is often the case that objects within this hierarchy must bind to dependencies within the same hierarchy to satisfy their requirements.

To achieve this, check_rtime uses the shared objects specified with the -D or -d options. If neither option is specified, and the $CODEMGR_WS and $ROOT environment variables are defined, the proto area for the workspace is used. The objects found are used to create runtime configuration files via crle(1), that establish the new shared objects as alternatives to their underlying system location. check_rtime passes these configuration files as LD_CONFIG environment variable settings to ldd(1) using its -e option.

The effect of these configuration files is that the execution of an object under ldd(1) will bind to the dependencies defined as alternatives. Simply put, an object inspected in the proto area will bind to its dependencies found in the proto area. Dependencies that have no alternative mapping will continue to bind to the underlying system.

ENVIRONMENT VARIABLES

When the -D or -d option isn't in use, check_rtime uses the following environment variables to establish an alternative dependency mapping:

CODEMGR_WS

ROOT

If ldd(1) supports the -U option, it will be used to determine any unreferenced dependencies. Otherwise ldd(1) uses the older -u option which only detects unused references. If the following environment variable exists, and indicates an earlier release than 5.10 then ldd(1) also falls back to using the -u option.

RELEASE

ERROR CONDITIONS

Inspection of an object with ldd(1) assumes it is compatible with the machine on which check_rtime is being run. Incompatible objects such as a 64-bit object encountered on a 32-bit system, or an i386 object encountered on a sparc system, can not be fully inspected. These objects are displayed as:

FILES

SEE ALSO

crle(1), elfdump(1), find_elf(1ONBLD), ldd(1), ld.so.1(1), mcs(1).