Provided by: libdebuginfod-dev_0.191-2ubuntu0.1_amd64 
NAME
debuginfod_find_debuginfo - request debuginfo from debuginfod
SYNOPSIS
#include <elfutils/debuginfod.h>
Link with -ldebuginfod.
CONNECTION HANDLE
debuginfod_client *debuginfod_begin(void);
void debuginfod_end(debuginfod_client *client);
LOOKUP FUNCTIONS
int debuginfod_find_debuginfo(debuginfod_client *client,
const unsigned char *build_id,
int build_id_len,
char ** path);
int debuginfod_find_executable(debuginfod_client *client,
const unsigned char *build_id,
int build_id_len,
char ** path);
int debuginfod_find_source(debuginfod_client *client,
const unsigned char *build_id,
int build_id_len,
const char *filename,
char ** path);
int debuginfod_find_section(debuginfod_client *client,
const unsigned char *build_id,
int build_id_len,
const char * section,
char ** path);
OPTIONAL FUNCTIONS
typedef int (*debuginfod_progressfn_t)(debuginfod_client *client,
long a, long b);
void debuginfod_set_progressfn(debuginfod_client *client,
debuginfod_progressfn_t progressfn);
void debuginfod_set_verbose_fd(debuginfod_client *client,
int fd);
void debuginfod_set_user_data(debuginfod_client *client,
void *data);
void* debuginfod_get_user_data(debuginfod_client *client);
const char* debuginfod_get_url(debuginfod_client *client);
int debuginfod_add_http_header(debuginfod_client *client,
const char* header);
const char* debuginfod_get_headers(debuginfod_client *client);
DESCRIPTION
debuginfod_begin() creates a debuginfod_client connection handle that should be used with all other
calls. debuginfod_end() should be called on the client handle to release all state and storage when
done.
debuginfod_find_debuginfo(), debuginfod_find_executable(), and debuginfod_find_source() query the
debuginfod server URLs contained in $DEBUGINFOD_URLS (see below) for the debuginfo, executable or source
file with the given build_id. build_id should be a pointer to either a null-terminated, lowercase hex
string or a binary blob. If build_id is given as a hex string, build_id_len should be 0. Otherwise
build_id_len should be the number of bytes in the binary blob.
debuginfod_find_source() also requires a filename in order to specify a particular source file. filename
should be an absolute path that includes the compilation directory of the CU associated with the source
file. Relative path names commonly appear in the DWARF file's source directory, but these paths are
relative to individual compilation unit AT_comp_dir paths, and yet an executable is made up of multiple
CUs. Therefore, to disambiguate, debuginfod expects source queries to prefix relative path names with the
CU compilation-directory, followed by a mandatory "/".
Note: the caller may or may not elide ../ or /./ or extraneous /// sorts of path components in the
directory names. debuginfod accepts both forms. Specifically, debuginfod canonicalizes path names
according to RFC3986 section 5.2.4 (Remove Dot Segments), plus reducing any // to / in the path.
debuginfod_find_section() queries the debuginfod server URLs contained in $DEBUGINFOD_URLS for the binary
contents of an ELF/DWARF section contained in a debuginfo or executable file with the given build_id.
section should be the name of the desired ELF/DWARF section. If a server does not support section
queries, debuginfod_find_section may query the server for the debuginfo and/or executable with build_id
in order to retrieve and extract the section.
If path is not NULL and the query is successful, path is set to the path of the file in the cache. The
caller must free() this value.
The URLs in $DEBUGINFOD_URLS may be queried in parallel. As soon as a debuginfod server begins
transferring the target file all of the connections to the other servers are closed.
A client handle should be used from only one thread at a time. A handle may be reused for a series of
lookups, which can improve performance due to retention of connections and caches.
RETURN VALUE
debuginfod_begin returns the debuginfod_client handle to use with all other calls. On error NULL will be
returned and errno will be set.
If a find family function is successful, the resulting file is saved to the client cache and a file
descriptor to that file is returned. The file descriptor points to the beginning of the file. The
caller needs to close() this descriptor. Otherwise, a negative error code is returned.
OPTIONAL FUNCTIONS
A small number of optional functions are available to tune or query the operation of the debuginfod
client.
PROGRESS CALLBACK
As the debuginfod_find_*() functions may block for seconds or longer, a progress callback function is
called periodically, if configured with debuginfod_set_progressfn(). This function sets a new progress
callback function (or NULL) for the client handle.
The given callback function is called from the context of each thread that is invoking any of the other
lookup functions. It is given two numeric parameters that, if thought of as a numerator a and
denominator b, together represent a completion fraction a/b. The denominator may be zero initially,
until a quantity such as an exact download size becomes known.
The progress callback function is also the supported way to interrupt the download operation. (The
library does not modify or trigger signals.) The progress callback must return 0 to continue the work,
or any other value to stop work as soon as possible. Consequently, the debuginfod_find_*() function will
likely return with an error, but might still succeed.
VERBOSE OUTPUT
The debuginfod_find_*() functions may use several techniques to retrieve the requested files, through the
cache or through one or multiple servers or file URLs. To show how a query is handled the
debuginfod_set_verbose_fd() can be used to set a particular file descriptor on which verbose output is
given about the query steps and eventual errors encountered.
USER DATA POINTER
A single void * pointer associated with the connection handle may be set any time via
debuginfod_set_user_data(), and retrieved via debuginfod_get_user_data(). The value is undefined if
unset.
URL
The URL of the current or most recent outgoing download, if known, may be retrieved via
debuginfod_get_url() from the progressfn callback, or afterwards. It may be NULL. The resulting string
is owned by the library, and must not be modified or freed. The caller should copy it if it is needed
beyond the release of the client object.
HTTP HEADER
Before each lookup function is initiated, a client application may add HTTP request headers. These are
reset after each lookup function. debuginfod_add_http_header() may be called with strings of the form
"Header: value". These strings are copied by the library. A zero return value indicates success, but
out-of-memory conditions may result in a non-zero -ENOMEM. If the string is in the wrong form -EINVAL
will be returned.
$DEBUGINFOD_HEADERS_FILE specifies a file to supply headers to outgoing requests. Each non-whitespace
line of this file is handled as if debuginfod_add_http_header() were called on the contents.
Note that the current debuginfod-client library implementation uses libcurl, but you shouldn't rely on
that fact. Don't use this function for replacing any standard headers, except for the User-Agent
mentioned below. You can use this function to add authorization information for access control, or to
provide optional headers to the server for logging purposes.
By default, the library adds a descriptive User-Agent: header to outgoing requests. If the client
application adds a header with the same name, this default is suppressed.
During or after a lookup, a client application may call debuginfod_get_headers() to gather the subset of
HTTP response headers received from the current or most recent debuginfod server. Only those headers
prefixed with X-DEBUGINFOD (case-insensitive) are kept. They are returned as a single string, with each
"header: value" terminated with a \n (not \r\n as in HTTP). It may be NULL. The resulting string is
owned by the library, and must not be modified or freed. The caller should copy the returned string if
it is needed beyond the release of the client object.
MACROS
DEBUGINFOD_SONAME
Defined to the string that could be passed to dlopen(3) if the library is loaded at runtime, for example
void *debuginfod_so = dlopen(DEBUGINFOD_SONAME, RTLD_LAZY);
SECURITY
debuginfod_find_*() functions do not include any particular security features. They trust that the
binaries returned by the debuginfod(s) are accurate. Therefore, the list of servers should include only
trustworthy ones. If accessed across HTTP rather than HTTPS, the network should be trustworthy. Passing
user authentication information through the internal libcurl library is not currently enabled, except for
the basic plaintext http[s]://userid:password@hostname/ style. (The debuginfod server does not perform
authentication, but a front-end proxy server could.)
ERRORS
The following list is not comprehensive. Error codes may also originate from calls to various C Library
functions.
EACCESS
Denied access to resource located at the URL.
ECONNREFUSED
Unable to connect to remote host. Also returned when an HTTPS connection couldn't be verified (bad
certificate).
ECONNRESET
Unable to either send or receive network data.
EHOSTUNREACH
Unable to resolve remote host.
EINVAL One or more arguments are incorrectly formatted. build_id may be too long (greater than 256
characters), filename may not be an absolute path or a debuginfod URL is malformed.
EIO Unable to write data received from server to local file.
EMLINK Too many HTTP redirects.
ENETUNREACH
Unable to initialize network connection.
ENOENT Could not find the resource located at URL. Often this error code indicates that a debuginfod
server was successfully contacted but the server could not find the target file.
ENOMEM System is unable to allocate resources.
ENOSYS $DEBUGINFOD_URLS is not defined.
ETIME Query failed due to timeout. $DEBUGINFOD_TIMEOUT and $DEBUGINFOD_MAXTIME control this.
EF2BIG Query aborted due to the file requested being too big. The $DEBUGINFOD_MAXSIZE controls this.
SEE ALSO
debuginfod(8)
DEBUGINFOD_FIND_*(3)