LIBSA(3) FreeBSD Library Functions Manual LIBSA(3)
NAME
libsa - support library for standalone executables
SYNOPSIS
#include <stand.h>
DESCRIPTION
The libsa library provides a set of supporting functions for standalone
applications, mimicking where possible the standard BSD programming
environment. The following sections group these functions by kind.
Unless specifically described here, see the corresponding section 3
manpages for the given functions.
STRING FUNCTIONS
String functions are available as documented in string(3) and bstring(3).
MEMORY ALLOCATION
void * malloc(size_t size)
Allocate size bytes of memory from the heap using a best-fit
algorithm.
void free(void *ptr)
Free the allocated object at ptr.
void setheap(void *start, void *limit)
Initialise the heap. This function must be called before
calling alloc() for the first time. The region between start
and limit will be used for the heap; attempting to allocate
beyond this will result in a panic.
char * sbrk(int junk)
Provides the behaviour of sbrk(0), i.e., returns the highest
point that the heap has reached. This value can be used
during testing to determine the actual heap usage. The junk
argument is ignored.
ENVIRONMENT
A set of functions are provided for manipulating a flat variable space
similar to the traditional shell-supported environment. Major
enhancements are support for set/unset hook functions.
char * getenv(const char *name)
int setenv(const char *name, const char *value, int overwrite)
int putenv(char *string)
int unsetenv(const char *name)
These functions behave similarly to their standard library
counterparts.
struct env_var * env_getenv(const char *name)
Looks up a variable in the environment and returns its entire
data structure.
int env_setenv(const char *name, int flags, const void *value,
ev_sethook_t sethook, ev_unsethook_t unsethook)
Creates a new or sets an existing environment variable called
name. If creating a new variable, the sethook and unsethook
arguments may be specified.
The set hook is invoked whenever an attempt is made to set
the variable, unless the EV_NOHOOK flag is set. Typically a
set hook will validate the value argument, and then call
env_setenv() again with EV_NOHOOK set to actually save the
value. The predefined function env_noset() may be specified
to refuse all attempts to set a variable.
The unset hook is invoked when an attempt is made to unset a
variable. If it returns zero, the variable will be unset.
The predefined function env_nounset may be used to prevent a
variable being unset.
STANDARD LIBRARY SUPPORT
int abs(int i)
int getopt(int argc, char * const *argv, const char *optstring)
long strtol(const char *nptr, char **endptr, int base)
long long strtoll(const char *nptr, char **endptr, int base)
long strtoul(const char *nptr, char **endptr, int base)
long long strtoull(const char *nptr, char **endptr, int base)
void srandom(unsigned int seed)
long random(void)
char * strerror(int error)
Returns error messages for the subset of errno values
supported by libsa.
assert(expression)
Requires <assert.h>.
int setjmp(jmp_buf env)
void longjmp(jmp_buf env, int val)
Defined as _setjmp() and _longjmp() respectively as there is
no signal state to manipulate. Requires <setjmp.h>.
CHARACTER I/O
void gets(char *buf)
Read characters from the console into buf. All of the
standard cautions apply to this function.
void ngets(char *buf, int size)
Read at most size - 1 characters from the console into buf.
If size is less than 1, the function's behaviour is as for
gets().
int fgetstr(char *buf, int size, int fd)
Read a line of at most size characters into buf. Line
terminating characters are stripped, and the buffer is always
NUL terminated. Returns the number of characters in buf if
successful, or -1 if a read error occurs.
int printf(const char *fmt, ...)
void vprintf(const char *fmt, va_list ap)
int sprintf(char *buf, const char *fmt, ...)
void vsprintf(char *buf, const char *fmt, va_list ap)
The *printf functions implement a subset of the standard
printf() family functionality and some extensions. The
following standard conversions are supported:
c,d,n,o,p,s,u,x. The following modifiers are supported:
+,-,#,*,0,field width,precision,l.
The b conversion is provided to decode error registers. Its
usage is:
printf( "reg=%b\n", regval, "<base><arg>*" );
where <base> is the output expressed as a control character,
e.g. \10 gives octal, \20 gives hex. Each <arg> is a
sequence of characters, the first of which gives the bit
number to be inspected (origin 1) and the next characters (up
to a character less than 32) give the text to be displayed if
the bit is set. Thus
printf( "reg=%b\n", 3, "\10\2BITTWO\1BITONE" );
would give the output
reg=3<BITTWO,BITONE>
The D conversion provides a hexdump facility, e.g.
printf( "%6D", ptr, ":" ); gives "XX:XX:XX:XX:XX:XX"
printf( "%*D", len, ptr, " " ); gives "XX XX XX ..."
CHARACTER TESTS AND CONVERSIONS
int isupper(int c)
int islower(int c)
int isspace(int c)
int isdigit(int c)
int isxdigit(int c)
int isascii(int c)
int isalpha(int c)
int isalnum(int c)
int iscntrl(int c)
int isgraph(int c)
int ispunct(int c)
int toupper(int c)
int tolower(int c)
FILE I/O
int open(const char *path, int flags)
Similar to the behaviour as specified in open(2), except that
file creation is not supported, so the mode parameter is not
required. The flags argument may be one of O_RDONLY,
O_WRONLY and O_RDWR. Only UFS currently supports writing.
int close(int fd)
void closeall(void)
Close all open files.
ssize_t read(int fd, void *buf, size_t len)
ssize_t write(int fd, void *buf, size_t len)
(No file systems currently support writing.)
off_t lseek(int fd, off_t offset, int whence)
Files being automatically uncompressed during reading cannot
seek backwards from the current point.
int stat(const char *path, struct stat *sb)
int fstat(int fd, struct stat *sb)
The stat() and fstat() functions only fill out the following
fields in the sb structure:
st_mode,st_nlink,st_uid,st_gid,st_size. The tftp file system
cannot provide meaningful values for this call, and the
cd9660 file system always reports files having uid/gid of
zero.
PAGER
The libsa library supplies a simple internal pager to ease reading the
output of large commands.
void pager_open()
Initialises the pager and tells it that the next line output
will be the top of the display. The environment variable
LINES is consulted to determine the number of lines to be
displayed before pausing.
void pager_close(void)
Closes the pager.
int pager_output(const char *lines)
Sends the lines in the NUL-terminated buffer at lines to the
pager. Newline characters are counted in order to determine
the number of lines being output (wrapped lines are not
accounted for). The pager_output() function will return zero
when all of the lines have been output, or nonzero if the
display was paused and the user elected to quit.
int pager_file(const char *fname)
Attempts to open and display the file fname. Returns -1 on
error, 0 at EOF, or 1 if the user elects to quit while
reading.
FEATURE SUPPORT
A set of functions are provided to communicate support of features from
the loader binary to the interpreter. These are used to do something
sensible if we are still operating with a loader binary that behaves
differently than expected.
void feature_enable(uint32_t mask)
Enable the referenced mask feature, which should be one of
the FEATURE_* macros defined in <stand.h>.
bool feature_name_is_enabled(const char *name)
Check if the referenced name feature is enabled. The name is
usually the same name as the FEATURE_* macro, but with the
FEATURE_ prefix stripped off. The authoritative source of
feature names is the mapping table near the top in
stand/libsa/features.c.
void (feature_iter_fn)(void *cookie, const char *name, const char *desc,
bool enabled)
The cookie argument is passed as-is from the argument of the
same name to feature_iter(). The name and desc arguments are
defined in the mapping table in stand/libsa/features.c. The
enabled argument indicates the current status of the feature,
though one could theoretically turn a feature off in later
execution. As such, this should likely not be trusted if it
is needed after the iteration has finished.
void feature_iter(feature_iter_fn *iter_fn, void *cookie)
Iterate over the current set of features.
MISC
char * devformat(struct devdesc *)
Format the specified device as a string.
int devparse(struct devdesc **dev, const char *devdesc, const char
**path)
Parse the devdesc string of the form
`device:[/path/to/file]'. The devsw table is used to match
the start of the `device' string with dv_name. If
dv_parsedev is non-NULL, then it will be called to parse the
rest of the string and allocate the struct devdesc for this
path. If NULL, then a default routine will be called that
will allocate a simple struct devdesc, parse a unit number
and ensure there's no trailing characters. If path is non-
NULL, then a pointer to the remainder of the devdesc string
after the device specification is written.
int devinit(void)
Calls all the dv_init routines in the devsw array, returning
the number of routines that returned an error.
void twiddle(void)
Successive calls emit the characters in the sequence |,/,-,\
followed by a backspace in order to provide reassurance to
the user.
REQUIRED LOW-LEVEL SUPPORT
The following resources are consumed by libsa - stack, heap, console and
devices.
The stack must be established before libsa functions can be invoked.
Stack requirements vary depending on the functions and file systems used
by the consumer and the support layer functions detailed below.
The heap must be established before calling alloc() or open() by calling
setheap(). Heap usage will vary depending on the number of
simultaneously open files, as well as client behaviour. Automatic
decompression will allocate more than 64K of data per open file.
Console access is performed via the getchar(), putchar() and ischar()
functions detailed below.
Device access is initiated via devopen() and is performed through the
dv_strategy(), dv_ioctl() and dv_close() functions in the device switch
structure that devopen() returns.
The consumer must provide the following support functions:
int getchar(void)
Return a character from the console, used by gets(), ngets()
and pager functions.
int ischar(void)
Returns nonzero if a character is waiting from the console.
void putchar(int)
Write a character to the console, used by gets(), ngets(),
*printf(), panic() and twiddle() and thus by many other
functions for debugging and informational output.
int devopen(struct open_file *of, const char *name, const char **file)
Open the appropriate device for the file named in name,
returning in file a pointer to the remaining body of name
which does not refer to the device. The f_dev field in of
will be set to point to the devsw structure for the opened
device if successful. Device identifiers must always precede
the path component, but may otherwise be arbitrarily
formatted. Used by open() and thus for all device-related
I/O.
int devclose(struct open_file *of)
Close the device allocated for of. The device driver itself
will already have been called for the close; this call should
clean up any allocation made by devopen only.
void __abort()
Calls panic() with a fixed string.
void panic(const char *msg, ...)
Signal a fatal and unrecoverable error condition. The msg
... arguments are as for printf().
INTERNAL FILE SYSTEMS
Internal file systems are enabled by the consumer exporting the array
struct fs_ops *file_system[], which should be initialised with pointers
to struct fs_ops structures. The following file system handlers are
supplied by libsa, the consumer may supply other file systems of their
own:
ufs_fsops The BSD UFS.
ext2fs_fsops Linux ext2fs file system.
tftp_fsops File access via TFTP.
nfs_fsops File access via NFS.
cd9660_fsops ISO 9660 (CD-ROM) file system.
gzipfs_fsops Stacked file system supporting gzipped files. When trying
the gzipfs file system, libsa appends .gz to the end of the
filename, and then tries to locate the file using the other
file systems. Placement of this file system in the
file_system[] array determines whether gzipped files will
be opened in preference to non-gzipped files. It is only
possible to seek a gzipped file forwards, and stat() and
fstat() on gzipped files will report an invalid length.
bzipfs_fsops The same as gzipfs_fsops, but for bzip2(1)-compressed
files.
pkgfs_fsops File access from a tar file typically streamed via TFTP.
The order of files in the tar file must match the order
they are to be consumed as rewind is not practical.
The array of struct fs_ops pointers should be terminated with a NULL.
DEVICES
Devices are exported by the supporting code via the array struct devsw
*devsw[] which is a NULL terminated array of pointers to device switch
structures.
DRIVER INTERFACE
The driver needs to provide a common set of entry points that are used by
libsa to interface with the device.
struct devsw {
const char dv_name[DEV_NAMLEN];
int dv_type;
int (*dv_init)(void);
int (*dv_strategy)(void *devdata, int rw, daddr_t blk,
size_t size, char *buf, size_t *rsize);
int (*dv_open)(struct open_file *f, ...);
int (*dv_close)(struct open_file *f);
int (*dv_ioctl)(struct open_file *f, u_long cmd, void *data);
int (*dv_print)(int verbose);
void (*dv_cleanup)(void);
char * (*dv_fmtdev)(struct devdesc *);
int (*dv_parsedev)(struct devdesc **dev, const char *devpart,
const char **path);
bool (*dv_match)(struct devsw *dv, const char *devspec);
};
dv_name() The device's name.
dv_type() Type of device. The supported types are:
DEVT_NONE
DEVT_DISK
DEVT_NET
DEVT_CD
DEVT_ZFS
DEVT_FD
Each type may have its own associated (struct type_devdesc),
which has the generic (struct devdesc) as its first member.
dv_init() Driver initialization routine. This routine should probe
for available units. Drivers are responsible for
maintaining lists of units for later enumeration. No other
driver routines may be called before dv_init() returns.
dv_open() The driver open routine.
dv_close() The driver close routine.
dv_ioctl() The driver ioctl routine.
dv_print() Prints information about the available devices. Information
should be presented with pager_output().
dv_cleanup()
Cleans up any memory used by the device before the next
stage is run.
dv_fmtdev() Converts the specified devdesc to the canonical string
representation for that device.
dv_parsedev()
Parses the device portion of a file path. The devpart will
point to the `tail' of device name, possibly followed by a
colon and a path within the device. The `tail' is, by
convention, the part of the device specification that
follows the dv_name part of the string. So when devparse is
parsing the string "disk3p5:/xxx", devpart will point to the
`3' in that string. The parsing routine is expected to
allocate a new struct devdesc or subclass and return it in
dev when successful. This routine should set path to point
to the portion of the string after device specification, or
"/xxx" in the earlier example. Generally, code needing to
parse a path will use devparse instead of calling this
routine directly.
dv_match() NULL to specify that all device paths starting with dv_name
match. Otherwise, this function returns 0 for a match and a
non-zero errno to indicate why it didn't match. This is
helpful when you claim the device path after using it to
query properties on systems that have uniform naming for
different types of devices.
HISTORY
The libsa library contains contributions from many sources, including:
o libsa from NetBSD
o libc and libkern from FreeBSD 3.0.
o zalloc from Matthew Dillon <dillon@backplane.com>
The reorganisation and port to FreeBSD 3.0, the environment functions and
this manpage were written by Mike Smith <msmith@FreeBSD.org>.
BUGS
The lack of detailed memory usage data is unhelpful.
FreeBSD 15.1-STABLE-HBSD September 9, 2022 LIBSA(3)