sem.c File Reference

Implementation of named semaphores that release on exit. More...

#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/stat.h>
#include <stdbool.h>
#include <signal.h>
#include <freeradius-devel/util/perm.h>
#include <freeradius-devel/util/sem.h>
#include <freeradius-devel/util/strerror.h>
#include <freeradius-devel/util/syserror.h>

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Macros
#define	DEFAULT_PROJ_ID   ((int)'f') /* Only 8 bits are used */

Functions
int	fr_sem_cgid (uid_t *gid, int sem_id)
	Return the GID that created the semaphore.
int	fr_sem_close (int sem_id, char const *file)
	Remove the semaphore, this helps with permissions issues.
int	fr_sem_cuid (uid_t *uid, int sem_id)
	Return the UID that created the semaphore.
int	fr_sem_get (char const *file, int proj_id, uid_t uid, gid_t gid, bool check_perm, bool must_exist)
	Returns a semid for the semaphore associated with the file.
int	fr_sem_gid (uid_t *gid, int sem_id)
	Return the GID that last operated on the semaphore.
int	fr_sem_pid (pid_t *pid, int sem_id)
	Return the PID of the process that last operated on the semaphore.
int	fr_sem_post (int sem_id, char const *file, bool undo_on_exit)
	Decrement the semaphore by 1.
int	fr_sem_take (int sem_id, char const *file, bool undo_on_exit)
	Increment the semaphore by 1.
int	fr_sem_uid (uid_t *uid, int sem_id)
	Return the UID that last operated on the semaphore.
int	fr_sem_wait (int sem_id, char const *file, bool undo_on_exit, bool nonblock)
	Wait for a semaphore to reach 0, then increment it by 1.
static bool	sem_check_gid (char const *file, int proj_id, char const *thing, gid_t expected, gid_t got)
static bool	sem_check_uid (char const *file, int proj_id, char const *thing, uid_t expected, uid_t got)

Detailed Description

Implementation of named semaphores that release on exit.

Copyright

2021 Arran Cudbard-Bell (a.cud.nosp@m.bard.nosp@m.b@fre.nosp@m.erad.nosp@m.ius.o.nosp@m.rg)

Definition in file sem.c.

Macro Definition Documentation

DEFAULT_PROJ_ID

#define DEFAULT_PROJ_ID   ((int)'f') /* Only 8 bits are used */

Definition at line 43 of file sem.c.

Function Documentation

fr_sem_cgid()

int fr_sem_cgid	(	uid_t *	gid,
		int	sem_id
	)

Return the GID that created the semaphore.

Parameters

[out]	gid	the last modified the semaphore.
[in]	sem_id	semaphore ID.

Returns

• 0 on success.
• -1 on failure.

Definition at line 154 of file sem.c.

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fr_sem_close()

int fr_sem_close	(	int	sem_id,
		char const *	file
	)

Remove the semaphore, this helps with permissions issues.

Parameters

[in]	sem_id	to close.
[in]	file	to use in error messages.

Returns

• 0 on success.
• -1 on failure.

Definition at line 329 of file sem.c.

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fr_sem_cuid()

int fr_sem_cuid	(	uid_t *	uid,
		int	sem_id
	)

Return the UID that created the semaphore.

Parameters

[out]	uid	the last modified the semaphore.
[in]	sem_id	semaphore ID.

Returns

• 0 on success.
• -1 on failure.

Definition at line 128 of file sem.c.

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fr_sem_get()

int fr_sem_get	(	char const *	file,
		int	proj_id,
		uid_t	uid,
		gid_t	gid,
		bool	check_perm,
		bool	must_exist
	)

Returns a semid for the semaphore associated with the file.

Parameters

[in]	file	to get or create semaphore from.
[in]	proj_id	if 0 will default to '0xf4ee4a31'.
[in]	uid	that should own the semaphore.
[in]	gid	that should own the semaphore.
[in]	check_perm	Verify the semaphore is owned by the specified uid/gid, and that it was created by the specified uid/gid or root. Also verify that it is not world writable.
[in]	must_exist	semaphore must already exist.

Returns

• >= 0 the semaphore id.
• -1 the file specified does not exist, or there is a permissions error.
• -2 failed getting semaphore.
• -3 failed creating semaphore.
• -4 must_exist was true, and the semaphore does not exist.

Definition at line 421 of file sem.c.

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fr_sem_gid()

int fr_sem_gid	(	uid_t *	gid,
		int	sem_id
	)

Return the GID that last operated on the semaphore.

Parameters

[out]	gid	the last modified the semaphore.
[in]	sem_id	semaphore ID.

Returns

• 0 on success.
• -1 on failure.

Definition at line 102 of file sem.c.

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fr_sem_pid()

int fr_sem_pid	(	pid_t *	pid,
		int	sem_id
	)

Return the PID of the process that last operated on the semaphore.

Parameters

[out]	pid	that last modified the semaphore.
[in]	sem_id	semaphore ID.

Returns

• 0 on success.
• -1 on failure.

Definition at line 53 of file sem.c.

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fr_sem_post()

int fr_sem_post	(	int	sem_id,
		char const *	file,
		bool	undo_on_exit
	)

Decrement the semaphore by 1.

Parameters

[in]	sem_id	to take.
[in]	file	to use in error messages.
[in]	undo_on_exit	decrement the semaphore on exit.

Returns

• 1 already at 0.
• 0 on success.
• -1 on failure.

Definition at line 182 of file sem.c.

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fr_sem_take()

int fr_sem_take	(	int	sem_id,
		char const *	file,
		bool	undo_on_exit
	)

Increment the semaphore by 1.

Parameters

[in]	sem_id	to take.
[in]	file	to use in error messages.
[in]	undo_on_exit	decrement the semaphore on exit.

Returns

• -1 on failure.
• 0 on success.

Definition at line 221 of file sem.c.

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fr_sem_uid()

int fr_sem_uid	(	uid_t *	uid,
		int	sem_id
	)

Return the UID that last operated on the semaphore.

Parameters

[out]	uid	the last modified the semaphore.
[in]	sem_id	semaphore ID.

Returns

• 0 on success.
• -1 on failure.

Definition at line 76 of file sem.c.

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fr_sem_wait()

int fr_sem_wait	(	int	sem_id,
		char const *	file,
		bool	undo_on_exit,
		bool	nonblock
	)

Wait for a semaphore to reach 0, then increment it by 1.

Parameters

[in]	sem_id	to operate on.
[in]	file	to use in error messages.
[in]	undo_on_exit	If true, semaphore will be decremented if this process exits.
[in]	nonblock	If true, don't wait and return 1 if the semaphore is not at 0.

Returns

• 1 would have blocked waiting for semaphore.
• 0 incremented the semaphore.
• -1 permissions error (EACCES).
• -2 another error occurred.

Definition at line 252 of file sem.c.

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sem_check_gid()

static bool sem_check_gid ( char const *  file, int  proj_id, char const *  thing, gid_t  expected, gid_t  got  )

static

Definition at line 370 of file sem.c.

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sem_check_uid()

static bool sem_check_uid ( char const *  file, int  proj_id, char const *  thing, uid_t  expected, uid_t  got  )

static

Definition at line 340 of file sem.c.

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