T-Kernel Specification (1.B0.02)

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222 CHAPTER 5. T-KERNEL/SM 5.2 Address Space Management Functions Memory access privilege is held as access privilege information for each task. Essentially access privilege information indicates the right to access at the protection level immediately before an extended SVC is called. If, for example, a task is running at protection level 3 when it calls an extended SVC, its access privilege information indicates the right to access at protection level 3. Since the protection level when an extended SVC is executing is protection level 0, in the case of nested calling of an extended SVC from another extended SVC, access privilege information in the extended SVC for which a nested call was made indicates the right to access at protection level 0. Memory access privilege information is set as follows. • Immediately after a task is started, its access privilege is that designated when the task was created. • When an extended SVC is called, the access privilege at the protection level at which it was running at the time of the call is set. • Upon return from the extended SVC, the access privilege reverts to that at the time the extended SVC was called. • Executing SetTaskSpace() copies the current access privilege of the target task to the invoking task. 5.2.1 Address Space Configuration • ER SetTaskSpace( ID tskid ) Assigns to the invoking task the task space and access privilege information of the task designated in tskid. As a result, both the invoking task and target task have the same task space and access privilege information. Note that this copying of task space information applies only at the time the function is called; if thereafter the task designated in tskid switches to a different address space and its access privilege changes, the invoking task is not affected by those changes (its address space and access privilege do not change accordingly). If the invoking task is calling an extended SVC, on return from the extended SVC its access privilege reverts to that prior to calling the extended SVC. Its task space, however, does not revert. The task ID of the invoking task cannot be designated in tskid. However, if TSK SELF is used to designate the invoking task, access privilege is set to the currently running protection level; task space is not switched in this case. E ID E NOEXS E OBJ tskid is invalid Object does not exist (the task designated in tskid does not exist) Invoking task designated by other than TSK SELF 5.2.2 Address Space Checking The following functions check whether access is allowed to the designated memory space, based on the current access privilege information. If access cannot be made (no privilege or the memory does not exist), they return error code E MACV. —R Check for read access privilege. —RW Check for read and write access privilege. —RE Check for read and execute access privilege. Copyright c○ 2002, 2003 by T-Engine Forum T-Kernel 1.B0.02
5.2. ADDRESS SPACE MANAGEMENT FUNCTIONS 223 • ER ChkSpaceR( VP addr, INT len ) • ER ChkSpaceRW( VP addr, INT len ) • ER ChkSpaceRE( VP addr, INT len ) Checks access privilege to the memory space of len bytes from location addr. • INT ChkSpaceBstrR( UB *str, INT max ) • INT ChkSpaceBstrRW( UB *str, INT max ) Checks access privilege to the memory space from str up to the string termination (’\0’) or up to the number of characters (bytes) designated in max, whichever comes first. If max = 0 is set, max is ignored and privilege is checked up to the string termination. If access is allowed, the length of the string (in bytes) is returned. If the string termination occurred up to the string length indicated in max, the length to the character before ’\0’ is returned; if max characters occurred before the string termination, max is returned. • INT ChkSpaceTstrR( TC *str, INT max ) • INT ChkSpaceTstrRW( TC *str, INT max ) typedef UH TC; /* TRON character code */ #define TNULL((TC)0) /* TRON code string termination */ Checks access privilege to the memory space from str up to the TRON Code string termination (TNULL) or up to the number of characters (TC count) designated in max, whichever comes first. If max = 0 is set, max is ignored and privilege is checked up to the string termination. If access is allowed, the length of the string (TC count) is returned. If the string termination occurred up to the string length indicated in max, the length to the character before TNULL is returned; if max characters occurred before the string termination, max is returned. str must be an even-numbered address. 5.2.3 Lock Address Space Generally memory is made resident or nonresident a page at a time and is managed in page units. For this reason, in many cases the OS does not check for matching of locked and unlocked spaces. It is the responsibility of the calling side to make sure the same spaces are designated in lock and unlock operations. • ER LockSpace( VP addr, INT len ) Locks (makes resident) the memory space of len bytes from location addr. E MACV The memory does not exist • ER UnlockSpace( VP addr, INT len ) Unlocks (makes nonresident) the memory space of len bytes from location addr. If the same space was locked more than once, it is not unlocked until the number of unlock operations equals the number of lock operations. Note that it is not possible to unlock just part of a locked space. Copyright c○ 2002, 2003 by T-Engine Forum T-Kernel 1.B0.02
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T-Kernel Specification T-Kernel 1.B
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Contents 1 T-Kernel Overview 1 1.1
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CONTENTS v tk set flg (Set Event Fl
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CONTENTS vii 5.2.2 Address Space Ch
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CONTENTS ix td cal que (Reference Q
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List of Figures 1.1 Position of T-K
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List of Tables 2.1 State Transition
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System Call Notation In the parts o
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Index of T-Kernel/OS System Calls T
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INDEX OF T-KERNEL/OS SYSTEM CALLS x
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Index of T-Kernel/SM Extended SVC L
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Index of T-Kernel/DS System Calls T
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Chapter 1 T-Kernel Overview 1.1 Pos
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1.2. SCALABILITY 3 • Middleware m
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Chapter 2 Concepts Underlying the T
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2.2. TASK STATES AND SCHEDULING RUL
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2.2. TASK STATES AND SCHEDULING RUL
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2.3. INTERRUPT HANDLING 11 preceden
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2.5. SYSTEM STATES 13 Transient sta
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2.7. MEMORY 15 which the upper and
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Chapter 3 Common T-Kernel Specifica
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3.2. SYSTEM CALLS 19 /* * Common co
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3.2. SYSTEM CALLS 21 Ordinarily a f
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3.3. HIGH-LEVEL LANGUAGE SUPPORT RO
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Chapter 4 T-Kernel/OS Functions Thi
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4.1. TASK MANAGEMENT FUNCTIONS 27 t
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4.3. TASK EXCEPTION HANDLING FUNCTI
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4.6. MEMORY POOL MANAGEMENT FUNCTIO
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4.7. TIME MANAGEMENT FUNCTIONS 163
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272 CHAPTER 6. T-KERNEL/DS FUNCTION
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284 CHAPTER 7. REFERENCE INT tevptn
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286 CHAPTER 7. REFERENCE ER ercd =
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288 CHAPTER 7. REFERENCE INT ct = t
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290 CHAPTER 7. REFERENCE E OACV ERC
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T-Kernel Specification (1.B0.02)

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