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Diffstat (limited to 'Documentation/parisc/registers')
| -rw-r--r-- | Documentation/parisc/registers | 129 |
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diff --git a/Documentation/parisc/registers b/Documentation/parisc/registers deleted file mode 100644 index 10c7d1730f5d..000000000000 --- a/Documentation/parisc/registers +++ /dev/null @@ -1,129 +0,0 @@ -Register Usage for Linux/PA-RISC - -[ an asterisk is used for planned usage which is currently unimplemented ] - - General Registers as specified by ABI - - Control Registers - -CR 0 (Recovery Counter) used for ptrace -CR 1-CR 7(undefined) unused -CR 8 (Protection ID) per-process value* -CR 9, 12, 13 (PIDS) unused -CR10 (CCR) lazy FPU saving* -CR11 as specified by ABI (SAR) -CR14 (interruption vector) initialized to fault_vector -CR15 (EIEM) initialized to all ones* -CR16 (Interval Timer) read for cycle count/write starts Interval Tmr -CR17-CR22 interruption parameters -CR19 Interrupt Instruction Register -CR20 Interrupt Space Register -CR21 Interrupt Offset Register -CR22 Interrupt PSW -CR23 (EIRR) read for pending interrupts/write clears bits -CR24 (TR 0) Kernel Space Page Directory Pointer -CR25 (TR 1) User Space Page Directory Pointer -CR26 (TR 2) not used -CR27 (TR 3) Thread descriptor pointer -CR28 (TR 4) not used -CR29 (TR 5) not used -CR30 (TR 6) current / 0 -CR31 (TR 7) Temporary register, used in various places - - Space Registers (kernel mode) - -SR0 temporary space register -SR4-SR7 set to 0 -SR1 temporary space register -SR2 kernel should not clobber this -SR3 used for userspace accesses (current process) - - Space Registers (user mode) - -SR0 temporary space register -SR1 temporary space register -SR2 holds space of linux gateway page -SR3 holds user address space value while in kernel -SR4-SR7 Defines short address space for user/kernel - - - Processor Status Word - -W (64-bit addresses) 0 -E (Little-endian) 0 -S (Secure Interval Timer) 0 -T (Taken Branch Trap) 0 -H (Higher-privilege trap) 0 -L (Lower-privilege trap) 0 -N (Nullify next instruction) used by C code -X (Data memory break disable) 0 -B (Taken Branch) used by C code -C (code address translation) 1, 0 while executing real-mode code -V (divide step correction) used by C code -M (HPMC mask) 0, 1 while executing HPMC handler* -C/B (carry/borrow bits) used by C code -O (ordered references) 1* -F (performance monitor) 0 -R (Recovery Counter trap) 0 -Q (collect interruption state) 1 (0 in code directly preceding an rfi) -P (Protection Identifiers) 1* -D (Data address translation) 1, 0 while executing real-mode code -I (external interrupt mask) used by cli()/sti() macros - - "Invisible" Registers - -PSW default W value 0 -PSW default E value 0 -Shadow Registers used by interruption handler code -TOC enable bit 1 - -========================================================================= - -The PA-RISC architecture defines 7 registers as "shadow registers". -Those are used in RETURN FROM INTERRUPTION AND RESTORE instruction to reduce -the state save and restore time by eliminating the need for general register -(GR) saves and restores in interruption handlers. -Shadow registers are the GRs 1, 8, 9, 16, 17, 24, and 25. - -========================================================================= -Register usage notes, originally from John Marvin, with some additional -notes from Randolph Chung. - -For the general registers: - -r1,r2,r19-r26,r28,r29 & r31 can be used without saving them first. And of -course, you need to save them if you care about them, before calling -another procedure. Some of the above registers do have special meanings -that you should be aware of: - - r1: The addil instruction is hardwired to place its result in r1, - so if you use that instruction be aware of that. - - r2: This is the return pointer. In general you don't want to - use this, since you need the pointer to get back to your - caller. However, it is grouped with this set of registers - since the caller can't rely on the value being the same - when you return, i.e. you can copy r2 to another register - and return through that register after trashing r2, and - that should not cause a problem for the calling routine. - - r19-r22: these are generally regarded as temporary registers. - Note that in 64 bit they are arg7-arg4. - - r23-r26: these are arg3-arg0, i.e. you can use them if you - don't care about the values that were passed in anymore. - - r28,r29: are ret0 and ret1. They are what you pass return values - in. r28 is the primary return. When returning small structures - r29 may also be used to pass data back to the caller. - - r30: stack pointer - - r31: the ble instruction puts the return pointer in here. - - -r3-r18,r27,r30 need to be saved and restored. r3-r18 are just - general purpose registers. r27 is the data pointer, and is - used to make references to global variables easier. r30 is - the stack pointer. - |