| /* |
| * TLB Exception Handling for ARC |
| * |
| * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| * |
| * Vineetg: April 2011 : |
| * -MMU v1: moved out legacy code into a seperate file |
| * -MMU v3: PD{0,1} bits layout changed: They don't overlap anymore, |
| * helps avoid a shift when preparing PD0 from PTE |
| * |
| * Vineetg: July 2009 |
| * -For MMU V2, we need not do heuristics at the time of commiting a D-TLB |
| * entry, so that it doesn't knock out it's I-TLB entry |
| * -Some more fine tuning: |
| * bmsk instead of add, asl.cc instead of branch, delay slot utilise etc |
| * |
| * Vineetg: July 2009 |
| * -Practically rewrote the I/D TLB Miss handlers |
| * Now 40 and 135 instructions a peice as compared to 131 and 449 resp. |
| * Hence Leaner by 1.5 K |
| * Used Conditional arithmetic to replace excessive branching |
| * Also used short instructions wherever possible |
| * |
| * Vineetg: Aug 13th 2008 |
| * -Passing ECR (Exception Cause REG) to do_page_fault( ) for printing |
| * more information in case of a Fatality |
| * |
| * Vineetg: March 25th Bug #92690 |
| * -Added Debug Code to check if sw-ASID == hw-ASID |
| |
| * Rahul Trivedi, Amit Bhor: Codito Technologies 2004 |
| */ |
| |
| .cpu A7 |
| |
| #include <linux/linkage.h> |
| #include <asm/entry.h> |
| #include <asm/tlb.h> |
| #include <asm/pgtable.h> |
| #include <asm/arcregs.h> |
| #include <asm/cache.h> |
| #include <asm/processor.h> |
| #if (CONFIG_ARC_MMU_VER == 1) |
| #include <asm/tlb-mmu1.h> |
| #endif |
| |
| ;-------------------------------------------------------------------------- |
| ; scratch memory to save the registers (r0-r3) used to code TLB refill Handler |
| ; For details refer to comments before TLBMISS_FREEUP_REGS below |
| ;-------------------------------------------------------------------------- |
| |
| .section .data |
| .global ex_saved_reg1 |
| .align 1 << L1_CACHE_SHIFT ; IMP: Must be Cache Line aligned |
| .type ex_saved_reg1, @object |
| .size ex_saved_reg1, 16 |
| ex_saved_reg1: |
| .zero 16 |
| |
| ;============================================================================ |
| ; Troubleshooting Stuff |
| ;============================================================================ |
| |
| ; Linux keeps ASID (Address Space ID) in task->active_mm->context.asid |
| ; When Creating TLB Entries, instead of doing 3 dependent loads from memory, |
| ; we use the MMU PID Reg to get current ASID. |
| ; In bizzare scenrios SW and HW ASID can get out-of-sync which is trouble. |
| ; So we try to detect this in TLB Mis shandler |
| |
| |
| .macro DBG_ASID_MISMATCH |
| |
| #ifdef CONFIG_ARC_DBG_TLB_PARANOIA |
| |
| ; make sure h/w ASID is same as s/w ASID |
| |
| GET_CURR_TASK_ON_CPU r3 |
| ld r0, [r3, TASK_ACT_MM] |
| ld r0, [r0, MM_CTXT+MM_CTXT_ASID] |
| |
| lr r1, [ARC_REG_PID] |
| and r1, r1, 0xFF |
| breq r1, r0, 5f |
| |
| ; Error if H/w and S/w ASID don't match, but NOT if in kernel mode |
| lr r0, [erstatus] |
| bbit0 r0, STATUS_U_BIT, 5f |
| |
| ; We sure are in troubled waters, Flag the error, but to do so |
| ; need to switch to kernel mode stack to call error routine |
| GET_TSK_STACK_BASE r3, sp |
| |
| ; Call printk to shoutout aloud |
| mov r0, 1 |
| j print_asid_mismatch |
| |
| 5: ; ASIDs match so proceed normally |
| nop |
| |
| #endif |
| |
| .endm |
| |
| ;============================================================================ |
| ;TLB Miss handling Code |
| ;============================================================================ |
| |
| ;----------------------------------------------------------------------------- |
| ; This macro does the page-table lookup for the faulting address. |
| ; OUT: r0 = PTE faulted on, r1 = ptr to PTE, r2 = Faulting V-address |
| .macro LOAD_FAULT_PTE |
| |
| lr r2, [efa] |
| |
| lr r1, [ARC_REG_SCRATCH_DATA0] ; current pgd |
| |
| lsr r0, r2, PGDIR_SHIFT ; Bits for indexing into PGD |
| ld.as r1, [r1, r0] ; PGD entry corresp to faulting addr |
| and.f r1, r1, PAGE_MASK ; Ignoring protection and other flags |
| ; contains Ptr to Page Table |
| bz.d do_slow_path_pf ; if no Page Table, do page fault |
| |
| ; Get the PTE entry: The idea is |
| ; (1) x = addr >> PAGE_SHIFT -> masks page-off bits from @fault-addr |
| ; (2) y = x & (PTRS_PER_PTE - 1) -> to get index |
| ; (3) z = pgtbl[y] |
| ; To avoid the multiply by in end, we do the -2, <<2 below |
| |
| lsr r0, r2, (PAGE_SHIFT - 2) |
| and r0, r0, ( (PTRS_PER_PTE - 1) << 2) |
| ld.aw r0, [r1, r0] ; get PTE and PTE ptr for fault addr |
| #ifdef CONFIG_ARC_DBG_TLB_MISS_COUNT |
| and.f 0, r0, _PAGE_PRESENT |
| bz 1f |
| ld r2, [num_pte_not_present] |
| add r2, r2, 1 |
| st r2, [num_pte_not_present] |
| 1: |
| #endif |
| |
| .endm |
| |
| ;----------------------------------------------------------------- |
| ; Convert Linux PTE entry into TLB entry |
| ; A one-word PTE entry is programmed as two-word TLB Entry [PD0:PD1] in mmu |
| ; IN: r0 = PTE, r1 = ptr to PTE |
| |
| .macro CONV_PTE_TO_TLB |
| and r3, r0, PTE_BITS_IN_PD1 ; Extract permission flags+PFN from PTE |
| sr r3, [ARC_REG_TLBPD1] ; these go in PD1 |
| |
| and r2, r0, PTE_BITS_IN_PD0 ; Extract other PTE flags: (V)alid, (G)lb |
| #if (CONFIG_ARC_MMU_VER <= 2) /* Neednot be done with v3 onwards */ |
| lsr r2, r2 ; shift PTE flags to match layout in PD0 |
| #endif |
| |
| lr r3,[ARC_REG_TLBPD0] ; MMU prepares PD0 with vaddr and asid |
| |
| or r3, r3, r2 ; S | vaddr | {sasid|asid} |
| sr r3,[ARC_REG_TLBPD0] ; rewrite PD0 |
| .endm |
| |
| ;----------------------------------------------------------------- |
| ; Commit the TLB entry into MMU |
| |
| .macro COMMIT_ENTRY_TO_MMU |
| |
| /* Get free TLB slot: Set = computed from vaddr, way = random */ |
| sr TLBGetIndex, [ARC_REG_TLBCOMMAND] |
| |
| /* Commit the Write */ |
| #if (CONFIG_ARC_MMU_VER >= 2) /* introduced in v2 */ |
| sr TLBWriteNI, [ARC_REG_TLBCOMMAND] |
| #else |
| sr TLBWrite, [ARC_REG_TLBCOMMAND] |
| #endif |
| .endm |
| |
| ;----------------------------------------------------------------- |
| ; ARC700 Exception Handling doesn't auto-switch stack and it only provides |
| ; ONE scratch AUX reg "ARC_REG_SCRATCH_DATA0" |
| ; |
| ; For Non-SMP, the scratch AUX reg is repurposed to cache task PGD, so a |
| ; "global" is used to free-up FIRST core reg to be able to code the rest of |
| ; exception prologue (IRQ auto-disabled on Exceptions, so it's IRQ-safe). |
| ; Since the Fast Path TLB Miss handler is coded with 4 regs, the remaining 3 |
| ; need to be saved as well by extending the "global" to be 4 words. Hence |
| ; ".size ex_saved_reg1, 16" |
| ; [All of this dance is to avoid stack switching for each TLB Miss, since we |
| ; only need to save only a handful of regs, as opposed to complete reg file] |
| |
| ; As simple as that.... |
| |
| .macro TLBMISS_FREEUP_REGS |
| st r0, [@ex_saved_reg1] |
| mov_s r0, @ex_saved_reg1 |
| st_s r1, [r0, 4] |
| st_s r2, [r0, 8] |
| st_s r3, [r0, 12] |
| |
| ; VERIFY if the ASID in MMU-PID Reg is same as |
| ; one in Linux data structures |
| |
| DBG_ASID_MISMATCH |
| .endm |
| |
| ;----------------------------------------------------------------- |
| .macro TLBMISS_RESTORE_REGS |
| mov_s r0, @ex_saved_reg1 |
| ld_s r3, [r0,12] |
| ld_s r2, [r0, 8] |
| ld_s r1, [r0, 4] |
| ld_s r0, [r0] |
| .endm |
| |
| .section .text, "ax",@progbits ;Fast Path Code, candidate for ICCM |
| |
| ;----------------------------------------------------------------------------- |
| ; I-TLB Miss Exception Handler |
| ;----------------------------------------------------------------------------- |
| |
| ARC_ENTRY EV_TLBMissI |
| |
| TLBMISS_FREEUP_REGS |
| |
| #ifdef CONFIG_ARC_DBG_TLB_MISS_COUNT |
| ld r0, [@numitlb] |
| add r0, r0, 1 |
| st r0, [@numitlb] |
| #endif |
| |
| ;---------------------------------------------------------------- |
| ; Get the PTE corresponding to V-addr accessed |
| LOAD_FAULT_PTE |
| |
| ;---------------------------------------------------------------- |
| ; VERIFY_PTE: Check if PTE permissions approp for executing code |
| cmp_s r2, VMALLOC_START |
| mov.lo r2, (_PAGE_PRESENT | _PAGE_READ | _PAGE_EXECUTE) |
| mov.hs r2, (_PAGE_PRESENT | _PAGE_K_READ | _PAGE_K_EXECUTE) |
| |
| and r3, r0, r2 ; Mask out NON Flag bits from PTE |
| xor.f r3, r3, r2 ; check ( ( pte & flags_test ) == flags_test ) |
| bnz do_slow_path_pf |
| |
| ; Let Linux VM know that the page was accessed |
| or r0, r0, (_PAGE_PRESENT | _PAGE_ACCESSED) ; set Accessed Bit |
| st_s r0, [r1] ; Write back PTE |
| |
| CONV_PTE_TO_TLB |
| COMMIT_ENTRY_TO_MMU |
| TLBMISS_RESTORE_REGS |
| rtie |
| |
| ARC_EXIT EV_TLBMissI |
| |
| ;----------------------------------------------------------------------------- |
| ; D-TLB Miss Exception Handler |
| ;----------------------------------------------------------------------------- |
| |
| ARC_ENTRY EV_TLBMissD |
| |
| TLBMISS_FREEUP_REGS |
| |
| #ifdef CONFIG_ARC_DBG_TLB_MISS_COUNT |
| ld r0, [@numdtlb] |
| add r0, r0, 1 |
| st r0, [@numdtlb] |
| #endif |
| |
| ;---------------------------------------------------------------- |
| ; Get the PTE corresponding to V-addr accessed |
| ; If PTE exists, it will setup, r0 = PTE, r1 = Ptr to PTE |
| LOAD_FAULT_PTE |
| |
| ;---------------------------------------------------------------- |
| ; VERIFY_PTE: Chk if PTE permissions approp for data access (R/W/R+W) |
| |
| mov_s r2, 0 |
| lr r3, [ecr] |
| btst_s r3, ECR_C_BIT_DTLB_LD_MISS ; Read Access |
| or.nz r2, r2, _PAGE_READ ; chk for Read flag in PTE |
| btst_s r3, ECR_C_BIT_DTLB_ST_MISS ; Write Access |
| or.nz r2, r2, _PAGE_WRITE ; chk for Write flag in PTE |
| ; Above laddering takes care of XCHG access |
| ; which is both Read and Write |
| |
| ; If kernel mode access, ; make _PAGE_xx flags as _PAGE_K_xx |
| ; For copy_(to|from)_user, despite exception taken in kernel mode, |
| ; this code is not hit, because EFA would still be the user mode |
| ; address (EFA < 0x6000_0000). |
| ; This code is for legit kernel mode faults, vmalloc specifically |
| ; (EFA: 0x7000_0000 to 0x7FFF_FFFF) |
| |
| lr r3, [efa] |
| cmp r3, VMALLOC_START - 1 ; If kernel mode access |
| asl.hi r2, r2, 3 ; make _PAGE_xx flags as _PAGE_K_xx |
| or r2, r2, _PAGE_PRESENT ; Common flag for K/U mode |
| |
| ; By now, r2 setup with all the Flags we need to check in PTE |
| and r3, r0, r2 ; Mask out NON Flag bits from PTE |
| brne.d r3, r2, do_slow_path_pf ; is ((pte & flags_test) == flags_test) |
| |
| ;---------------------------------------------------------------- |
| ; UPDATE_PTE: Let Linux VM know that page was accessed/dirty |
| lr r3, [ecr] |
| or r0, r0, (_PAGE_PRESENT | _PAGE_ACCESSED) ; Accessed bit always |
| btst_s r3, ECR_C_BIT_DTLB_ST_MISS ; See if it was a Write Access ? |
| or.nz r0, r0, _PAGE_MODIFIED ; if Write, set Dirty bit as well |
| st_s r0, [r1] ; Write back PTE |
| |
| CONV_PTE_TO_TLB |
| |
| #if (CONFIG_ARC_MMU_VER == 1) |
| ; MMU with 2 way set assoc J-TLB, needs some help in pathetic case of |
| ; memcpy where 3 parties contend for 2 ways, ensuing a livelock. |
| ; But only for old MMU or one with Metal Fix |
| TLB_WRITE_HEURISTICS |
| #endif |
| |
| COMMIT_ENTRY_TO_MMU |
| TLBMISS_RESTORE_REGS |
| rtie |
| |
| ;-------- Common routine to call Linux Page Fault Handler ----------- |
| do_slow_path_pf: |
| |
| ; Restore the 4-scratch regs saved by fast path miss handler |
| TLBMISS_RESTORE_REGS |
| |
| ; Slow path TLB Miss handled as a regular ARC Exception |
| ; (stack switching / save the complete reg-file). |
| ; That requires freeing up r9 |
| EXCPN_PROLOG_FREEUP_REG r9 |
| |
| lr r9, [erstatus] |
| |
| SWITCH_TO_KERNEL_STK |
| SAVE_ALL_SYS |
| |
| ; ------- setup args for Linux Page fault Hanlder --------- |
| mov_s r0, sp |
| lr r2, [efa] |
| lr r3, [ecr] |
| |
| ; Both st and ex imply WRITE access of some sort, hence do_page_fault( ) |
| ; invoked with write=1 for DTLB-st/ex Miss and write=0 for ITLB miss or |
| ; DTLB-ld Miss |
| ; DTLB Miss Cause code is ld = 0x01 , st = 0x02, ex = 0x03 |
| ; Following code uses that fact that st/ex have one bit in common |
| |
| btst_s r3, ECR_C_BIT_DTLB_ST_MISS |
| mov.z r1, 0 |
| mov.nz r1, 1 |
| |
| ; We don't want exceptions to be disabled while the fault is handled. |
| ; Now that we have saved the context we return from exception hence |
| ; exceptions get re-enable |
| |
| FAKE_RET_FROM_EXCPN r9 |
| |
| bl do_page_fault |
| b ret_from_exception |
| |
| ARC_EXIT EV_TLBMissD |
| |
| ARC_ENTRY EV_TLBMissB ; Bogus entry to measure sz of DTLBMiss hdlr |