385 lines
12 KiB
ArmAsm
385 lines
12 KiB
ArmAsm
/*
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* TLB Exception Handling for ARC
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*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Vineetg: April 2011 :
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* -MMU v1: moved out legacy code into a seperate file
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* -MMU v3: PD{0,1} bits layout changed: They don't overlap anymore,
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* helps avoid a shift when preparing PD0 from PTE
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*
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* Vineetg: July 2009
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* -For MMU V2, we need not do heuristics at the time of commiting a D-TLB
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* entry, so that it doesn't knock out it's I-TLB entry
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* -Some more fine tuning:
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* bmsk instead of add, asl.cc instead of branch, delay slot utilise etc
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*
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* Vineetg: July 2009
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* -Practically rewrote the I/D TLB Miss handlers
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* Now 40 and 135 instructions a peice as compared to 131 and 449 resp.
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* Hence Leaner by 1.5 K
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* Used Conditional arithmetic to replace excessive branching
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* Also used short instructions wherever possible
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*
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* Vineetg: Aug 13th 2008
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* -Passing ECR (Exception Cause REG) to do_page_fault( ) for printing
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* more information in case of a Fatality
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*
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* Vineetg: March 25th Bug #92690
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* -Added Debug Code to check if sw-ASID == hw-ASID
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* Rahul Trivedi, Amit Bhor: Codito Technologies 2004
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*/
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.cpu A7
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#include <linux/linkage.h>
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#include <asm/entry.h>
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#include <asm/mmu.h>
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#include <asm/pgtable.h>
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#include <asm/arcregs.h>
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#include <asm/cache.h>
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#include <asm/processor.h>
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#include <asm/tlb-mmu1.h>
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;-----------------------------------------------------------------
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; ARC700 Exception Handling doesn't auto-switch stack and it only provides
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; ONE scratch AUX reg "ARC_REG_SCRATCH_DATA0"
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;
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; For Non-SMP, the scratch AUX reg is repurposed to cache task PGD, so a
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; "global" is used to free-up FIRST core reg to be able to code the rest of
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; exception prologue (IRQ auto-disabled on Exceptions, so it's IRQ-safe).
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; Since the Fast Path TLB Miss handler is coded with 4 regs, the remaining 3
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; need to be saved as well by extending the "global" to be 4 words. Hence
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; ".size ex_saved_reg1, 16"
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; [All of this dance is to avoid stack switching for each TLB Miss, since we
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; only need to save only a handful of regs, as opposed to complete reg file]
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;
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; For ARC700 SMP, the "global" obviously can't be used for free up the FIRST
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; core reg as it will not be SMP safe.
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; Thus scratch AUX reg is used (and no longer used to cache task PGD).
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; To save the rest of 3 regs - per cpu, the global is made "per-cpu".
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; Epilogue thus has to locate the "per-cpu" storage for regs.
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; To avoid cache line bouncing the per-cpu global is aligned/sized per
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; L1_CACHE_SHIFT, despite fundamentally needing to be 12 bytes only. Hence
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; ".size ex_saved_reg1, (CONFIG_NR_CPUS << L1_CACHE_SHIFT)"
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; As simple as that....
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;--------------------------------------------------------------------------
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; scratch memory to save [r0-r3] used to code TLB refill Handler
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ARCFP_DATA ex_saved_reg1
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.align 1 << L1_CACHE_SHIFT
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.type ex_saved_reg1, @object
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#ifdef CONFIG_SMP
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.size ex_saved_reg1, (CONFIG_NR_CPUS << L1_CACHE_SHIFT)
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ex_saved_reg1:
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.zero (CONFIG_NR_CPUS << L1_CACHE_SHIFT)
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#else
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.size ex_saved_reg1, 16
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ex_saved_reg1:
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.zero 16
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#endif
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.macro TLBMISS_FREEUP_REGS
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#ifdef CONFIG_SMP
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sr r0, [ARC_REG_SCRATCH_DATA0] ; freeup r0 to code with
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GET_CPU_ID r0 ; get to per cpu scratch mem,
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lsl r0, r0, L1_CACHE_SHIFT ; cache line wide per cpu
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add r0, @ex_saved_reg1, r0
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#else
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st r0, [@ex_saved_reg1]
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mov_s r0, @ex_saved_reg1
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#endif
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st_s r1, [r0, 4]
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st_s r2, [r0, 8]
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st_s r3, [r0, 12]
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; VERIFY if the ASID in MMU-PID Reg is same as
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; one in Linux data structures
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tlb_paranoid_check_asm
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.endm
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.macro TLBMISS_RESTORE_REGS
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#ifdef CONFIG_SMP
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GET_CPU_ID r0 ; get to per cpu scratch mem
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lsl r0, r0, L1_CACHE_SHIFT ; each is cache line wide
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add r0, @ex_saved_reg1, r0
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ld_s r3, [r0,12]
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ld_s r2, [r0, 8]
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ld_s r1, [r0, 4]
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lr r0, [ARC_REG_SCRATCH_DATA0]
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#else
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mov_s r0, @ex_saved_reg1
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ld_s r3, [r0,12]
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ld_s r2, [r0, 8]
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ld_s r1, [r0, 4]
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ld_s r0, [r0]
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#endif
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.endm
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;============================================================================
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; Troubleshooting Stuff
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;============================================================================
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; Linux keeps ASID (Address Space ID) in task->active_mm->context.asid
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; When Creating TLB Entries, instead of doing 3 dependent loads from memory,
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; we use the MMU PID Reg to get current ASID.
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; In bizzare scenrios SW and HW ASID can get out-of-sync which is trouble.
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; So we try to detect this in TLB Mis shandler
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.macro tlb_paranoid_check_asm
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#ifdef CONFIG_ARC_DBG_TLB_PARANOIA
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GET_CURR_TASK_ON_CPU r3
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ld r0, [r3, TASK_ACT_MM]
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ld r0, [r0, MM_CTXT+MM_CTXT_ASID]
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breq r0, 0, 55f ; Error if no ASID allocated
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lr r1, [ARC_REG_PID]
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and r1, r1, 0xFF
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and r2, r0, 0xFF ; MMU PID bits only for comparison
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breq r1, r2, 5f
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55:
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; Error if H/w and S/w ASID don't match, but NOT if in kernel mode
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lr r2, [erstatus]
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bbit0 r2, STATUS_U_BIT, 5f
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; We sure are in troubled waters, Flag the error, but to do so
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; need to switch to kernel mode stack to call error routine
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GET_TSK_STACK_BASE r3, sp
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; Call printk to shoutout aloud
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mov r2, 1
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j print_asid_mismatch
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5: ; ASIDs match so proceed normally
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nop
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#endif
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.endm
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;============================================================================
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;TLB Miss handling Code
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;============================================================================
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;-----------------------------------------------------------------------------
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; This macro does the page-table lookup for the faulting address.
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; OUT: r0 = PTE faulted on, r1 = ptr to PTE, r2 = Faulting V-address
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.macro LOAD_FAULT_PTE
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lr r2, [efa]
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#ifndef CONFIG_SMP
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lr r1, [ARC_REG_SCRATCH_DATA0] ; current pgd
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#else
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GET_CURR_TASK_ON_CPU r1
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ld r1, [r1, TASK_ACT_MM]
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ld r1, [r1, MM_PGD]
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#endif
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lsr r0, r2, PGDIR_SHIFT ; Bits for indexing into PGD
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ld.as r1, [r1, r0] ; PGD entry corresp to faulting addr
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and.f r1, r1, PAGE_MASK ; Ignoring protection and other flags
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; contains Ptr to Page Table
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bz.d do_slow_path_pf ; if no Page Table, do page fault
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; Get the PTE entry: The idea is
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; (1) x = addr >> PAGE_SHIFT -> masks page-off bits from @fault-addr
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; (2) y = x & (PTRS_PER_PTE - 1) -> to get index
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; (3) z = pgtbl[y]
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; To avoid the multiply by in end, we do the -2, <<2 below
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lsr r0, r2, (PAGE_SHIFT - 2)
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and r0, r0, ( (PTRS_PER_PTE - 1) << 2)
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ld.aw r0, [r1, r0] ; get PTE and PTE ptr for fault addr
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#ifdef CONFIG_ARC_DBG_TLB_MISS_COUNT
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and.f 0, r0, _PAGE_PRESENT
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bz 1f
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ld r3, [num_pte_not_present]
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add r3, r3, 1
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st r3, [num_pte_not_present]
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1:
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#endif
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.endm
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;-----------------------------------------------------------------
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; Convert Linux PTE entry into TLB entry
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; A one-word PTE entry is programmed as two-word TLB Entry [PD0:PD1] in mmu
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; IN: r0 = PTE, r1 = ptr to PTE
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.macro CONV_PTE_TO_TLB
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and r3, r0, PTE_BITS_RWX ; r w x
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lsl r2, r3, 3 ; r w x 0 0 0
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and.f 0, r0, _PAGE_GLOBAL
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or.z r2, r2, r3 ; r w x r w x
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and r3, r0, PTE_BITS_NON_RWX_IN_PD1 ; Extract PFN+cache bits from PTE
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or r3, r3, r2
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sr r3, [ARC_REG_TLBPD1] ; these go in PD1
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and r2, r0, PTE_BITS_IN_PD0 ; Extract other PTE flags: (V)alid, (G)lb
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lr r3,[ARC_REG_TLBPD0] ; MMU prepares PD0 with vaddr and asid
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or r3, r3, r2 ; S | vaddr | {sasid|asid}
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sr r3,[ARC_REG_TLBPD0] ; rewrite PD0
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.endm
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;-----------------------------------------------------------------
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; Commit the TLB entry into MMU
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.macro COMMIT_ENTRY_TO_MMU
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/* Get free TLB slot: Set = computed from vaddr, way = random */
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sr TLBGetIndex, [ARC_REG_TLBCOMMAND]
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/* Commit the Write */
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#if (CONFIG_ARC_MMU_VER >= 2) /* introduced in v2 */
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sr TLBWriteNI, [ARC_REG_TLBCOMMAND]
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#else
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sr TLBWrite, [ARC_REG_TLBCOMMAND]
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#endif
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.endm
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ARCFP_CODE ;Fast Path Code, candidate for ICCM
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;-----------------------------------------------------------------------------
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; I-TLB Miss Exception Handler
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;-----------------------------------------------------------------------------
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ENTRY(EV_TLBMissI)
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TLBMISS_FREEUP_REGS
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#ifdef CONFIG_ARC_DBG_TLB_MISS_COUNT
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ld r0, [@numitlb]
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add r0, r0, 1
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st r0, [@numitlb]
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#endif
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;----------------------------------------------------------------
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; Get the PTE corresponding to V-addr accessed, r2 is setup with EFA
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LOAD_FAULT_PTE
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;----------------------------------------------------------------
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; VERIFY_PTE: Check if PTE permissions approp for executing code
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cmp_s r2, VMALLOC_START
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mov_s r2, (_PAGE_PRESENT | _PAGE_EXECUTE)
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or.hs r2, r2, _PAGE_GLOBAL
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and r3, r0, r2 ; Mask out NON Flag bits from PTE
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xor.f r3, r3, r2 ; check ( ( pte & flags_test ) == flags_test )
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bnz do_slow_path_pf
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; Let Linux VM know that the page was accessed
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or r0, r0, _PAGE_ACCESSED ; set Accessed Bit
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st_s r0, [r1] ; Write back PTE
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CONV_PTE_TO_TLB
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COMMIT_ENTRY_TO_MMU
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TLBMISS_RESTORE_REGS
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rtie
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END(EV_TLBMissI)
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;-----------------------------------------------------------------------------
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; D-TLB Miss Exception Handler
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;-----------------------------------------------------------------------------
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ENTRY(EV_TLBMissD)
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TLBMISS_FREEUP_REGS
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#ifdef CONFIG_ARC_DBG_TLB_MISS_COUNT
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ld r0, [@numdtlb]
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add r0, r0, 1
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st r0, [@numdtlb]
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#endif
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;----------------------------------------------------------------
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; Get the PTE corresponding to V-addr accessed
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; If PTE exists, it will setup, r0 = PTE, r1 = Ptr to PTE, r2 = EFA
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LOAD_FAULT_PTE
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;----------------------------------------------------------------
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; VERIFY_PTE: Chk if PTE permissions approp for data access (R/W/R+W)
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cmp_s r2, VMALLOC_START
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mov_s r2, _PAGE_PRESENT ; common bit for K/U PTE
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or.hs r2, r2, _PAGE_GLOBAL ; kernel PTE only
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; Linux PTE [RWX] bits are semantically overloaded:
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; -If PAGE_GLOBAL set, they refer to kernel-only flags (vmalloc)
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; -Otherwise they are user-mode permissions, and those are exactly
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; same for kernel mode as well (e.g. copy_(to|from)_user)
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lr r3, [ecr]
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btst_s r3, ECR_C_BIT_DTLB_LD_MISS ; Read Access
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or.nz r2, r2, _PAGE_READ ; chk for Read flag in PTE
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btst_s r3, ECR_C_BIT_DTLB_ST_MISS ; Write Access
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or.nz r2, r2, _PAGE_WRITE ; chk for Write flag in PTE
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; Above laddering takes care of XCHG access (both R and W)
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; By now, r2 setup with all the Flags we need to check in PTE
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and r3, r0, r2 ; Mask out NON Flag bits from PTE
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brne.d r3, r2, do_slow_path_pf ; is ((pte & flags_test) == flags_test)
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;----------------------------------------------------------------
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; UPDATE_PTE: Let Linux VM know that page was accessed/dirty
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lr r3, [ecr]
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or r0, r0, _PAGE_ACCESSED ; Accessed bit always
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btst_s r3, ECR_C_BIT_DTLB_ST_MISS ; See if it was a Write Access ?
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or.nz r0, r0, _PAGE_MODIFIED ; if Write, set Dirty bit as well
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st_s r0, [r1] ; Write back PTE
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CONV_PTE_TO_TLB
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#if (CONFIG_ARC_MMU_VER == 1)
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; MMU with 2 way set assoc J-TLB, needs some help in pathetic case of
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; memcpy where 3 parties contend for 2 ways, ensuing a livelock.
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; But only for old MMU or one with Metal Fix
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TLB_WRITE_HEURISTICS
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#endif
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COMMIT_ENTRY_TO_MMU
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TLBMISS_RESTORE_REGS
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rtie
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;-------- Common routine to call Linux Page Fault Handler -----------
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do_slow_path_pf:
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; Restore the 4-scratch regs saved by fast path miss handler
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TLBMISS_RESTORE_REGS
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; Slow path TLB Miss handled as a regular ARC Exception
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; (stack switching / save the complete reg-file).
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EXCEPTION_PROLOGUE
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; ------- setup args for Linux Page fault Hanlder ---------
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mov_s r1, sp
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lr r0, [efa]
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; We don't want exceptions to be disabled while the fault is handled.
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; Now that we have saved the context we return from exception hence
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; exceptions get re-enable
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FAKE_RET_FROM_EXCPN r9
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bl do_page_fault
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b ret_from_exception
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END(EV_TLBMissD)
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