/* SPDX-License-Identifier: GPL-2.0-only */
/*
* TLB Exception Handling for ARC
*
* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
*
* 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
*/
#include <linux/linkage.h>
#include <linux/pgtable.h>
#include <asm/entry.h>
#include <asm/mmu.h>
#include <asm/arcregs.h>
#include <asm/cache.h>
#include <asm/processor.h>
#ifdef CONFIG_ISA_ARCOMPACT
;-----------------------------------------------------------------
; 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]
;
; For ARC700 SMP, the "global" obviously can't be used for free up the FIRST
; core reg as it will not be SMP safe.
; Thus scratch AUX reg is used (and no longer used to cache task PGD).
; To save the rest of 3 regs - per cpu, the global is made "per-cpu".
; Epilogue thus has to locate the "per-cpu" storage for regs.
; To avoid cache line bouncing the per-cpu global is aligned/sized per
; L1_CACHE_SHIFT, despite fundamentally needing to be 12 bytes only. Hence
; ".size ex_saved_reg1, (CONFIG_NR_CPUS << L1_CACHE_SHIFT)"
; As simple as that....
;--------------------------------------------------------------------------
; scratch memory to save [r0-r3] used to code TLB refill Handler
ARCFP_DATA ex_saved_reg1
.align 1 << L1_CACHE_SHIFT
.type ex_saved_reg1, @object
#ifdef CONFIG_SMP
.size ex_saved_reg1, (CONFIG_NR_CPUS << L1_CACHE_SHIFT)
ex_saved_reg1:
.zero (CONFIG_NR_CPUS << L1_CACHE_SHIFT)
#else
.size ex_saved_reg1, 16
ex_saved_reg1:
.zero 16
#endif
.macro TLBMISS_FREEUP_REGS
#ifdef CONFIG_SMP
sr r0, [ARC_REG_SCRATCH_DATA0] ; freeup r0 to code with
GET_CPU_ID r0 ; get to per cpu scratch mem,
asl r0, r0, L1_CACHE_SHIFT ; cache line wide per cpu
add r0, @ex_saved_reg1, r0
#else
st r0, [@ex_saved_reg1]
mov_s r0, @ex_saved_reg1
#endif
st_s r1, [r0, 4]
st_s r2, [r0, 8]
st_s r3, [r0, 12]
.endm
.macro TLBMISS_RESTORE_REGS
#ifdef CONFIG_SMP
GET_CPU_ID r0 ; get to per cpu scratch mem
asl r0, r0, L1_CACHE_SHIFT ; each is cache line wide
add r0, @ex_saved_reg1, r0
ld_s r3, [r0,12]
ld_s r2, [r0, 8]
ld_s r1, [r0, 4]
lr r0, [ARC_REG_SCRATCH_DATA0]
#else
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]
#endif
.endm
#else /* ARCv2 */
.macro TLBMISS_FREEUP_REGS
#ifdef CONFIG_ARC_HAS_LL64
std r0, [sp, -16]
std r2, [sp, -8]
#else
PUSH r0
PUSH r1
PUSH r2
PUSH r3
#endif
.endm
.macro TLBMISS_RESTORE_REGS
#ifdef CONFIG_ARC_HAS_LL64
ldd r0, [sp, -16]
ldd r2, [sp, -8]
#else
POP r3
POP r2
POP r1
POP r0
#endif
.endm
#endif
;============================================================================
;TLB Miss handling Code
;============================================================================
#ifndef PMD_SHIFT
#define PMD_SHIFT PUD_SHIFT
#endif
#ifndef PUD_SHIFT
#define PUD_SHIFT PGDIR_SHIFT
#endif
;-----------------------------------------------------------------------------
; 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]
#ifdef CONFIG_ISA_ARCV2
lr r1, [ARC_REG_SCRATCH_DATA0] ; current pgd
#else
GET_CURR_TASK_ON_CPU r1
ld r1, [r1, TASK_ACT_MM]
ld r1, [r1, MM_PGD]
#endif
lsr r0, r2, PGDIR_SHIFT ; Bits for indexing into PGD
ld.as r3, [r1, r0] ; PGD entry corresp to faulting addr
tst r3, r3
bz do_slow_path_pf ; if no Page Table, do page fault
#if CONFIG_PGTABLE_LEVELS > 3
lsr r0, r2, PUD_SHIFT ; Bits for indexing into PUD
and r0, r0, (PTRS_PER_PUD - 1)
ld.as r1, [r3, r0] ; PMD entry
tst r1, r1
bz do_slow_path_pf
mov r3, r1
#endif
#if CONFIG_PGTABLE_LEVELS > 2
lsr r0, r2, PMD_SHIFT ; Bits for indexing into PMD
and r0, r0, (PTRS_PER_PMD - 1)
ld.as r1, [r3, r0] ; PMD entry
tst r1, r1
bz do_slow_path_pf
mov r3, r1
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
and.f 0, r3, _PAGE_HW_SZ ; Is this Huge PMD (thp)
add2.nz r1, r1, r0
bnz.d 2f ; YES: PGD == PMD has THP PTE: stop pgd walk
mov.nz r0, r3
#endif
and r1, r3, PAGE_MASK
; 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 * 4)
#ifdef CONFIG_ARC_HAS_PAE40
#define PTE_SIZE_LOG 3 /* 8 == 2 ^ 3 */
#else
#define PTE_SIZE_LOG 2 /* 4 == 2 ^ 2 */
#endif
; multiply in step (3) above avoided by shifting lesser in step (1)
lsr r0, r2, ( PAGE_SHIFT - PTE_SIZE_LOG )
and r0, r0, ( (PTRS_PER_PTE - 1) << PTE_SIZE_LOG )
ld.aw r0, [r1, r0] ; r0: PTE (lower word only for PAE40)
; r1: PTE ptr
2:
.endm
;-----------------------------------------------------------------
; Convert Linux PTE entry into TLB entry
; A one-word PTE entry is programmed as two-word TLB Entry [PD0:PD1] in mmu
; (for PAE40, two-words PTE, while three-word TLB Entry [PD0:PD1:PD1HI])
; IN: r0 = PTE, r1 = ptr to PTE
.macro CONV_PTE_TO_TLB
and r3, r0, PTE_BITS_RWX ; r w x
asl r2, r3, 3 ; Kr Kw Kx 0 0 0 (GLOBAL, kernel only)
and.f 0, r0, _PAGE_GLOBAL
or.z r2, r2, r3 ; Kr Kw Kx Ur Uw Ux (!GLOBAL, user page)
and r3, r0, PTE_BITS_NON_RWX_IN_PD1 ; Extract PFN+cache bits from PTE
or r3, r3, r2
sr r3, [ARC_REG_TLBPD1] ; paddr[31..13] | Kr Kw Kx Ur Uw Ux | C
#ifdef CONFIG_ARC_HAS_PAE40
ld r3, [r1, 4] ; paddr[39..32]
sr r3, [ARC_REG_TLBPD1HI]
#endif
and r2, r0, PTE_BITS_IN_PD0 ; Extract other PTE flags: (V)alid, (G)lb
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
#ifdef CONFIG_ARC_MMU_V3
/* Get free TLB slot: Set = computed from vaddr, way = random */
sr TLBGetIndex, [ARC_REG_TLBCOMMAND]
/* Commit the Write */
sr TLBWriteNI, [ARC_REG_TLBCOMMAND]
#else
sr TLBInsertEntry, [ARC_REG_TLBCOMMAND]
#endif
88:
.endm
ARCFP_CODE ;Fast Path Code, candidate for ICCM
;-----------------------------------------------------------------------------
; I-TLB Miss Exception Handler
;-----------------------------------------------------------------------------
ENTRY(EV_TLBMissI)
TLBMISS_FREEUP_REGS
;----------------------------------------------------------------
; Get the PTE corresponding to V-addr accessed, r2 is setup with EFA
LOAD_FAULT_PTE
;----------------------------------------------------------------
; VERIFY_PTE: Check if PTE permissions approp for executing code
cmp_s r2, VMALLOC_START
mov_s r2, (_PAGE_PRESENT | _PAGE_EXECUTE)
or.hs r2, r2, _PAGE_GLOBAL
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_ACCESSED ; set Accessed Bit
st_s r0, [r1] ; Write back PTE
CONV_PTE_TO_TLB
COMMIT_ENTRY_TO_MMU
TLBMISS_RESTORE_REGS
EV_TLBMissI_fast_ret: ; additional label for VDK OS-kit instrumentation
rtie
END(EV_TLBMissI)
;-----------------------------------------------------------------------------
; D-TLB Miss Exception Handler
;-----------------------------------------------------------------------------
ENTRY(EV_TLBMissD)
TLBMISS_FREEUP_REGS
;----------------------------------------------------------------
; Get the PTE corresponding to V-addr accessed
; If PTE exists, it will setup, r0 = PTE, r1 = Ptr to PTE, r2 = EFA
LOAD_FAULT_PTE
;----------------------------------------------------------------
; VERIFY_PTE: Chk if PTE permissions approp for data access (R/W/R+W)
cmp_s r2, VMALLOC_START
mov_s r2, _PAGE_PRESENT ; common bit for K/U PTE
or.hs r2, r2, _PAGE_GLOBAL ; kernel PTE only
; Linux PTE [RWX] bits are semantically overloaded:
; -If PAGE_GLOBAL set, they refer to kernel-only flags (vmalloc)
; -Otherwise they are user-mode permissions, and those are exactly
; same for kernel mode as well (e.g. copy_(to|from)_user)
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 (both R and W)
; 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
or r0, r0, _PAGE_ACCESSED ; Accessed bit always
or.nz r0, r0, _PAGE_DIRTY ; if Write, set Dirty bit as well
st_s r0, [r1] ; Write back PTE
CONV_PTE_TO_TLB
COMMIT_ENTRY_TO_MMU
TLBMISS_RESTORE_REGS
EV_TLBMissD_fast_ret: ; additional label for VDK OS-kit instrumentation
rtie
;-------- Common routine to call Linux Page Fault Handler -----------
do_slow_path_pf:
#ifdef CONFIG_ISA_ARCV2
; Set Z flag if exception in U mode. Hardware micro-ops do this on any
; taken interrupt/exception, and thus is already the case at the entry
; above, but ensuing code would have already clobbered.
; EXCEPTION_PROLOGUE called in slow path, relies on correct Z flag set
lr r2, [erstatus]
and r2, r2, STATUS_U_MASK
bxor.f 0, r2, STATUS_U_BIT
#endif
; 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).
b call_do_page_fault
END(EV_TLBMissD)