1/* 2 * TLB Exception Handling for ARC 3 * 4 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 * 10 * Vineetg: April 2011 : 11 * -MMU v1: moved out legacy code into a seperate file 12 * -MMU v3: PD{0,1} bits layout changed: They don't overlap anymore, 13 * helps avoid a shift when preparing PD0 from PTE 14 * 15 * Vineetg: July 2009 16 * -For MMU V2, we need not do heuristics at the time of commiting a D-TLB 17 * entry, so that it doesn't knock out it's I-TLB entry 18 * -Some more fine tuning: 19 * bmsk instead of add, asl.cc instead of branch, delay slot utilise etc 20 * 21 * Vineetg: July 2009 22 * -Practically rewrote the I/D TLB Miss handlers 23 * Now 40 and 135 instructions a peice as compared to 131 and 449 resp. 24 * Hence Leaner by 1.5 K 25 * Used Conditional arithmetic to replace excessive branching 26 * Also used short instructions wherever possible 27 * 28 * Vineetg: Aug 13th 2008 29 * -Passing ECR (Exception Cause REG) to do_page_fault( ) for printing 30 * more information in case of a Fatality 31 * 32 * Vineetg: March 25th Bug #92690 33 * -Added Debug Code to check if sw-ASID == hw-ASID 34 35 * Rahul Trivedi, Amit Bhor: Codito Technologies 2004 36 */ 37 38#include <linux/linkage.h> 39#include <asm/entry.h> 40#include <asm/mmu.h> 41#include <asm/pgtable.h> 42#include <asm/arcregs.h> 43#include <asm/cache.h> 44#include <asm/processor.h> 45#include <asm/tlb-mmu1.h> 46 47#ifdef CONFIG_ISA_ARCOMPACT 48;----------------------------------------------------------------- 49; ARC700 Exception Handling doesn't auto-switch stack and it only provides 50; ONE scratch AUX reg "ARC_REG_SCRATCH_DATA0" 51; 52; For Non-SMP, the scratch AUX reg is repurposed to cache task PGD, so a 53; "global" is used to free-up FIRST core reg to be able to code the rest of 54; exception prologue (IRQ auto-disabled on Exceptions, so it's IRQ-safe). 55; Since the Fast Path TLB Miss handler is coded with 4 regs, the remaining 3 56; need to be saved as well by extending the "global" to be 4 words. Hence 57; ".size ex_saved_reg1, 16" 58; [All of this dance is to avoid stack switching for each TLB Miss, since we 59; only need to save only a handful of regs, as opposed to complete reg file] 60; 61; For ARC700 SMP, the "global" obviously can't be used for free up the FIRST 62; core reg as it will not be SMP safe. 63; Thus scratch AUX reg is used (and no longer used to cache task PGD). 64; To save the rest of 3 regs - per cpu, the global is made "per-cpu". 65; Epilogue thus has to locate the "per-cpu" storage for regs. 66; To avoid cache line bouncing the per-cpu global is aligned/sized per 67; L1_CACHE_SHIFT, despite fundamentally needing to be 12 bytes only. Hence 68; ".size ex_saved_reg1, (CONFIG_NR_CPUS << L1_CACHE_SHIFT)" 69 70; As simple as that.... 71;-------------------------------------------------------------------------- 72 73; scratch memory to save [r0-r3] used to code TLB refill Handler 74ARCFP_DATA ex_saved_reg1 75 .align 1 << L1_CACHE_SHIFT 76 .type ex_saved_reg1, @object 77#ifdef CONFIG_SMP 78 .size ex_saved_reg1, (CONFIG_NR_CPUS << L1_CACHE_SHIFT) 79ex_saved_reg1: 80 .zero (CONFIG_NR_CPUS << L1_CACHE_SHIFT) 81#else 82 .size ex_saved_reg1, 16 83ex_saved_reg1: 84 .zero 16 85#endif 86 87.macro TLBMISS_FREEUP_REGS 88#ifdef CONFIG_SMP 89 sr r0, [ARC_REG_SCRATCH_DATA0] ; freeup r0 to code with 90 GET_CPU_ID r0 ; get to per cpu scratch mem, 91 asl r0, r0, L1_CACHE_SHIFT ; cache line wide per cpu 92 add r0, @ex_saved_reg1, r0 93#else 94 st r0, [@ex_saved_reg1] 95 mov_s r0, @ex_saved_reg1 96#endif 97 st_s r1, [r0, 4] 98 st_s r2, [r0, 8] 99 st_s r3, [r0, 12] 100 101 ; VERIFY if the ASID in MMU-PID Reg is same as 102 ; one in Linux data structures 103 104 tlb_paranoid_check_asm 105.endm 106 107.macro TLBMISS_RESTORE_REGS 108#ifdef CONFIG_SMP 109 GET_CPU_ID r0 ; get to per cpu scratch mem 110 asl r0, r0, L1_CACHE_SHIFT ; each is cache line wide 111 add r0, @ex_saved_reg1, r0 112 ld_s r3, [r0,12] 113 ld_s r2, [r0, 8] 114 ld_s r1, [r0, 4] 115 lr r0, [ARC_REG_SCRATCH_DATA0] 116#else 117 mov_s r0, @ex_saved_reg1 118 ld_s r3, [r0,12] 119 ld_s r2, [r0, 8] 120 ld_s r1, [r0, 4] 121 ld_s r0, [r0] 122#endif 123.endm 124 125#else /* ARCv2 */ 126 127.macro TLBMISS_FREEUP_REGS 128 PUSH r0 129 PUSH r1 130 PUSH r2 131 PUSH r3 132.endm 133 134.macro TLBMISS_RESTORE_REGS 135 POP r3 136 POP r2 137 POP r1 138 POP r0 139.endm 140 141#endif 142 143;============================================================================ 144; Troubleshooting Stuff 145;============================================================================ 146 147; Linux keeps ASID (Address Space ID) in task->active_mm->context.asid 148; When Creating TLB Entries, instead of doing 3 dependent loads from memory, 149; we use the MMU PID Reg to get current ASID. 150; In bizzare scenrios SW and HW ASID can get out-of-sync which is trouble. 151; So we try to detect this in TLB Mis shandler 152 153.macro tlb_paranoid_check_asm 154 155#ifdef CONFIG_ARC_DBG_TLB_PARANOIA 156 157 GET_CURR_TASK_ON_CPU r3 158 ld r0, [r3, TASK_ACT_MM] 159 ld r0, [r0, MM_CTXT+MM_CTXT_ASID] 160 breq r0, 0, 55f ; Error if no ASID allocated 161 162 lr r1, [ARC_REG_PID] 163 and r1, r1, 0xFF 164 165 and r2, r0, 0xFF ; MMU PID bits only for comparison 166 breq r1, r2, 5f 167 16855: 169 ; Error if H/w and S/w ASID don't match, but NOT if in kernel mode 170 lr r2, [erstatus] 171 bbit0 r2, STATUS_U_BIT, 5f 172 173 ; We sure are in troubled waters, Flag the error, but to do so 174 ; need to switch to kernel mode stack to call error routine 175 GET_TSK_STACK_BASE r3, sp 176 177 ; Call printk to shoutout aloud 178 mov r2, 1 179 j print_asid_mismatch 180 1815: ; ASIDs match so proceed normally 182 nop 183 184#endif 185 186.endm 187 188;============================================================================ 189;TLB Miss handling Code 190;============================================================================ 191 192;----------------------------------------------------------------------------- 193; This macro does the page-table lookup for the faulting address. 194; OUT: r0 = PTE faulted on, r1 = ptr to PTE, r2 = Faulting V-address 195.macro LOAD_FAULT_PTE 196 197 lr r2, [efa] 198 199#ifndef CONFIG_SMP 200 lr r1, [ARC_REG_SCRATCH_DATA0] ; current pgd 201#else 202 GET_CURR_TASK_ON_CPU r1 203 ld r1, [r1, TASK_ACT_MM] 204 ld r1, [r1, MM_PGD] 205#endif 206 207 lsr r0, r2, PGDIR_SHIFT ; Bits for indexing into PGD 208 ld.as r3, [r1, r0] ; PGD entry corresp to faulting addr 209 tst r3, r3 210 bz do_slow_path_pf ; if no Page Table, do page fault 211 212#ifdef CONFIG_TRANSPARENT_HUGEPAGE 213 and.f 0, r3, _PAGE_HW_SZ ; Is this Huge PMD (thp) 214 add2.nz r1, r1, r0 215 bnz.d 2f ; YES: PGD == PMD has THP PTE: stop pgd walk 216 mov.nz r0, r3 217 218#endif 219 and r1, r3, PAGE_MASK 220 221 ; Get the PTE entry: The idea is 222 ; (1) x = addr >> PAGE_SHIFT -> masks page-off bits from @fault-addr 223 ; (2) y = x & (PTRS_PER_PTE - 1) -> to get index 224 ; (3) z = (pgtbl + y * 4) 225 226#ifdef CONFIG_ARC_HAS_PAE40 227#define PTE_SIZE_LOG 3 /* 8 == 2 ^ 3 */ 228#else 229#define PTE_SIZE_LOG 2 /* 4 == 2 ^ 2 */ 230#endif 231 232 ; multiply in step (3) above avoided by shifting lesser in step (1) 233 lsr r0, r2, ( PAGE_SHIFT - PTE_SIZE_LOG ) 234 and r0, r0, ( (PTRS_PER_PTE - 1) << PTE_SIZE_LOG ) 235 ld.aw r0, [r1, r0] ; r0: PTE (lower word only for PAE40) 236 ; r1: PTE ptr 237 2382: 239 240.endm 241 242;----------------------------------------------------------------- 243; Convert Linux PTE entry into TLB entry 244; A one-word PTE entry is programmed as two-word TLB Entry [PD0:PD1] in mmu 245; (for PAE40, two-words PTE, while three-word TLB Entry [PD0:PD1:PD1HI]) 246; IN: r0 = PTE, r1 = ptr to PTE 247 248.macro CONV_PTE_TO_TLB 249 and r3, r0, PTE_BITS_RWX ; r w x 250 asl r2, r3, 3 ; Kr Kw Kx 0 0 0 (GLOBAL, kernel only) 251 and.f 0, r0, _PAGE_GLOBAL 252 or.z r2, r2, r3 ; Kr Kw Kx Ur Uw Ux (!GLOBAL, user page) 253 254 and r3, r0, PTE_BITS_NON_RWX_IN_PD1 ; Extract PFN+cache bits from PTE 255 or r3, r3, r2 256 257 sr r3, [ARC_REG_TLBPD1] ; paddr[31..13] | Kr Kw Kx Ur Uw Ux | C 258#ifdef CONFIG_ARC_HAS_PAE40 259 ld r3, [r1, 4] ; paddr[39..32] 260 sr r3, [ARC_REG_TLBPD1HI] 261#endif 262 263 and r2, r0, PTE_BITS_IN_PD0 ; Extract other PTE flags: (V)alid, (G)lb 264 265 lr r3,[ARC_REG_TLBPD0] ; MMU prepares PD0 with vaddr and asid 266 267 or r3, r3, r2 ; S | vaddr | {sasid|asid} 268 sr r3,[ARC_REG_TLBPD0] ; rewrite PD0 269.endm 270 271;----------------------------------------------------------------- 272; Commit the TLB entry into MMU 273 274.macro COMMIT_ENTRY_TO_MMU 275#if (CONFIG_ARC_MMU_VER < 4) 276 277 /* Get free TLB slot: Set = computed from vaddr, way = random */ 278 sr TLBGetIndex, [ARC_REG_TLBCOMMAND] 279 280 /* Commit the Write */ 281#if (CONFIG_ARC_MMU_VER >= 2) /* introduced in v2 */ 282 sr TLBWriteNI, [ARC_REG_TLBCOMMAND] 283#else 284 sr TLBWrite, [ARC_REG_TLBCOMMAND] 285#endif 286 287#else 288 sr TLBInsertEntry, [ARC_REG_TLBCOMMAND] 289#endif 290.endm 291 292 293ARCFP_CODE ;Fast Path Code, candidate for ICCM 294 295;----------------------------------------------------------------------------- 296; I-TLB Miss Exception Handler 297;----------------------------------------------------------------------------- 298 299ENTRY(EV_TLBMissI) 300 301 TLBMISS_FREEUP_REGS 302 303 ;---------------------------------------------------------------- 304 ; Get the PTE corresponding to V-addr accessed, r2 is setup with EFA 305 LOAD_FAULT_PTE 306 307 ;---------------------------------------------------------------- 308 ; VERIFY_PTE: Check if PTE permissions approp for executing code 309 cmp_s r2, VMALLOC_START 310 mov_s r2, (_PAGE_PRESENT | _PAGE_EXECUTE) 311 or.hs r2, r2, _PAGE_GLOBAL 312 313 and r3, r0, r2 ; Mask out NON Flag bits from PTE 314 xor.f r3, r3, r2 ; check ( ( pte & flags_test ) == flags_test ) 315 bnz do_slow_path_pf 316 317 ; Let Linux VM know that the page was accessed 318 or r0, r0, _PAGE_ACCESSED ; set Accessed Bit 319 st_s r0, [r1] ; Write back PTE 320 321 CONV_PTE_TO_TLB 322 COMMIT_ENTRY_TO_MMU 323 TLBMISS_RESTORE_REGS 324EV_TLBMissI_fast_ret: ; additional label for VDK OS-kit instrumentation 325 rtie 326 327END(EV_TLBMissI) 328 329;----------------------------------------------------------------------------- 330; D-TLB Miss Exception Handler 331;----------------------------------------------------------------------------- 332 333ENTRY(EV_TLBMissD) 334 335 TLBMISS_FREEUP_REGS 336 337 ;---------------------------------------------------------------- 338 ; Get the PTE corresponding to V-addr accessed 339 ; If PTE exists, it will setup, r0 = PTE, r1 = Ptr to PTE, r2 = EFA 340 LOAD_FAULT_PTE 341 342 ;---------------------------------------------------------------- 343 ; VERIFY_PTE: Chk if PTE permissions approp for data access (R/W/R+W) 344 345 cmp_s r2, VMALLOC_START 346 mov_s r2, _PAGE_PRESENT ; common bit for K/U PTE 347 or.hs r2, r2, _PAGE_GLOBAL ; kernel PTE only 348 349 ; Linux PTE [RWX] bits are semantically overloaded: 350 ; -If PAGE_GLOBAL set, they refer to kernel-only flags (vmalloc) 351 ; -Otherwise they are user-mode permissions, and those are exactly 352 ; same for kernel mode as well (e.g. copy_(to|from)_user) 353 354 lr r3, [ecr] 355 btst_s r3, ECR_C_BIT_DTLB_LD_MISS ; Read Access 356 or.nz r2, r2, _PAGE_READ ; chk for Read flag in PTE 357 btst_s r3, ECR_C_BIT_DTLB_ST_MISS ; Write Access 358 or.nz r2, r2, _PAGE_WRITE ; chk for Write flag in PTE 359 ; Above laddering takes care of XCHG access (both R and W) 360 361 ; By now, r2 setup with all the Flags we need to check in PTE 362 and r3, r0, r2 ; Mask out NON Flag bits from PTE 363 brne.d r3, r2, do_slow_path_pf ; is ((pte & flags_test) == flags_test) 364 365 ;---------------------------------------------------------------- 366 ; UPDATE_PTE: Let Linux VM know that page was accessed/dirty 367 lr r3, [ecr] 368 or r0, r0, _PAGE_ACCESSED ; Accessed bit always 369 btst_s r3, ECR_C_BIT_DTLB_ST_MISS ; See if it was a Write Access ? 370 or.nz r0, r0, _PAGE_DIRTY ; if Write, set Dirty bit as well 371 st_s r0, [r1] ; Write back PTE 372 373 CONV_PTE_TO_TLB 374 375#if (CONFIG_ARC_MMU_VER == 1) 376 ; MMU with 2 way set assoc J-TLB, needs some help in pathetic case of 377 ; memcpy where 3 parties contend for 2 ways, ensuing a livelock. 378 ; But only for old MMU or one with Metal Fix 379 TLB_WRITE_HEURISTICS 380#endif 381 382 COMMIT_ENTRY_TO_MMU 383 TLBMISS_RESTORE_REGS 384EV_TLBMissD_fast_ret: ; additional label for VDK OS-kit instrumentation 385 rtie 386 387;-------- Common routine to call Linux Page Fault Handler ----------- 388do_slow_path_pf: 389 390 ; Restore the 4-scratch regs saved by fast path miss handler 391 TLBMISS_RESTORE_REGS 392 393 ; Slow path TLB Miss handled as a regular ARC Exception 394 ; (stack switching / save the complete reg-file). 395 b call_do_page_fault 396END(EV_TLBMissD) 397