1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * wof.S: Sparc window overflow handler. 4 * 5 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu) 6 */ 7 8 #include <asm/contregs.h> 9 #include <asm/page.h> 10 #include <asm/ptrace.h> 11 #include <asm/psr.h> 12 #include <asm/smp.h> 13 #include <asm/asi.h> 14 #include <asm/winmacro.h> 15 #include <asm/asmmacro.h> 16 #include <asm/thread_info.h> 17 18 /* WARNING: This routine is hairy and _very_ complicated, but it 19 * must be as fast as possible as it handles the allocation 20 * of register windows to the user and kernel. If you touch 21 * this code be _very_ careful as many other pieces of the 22 * kernel depend upon how this code behaves. You have been 23 * duly warned... 24 */ 25 26 /* We define macro's for registers which have a fixed 27 * meaning throughout this entire routine. The 'T' in 28 * the comments mean that the register can only be 29 * accessed when in the 'trap' window, 'G' means 30 * accessible in any window. Do not change these registers 31 * after they have been set, until you are ready to return 32 * from the trap. 33 */ 34 #define t_psr l0 /* %psr at trap time T */ 35 #define t_pc l1 /* PC for trap return T */ 36 #define t_npc l2 /* NPC for trap return T */ 37 #define t_wim l3 /* %wim at trap time T */ 38 #define saved_g5 l5 /* Global save register T */ 39 #define saved_g6 l6 /* Global save register T */ 40 #define curptr g6 /* Gets set to 'current' then stays G */ 41 42 /* Now registers whose values can change within the handler. */ 43 #define twin_tmp l4 /* Temp reg, only usable in trap window T */ 44 #define glob_tmp g5 /* Global temporary reg, usable anywhere G */ 45 46 .text 47 .align 4 48 /* BEGINNING OF PATCH INSTRUCTIONS */ 49 /* On a 7-window Sparc the boot code patches spnwin_* 50 * instructions with the following ones. 51 */ 52 .globl spnwin_patch1_7win, spnwin_patch2_7win, spnwin_patch3_7win 53 spnwin_patch1_7win: sll %t_wim, 6, %glob_tmp 54 spnwin_patch2_7win: and %glob_tmp, 0x7f, %glob_tmp 55 spnwin_patch3_7win: and %twin_tmp, 0x7f, %twin_tmp 56 /* END OF PATCH INSTRUCTIONS */ 57 58 /* The trap entry point has done the following: 59 * 60 * rd %psr, %l0 61 * rd %wim, %l3 62 * b spill_window_entry 63 * andcc %l0, PSR_PS, %g0 64 */ 65 66 /* Datum current_thread_info->uwinmask contains at all times a bitmask 67 * where if any user windows are active, at least one bit will 68 * be set in to mask. If no user windows are active, the bitmask 69 * will be all zeroes. 70 */ 71 .globl spill_window_entry 72 .globl spnwin_patch1, spnwin_patch2, spnwin_patch3 73 spill_window_entry: 74 /* LOCATION: Trap Window */ 75 76 mov %g5, %saved_g5 ! save away global temp register 77 mov %g6, %saved_g6 ! save away 'current' ptr register 78 79 /* Compute what the new %wim will be if we save the 80 * window properly in this trap handler. 81 * 82 * newwim = ((%wim>>1) | (%wim<<(nwindows - 1))); 83 */ 84 srl %t_wim, 0x1, %twin_tmp 85 spnwin_patch1: sll %t_wim, 7, %glob_tmp 86 or %glob_tmp, %twin_tmp, %glob_tmp 87 spnwin_patch2: and %glob_tmp, 0xff, %glob_tmp 88 89 /* The trap entry point has set the condition codes 90 * up for us to see if this is from user or kernel. 91 * Get the load of 'curptr' out of the way. 92 */ 93 LOAD_CURRENT(curptr, twin_tmp) 94 95 andcc %t_psr, PSR_PS, %g0 96 be,a spwin_fromuser ! all user wins, branch 97 save %g0, %g0, %g0 ! Go where saving will occur 98 99 /* See if any user windows are active in the set. */ 100 ld [%curptr + TI_UWINMASK], %twin_tmp ! grab win mask 101 orcc %g0, %twin_tmp, %g0 ! check for set bits 102 bne spwin_exist_uwins ! yep, there are some 103 andn %twin_tmp, %glob_tmp, %twin_tmp ! compute new uwinmask 104 105 /* Save into the window which must be saved and do it. 106 * Basically if we are here, this means that we trapped 107 * from kernel mode with only kernel windows in the register 108 * file. 109 */ 110 save %g0, %g0, %g0 ! save into the window to stash away 111 wr %glob_tmp, 0x0, %wim ! set new %wim, this is safe now 112 113 spwin_no_userwins_from_kernel: 114 /* LOCATION: Window to be saved */ 115 116 STORE_WINDOW(sp) ! stash the window 117 restore %g0, %g0, %g0 ! go back into trap window 118 119 /* LOCATION: Trap window */ 120 mov %saved_g5, %g5 ! restore %glob_tmp 121 mov %saved_g6, %g6 ! restore %curptr 122 wr %t_psr, 0x0, %psr ! restore condition codes in %psr 123 WRITE_PAUSE ! waste some time 124 jmp %t_pc ! Return from trap 125 rett %t_npc ! we are done 126 127 spwin_exist_uwins: 128 /* LOCATION: Trap window */ 129 130 /* Wow, user windows have to be dealt with, this is dirty 131 * and messy as all hell. And difficult to follow if you 132 * are approaching the infamous register window trap handling 133 * problem for the first time. DON'T LOOK! 134 * 135 * Note that how the execution path works out, the new %wim 136 * will be left for us in the global temporary register, 137 * %glob_tmp. We cannot set the new %wim first because we 138 * need to save into the appropriate window without inducing 139 * a trap (traps are off, we'd get a watchdog wheee)... 140 * But first, store the new user window mask calculated 141 * above. 142 */ 143 st %twin_tmp, [%curptr + TI_UWINMASK] 144 save %g0, %g0, %g0 ! Go to where the saving will occur 145 146 spwin_fromuser: 147 /* LOCATION: Window to be saved */ 148 wr %glob_tmp, 0x0, %wim ! Now it is safe to set new %wim 149 150 /* LOCATION: Window to be saved */ 151 152 /* This instruction branches to a routine which will check 153 * to validity of the users stack pointer by whatever means 154 * are necessary. This means that this is architecture 155 * specific and thus this branch instruction will need to 156 * be patched at boot time once the machine type is known. 157 * This routine _shall not_ touch %curptr under any 158 * circumstances whatsoever! It will branch back to the 159 * label 'spwin_good_ustack' if the stack is ok but still 160 * needs to be dumped (SRMMU for instance will not need to 161 * do this) or 'spwin_finish_up' if the stack is ok and the 162 * registers have already been saved. If the stack is found 163 * to be bogus for some reason the routine shall branch to 164 * the label 'spwin_user_stack_is_bolixed' which will take 165 * care of things at that point. 166 */ 167 b spwin_srmmu_stackchk 168 andcc %sp, 0x7, %g0 169 170 spwin_good_ustack: 171 /* LOCATION: Window to be saved */ 172 173 /* The users stack is ok and we can safely save it at 174 * %sp. 175 */ 176 STORE_WINDOW(sp) 177 178 spwin_finish_up: 179 restore %g0, %g0, %g0 /* Back to trap window. */ 180 181 /* LOCATION: Trap window */ 182 183 /* We have spilled successfully, and we have properly stored 184 * the appropriate window onto the stack. 185 */ 186 187 /* Restore saved globals */ 188 mov %saved_g5, %g5 189 mov %saved_g6, %g6 190 191 wr %t_psr, 0x0, %psr 192 WRITE_PAUSE 193 jmp %t_pc 194 rett %t_npc 195 196 spwin_user_stack_is_bolixed: 197 /* LOCATION: Window to be saved */ 198 199 /* Wheee, user has trashed his/her stack. We have to decide 200 * how to proceed based upon whether we came from kernel mode 201 * or not. If we came from kernel mode, toss the window into 202 * a special buffer and proceed, the kernel _needs_ a window 203 * and we could be in an interrupt handler so timing is crucial. 204 * If we came from user land we build a full stack frame and call 205 * c-code to gun down the process. 206 */ 207 rd %psr, %glob_tmp 208 andcc %glob_tmp, PSR_PS, %g0 209 bne spwin_bad_ustack_from_kernel 210 nop 211 212 /* Oh well, throw this one window into the per-task window 213 * buffer, the first one. 214 */ 215 st %sp, [%curptr + TI_RWIN_SPTRS] 216 STORE_WINDOW(curptr + TI_REG_WINDOW) 217 restore %g0, %g0, %g0 218 219 /* LOCATION: Trap Window */ 220 221 /* Back in the trap window, update winbuffer save count. */ 222 mov 1, %twin_tmp 223 st %twin_tmp, [%curptr + TI_W_SAVED] 224 225 /* Compute new user window mask. What we are basically 226 * doing is taking two windows, the invalid one at trap 227 * time and the one we attempted to throw onto the users 228 * stack, and saying that everything else is an ok user 229 * window. umask = ((~(%t_wim | %wim)) & valid_wim_bits) 230 */ 231 rd %wim, %twin_tmp 232 or %twin_tmp, %t_wim, %twin_tmp 233 not %twin_tmp 234 spnwin_patch3: and %twin_tmp, 0xff, %twin_tmp ! patched on 7win Sparcs 235 st %twin_tmp, [%curptr + TI_UWINMASK] 236 237 #define STACK_OFFSET (THREAD_SIZE - TRACEREG_SZ - STACKFRAME_SZ) 238 239 sethi %hi(STACK_OFFSET), %sp 240 or %sp, %lo(STACK_OFFSET), %sp 241 add %curptr, %sp, %sp 242 243 /* Restore the saved globals and build a pt_regs frame. */ 244 mov %saved_g5, %g5 245 mov %saved_g6, %g6 246 STORE_PT_ALL(sp, t_psr, t_pc, t_npc, g1) 247 248 sethi %hi(STACK_OFFSET), %g6 249 or %g6, %lo(STACK_OFFSET), %g6 250 sub %sp, %g6, %g6 ! curptr 251 252 /* Turn on traps and call c-code to deal with it. */ 253 wr %t_psr, PSR_ET, %psr 254 nop 255 call window_overflow_fault 256 nop 257 258 /* Return from trap if C-code actually fixes things, if it 259 * doesn't then we never get this far as the process will 260 * be given the look of death from Commander Peanut. 261 */ 262 b ret_trap_entry 263 clr %l6 264 265 spwin_bad_ustack_from_kernel: 266 /* LOCATION: Window to be saved */ 267 268 /* The kernel provoked a spill window trap, but the window we 269 * need to save is a user one and the process has trashed its 270 * stack pointer. We need to be quick, so we throw it into 271 * a per-process window buffer until we can properly handle 272 * this later on. 273 */ 274 SAVE_BOLIXED_USER_STACK(curptr, glob_tmp) 275 restore %g0, %g0, %g0 276 277 /* LOCATION: Trap window */ 278 279 /* Restore globals, condition codes in the %psr and 280 * return from trap. Note, restoring %g6 when returning 281 * to kernel mode is not necessarily these days. ;-) 282 */ 283 mov %saved_g5, %g5 284 mov %saved_g6, %g6 285 286 wr %t_psr, 0x0, %psr 287 WRITE_PAUSE 288 289 jmp %t_pc 290 rett %t_npc 291 292 /* Undefine the register macros which would only cause trouble 293 * if used below. This helps find 'stupid' coding errors that 294 * produce 'odd' behavior. The routines below are allowed to 295 * make usage of glob_tmp and t_psr so we leave them defined. 296 */ 297 #undef twin_tmp 298 #undef curptr 299 #undef t_pc 300 #undef t_npc 301 #undef t_wim 302 #undef saved_g5 303 #undef saved_g6 304 305 /* Now come the per-architecture window overflow stack checking routines. 306 * As noted above %curptr cannot be touched by this routine at all. 307 */ 308 309 /* This is a generic SRMMU routine. As far as I know this 310 * works for all current v8/srmmu implementations, we'll 311 * see... 312 */ 313 .globl spwin_srmmu_stackchk 314 spwin_srmmu_stackchk: 315 /* LOCATION: Window to be saved on the stack */ 316 317 /* Because of SMP concerns and speed we play a trick. 318 * We disable fault traps in the MMU control register, 319 * Execute the stores, then check the fault registers 320 * to see what happens. I can hear Linus now 321 * "disgusting... broken hardware...". 322 * 323 * But first, check to see if the users stack has ended 324 * up in kernel vma, then we would succeed for the 'wrong' 325 * reason... ;( Note that the 'sethi' below assumes the 326 * kernel is page aligned, which should always be the case. 327 */ 328 /* Check results of callers andcc %sp, 0x7, %g0 */ 329 bne spwin_user_stack_is_bolixed 330 sethi %hi(PAGE_OFFSET), %glob_tmp 331 cmp %glob_tmp, %sp 332 bleu spwin_user_stack_is_bolixed 333 mov AC_M_SFSR, %glob_tmp 334 335 /* Clear the fault status and turn on the no_fault bit. */ 336 LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %g0) ! eat SFSR 337 SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %g0) ! eat SFSR 338 339 LEON_PI(lda [%g0] ASI_LEON_MMUREGS, %glob_tmp) ! read MMU control 340 SUN_PI_(lda [%g0] ASI_M_MMUREGS, %glob_tmp) ! read MMU control 341 or %glob_tmp, 0x2, %glob_tmp ! or in no_fault bit 342 LEON_PI(sta %glob_tmp, [%g0] ASI_LEON_MMUREGS) ! set it 343 SUN_PI_(sta %glob_tmp, [%g0] ASI_M_MMUREGS) ! set it 344 345 /* Dump the registers and cross fingers. */ 346 STORE_WINDOW(sp) 347 348 /* Clear the no_fault bit and check the status. */ 349 andn %glob_tmp, 0x2, %glob_tmp 350 LEON_PI(sta %glob_tmp, [%g0] ASI_LEON_MMUREGS) 351 SUN_PI_(sta %glob_tmp, [%g0] ASI_M_MMUREGS) 352 353 mov AC_M_SFAR, %glob_tmp 354 LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %g0) 355 SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %g0) 356 357 mov AC_M_SFSR, %glob_tmp 358 LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %glob_tmp) 359 SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %glob_tmp) 360 andcc %glob_tmp, 0x2, %g0 ! did we fault? 361 be,a spwin_finish_up + 0x4 ! cool beans, success 362 restore %g0, %g0, %g0 363 364 rd %psr, %glob_tmp 365 b spwin_user_stack_is_bolixed + 0x4 ! we faulted, ugh 366 nop