1 /* SPDX-License-Identifier: GPL-2.0-or-later */
4 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
5 * Rewritten by Cort Dougan (cort@cs.nmt.edu) for PReP
6 * Copyright (C) 1996 Cort Dougan <cort@cs.nmt.edu>
7 * Adapted for Power Macintosh by Paul Mackerras.
8 * Low-level exception handlers and MMU support
9 * rewritten by Paul Mackerras.
10 * Copyright (C) 1996 Paul Mackerras.
11 * MPC8xx modifications Copyright (C) 1997 Dan Malek (dmalek@jlc.net).
13 * This file contains the system call entry code, context switch
14 * code, and exception/interrupt return code for PowerPC.
17 #include <linux/errno.h>
18 #include <linux/err.h>
19 #include <asm/cache.h>
20 #include <asm/unistd.h>
21 #include <asm/processor.h>
24 #include <asm/thread_info.h>
25 #include <asm/code-patching-asm.h>
26 #include <asm/ppc_asm.h>
27 #include <asm/asm-offsets.h>
28 #include <asm/cputable.h>
29 #include <asm/firmware.h>
31 #include <asm/ptrace.h>
32 #include <asm/irqflags.h>
33 #include <asm/hw_irq.h>
34 #include <asm/context_tracking.h>
35 #include <asm/ppc-opcode.h>
36 #include <asm/barrier.h>
37 #include <asm/export.h>
38 #include <asm/asm-compat.h>
39 #ifdef CONFIG_PPC_BOOK3S
40 #include <asm/exception-64s.h>
42 #include <asm/exception-64e.h>
44 #include <asm/feature-fixups.h>
52 #ifdef CONFIG_PPC_BOOK3S_64
54 #define FLUSH_COUNT_CACHE \
56 patch_site 1b, patch__call_flush_branch_caches1; \
58 patch_site 1b, patch__call_flush_branch_caches2; \
60 patch_site 1b, patch__call_flush_branch_caches3
69 .global flush_branch_caches
74 // Flush the link stack
85 // If we're just flushing the link stack, return here
87 patch_site 3b patch__flush_link_stack_return
95 patch_site 2b patch__flush_count_cache_return
107 #define FLUSH_COUNT_CACHE
108 #endif /* CONFIG_PPC_BOOK3S_64 */
111 * This routine switches between two different tasks. The process
112 * state of one is saved on its kernel stack. Then the state
113 * of the other is restored from its kernel stack. The memory
114 * management hardware is updated to the second process's state.
115 * Finally, we can return to the second process, via interrupt_return.
116 * On entry, r3 points to the THREAD for the current task, r4
117 * points to the THREAD for the new task.
119 * Note: there are two ways to get to the "going out" portion
120 * of this code; either by coming in via the entry (_switch)
121 * or via "fork" which must set up an environment equivalent
122 * to the "_switch" path. If you change this you'll have to change
123 * the fork code also.
125 * The code which creates the new task context is in 'copy_thread'
126 * in arch/powerpc/kernel/process.c
132 stdu r1,-SWITCH_FRAME_SIZE(r1)
133 /* r3-r13 are caller saved -- Cort */
135 std r0,_NIP(r1) /* Return to switch caller */
138 std r1,KSP(r3) /* Set old stack pointer */
140 kuap_check_amr r9, r10
142 FLUSH_COUNT_CACHE /* Clobbers r9, ctr */
145 * On SMP kernels, care must be taken because a task may be
146 * scheduled off CPUx and on to CPUy. Memory ordering must be
149 * Cacheable stores on CPUx will be visible when the task is
150 * scheduled on CPUy by virtue of the core scheduler barriers
151 * (see "Notes on Program-Order guarantees on SMP systems." in
152 * kernel/sched/core.c).
154 * Uncacheable stores in the case of involuntary preemption must
155 * be taken care of. The smp_mb__after_spinlock() in __schedule()
156 * is implemented as hwsync on powerpc, which orders MMIO too. So
157 * long as there is an hwsync in the context switch path, it will
158 * be executed on the source CPU after the task has performed
159 * all MMIO ops on that CPU, and on the destination CPU before the
160 * task performs any MMIO ops there.
164 * The kernel context switch path must contain a spin_lock,
165 * which contains larx/stcx, which will clear any reservation
166 * of the task being switched.
168 #ifdef CONFIG_PPC_BOOK3S
169 /* Cancel all explict user streams as they will have no use after context
170 * switch and will stop the HW from creating streams itself
172 DCBT_BOOK3S_STOP_ALL_STREAM_IDS(r6)
175 addi r6,r4,-THREAD /* Convert THREAD to 'current' */
176 std r6,PACACURRENT(r13) /* Set new 'current' */
177 #if defined(CONFIG_STACKPROTECTOR)
178 ld r6, TASK_CANARY(r6)
179 std r6, PACA_CANARY(r13)
182 ld r8,KSP(r4) /* new stack pointer */
183 #ifdef CONFIG_PPC_BOOK3S_64
184 BEGIN_MMU_FTR_SECTION
186 END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_RADIX)
188 clrrdi r6,r8,28 /* get its ESID */
189 clrrdi r9,r1,28 /* get current sp ESID */
191 clrrdi r6,r8,40 /* get its 1T ESID */
192 clrrdi r9,r1,40 /* get current sp 1T ESID */
193 ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_1T_SEGMENT)
194 clrldi. r0,r6,2 /* is new ESID c00000000? */
195 cmpd cr1,r6,r9 /* or is new ESID the same as current ESID? */
197 beq 2f /* if yes, don't slbie it */
199 /* Bolt in the new stack SLB entry */
200 ld r7,KSP_VSID(r4) /* Get new stack's VSID */
201 oris r0,r6,(SLB_ESID_V)@h
202 ori r0,r0,(SLB_NUM_BOLTED-1)@l
204 li r9,MMU_SEGSIZE_1T /* insert B field */
205 oris r6,r6,(MMU_SEGSIZE_1T << SLBIE_SSIZE_SHIFT)@h
206 rldimi r7,r9,SLB_VSID_SSIZE_SHIFT,0
207 END_MMU_FTR_SECTION_IFSET(MMU_FTR_1T_SEGMENT)
209 /* Update the last bolted SLB. No write barriers are needed
210 * here, provided we only update the current CPU's SLB shadow
213 ld r9,PACA_SLBSHADOWPTR(r13)
215 std r12,SLBSHADOW_STACKESID(r9) /* Clear ESID */
216 li r12,SLBSHADOW_STACKVSID
217 STDX_BE r7,r12,r9 /* Save VSID */
218 li r12,SLBSHADOW_STACKESID
219 STDX_BE r0,r12,r9 /* Save ESID */
221 /* No need to check for MMU_FTR_NO_SLBIE_B here, since when
222 * we have 1TB segments, the only CPUs known to have the errata
223 * only support less than 1TB of system memory and we'll never
224 * actually hit this code path.
230 slbie r6 /* Workaround POWER5 < DD2.1 issue */
231 END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S)
235 #endif /* CONFIG_PPC_BOOK3S_64 */
237 clrrdi r7, r8, THREAD_SHIFT /* base of new stack */
238 /* Note: this uses SWITCH_FRAME_SIZE rather than INT_FRAME_SIZE
239 because we don't need to leave the 288-byte ABI gap at the
240 top of the kernel stack. */
241 addi r7,r7,THREAD_SIZE-SWITCH_FRAME_SIZE
244 * PMU interrupts in radix may come in here. They will use r1, not
245 * PACAKSAVE, so this stack switch will not cause a problem. They
246 * will store to the process stack, which may then be migrated to
247 * another CPU. However the rq lock release on this CPU paired with
248 * the rq lock acquire on the new CPU before the stack becomes
249 * active on the new CPU, will order those stores.
251 mr r1,r8 /* start using new stack pointer */
252 std r7,PACAKSAVE(r13)
257 /* r3-r13 are destroyed -- Cort */
260 /* convert old thread to its task_struct for return value */
262 ld r7,_NIP(r1) /* Return to _switch caller in new task */
264 addi r1,r1,SWITCH_FRAME_SIZE
267 #ifdef CONFIG_PPC_RTAS
269 * On CHRP, the Run-Time Abstraction Services (RTAS) have to be
270 * called with the MMU off.
272 * In addition, we need to be in 32b mode, at least for now.
274 * Note: r3 is an input parameter to rtas, so don't trash it...
279 stdu r1,-SWITCH_FRAME_SIZE(r1) /* Save SP and create stack space. */
281 /* Because RTAS is running in 32b mode, it clobbers the high order half
282 * of all registers that it saves. We therefore save those registers
283 * RTAS might touch to the stack. (r0, r3-r13 are caller saved)
285 SAVE_GPR(2, r1) /* Save the TOC */
286 SAVE_GPR(13, r1) /* Save paca */
287 SAVE_NVGPRS(r1) /* Save the non-volatiles */
300 /* Temporary workaround to clear CR until RTAS can be modified to
307 /* There is no way it is acceptable to get here with interrupts enabled,
308 * check it with the asm equivalent of WARN_ON
310 lbz r0,PACAIRQSOFTMASK(r13)
311 1: tdeqi r0,IRQS_ENABLED
312 EMIT_WARN_ENTRY 1b,__FILE__,__LINE__,BUGFLAG_WARNING
315 /* Hard-disable interrupts */
321 /* Unfortunately, the stack pointer and the MSR are also clobbered,
322 * so they are saved in the PACA which allows us to restore
323 * our original state after RTAS returns.
326 std r6,PACASAVEDMSR(r13)
328 /* Setup our real return addr */
329 LOAD_REG_ADDR(r4,rtas_return_loc)
330 clrldi r4,r4,2 /* convert to realmode address */
334 LOAD_REG_ADDR(r4, rtas)
335 ld r5,RTASENTRY(r4) /* get the rtas->entry value */
336 ld r4,RTASBASE(r4) /* get the rtas->base value */
339 * RTAS runs in 32-bit big endian real mode, but leave MSR[RI] on as we
340 * may hit NMI (SRESET or MCE) while in RTAS. RTAS should disable RI in
341 * its critical regions (as specified in PAPR+ section 7.2.1). MSR[S]
342 * is not impacted by RFI_TO_KERNEL (only urfid can unset it). So if
343 * MSR[S] is set, it will remain when entering RTAS.
345 LOAD_REG_IMMEDIATE(r6, MSR_ME | MSR_RI)
348 mtmsrd r0,1 /* disable RI before using SRR0/1 */
353 b . /* prevent speculative execution */
359 * Clear RI and set SF before anything.
364 sldi r0,r0,(MSR_SF_LG - MSR_RI_LG)
369 /* relocation is off at this point */
371 clrldi r4,r4,2 /* convert to realmode address */
375 ld r3,(1f-0b)(r3) /* get &rtas_restore_regs */
377 ld r1,PACAR1(r4) /* Restore our SP */
378 ld r4,PACASAVEDMSR(r4) /* Restore our MSR */
383 b . /* prevent speculative execution */
384 _ASM_NOKPROBE_SYMBOL(__enter_rtas)
385 _ASM_NOKPROBE_SYMBOL(rtas_return_loc)
388 1: .8byte rtas_restore_regs
391 /* relocation is on at this point */
392 REST_GPR(2, r1) /* Restore the TOC */
393 REST_GPR(13, r1) /* Restore paca */
394 REST_NVGPRS(r1) /* Restore the non-volatiles */
409 addi r1,r1,SWITCH_FRAME_SIZE /* Unstack our frame */
410 ld r0,16(r1) /* get return address */
413 blr /* return to caller */
415 #endif /* CONFIG_PPC_RTAS */
420 stdu r1,-SWITCH_FRAME_SIZE(r1) /* Save SP and create stack space */
422 /* Because PROM is running in 32b mode, it clobbers the high order half
423 * of all registers that it saves. We therefore save those registers
424 * PROM might touch to the stack. (r0, r3-r13 are caller saved)
434 /* Put PROM address in SRR0 */
437 /* Setup our trampoline return addr in LR */
443 /* Prepare a 32-bit mode big endian MSR
445 #ifdef CONFIG_PPC_BOOK3E
446 rlwinm r11,r11,0,1,31
449 #else /* CONFIG_PPC_BOOK3E */
450 LOAD_REG_IMMEDIATE(r12, MSR_SF | MSR_LE)
454 #endif /* CONFIG_PPC_BOOK3E */
456 1: /* Return from OF */
459 /* Just make sure that r1 top 32 bits didn't get
464 /* Restore the MSR (back to 64 bits) */
469 /* Restore other registers */
476 addi r1,r1,SWITCH_FRAME_SIZE