diff options
Diffstat (limited to 'arch/powerpc/kernel/switch.S')
| -rw-r--r-- | arch/powerpc/kernel/switch.S | 258 |
1 files changed, 258 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/switch.S b/arch/powerpc/kernel/switch.S new file mode 100644 index 000000000000..608c0ce7cec6 --- /dev/null +++ b/arch/powerpc/kernel/switch.S @@ -0,0 +1,258 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +#include <linux/objtool.h> +#include <asm/asm-offsets.h> +#include <asm/code-patching-asm.h> +#include <asm/mmu.h> +#include <asm/ppc_asm.h> +#include <asm/kup.h> +#include <asm/thread_info.h> + +.section ".text","ax",@progbits + +#ifdef CONFIG_PPC_BOOK3S_64 +/* + * Cancel all explict user streams as they will have no use after context + * switch and will stop the HW from creating streams itself + */ +#define STOP_STREAMS \ + DCBT_BOOK3S_STOP_ALL_STREAM_IDS(r6) + +#define FLUSH_COUNT_CACHE \ +1: nop; \ + patch_site 1b, patch__call_flush_branch_caches1; \ +1: nop; \ + patch_site 1b, patch__call_flush_branch_caches2; \ +1: nop; \ + patch_site 1b, patch__call_flush_branch_caches3 + +.macro nops number + .rept \number + nop + .endr +.endm + +.balign 32 +.global flush_branch_caches +flush_branch_caches: + /* Save LR into r9 */ + mflr r9 + + // Flush the link stack + .rept 64 + ANNOTATE_INTRA_FUNCTION_CALL + bl .+4 + .endr + b 1f + nops 6 + + .balign 32 + /* Restore LR */ +1: mtlr r9 + + // If we're just flushing the link stack, return here +3: nop + patch_site 3b patch__flush_link_stack_return + + li r9,0x7fff + mtctr r9 + + PPC_BCCTR_FLUSH + +2: nop + patch_site 2b patch__flush_count_cache_return + + nops 3 + + .rept 278 + .balign 32 + PPC_BCCTR_FLUSH + nops 7 + .endr + + blr + +#ifdef CONFIG_PPC_64S_HASH_MMU +.balign 32 +/* + * New stack pointer in r8, old stack pointer in r1, must not clobber r3 + */ +pin_stack_slb: +BEGIN_FTR_SECTION + clrrdi r6,r8,28 /* get its ESID */ + clrrdi r9,r1,28 /* get current sp ESID */ +FTR_SECTION_ELSE + clrrdi r6,r8,40 /* get its 1T ESID */ + clrrdi r9,r1,40 /* get current sp 1T ESID */ +ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_1T_SEGMENT) + clrldi. r0,r6,2 /* is new ESID c00000000? */ + cmpd cr1,r6,r9 /* or is new ESID the same as current ESID? */ + cror eq,4*cr1+eq,eq + beq 2f /* if yes, don't slbie it */ + + /* Bolt in the new stack SLB entry */ + ld r7,KSP_VSID(r4) /* Get new stack's VSID */ + oris r0,r6,(SLB_ESID_V)@h + ori r0,r0,(SLB_NUM_BOLTED-1)@l +BEGIN_FTR_SECTION + li r9,MMU_SEGSIZE_1T /* insert B field */ + oris r6,r6,(MMU_SEGSIZE_1T << SLBIE_SSIZE_SHIFT)@h + rldimi r7,r9,SLB_VSID_SSIZE_SHIFT,0 +END_MMU_FTR_SECTION_IFSET(MMU_FTR_1T_SEGMENT) + + /* Update the last bolted SLB. No write barriers are needed + * here, provided we only update the current CPU's SLB shadow + * buffer. + */ + ld r9,PACA_SLBSHADOWPTR(r13) + li r12,0 + std r12,SLBSHADOW_STACKESID(r9) /* Clear ESID */ + li r12,SLBSHADOW_STACKVSID + STDX_BE r7,r12,r9 /* Save VSID */ + li r12,SLBSHADOW_STACKESID + STDX_BE r0,r12,r9 /* Save ESID */ + + /* No need to check for MMU_FTR_NO_SLBIE_B here, since when + * we have 1TB segments, the only CPUs known to have the errata + * only support less than 1TB of system memory and we'll never + * actually hit this code path. + */ + + isync + slbie r6 +BEGIN_FTR_SECTION + slbie r6 /* Workaround POWER5 < DD2.1 issue */ +END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S) + slbmte r7,r0 + isync +2: blr + .size pin_stack_slb,.-pin_stack_slb +#endif /* CONFIG_PPC_64S_HASH_MMU */ + +#else +#define STOP_STREAMS +#define FLUSH_COUNT_CACHE +#endif /* CONFIG_PPC_BOOK3S_64 */ + +/* + * do_switch_32/64 have the same calling convention as _switch, i.e., r3,r4 + * are prev and next thread_struct *, and returns prev task_struct * in r3. + + * This switches the stack, current, and does other task switch housekeeping. + */ +.macro do_switch_32 + tophys(r0,r4) + mtspr SPRN_SPRG_THREAD,r0 /* Update current THREAD phys addr */ + lwz r1,KSP(r4) /* Load new stack pointer */ + + /* save the old current 'last' for return value */ + mr r3,r2 + addi r2,r4,-THREAD /* Update current */ +.endm + +.macro do_switch_64 + ld r8,KSP(r4) /* Load new stack pointer */ + + kuap_check_amr r9, r10 + + FLUSH_COUNT_CACHE /* Clobbers r9, ctr */ + + STOP_STREAMS /* Clobbers r6 */ + + addi r3,r3,-THREAD /* old thread -> task_struct for return value */ + addi r6,r4,-THREAD /* new thread -> task_struct */ + std r6,PACACURRENT(r13) /* Set new task_struct to 'current' */ +#if defined(CONFIG_STACKPROTECTOR) + ld r6, TASK_CANARY(r6) + std r6, PACA_CANARY(r13) +#endif + /* Set new PACAKSAVE */ + clrrdi r7,r8,THREAD_SHIFT /* base of new stack */ + addi r7,r7,THREAD_SIZE-SWITCH_FRAME_SIZE + std r7,PACAKSAVE(r13) + +#ifdef CONFIG_PPC_64S_HASH_MMU +BEGIN_MMU_FTR_SECTION + bl pin_stack_slb +END_MMU_FTR_SECTION_IFCLR(MMU_FTR_TYPE_RADIX) +#endif + /* + * PMU interrupts in radix may come in here. They will use r1, not + * PACAKSAVE, so this stack switch will not cause a problem. They + * will store to the process stack, which may then be migrated to + * another CPU. However the rq lock release on this CPU paired with + * the rq lock acquire on the new CPU before the stack becomes + * active on the new CPU, will order those stores. + */ + mr r1,r8 /* start using new stack pointer */ +.endm + +/* + * This routine switches between two different tasks. The process + * state of one is saved on its kernel stack. Then the state + * of the other is restored from its kernel stack. The memory + * management hardware is updated to the second process's state. + * Finally, we can return to the second process. + * On entry, r3 points to the THREAD for the current task, r4 + * points to the THREAD for the new task. + * + * This routine is always called with interrupts disabled. + * + * Note: there are two ways to get to the "going out" portion + * of this code; either by coming in via the entry (_switch) + * or via "fork" which must set up an environment equivalent + * to the "_switch" path. If you change this , you'll have to + * change the fork code also. + * + * The code which creates the new task context is in 'copy_thread' + * in arch/ppc/kernel/process.c + * + * Note: this uses SWITCH_FRAME_SIZE rather than USER_INT_FRAME_SIZE + * because we don't need to leave the redzone ABI gap at the top of + * the kernel stack. + */ +_GLOBAL(_switch) + PPC_CREATE_STACK_FRAME(SWITCH_FRAME_SIZE) + PPC_STL r1,KSP(r3) /* Set old stack pointer */ + SAVE_NVGPRS(r1) /* volatiles are caller-saved -- Cort */ + PPC_STL r0,_NIP(r1) /* Return to switch caller */ + mfcr r0 + stw r0,_CCR(r1) + + /* + * On SMP kernels, care must be taken because a task may be + * scheduled off CPUx and on to CPUy. Memory ordering must be + * considered. + * + * Cacheable stores on CPUx will be visible when the task is + * scheduled on CPUy by virtue of the core scheduler barriers + * (see "Notes on Program-Order guarantees on SMP systems." in + * kernel/sched/core.c). + * + * Uncacheable stores in the case of involuntary preemption must + * be taken care of. The smp_mb__after_spinlock() in __schedule() + * is implemented as hwsync on powerpc, which orders MMIO too. So + * long as there is an hwsync in the context switch path, it will + * be executed on the source CPU after the task has performed + * all MMIO ops on that CPU, and on the destination CPU before the + * task performs any MMIO ops there. + */ + + /* + * The kernel context switch path must contain a spin_lock, + * which contains larx/stcx, which will clear any reservation + * of the task being switched. + */ + +#ifdef CONFIG_PPC32 + do_switch_32 +#else + do_switch_64 +#endif + + lwz r0,_CCR(r1) + mtcrf 0xFF,r0 + REST_NVGPRS(r1) /* volatiles are destroyed -- Cort */ + PPC_LL r0,_NIP(r1) /* Return to _switch caller in new task */ + mtlr r0 + addi r1,r1,SWITCH_FRAME_SIZE + blr |