Merge tag 'sched-urgent-2020-12-27' of git://git.kernel.org/pub/scm/linux/kernel...

[linux/fpc-iii.git] / arch / powerpc / kernel / syscall_64.c

// SPDX-License-Identifier: GPL-2.0-or-later

#include <linux/err.h>
#include <asm/asm-prototypes.h>
#include <asm/kup.h>
#include <asm/cputime.h>
#include <asm/hw_irq.h>
#include <asm/kprobes.h>
#include <asm/paca.h>
#include <asm/ptrace.h>
#include <asm/reg.h>
#include <asm/signal.h>
#include <asm/switch_to.h>
#include <asm/syscall.h>
#include <asm/time.h>
#include <asm/unistd.h>

typedef long (*syscall_fn)(long, long, long, long, long, long);

/* Has to run notrace because it is entered not completely "reconciled" */
notrace long system_call_exception(long r3, long r4, long r5,
                                   long r6, long r7, long r8,
                                   unsigned long r0, struct pt_regs *regs)
{
        syscall_fn f;

        if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
                BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED);

        trace_hardirqs_off(); /* finish reconciling */

        if (IS_ENABLED(CONFIG_PPC_BOOK3S))
                BUG_ON(!(regs->msr & MSR_RI));
        BUG_ON(!(regs->msr & MSR_PR));
        BUG_ON(!FULL_REGS(regs));
        BUG_ON(regs->softe != IRQS_ENABLED);

#ifdef CONFIG_PPC_PKEY
        if (mmu_has_feature(MMU_FTR_PKEY)) {
                unsigned long amr, iamr;
                bool flush_needed = false;
                /*
                 * When entering from userspace we mostly have the AMR/IAMR
                 * different from kernel default values. Hence don't compare.
                 */
                amr = mfspr(SPRN_AMR);
                iamr = mfspr(SPRN_IAMR);
                regs->amr  = amr;
                regs->iamr = iamr;
                if (mmu_has_feature(MMU_FTR_BOOK3S_KUAP)) {
                        mtspr(SPRN_AMR, AMR_KUAP_BLOCKED);
                        flush_needed = true;
                }
                if (mmu_has_feature(MMU_FTR_BOOK3S_KUEP)) {
                        mtspr(SPRN_IAMR, AMR_KUEP_BLOCKED);
                        flush_needed = true;
                }
                if (flush_needed)
                        isync();
        } else
#endif
                kuap_check_amr();

        account_cpu_user_entry();

#ifdef CONFIG_PPC_SPLPAR
        if (IS_ENABLED(CONFIG_VIRT_CPU_ACCOUNTING_NATIVE) &&
            firmware_has_feature(FW_FEATURE_SPLPAR)) {
                struct lppaca *lp = local_paca->lppaca_ptr;

                if (unlikely(local_paca->dtl_ridx != be64_to_cpu(lp->dtl_idx)))
                        accumulate_stolen_time();
        }
#endif

        /*
         * This is not required for the syscall exit path, but makes the
         * stack frame look nicer. If this was initialised in the first stack
         * frame, or if the unwinder was taught the first stack frame always
         * returns to user with IRQS_ENABLED, this store could be avoided!
         */
        regs->softe = IRQS_ENABLED;

        local_irq_enable();

        if (unlikely(current_thread_info()->flags & _TIF_SYSCALL_DOTRACE)) {
                if (unlikely(regs->trap == 0x7ff0)) {
                        /* Unsupported scv vector */
                        _exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
                        return regs->gpr[3];
                }
                /*
                 * We use the return value of do_syscall_trace_enter() as the
                 * syscall number. If the syscall was rejected for any reason
                 * do_syscall_trace_enter() returns an invalid syscall number
                 * and the test against NR_syscalls will fail and the return
                 * value to be used is in regs->gpr[3].
                 */
                r0 = do_syscall_trace_enter(regs);
                if (unlikely(r0 >= NR_syscalls))
                        return regs->gpr[3];
                r3 = regs->gpr[3];
                r4 = regs->gpr[4];
                r5 = regs->gpr[5];
                r6 = regs->gpr[6];
                r7 = regs->gpr[7];
                r8 = regs->gpr[8];

        } else if (unlikely(r0 >= NR_syscalls)) {
                if (unlikely(regs->trap == 0x7ff0)) {
                        /* Unsupported scv vector */
                        _exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
                        return regs->gpr[3];
                }
                return -ENOSYS;
        }

        /* May be faster to do array_index_nospec? */
        barrier_nospec();

        if (unlikely(is_32bit_task())) {
                f = (void *)compat_sys_call_table[r0];

                r3 &= 0x00000000ffffffffULL;
                r4 &= 0x00000000ffffffffULL;
                r5 &= 0x00000000ffffffffULL;
                r6 &= 0x00000000ffffffffULL;
                r7 &= 0x00000000ffffffffULL;
                r8 &= 0x00000000ffffffffULL;

        } else {
                f = (void *)sys_call_table[r0];
        }

        return f(r3, r4, r5, r6, r7, r8);
}

/*
 * local irqs must be disabled. Returns false if the caller must re-enable
 * them, check for new work, and try again.
 */
static notrace inline bool prep_irq_for_enabled_exit(bool clear_ri)
{
        /* This must be done with RI=1 because tracing may touch vmaps */
        trace_hardirqs_on();

        /* This pattern matches prep_irq_for_idle */
        if (clear_ri)
                __hard_EE_RI_disable();
        else
                __hard_irq_disable();
        if (unlikely(lazy_irq_pending_nocheck())) {
                /* Took an interrupt, may have more exit work to do. */
                if (clear_ri)
                        __hard_RI_enable();
                trace_hardirqs_off();
                local_paca->irq_happened |= PACA_IRQ_HARD_DIS;

                return false;
        }
        local_paca->irq_happened = 0;
        irq_soft_mask_set(IRQS_ENABLED);

        return true;
}

/*
 * This should be called after a syscall returns, with r3 the return value
 * from the syscall. If this function returns non-zero, the system call
 * exit assembly should additionally load all GPR registers and CTR and XER
 * from the interrupt frame.
 *
 * The function graph tracer can not trace the return side of this function,
 * because RI=0 and soft mask state is "unreconciled", so it is marked notrace.
 */
notrace unsigned long syscall_exit_prepare(unsigned long r3,
                                           struct pt_regs *regs,
                                           long scv)
{
        unsigned long *ti_flagsp = &current_thread_info()->flags;
        unsigned long ti_flags;
        unsigned long ret = 0;

        kuap_check_amr();

        regs->result = r3;

        /* Check whether the syscall is issued inside a restartable sequence */
        rseq_syscall(regs);

        ti_flags = *ti_flagsp;

        if (unlikely(r3 >= (unsigned long)-MAX_ERRNO) && !scv) {
                if (likely(!(ti_flags & (_TIF_NOERROR | _TIF_RESTOREALL)))) {
                        r3 = -r3;
                        regs->ccr |= 0x10000000; /* Set SO bit in CR */
                }
        }

        if (unlikely(ti_flags & _TIF_PERSYSCALL_MASK)) {
                if (ti_flags & _TIF_RESTOREALL)
                        ret = _TIF_RESTOREALL;
                else
                        regs->gpr[3] = r3;
                clear_bits(_TIF_PERSYSCALL_MASK, ti_flagsp);
        } else {
                regs->gpr[3] = r3;
        }

        if (unlikely(ti_flags & _TIF_SYSCALL_DOTRACE)) {
                do_syscall_trace_leave(regs);
                ret |= _TIF_RESTOREALL;
        }

again:
        local_irq_disable();
        ti_flags = READ_ONCE(*ti_flagsp);
        while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
                local_irq_enable();
                if (ti_flags & _TIF_NEED_RESCHED) {
                        schedule();
                } else {
                        /*
                         * SIGPENDING must restore signal handler function
                         * argument GPRs, and some non-volatiles (e.g., r1).
                         * Restore all for now. This could be made lighter.
                         */
                        if (ti_flags & _TIF_SIGPENDING)
                                ret |= _TIF_RESTOREALL;
                        do_notify_resume(regs, ti_flags);
                }
                local_irq_disable();
                ti_flags = READ_ONCE(*ti_flagsp);
        }

        if (IS_ENABLED(CONFIG_PPC_BOOK3S) && IS_ENABLED(CONFIG_PPC_FPU)) {
                if (IS_ENABLED(CONFIG_PPC_TRANSACTIONAL_MEM) &&
                                unlikely((ti_flags & _TIF_RESTORE_TM))) {
                        restore_tm_state(regs);
                } else {
                        unsigned long mathflags = MSR_FP;

                        if (cpu_has_feature(CPU_FTR_VSX))
                                mathflags |= MSR_VEC | MSR_VSX;
                        else if (cpu_has_feature(CPU_FTR_ALTIVEC))
                                mathflags |= MSR_VEC;

                        /*
                         * If userspace MSR has all available FP bits set,
                         * then they are live and no need to restore. If not,
                         * it means the regs were given up and restore_math
                         * may decide to restore them (to avoid taking an FP
                         * fault).
                         */
                        if ((regs->msr & mathflags) != mathflags)
                                restore_math(regs);
                }
        }

        /* scv need not set RI=0 because SRRs are not used */
        if (unlikely(!prep_irq_for_enabled_exit(!scv))) {
                local_irq_enable();
                goto again;
        }

#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
        local_paca->tm_scratch = regs->msr;
#endif

        account_cpu_user_exit();

#ifdef CONFIG_PPC_BOOK3S /* BOOK3E not yet using this */
        /*
         * We do this at the end so that we do context switch with KERNEL AMR
         */
        kuap_user_restore(regs);
#endif
        return ret;
}

#ifdef CONFIG_PPC_BOOK3S /* BOOK3E not yet using this */
notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs, unsigned long msr)
{
#ifdef CONFIG_PPC_BOOK3E
        struct thread_struct *ts = &current->thread;
#endif
        unsigned long *ti_flagsp = &current_thread_info()->flags;
        unsigned long ti_flags;
        unsigned long flags;
        unsigned long ret = 0;

        if (IS_ENABLED(CONFIG_PPC_BOOK3S))
                BUG_ON(!(regs->msr & MSR_RI));
        BUG_ON(!(regs->msr & MSR_PR));
        BUG_ON(!FULL_REGS(regs));
        BUG_ON(regs->softe != IRQS_ENABLED);

        /*
         * We don't need to restore AMR on the way back to userspace for KUAP.
         * AMR can only have been unlocked if we interrupted the kernel.
         */
        kuap_check_amr();

        local_irq_save(flags);

again:
        ti_flags = READ_ONCE(*ti_flagsp);
        while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
                local_irq_enable(); /* returning to user: may enable */
                if (ti_flags & _TIF_NEED_RESCHED) {
                        schedule();
                } else {
                        if (ti_flags & _TIF_SIGPENDING)
                                ret |= _TIF_RESTOREALL;
                        do_notify_resume(regs, ti_flags);
                }
                local_irq_disable();
                ti_flags = READ_ONCE(*ti_flagsp);
        }

        if (IS_ENABLED(CONFIG_PPC_BOOK3S) && IS_ENABLED(CONFIG_PPC_FPU)) {
                if (IS_ENABLED(CONFIG_PPC_TRANSACTIONAL_MEM) &&
                                unlikely((ti_flags & _TIF_RESTORE_TM))) {
                        restore_tm_state(regs);
                } else {
                        unsigned long mathflags = MSR_FP;

                        if (cpu_has_feature(CPU_FTR_VSX))
                                mathflags |= MSR_VEC | MSR_VSX;
                        else if (cpu_has_feature(CPU_FTR_ALTIVEC))
                                mathflags |= MSR_VEC;

                        /* See above restore_math comment */
                        if ((regs->msr & mathflags) != mathflags)
                                restore_math(regs);
                }
        }

        if (unlikely(!prep_irq_for_enabled_exit(true))) {
                local_irq_enable();
                local_irq_disable();
                goto again;
        }

#ifdef CONFIG_PPC_BOOK3E
        if (unlikely(ts->debug.dbcr0 & DBCR0_IDM)) {
                /*
                 * Check to see if the dbcr0 register is set up to debug.
                 * Use the internal debug mode bit to do this.
                 */
                mtmsr(mfmsr() & ~MSR_DE);
                mtspr(SPRN_DBCR0, ts->debug.dbcr0);
                mtspr(SPRN_DBSR, -1);
        }
#endif

#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
        local_paca->tm_scratch = regs->msr;
#endif

        account_cpu_user_exit();

        /*
         * We do this at the end so that we do context switch with KERNEL AMR
         */
        kuap_user_restore(regs);
        return ret;
}

void unrecoverable_exception(struct pt_regs *regs);
void preempt_schedule_irq(void);

notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs, unsigned long msr)
{
        unsigned long *ti_flagsp = &current_thread_info()->flags;
        unsigned long flags;
        unsigned long ret = 0;
        unsigned long amr;

        if (IS_ENABLED(CONFIG_PPC_BOOK3S) && unlikely(!(regs->msr & MSR_RI)))
                unrecoverable_exception(regs);
        BUG_ON(regs->msr & MSR_PR);
        BUG_ON(!FULL_REGS(regs));

        amr = kuap_get_and_check_amr();

        if (unlikely(*ti_flagsp & _TIF_EMULATE_STACK_STORE)) {
                clear_bits(_TIF_EMULATE_STACK_STORE, ti_flagsp);
                ret = 1;
        }

        local_irq_save(flags);

        if (regs->softe == IRQS_ENABLED) {
                /* Returning to a kernel context with local irqs enabled. */
                WARN_ON_ONCE(!(regs->msr & MSR_EE));
again:
                if (IS_ENABLED(CONFIG_PREEMPT)) {
                        /* Return to preemptible kernel context */
                        if (unlikely(*ti_flagsp & _TIF_NEED_RESCHED)) {
                                if (preempt_count() == 0)
                                        preempt_schedule_irq();
                        }
                }

                if (unlikely(!prep_irq_for_enabled_exit(true))) {
                        /*
                         * Can't local_irq_restore to replay if we were in
                         * interrupt context. Must replay directly.
                         */
                        if (irqs_disabled_flags(flags)) {
                                replay_soft_interrupts();
                        } else {
                                local_irq_restore(flags);
                                local_irq_save(flags);
                        }
                        /* Took an interrupt, may have more exit work to do. */
                        goto again;
                }
        } else {
                /* Returning to a kernel context with local irqs disabled. */
                __hard_EE_RI_disable();
                if (regs->msr & MSR_EE)
                        local_paca->irq_happened &= ~PACA_IRQ_HARD_DIS;
        }


#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
        local_paca->tm_scratch = regs->msr;
#endif

        /*
         * Don't want to mfspr(SPRN_AMR) here, because this comes after mtmsr,
         * which would cause Read-After-Write stalls. Hence, we take the AMR
         * value from the check above.
         */
        kuap_kernel_restore(regs, amr);

        return ret;
}
#endif