path: root/arch/powerpc/kernel/interrupt.c

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

#include <linux/context_tracking.h>
#include <linux/err.h>
#include <linux/compat.h>
#include <linux/sched/debug.h> /* for show_regs */

#include <asm/asm-prototypes.h>
#include <asm/kup.h>
#include <asm/cputime.h>
#include <asm/hw_irq.h>
#include <asm/interrupt.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/tm.h>
#include <asm/unistd.h>

#if defined(CONFIG_PPC_ADV_DEBUG_REGS) && defined(CONFIG_PPC32)
unsigned long global_dbcr0[NR_CPUS];
#endif

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

#ifdef CONFIG_PPC_BOOK3S_64
DEFINE_STATIC_KEY_FALSE(interrupt_exit_not_reentrant);
static inline bool exit_must_hard_disable(void)
{
	return static_branch_unlikely(&interrupt_exit_not_reentrant);
}
#else
static inline bool exit_must_hard_disable(void)
{
	return true;
}
#endif

/*
 * local irqs must be disabled. Returns false if the caller must re-enable
 * them, check for new work, and try again.
 *
 * This should be called with local irqs disabled, but if they were previously
 * enabled when the interrupt handler returns (indicating a process-context /
 * synchronous interrupt) then irqs_enabled should be true.
 *
 * restartable is true then EE/RI can be left on because interrupts are handled
 * with a restart sequence.
 */
static notrace __always_inline bool prep_irq_for_enabled_exit(bool restartable)
{
	/* This must be done with RI=1 because tracing may touch vmaps */
	trace_hardirqs_on();

	if (exit_must_hard_disable() || !restartable)
		__hard_EE_RI_disable();

#ifdef CONFIG_PPC64
	/* This pattern matches prep_irq_for_idle */
	if (unlikely(lazy_irq_pending_nocheck())) {
		if (exit_must_hard_disable() || !restartable) {
			local_paca->irq_happened |= PACA_IRQ_HARD_DIS;
			__hard_RI_enable();
		}
		trace_hardirqs_off();

		return false;
	}
#endif
	return true;
}

/* 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;

	kuep_lock();

	regs->orig_gpr3 = r3;

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

	trace_hardirqs_off(); /* finish reconciling */

	CT_WARN_ON(ct_state() == CONTEXT_KERNEL);
	user_exit_irqoff();

	BUG_ON(regs_is_unrecoverable(regs));
	BUG_ON(!(regs->msr & MSR_PR));
	BUG_ON(arch_irq_disabled_regs(regs));

#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_assert_locked();

	booke_restore_dbcr0();

	account_cpu_user_entry();

	account_stolen_time();

	/*
	 * 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!
	 */
	irq_soft_mask_regs_set_state(regs, IRQS_ENABLED);

	/*
	 * If system call is called with TM active, set _TIF_RESTOREALL to
	 * prevent RFSCV being used to return to userspace, because POWER9
	 * TM implementation has problems with this instruction returning to
	 * transactional state. Final register values are not relevant because
	 * the transaction will be aborted upon return anyway. Or in the case
	 * of unsupported_scv SIGILL fault, the return state does not much
	 * matter because it's an edge case.
	 */
	if (IS_ENABLED(CONFIG_PPC_TRANSACTIONAL_MEM) &&
			unlikely(MSR_TM_TRANSACTIONAL(regs->msr)))
		current_thread_info()->flags |= _TIF_RESTOREALL;

	/*
	 * If the system call was made with a transaction active, doom it and
	 * return without performing the system call. Unless it was an
	 * unsupported scv vector, in which case it's treated like an illegal
	 * instruction.
	 */
#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
	if (unlikely(MSR_TM_TRANSACTIONAL(regs->msr)) &&
	    !trap_is_unsupported_scv(regs)) {
		/* Enable TM in the kernel, and disable EE (for scv) */
		hard_irq_disable();
		mtmsr(mfmsr() | MSR_TM);

		/* tabort, this dooms the transaction, nothing else */
		asm volatile(".long 0x7c00071d | ((%0) << 16)"
				:: "r"(TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT));

		/*
		 * Userspace will never see the return value. Execution will
		 * resume after the tbegin. of the aborted transaction with the
		 * checkpointed register state. A context switch could occur
		 * or signal delivered to the process before resuming the
		 * doomed transaction context, but that should all be handled
		 * as expected.
		 */
		return -ENOSYS;
	}
#endif // CONFIG_PPC_TRANSACTIONAL_MEM

	local_irq_enable();

	if (unlikely(current_thread_info()->flags & _TIF_SYSCALL_DOTRACE)) {
		if (unlikely(trap_is_unsupported_scv(regs))) {
			/* 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(trap_is_unsupported_scv(regs))) {
			/* 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_compat_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);
}

static notrace void booke_load_dbcr0(void)
{
#ifdef CONFIG_PPC_ADV_DEBUG_REGS
	unsigned long dbcr0 = current->thread.debug.dbcr0;

	if (likely(!(dbcr0 & DBCR0_IDM)))
		return;

	/*
	 * 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);
	if (IS_ENABLED(CONFIG_PPC32)) {
		isync();
		global_dbcr0[smp_processor_id()] = mfspr(SPRN_DBCR0);
	}
	mtspr(SPRN_DBCR0, dbcr0);
	mtspr(SPRN_DBSR, -1);
#endif
}

static void check_return_regs_