/* SPDX-License-Identifier: GPL-2.0-only */
#ifndef _ASM_X86_ENTRY_COMMON_H
#define _ASM_X86_ENTRY_COMMON_H

#include <linux/randomize_kstack.h>
#include <linux/user-return-notifier.h>

#include <asm/nospec-branch.h>
#include <asm/io_bitmap.h>
#include <asm/fpu/api.h>
#include <asm/fred.h>

/* Check that the stack and regs on entry from user mode are sane. */
static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs)
{
        if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) {
                /*
                 * Make sure that the entry code gave us a sensible EFLAGS
                 * register.  Native because we want to check the actual CPU
                 * state, not the interrupt state as imagined by Xen.
                 */
                unsigned long flags = native_save_fl();
                unsigned long mask = X86_EFLAGS_DF | X86_EFLAGS_NT;

                /*
                 * For !SMAP hardware we patch out CLAC on entry.
                 */
                if (cpu_feature_enabled(X86_FEATURE_SMAP) ||
                    cpu_feature_enabled(X86_FEATURE_XENPV))
                        mask |= X86_EFLAGS_AC;

                WARN_ON_ONCE(flags & mask);

                /* We think we came from user mode. Make sure pt_regs agrees. */
                WARN_ON_ONCE(!user_mode(regs));

                /*
                 * All entries from user mode (except #DF) should be on the
                 * normal thread stack and should have user pt_regs in the
                 * correct location.
                 */
                WARN_ON_ONCE(!on_thread_stack());
                WARN_ON_ONCE(regs != task_pt_regs(current));
        }
}
#define arch_enter_from_user_mode arch_enter_from_user_mode

static inline void arch_exit_work(unsigned long ti_work)
{
        if (ti_work & _TIF_USER_RETURN_NOTIFY)
                fire_user_return_notifiers();

        if (unlikely(ti_work & _TIF_IO_BITMAP))
                tss_update_io_bitmap();

        if (unlikely(ti_work & _TIF_NEED_FPU_LOAD))
                switch_fpu_return();
}

static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
                                                  unsigned long ti_work)
{
        fpregs_assert_state_consistent();

        if (unlikely(ti_work))
                arch_exit_work(ti_work);

        fred_update_rsp0();

#ifdef CONFIG_COMPAT
        /*
         * Compat syscalls set TS_COMPAT.  Make sure we clear it before
         * returning to user mode.  We need to clear it *after* signal
         * handling, because syscall restart has a fixup for compat
         * syscalls.  The fixup is exercised by the ptrace_syscall_32
         * selftest.
         *
         * We also need to clear TS_REGS_POKED_I386: the 32-bit tracer
         * special case only applies after poking regs and before the
         * very next return to user mode.
         */
        current_thread_info()->status &= ~(TS_COMPAT | TS_I386_REGS_POKED);
#endif

        /*
         * This value will get limited by KSTACK_OFFSET_MAX(), which is 10
         * bits. The actual entropy will be further reduced by the compiler
         * when applying stack alignment constraints (see cc_stack_align4/8 in
         * arch/x86/Makefile), which will remove the 3 (x86_64) or 2 (ia32)
         * low bits from any entropy chosen here.
         *
         * Therefore, final stack offset entropy will be 7 (x86_64) or
         * 8 (ia32) bits.
         */
        choose_random_kstack_offset(rdtsc());

        /* Avoid unnecessary reads of 'x86_ibpb_exit_to_user' */
        if (cpu_feature_enabled(X86_FEATURE_IBPB_EXIT_TO_USER) &&
            this_cpu_read(x86_ibpb_exit_to_user)) {
                indirect_branch_prediction_barrier();
                this_cpu_write(x86_ibpb_exit_to_user, false);
        }
}
#define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare

static __always_inline void arch_exit_to_user_mode(void)
{
        amd_clear_divider();
}
#define arch_exit_to_user_mode arch_exit_to_user_mode

#endif