// SPDX-License-Identifier: GPL-2.0
/*
 *  PA-RISC architecture-specific signal handling support.
 *
 *  Copyright (C) 2000 David Huggins-Daines <dhd@debian.org>
 *  Copyright (C) 2000 Linuxcare, Inc.
 *  Copyright (C) 2000-2022 Helge Deller <deller@gmx.de>
 *  Copyright (C) 2022 John David Anglin <dave.anglin@bell.net>
 *
 *  Based on the ia64, i386, and alpha versions.
 */

#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/resume_user_mode.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/compat.h>
#include <linux/elf.h>
#include <asm/ucontext.h>
#include <asm/rt_sigframe.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/asm-offsets.h>
#include <asm/vdso.h>

#ifdef CONFIG_COMPAT
#include "signal32.h"
#endif

#define DEBUG_SIG 0 
#define DEBUG_SIG_LEVEL 2

#if DEBUG_SIG
#define DBG(LEVEL, ...) \
        ((DEBUG_SIG_LEVEL >= LEVEL) \
        ? printk(__VA_ARGS__) : (void) 0)
#else
#define DBG(LEVEL, ...)
#endif
        
/* gcc will complain if a pointer is cast to an integer of different
 * size.  If you really need to do this (and we do for an ELF32 user
 * application in an ELF64 kernel) then you have to do a cast to an
 * integer of the same size first.  The A() macro accomplishes
 * this. */
#define A(__x)  ((unsigned long)(__x))

/*
 * Do a signal return - restore sigcontext.
 */

static long
restore_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
{
        long err = 0;

        err |= __copy_from_user(regs->gr, sc->sc_gr, sizeof(regs->gr));
        err |= __copy_from_user(regs->fr, sc->sc_fr, sizeof(regs->fr));
        err |= __copy_from_user(regs->iaoq, sc->sc_iaoq, sizeof(regs->iaoq));
        err |= __copy_from_user(regs->iasq, sc->sc_iasq, sizeof(regs->iasq));
        err |= __get_user(regs->sar, &sc->sc_sar);
        DBG(2, "%s: iaoq is %#lx / %#lx\n",
                        __func__, regs->iaoq[0], regs->iaoq[1]);
        DBG(2, "%s: r28 is %ld\n", __func__, regs->gr[28]);
        return err;
}

asmlinkage void
sys_rt_sigreturn(struct pt_regs *regs, int in_syscall)
{
        struct rt_sigframe __user *frame;
        sigset_t set;
        unsigned long usp = (regs->gr[30] & ~(0x01UL));
        unsigned long sigframe_size = PARISC_RT_SIGFRAME_SIZE;
#ifdef CONFIG_64BIT
        struct compat_rt_sigframe __user * compat_frame;
        
        if (is_compat_task())
                sigframe_size = PARISC_RT_SIGFRAME_SIZE32;
#endif

        current->restart_block.fn = do_no_restart_syscall;

        /* Unwind the user stack to get the rt_sigframe structure. */
        frame = (struct rt_sigframe __user *)
                (usp - sigframe_size);
        DBG(2, "%s: frame is %p pid %d\n", __func__, frame, task_pid_nr(current));

        regs->orig_r28 = 1; /* no restarts for sigreturn */

#ifdef CONFIG_64BIT
        compat_frame = (struct compat_rt_sigframe __user *)frame;
        
        if (is_compat_task()) {
                if (get_compat_sigset(&set, &compat_frame->uc.uc_sigmask))
                        goto give_sigsegv;
        } else
#endif
        {
                if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
                        goto give_sigsegv;
        }
                
        set_current_blocked(&set);

        /* Good thing we saved the old gr[30], eh? */
#ifdef CONFIG_64BIT
        if (is_compat_task()) {
                DBG(1, "%s: compat_frame->uc.uc_mcontext 0x%p\n",
                                __func__, &compat_frame->uc.uc_mcontext);
// FIXME: Load upper half from register file
                if (restore_sigcontext32(&compat_frame->uc.uc_mcontext, 
                                        &compat_frame->regs, regs))
                        goto give_sigsegv;
                DBG(1, "%s: usp %#08lx stack 0x%p\n",
                                __func__, usp, &compat_frame->uc.uc_stack);
                if (compat_restore_altstack(&compat_frame->uc.uc_stack))
                        goto give_sigsegv;
        } else
#endif
        {
                DBG(1, "%s: frame->uc.uc_mcontext 0x%p\n",
                                __func__, &frame->uc.uc_mcontext);
                if (restore_sigcontext(&frame->uc.uc_mcontext, regs))
                        goto give_sigsegv;
                DBG(1, "%s: usp %#08lx stack 0x%p\n",
                                __func__, usp, &frame->uc.uc_stack);
                if (restore_altstack(&frame->uc.uc_stack))
                        goto give_sigsegv;
        }
                


        /* If we are on the syscall path IAOQ will not be restored, and
         * if we are on the interrupt path we must not corrupt gr31.
         */
        if (in_syscall)
                regs->gr[31] = regs->iaoq[0];

        return;

give_sigsegv:
        DBG(1, "%s: Sending SIGSEGV\n", __func__);
        force_sig(SIGSEGV);
        return;
}

/*
 * Set up a signal frame.
 */

static inline void __user *
get_sigframe(struct k_sigaction *ka, unsigned long sp, size_t frame_size)
{
        /*FIXME: ELF32 vs. ELF64 has different frame_size, but since we
          don't use the parameter it doesn't matter */

        DBG(1, "%s: ka = %#lx, sp = %#lx, frame_size = %zu\n",
                        __func__, (unsigned long)ka, sp, frame_size);
        
        /* Align alternate stack and reserve 64 bytes for the signal
           handler's frame marker.  */
        if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && ! sas_ss_flags(sp))
                sp = (current->sas_ss_sp + 0x7f) & ~0x3f; /* Stacks grow up! */

        DBG(1, "%s: Returning sp = %#lx\n", __func__, (unsigned long)sp);
        return (void __user *) sp; /* Stacks grow up.  Fun. */
}

static long
setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, long in_syscall)
                 
{
        unsigned long flags = 0;
        long err = 0;

        if (on_sig_stack((unsigned long) sc))
                flags |= PARISC_SC_FLAG_ONSTACK;
        if (in_syscall) {
                flags |= PARISC_SC_FLAG_IN_SYSCALL;
                /* regs->iaoq is undefined in the syscall return path */
                err |= __put_user(regs->gr[31], &sc->sc_iaoq[0]);
                err |= __put_user(regs->gr[31]+4, &sc->sc_iaoq[1]);
                err |= __put_user(regs->sr[3], &sc->sc_iasq[0]);
                err |= __put_user(regs->sr[3], &sc->sc_iasq[1]);
                DBG(1, "%s: iaoq %#lx / %#lx (in syscall)\n",
                        __func__, regs->gr[31], regs->gr[31]+4);
        } else {
                err |= __copy_to_user(sc->sc_iaoq, regs->iaoq, sizeof(regs->iaoq));
                err |= __copy_to_user(sc->sc_iasq, regs->iasq, sizeof(regs->iasq));
                DBG(1, "%s: iaoq %#lx / %#lx (not in syscall)\n",
                        __func__, regs->iaoq[0], regs->iaoq[1]);
        }

        err |= __put_user(flags, &sc->sc_flags);
        err |= __copy_to_user(sc->sc_gr, regs->gr, sizeof(regs->gr));
        err |= __copy_to_user(sc->sc_fr, regs->fr, sizeof(regs->fr));
        err |= __put_user(regs->sar, &sc->sc_sar);
        DBG(1, "%s: r28 is %ld\n", __func__, regs->gr[28]);

        return err;
}

static long
setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs,
               long in_syscall)
{
        struct rt_sigframe __user *frame;
        unsigned long rp, usp;
        unsigned long haddr, sigframe_size;
        unsigned long start;
        int err = 0;
#ifdef CONFIG_64BIT
        struct compat_rt_sigframe __user * compat_frame;
#endif
        
        usp = (regs->gr[30] & ~(0x01UL));
        sigframe_size = PARISC_RT_SIGFRAME_SIZE;
#ifdef CONFIG_64BIT
        if (is_compat_task()) {
                /* The gcc alloca implementation leaves garbage in the upper 32 bits of sp */
                usp = (compat_uint_t)usp;
                sigframe_size = PARISC_RT_SIGFRAME_SIZE32;
        }
#endif
        frame = get_sigframe(&ksig->ka, usp, sigframe_size);

        DBG(1, "%s: frame %p info %p\n", __func__, frame, &ksig->info);

        start = (unsigned long) frame;
        if (start >= TASK_SIZE_MAX - sigframe_size)
                return -EFAULT;
        
#ifdef CONFIG_64BIT

        compat_frame = (struct compat_rt_sigframe __user *)frame;
        
        if (is_compat_task()) {
                DBG(1, "%s: frame->info = 0x%p\n", __func__, &compat_frame->info);
                err |= copy_siginfo_to_user32(&compat_frame->info, &ksig->info);
                err |= __compat_save_altstack( &compat_frame->uc.uc_stack, regs->gr[30]);
                DBG(1, "%s: frame->uc = 0x%p\n", __func__, &compat_frame->uc);
                DBG(1, "%s: frame->uc.uc_mcontext = 0x%p\n",
                        __func__, &compat_frame->uc.uc_mcontext);
                err |= setup_sigcontext32(&compat_frame->uc.uc_mcontext, 
                                        &compat_frame->regs, regs, in_syscall);
                err |= put_compat_sigset(&compat_frame->uc.uc_sigmask, set,
                                         sizeof(compat_sigset_t));
        } else
#endif
        {       
                DBG(1, "%s: frame->info = 0x%p\n", __func__, &frame->info);
                err |= copy_siginfo_to_user(&frame->info, &ksig->info);
                err |= __save_altstack(&frame->uc.uc_stack, regs->gr[30]);
                DBG(1, "%s: frame->uc = 0x%p\n", __func__, &frame->uc);
                DBG(1, "%s: frame->uc.uc_mcontext = 0x%p\n",
                        __func__, &frame->uc.uc_mcontext);
                err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, in_syscall);
                /* FIXME: Should probably be converted as well for the compat case */
                err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
        }
        
        if (err)
                return -EFAULT;

#ifdef CONFIG_64BIT
        if (!is_compat_task())
                rp = VDSO64_SYMBOL(current, sigtramp_rt);
        else
#endif
                rp = VDSO32_SYMBOL(current, sigtramp_rt);

        if (in_syscall)
                rp += 4*4; /* skip 4 instructions and start at ldi 1,%r25 */

        haddr = A(ksig->ka.sa.sa_handler);
        /* The sa_handler may be a pointer to a function descriptor */
#ifdef CONFIG_64BIT
        if (is_compat_task()) {
#endif
                if (haddr & PA_PLABEL_FDESC) {
                        Elf32_Fdesc fdesc;
                        Elf32_Fdesc __user *ufdesc = (Elf32_Fdesc __user *)A(haddr & ~3);

                        err = __copy_from_user(&fdesc, ufdesc, sizeof(fdesc));

                        if (err)
                                return -EFAULT;

                        haddr = fdesc.addr;
                        regs->gr[19] = fdesc.gp;
                }
#ifdef CONFIG_64BIT
        } else {
                Elf64_Fdesc fdesc;
                Elf64_Fdesc __user *ufdesc = (Elf64_Fdesc __user *)A(haddr & ~3);
                
                err = __copy_from_user(&fdesc, ufdesc, sizeof(fdesc));
                
                if (err)
                        return -EFAULT;
                
                haddr = fdesc.addr;
                regs->gr[19] = fdesc.gp;
                DBG(1, "%s: 64 bit signal, exe=%#lx, r19=%#lx, in_syscall=%d\n",
                     __func__, haddr, regs->gr[19], in_syscall);
        }
#endif

        /* The syscall return path will create IAOQ values from r31.
         */
        if (in_syscall) {
                regs->gr[31] = haddr;
#ifdef CONFIG_64BIT
                if (!test_thread_flag(TIF_32BIT))
                        sigframe_size |= 1; /* XXX ???? */
#endif
        } else {
                unsigned long psw = USER_PSW;
#ifdef CONFIG_64BIT
                if (!test_thread_flag(TIF_32BIT))
                        psw |= PSW_W;
#endif

                /* If we are singlestepping, arrange a trap to be delivered
                   when we return to userspace. Note the semantics -- we
                   should trap before the first insn in the handler is
                   executed. Ref:
                        http://sources.redhat.com/ml/gdb/2004-11/msg00245.html
                 */
                if (pa_psw(current)->r) {
                        pa_psw(current)->r = 0;
                        psw |= PSW_R;
                        mtctl(-1, 0);
                }

                regs->gr[0] = psw;
                regs->iaoq[0] = haddr | PRIV_USER;
                regs->iaoq[1] = regs->iaoq[0] + 4;
        }

        regs->gr[2]  = rp;                      /* userland return pointer */
        regs->gr[26] = ksig->sig;               /* signal number */
        
#ifdef CONFIG_64BIT
        if (is_compat_task()) {
                regs->gr[25] = A(&compat_frame->info); /* siginfo pointer */
                regs->gr[24] = A(&compat_frame->uc);   /* ucontext pointer */
        } else
#endif
        {               
                regs->gr[25] = A(&frame->info); /* siginfo pointer */
                regs->gr[24] = A(&frame->uc);   /* ucontext pointer */
        }
        
        DBG(1, "%s: making sigreturn frame: %#lx + %#lx = %#lx\n", __func__,
               regs->gr[30], sigframe_size,
               regs->gr[30] + sigframe_size);
        /* Raise the user stack pointer to make a proper call frame. */
        regs->gr[30] = (A(frame) + sigframe_size);


        DBG(1, "%s: sig deliver (%s,%d) frame=0x%p sp=%#lx iaoq=%#lx/%#lx rp=%#lx\n",
               __func__, current->comm, current->pid, frame, regs->gr[30],
               regs->iaoq[0], regs->iaoq[1], rp);

        return 0;
}

/*
 * OK, we're invoking a handler.
 */     

static void
handle_signal(struct ksignal *ksig, struct pt_regs *regs, long in_syscall)
{
        int ret;
        sigset_t *oldset = sigmask_to_save();

        DBG(1, "%s: sig=%d, ka=%p, info=%p, oldset=%p, regs=%p\n",
               __func__, ksig->sig, &ksig->ka, &ksig->info, oldset, regs);
        
        /* Set up the stack frame */
        ret = setup_rt_frame(ksig, oldset, regs, in_syscall);

        signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP) ||
                          test_thread_flag(TIF_BLOCKSTEP));

        DBG(1, "%s: Exit (success), regs->gr[28] = %ld\n",
                __func__, regs->gr[28]);
}

/*
 * Check how the syscall number gets loaded into %r20 within
 * the delay branch in userspace and adjust as needed.
 */

static void check_syscallno_in_delay_branch(struct pt_regs *regs)
{
        u32 opcode, source_reg;
        u32 __user *uaddr;
        int err;

        /* Usually we don't have to restore %r20 (the system call number)
         * because it gets loaded in the delay slot of the branch external
         * instruction via the ldi instruction.
         * In some cases a register-to-register copy instruction might have
         * been used instead, in which case we need to copy the syscall
         * number into the source register before returning to userspace.
         */

        /* A syscall is just a branch, so all we have to do is fiddle the
         * return pointer so that the ble instruction gets executed again.
         */
        regs->gr[31] -= 8; /* delayed branching */

        /* Get assembler opcode of code in delay branch */
        uaddr = (u32 __user *) ((regs->gr[31] & ~3) + 4);
        err = get_user(opcode, uaddr);
        if (err)
                return;

        /* Check if delay branch uses "ldi int,%r20" */
        if ((opcode & 0xffff0000) == 0x34140000)
                return; /* everything ok, just return */

        /* Check if delay branch uses "nop" */
        if (opcode == INSN_NOP)
                return;

        /* Check if delay branch uses "copy %rX,%r20" */
        if ((opcode & 0xffe0ffff) == 0x08000254) {
                source_reg = (opcode >> 16) & 31;
                regs->gr[source_reg] = regs->gr[20];
                return;
        }

        pr_warn("syscall restart: %s (pid %d): unexpected opcode 0x%08x\n",
                current->comm, task_pid_nr(current), opcode);
}

static inline void
syscall_restart(struct pt_regs *regs, struct k_sigaction *ka)
{
        if (regs->orig_r28)
                return;
        regs->orig_r28 = 1; /* no more restarts */

        DBG(1, "%s:  orig_r28 = %ld  pid %d  r20 %ld\n",
                __func__, regs->orig_r28, task_pid_nr(current), regs->gr[20]);

        /* Check the return code */
        switch (regs->gr[28]) {
        case -ERESTART_RESTARTBLOCK:
        case -ERESTARTNOHAND:
                DBG(1, "%s: ERESTARTNOHAND: returning -EINTR\n", __func__);
                regs->gr[28] = -EINTR;
                break;
        case -ERESTARTSYS:
                if (!(ka->sa.sa_flags & SA_RESTART)) {
                        DBG(1, "%s: ERESTARTSYS: putting -EINTR pid %d\n",
                                __func__, task_pid_nr(current));
                        regs->gr[28] = -EINTR;
                        break;
                }
                fallthrough;
        case -ERESTARTNOINTR:
                DBG(1, "%s: %ld\n", __func__, regs->gr[28]);
                check_syscallno_in_delay_branch(regs);
                break;
        }
}

static inline void
insert_restart_trampoline(struct pt_regs *regs)
{
        if (regs->orig_r28)
                return;
        regs->orig_r28 = 1; /* no more restarts */

        DBG(2, "%s: gr28 = %ld pid %d\n",
                __func__, regs->gr[28], task_pid_nr(current));

        switch (regs->gr[28]) {
        case -ERESTART_RESTARTBLOCK: {
                /* Restart the system call - no handlers present */
                unsigned int *usp = (unsigned int *)regs->gr[30];
                unsigned long rp;
                long err = 0;

                /* check that we don't exceed the stack */
                if (A(&usp[0]) >= TASK_SIZE_MAX - 5 * sizeof(int))
                        return;

                /* Call trampoline in vdso to restart the syscall
                 * with __NR_restart_syscall.
                 * Original return addresses are on stack like this:
                 *
                 *  0: <return address (orig r31)>
                 *  4: <2nd half for 64-bit>
                 */
#ifdef CONFIG_64BIT
                if (!is_compat_task()) {
                        err |= put_user(regs->gr[31] >> 32, &usp[0]);
                        err |= put_user(regs->gr[31] & 0xffffffff, &usp[1]);
                        rp = VDSO64_SYMBOL(current, restart_syscall);
                } else
#endif
                {
                        err |= put_user(regs->gr[31], &usp[0]);
                        rp = VDSO32_SYMBOL(current, restart_syscall);
                }
                WARN_ON(err);

                regs->gr[31] = rp;
                DBG(1, "%s: ERESTART_RESTARTBLOCK\n", __func__);
                return;
        }
        case -EINTR:
                /* ok, was handled before and should be returned. */
                break;
        case -ERESTARTNOHAND:
        case -ERESTARTSYS:
        case -ERESTARTNOINTR:
                DBG(1, "%s: Type %ld\n", __func__, regs->gr[28]);
                check_syscallno_in_delay_branch(regs);
                return;
        default:
                break;
        }
}

/*
 * We need to be able to restore the syscall arguments (r21-r26) to
 * restart syscalls.  Thus, the syscall path should save them in the
 * pt_regs structure (it's okay to do so since they are caller-save
 * registers).  As noted below, the syscall number gets restored for
 * us due to the magic of delayed branching.
 */
static void do_signal(struct pt_regs *regs, long in_syscall)
{
        struct ksignal ksig;
        int restart_syscall;
        bool has_handler;

        has_handler = get_signal(&ksig);

        restart_syscall = 0;
        if (in_syscall)
                restart_syscall = 1;

        if (has_handler) {
                /* Restart a system call if necessary. */
                if (restart_syscall)
                        syscall_restart(regs, &ksig.ka);

                handle_signal(&ksig, regs, in_syscall);
                DBG(1, "%s: Handled signal pid %d\n",
                        __func__, task_pid_nr(current));
                return;
        }

        /* Do we need to restart the system call? */
        if (restart_syscall)
                insert_restart_trampoline(regs);
        
        DBG(1, "%s: Exit (not delivered), regs->gr[28] = %ld  orig_r28 = %ld  pid %d\n",
                __func__, regs->gr[28], regs->orig_r28, task_pid_nr(current));

        restore_saved_sigmask();
}

asmlinkage void do_notify_resume(struct pt_regs *regs, long in_syscall)
{
        if (test_thread_flag(TIF_SIGPENDING) ||
            test_thread_flag(TIF_NOTIFY_SIGNAL))
                do_signal(regs, in_syscall);

        if (test_thread_flag(TIF_NOTIFY_RESUME))
                resume_user_mode_work(regs);
}