// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/arch/x86_64/ia32/ia32_signal.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
 *  2000-12-*   x86-64 compatibility mode signal handling by Andi Kleen
 */

#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/personality.h>
#include <linux/compat.h>
#include <linux/binfmts.h>
#include <asm/ucontext.h>
#include <linux/uaccess.h>
#include <asm/fpu/internal.h>
#include <asm/fpu/signal.h>
#include <asm/ptrace.h>
#include <asm/ia32_unistd.h>
#include <asm/user32.h>
#include <uapi/asm/sigcontext.h>
#include <asm/proto.h>
#include <asm/vdso.h>
#include <asm/sigframe.h>
#include <asm/sighandling.h>
#include <asm/sys_ia32.h>
#include <asm/smap.h>

/*
 * Do a signal return; undo the signal stack.
 */
#define loadsegment_gs(v)       load_gs_index(v)
#define loadsegment_fs(v)       loadsegment(fs, v)
#define loadsegment_ds(v)       loadsegment(ds, v)
#define loadsegment_es(v)       loadsegment(es, v)

#define get_user_seg(seg)       ({ unsigned int v; savesegment(seg, v); v; })
#define set_user_seg(seg, v)    loadsegment_##seg(v)

#define COPY(x)                 {               \
        get_user_ex(regs->x, &sc->x);           \
}

#define GET_SEG(seg)            ({                      \
        unsigned short tmp;                             \
        get_user_ex(tmp, &sc->seg);                     \
        tmp;                                            \
})

#define COPY_SEG_CPL3(seg)      do {                    \
        regs->seg = GET_SEG(seg) | 3;                   \
} while (0)

#define RELOAD_SEG(seg)         {               \
        unsigned int pre = GET_SEG(seg);        \
        unsigned int cur = get_user_seg(seg);   \
        pre |= 3;                               \
        if (pre != cur)                         \
                set_user_seg(seg, pre);         \
}

static int ia32_restore_sigcontext(struct pt_regs *regs,
                                   struct sigcontext_32 __user *sc)
{
        unsigned int tmpflags, err = 0;
        void __user *buf;
        u32 tmp;

        /* Always make any pending restarted system calls return -EINTR */
        current->restart_block.fn = do_no_restart_syscall;

        get_user_try {
                /*
                 * Reload fs and gs if they have changed in the signal
                 * handler.  This does not handle long fs/gs base changes in
                 * the handler, but does not clobber them at least in the
                 * normal case.
                 */
                RELOAD_SEG(gs);
                RELOAD_SEG(fs);
                RELOAD_SEG(ds);
                RELOAD_SEG(es);

                COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
                COPY(dx); COPY(cx); COPY(ip); COPY(ax);
                /* Don't touch extended registers */

                COPY_SEG_CPL3(cs);
                COPY_SEG_CPL3(ss);

                get_user_ex(tmpflags, &sc->flags);
                regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
                /* disable syscall checks */
                regs->orig_ax = -1;

                get_user_ex(tmp, &sc->fpstate);
                buf = compat_ptr(tmp);
        } get_user_catch(err);

        err |= fpu__restore_sig(buf, 1);

        force_iret();

        return err;
}

asmlinkage long sys32_sigreturn(void)
{
        struct pt_regs *regs = current_pt_regs();
        struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);
        sigset_t set;

        if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
                goto badframe;
        if (__get_user(set.sig[0], &frame->sc.oldmask)
            || (_COMPAT_NSIG_WORDS > 1
                && __copy_from_user((((char *) &set.sig) + 4),
                                    &frame->extramask,
                                    sizeof(frame->extramask))))
                goto badframe;

        set_current_blocked(&set);

        if (ia32_restore_sigcontext(regs, &frame->sc))
                goto badframe;
        return regs->ax;

badframe:
        signal_fault(regs, frame, "32bit sigreturn");
        return 0;
}

asmlinkage long sys32_rt_sigreturn(void)
{
        struct pt_regs *regs = current_pt_regs();
        struct rt_sigframe_ia32 __user *frame;
        sigset_t set;

        frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4);

        if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
                goto badframe;
        if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
                goto badframe;

        set_current_blocked(&set);

        if (ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext))
                goto badframe;

        if (compat_restore_altstack(&frame->uc.uc_stack))
                goto badframe;

        return regs->ax;

badframe:
        signal_fault(regs, frame, "32bit rt sigreturn");
        return 0;
}

/*
 * Set up a signal frame.
 */

static int ia32_setup_sigcontext(struct sigcontext_32 __user *sc,
                                 void __user *fpstate,
                                 struct pt_regs *regs, unsigned int mask)
{
        int err = 0;

        put_user_try {
                put_user_ex(get_user_seg(gs), (unsigned int __user *)&sc->gs);
                put_user_ex(get_user_seg(fs), (unsigned int __user *)&sc->fs);
                put_user_ex(get_user_seg(ds), (unsigned int __user *)&sc->ds);
                put_user_ex(get_user_seg(es), (unsigned int __user *)&sc->es);

                put_user_ex(regs->di, &sc->di);
                put_user_ex(regs->si, &sc->si);
                put_user_ex(regs->bp, &sc->bp);
                put_user_ex(regs->sp, &sc->sp);
                put_user_ex(regs->bx, &sc->bx);
                put_user_ex(regs->dx, &sc->dx);
                put_user_ex(regs->cx, &sc->cx);
                put_user_ex(regs->ax, &sc->ax);
                put_user_ex(current->thread.trap_nr, &sc->trapno);
                put_user_ex(current->thread.error_code, &sc->err);
                put_user_ex(regs->ip, &sc->ip);
                put_user_ex(regs->cs, (unsigned int __user *)&sc->cs);
                put_user_ex(regs->flags, &sc->flags);
                put_user_ex(regs->sp, &sc->sp_at_signal);
                put_user_ex(regs->ss, (unsigned int __user *)&sc->ss);

                put_user_ex(ptr_to_compat(fpstate), &sc->fpstate);

                /* non-iBCS2 extensions.. */
                put_user_ex(mask, &sc->oldmask);
                put_user_ex(current->thread.cr2, &sc->cr2);
        } put_user_catch(err);

        return err;
}

/*
 * Determine which stack to use..
 */
static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs,
                                 size_t frame_size,
                                 void __user **fpstate)
{
        struct fpu *fpu = &current->thread.fpu;
        unsigned long sp;

        /* Default to using normal stack */
        sp = regs->sp;

        /* This is the X/Open sanctioned signal stack switching.  */
        if (ksig->ka.sa.sa_flags & SA_ONSTACK)
                sp = sigsp(sp, ksig);
        /* This is the legacy signal stack switching. */
        else if (regs->ss != __USER32_DS &&
                !(ksig->ka.sa.sa_flags & SA_RESTORER) &&
                 ksig->ka.sa.sa_restorer)
                sp = (unsigned long) ksig->ka.sa.sa_restorer;

        if (fpu->initialized) {
                unsigned long fx_aligned, math_size;

                sp = fpu__alloc_mathframe(sp, 1, &fx_aligned, &math_size);
                *fpstate = (struct _fpstate_32 __user *) sp;
                if (copy_fpstate_to_sigframe(*fpstate, (void __user *)fx_aligned,
                                    math_size) < 0)
                        return (void __user *) -1L;
        }

        sp -= frame_size;
        /* Align the stack pointer according to the i386 ABI,
         * i.e. so that on function entry ((sp + 4) & 15) == 0. */
        sp = ((sp + 4) & -16ul) - 4;
        return (void __user *) sp;
}

int ia32_setup_frame(int sig, struct ksignal *ksig,
                     compat_sigset_t *set, struct pt_regs *regs)
{
        struct sigframe_ia32 __user *frame;
        void __user *restorer;
        int err = 0;
        void __user *fpstate = NULL;

        /* copy_to_user optimizes that into a single 8 byte store */
        static const struct {
                u16 poplmovl;
                u32 val;
                u16 int80;
        } __attribute__((packed)) code = {
                0xb858,          /* popl %eax ; movl $...,%eax */
                __NR_ia32_sigreturn,
                0x80cd,         /* int $0x80 */
        };

        frame = get_sigframe(ksig, regs, sizeof(*frame), &fpstate);

        if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
                return -EFAULT;

        if (__put_user(sig, &frame->sig))
                return -EFAULT;

        if (ia32_setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]))
                return -EFAULT;

        if (_COMPAT_NSIG_WORDS > 1) {
                if (__copy_to_user(frame->extramask, &set->sig[1],
                                   sizeof(frame->extramask)))
                        return -EFAULT;
        }

        if (ksig->ka.sa.sa_flags & SA_RESTORER) {
                restorer = ksig->ka.sa.sa_restorer;
        } else {
                /* Return stub is in 32bit vsyscall page */
                if (current->mm->context.vdso)
                        restorer = current->mm->context.vdso +
                                vdso_image_32.sym___kernel_sigreturn;
                else
                        restorer = &frame->retcode;
        }

        put_user_try {
                put_user_ex(ptr_to_compat(restorer), &frame->pretcode);

                /*
                 * These are actually not used anymore, but left because some
                 * gdb versions depend on them as a marker.
                 */
                put_user_ex(*((u64 *)&code), (u64 __user *)frame->retcode);
        } put_user_catch(err);

        if (err)
                return -EFAULT;

        /* Set up registers for signal handler */
        regs->sp = (unsigned long) frame;
        regs->ip = (unsigned long) ksig->ka.sa.sa_handler;

        /* Make -mregparm=3 work */
        regs->ax = sig;
        regs->dx = 0;
        regs->cx = 0;

        loadsegment(ds, __USER32_DS);
        loadsegment(es, __USER32_DS);

        regs->cs = __USER32_CS;
        regs->ss = __USER32_DS;

        return 0;
}

int ia32_setup_rt_frame(int sig, struct ksignal *ksig,
                        compat_sigset_t *set, struct pt_regs *regs)
{
        struct rt_sigframe_ia32 __user *frame;
        void __user *restorer;
        int err = 0;
        void __user *fpstate = NULL;

        /* __copy_to_user optimizes that into a single 8 byte store */
        static const struct {
                u8 movl;
                u32 val;
                u16 int80;
                u8  pad;
        } __attribute__((packed)) code = {
                0xb8,
                __NR_ia32_rt_sigreturn,
                0x80cd,
                0,
        };

        frame = get_sigframe(ksig, regs, sizeof(*frame), &fpstate);

        if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
                return -EFAULT;

        put_user_try {
                put_user_ex(sig, &frame->sig);
                put_user_ex(ptr_to_compat(&frame->info), &frame->pinfo);
                put_user_ex(ptr_to_compat(&frame->uc), &frame->puc);

                /* Create the ucontext.  */
                if (boot_cpu_has(X86_FEATURE_XSAVE))
                        put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
                else
                        put_user_ex(0, &frame->uc.uc_flags);
                put_user_ex(0, &frame->uc.uc_link);
                compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);

                if (ksig->ka.sa.sa_flags & SA_RESTORER)
                        restorer = ksig->ka.sa.sa_restorer;
                else
                        restorer = current->mm->context.vdso +
                                vdso_image_32.sym___kernel_rt_sigreturn;
                put_user_ex(ptr_to_compat(restorer), &frame->pretcode);

                /*
                 * Not actually used anymore, but left because some gdb
                 * versions need it.
                 */
                put_user_ex(*((u64 *)&code), (u64 __user *)frame->retcode);
        } put_user_catch(err);

        err |= __copy_siginfo_to_user32(&frame->info, &ksig->info, false);
        err |= ia32_setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
                                     regs, set->sig[0]);
        err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

        if (err)
                return -EFAULT;

        /* Set up registers for signal handler */
        regs->sp = (unsigned long) frame;
        regs->ip = (unsigned long) ksig->ka.sa.sa_handler;

        /* Make -mregparm=3 work */
        regs->ax = sig;
        regs->dx = (unsigned long) &frame->info;
        regs->cx = (unsigned long) &frame->uc;

        loadsegment(ds, __USER32_DS);
        loadsegment(es, __USER32_DS);

        regs->cs = __USER32_CS;
        regs->ss = __USER32_DS;

        return 0;
}