// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
 *
 *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
 *  2000-2002   x86-64 support by Andi Kleen
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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/tracehook.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/personality.h>
#include <linux/uaccess.h>
#include <linux/user-return-notifier.h>
#include <linux/uprobes.h>
#include <linux/context_tracking.h>
#include <linux/entry-common.h>
#include <linux/syscalls.h>

#include <asm/processor.h>
#include <asm/ucontext.h>
#include <asm/fpu/internal.h>
#include <asm/fpu/signal.h>
#include <asm/vdso.h>
#include <asm/mce.h>
#include <asm/sighandling.h>
#include <asm/vm86.h>

#ifdef CONFIG_X86_64
#include <linux/compat.h>
#include <asm/proto.h>
#include <asm/ia32_unistd.h>
#endif /* CONFIG_X86_64 */

#include <asm/syscall.h>
#include <asm/sigframe.h>
#include <asm/signal.h>

#ifdef CONFIG_X86_64
/*
 * If regs->ss will cause an IRET fault, change it.  Otherwise leave it
 * alone.  Using this generally makes no sense unless
 * user_64bit_mode(regs) would return true.
 */
static void force_valid_ss(struct pt_regs *regs)
{
        u32 ar;
        asm volatile ("lar %[old_ss], %[ar]\n\t"
                      "jz 1f\n\t"               /* If invalid: */
                      "xorl %[ar], %[ar]\n\t"   /* set ar = 0 */
                      "1:"
                      : [ar] "=r" (ar)
                      : [old_ss] "rm" ((u16)regs->ss));

        /*
         * For a valid 64-bit user context, we need DPL 3, type
         * read-write data or read-write exp-down data, and S and P
         * set.  We can't use VERW because VERW doesn't check the
         * P bit.
         */
        ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
        if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
            ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
                regs->ss = __USER_DS;
}
# define CONTEXT_COPY_SIZE      offsetof(struct sigcontext, reserved1)
#else
# define CONTEXT_COPY_SIZE      sizeof(struct sigcontext)
#endif

static int restore_sigcontext(struct pt_regs *regs,
                              struct sigcontext __user *usc,
                              unsigned long uc_flags)
{
        struct sigcontext sc;

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

        if (copy_from_user(&sc, usc, CONTEXT_COPY_SIZE))
                return -EFAULT;

#ifdef CONFIG_X86_32
        set_user_gs(regs, sc.gs);
        regs->fs = sc.fs;
        regs->es = sc.es;
        regs->ds = sc.ds;
#endif /* CONFIG_X86_32 */

        regs->bx = sc.bx;
        regs->cx = sc.cx;
        regs->dx = sc.dx;
        regs->si = sc.si;
        regs->di = sc.di;
        regs->bp = sc.bp;
        regs->ax = sc.ax;
        regs->sp = sc.sp;
        regs->ip = sc.ip;

#ifdef CONFIG_X86_64
        regs->r8 = sc.r8;
        regs->r9 = sc.r9;
        regs->r10 = sc.r10;
        regs->r11 = sc.r11;
        regs->r12 = sc.r12;
        regs->r13 = sc.r13;
        regs->r14 = sc.r14;
        regs->r15 = sc.r15;
#endif /* CONFIG_X86_64 */

        /* Get CS/SS and force CPL3 */
        regs->cs = sc.cs | 0x03;
        regs->ss = sc.ss | 0x03;

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

#ifdef CONFIG_X86_64
        /*
         * Fix up SS if needed for the benefit of old DOSEMU and
         * CRIU.
         */
        if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs)))
                force_valid_ss(regs);
#endif

        return fpu__restore_sig((void __user *)sc.fpstate,
                               IS_ENABLED(CONFIG_X86_32));
}

static __always_inline int
__unsafe_setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
                     struct pt_regs *regs, unsigned long mask)
{
#ifdef CONFIG_X86_32
        unsafe_put_user(get_user_gs(regs),
                                  (unsigned int __user *)&sc->gs, Efault);
        unsafe_put_user(regs->fs, (unsigned int __user *)&sc->fs, Efault);
        unsafe_put_user(regs->es, (unsigned int __user *)&sc->es, Efault);
        unsafe_put_user(regs->ds, (unsigned int __user *)&sc->ds, Efault);
#endif /* CONFIG_X86_32 */

        unsafe_put_user(regs->di, &sc->di, Efault);
        unsafe_put_user(regs->si, &sc->si, Efault);
        unsafe_put_user(regs->bp, &sc->bp, Efault);
        unsafe_put_user(regs->sp, &sc->sp, Efault);
        unsafe_put_user(regs->bx, &sc->bx, Efault);
        unsafe_put_user(regs->dx, &sc->dx, Efault);
        unsafe_put_user(regs->cx, &sc->cx, Efault);
        unsafe_put_user(regs->ax, &sc->ax, Efault);
#ifdef CONFIG_X86_64
        unsafe_put_user(regs->r8, &sc->r8, Efault);
        unsafe_put_user(regs->r9, &sc->r9, Efault);
        unsafe_put_user(regs->r10, &sc->r10, Efault);
        unsafe_put_user(regs->r11, &sc->r11, Efault);
        unsafe_put_user(regs->r12, &sc->r12, Efault);
        unsafe_put_user(regs->r13, &sc->r13, Efault);
        unsafe_put_user(regs->r14, &sc->r14, Efault);
        unsafe_put_user(regs->r15, &sc->r15, Efault);
#endif /* CONFIG_X86_64 */

        unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
        unsafe_put_user(current->thread.error_code, &sc->err, Efault);
        unsafe_put_user(regs->ip, &sc->ip, Efault);
#ifdef CONFIG_X86_32
        unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault);
        unsafe_put_user(regs->flags, &sc->flags, Efault);
        unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault);
        unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault);
#else /* !CONFIG_X86_32 */
        unsafe_put_user(regs->flags, &sc->flags, Efault);
        unsafe_put_user(regs->cs, &sc->cs, Efault);
        unsafe_put_user(0, &sc->gs, Efault);
        unsafe_put_user(0, &sc->fs, Efault);
        unsafe_put_user(regs->ss, &sc->ss, Efault);
#endif /* CONFIG_X86_32 */

        unsafe_put_user(fpstate, (unsigned long __user *)&sc->fpstate, Efault);

        /* non-iBCS2 extensions.. */
        unsafe_put_user(mask, &sc->oldmask, Efault);
        unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
        return 0;
Efault:
        return -EFAULT;
}

#define unsafe_put_sigcontext(sc, fp, regs, set, label)                 \
do {                                                                    \
        if (__unsafe_setup_sigcontext(sc, fp, regs, set->sig[0]))       \
                goto label;                                             \
} while(0);

#define unsafe_put_sigmask(set, frame, label) \
        unsafe_put_user(*(__u64 *)(set), \
                        (__u64 __user *)&(frame)->uc.uc_sigmask, \
                        label)

/*
 * Set up a signal frame.
 */

/* x86 ABI requires 16-byte alignment */
#define FRAME_ALIGNMENT 16UL

#define MAX_FRAME_PADDING       (FRAME_ALIGNMENT - 1)

/*
 * Determine which stack to use..
 */
static unsigned long align_sigframe(unsigned long sp)
{
#ifdef CONFIG_X86_32
        /*
         * Align the stack pointer according to the i386 ABI,
         * i.e. so that on function entry ((sp + 4) & 15) == 0.
         */
        sp = ((sp + 4) & -FRAME_ALIGNMENT) - 4;
#else /* !CONFIG_X86_32 */
        sp = round_down(sp, FRAME_ALIGNMENT) - 8;
#endif
        return sp;
}

static void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
             void __user **fpstate)
{
        /* Default to using normal stack */
        bool nested_altstack = on_sig_stack(regs->sp);
        bool entering_altstack = false;
        unsigned long math_size = 0;
        unsigned long sp = regs->sp;
        unsigned long buf_fx = 0;
        int ret;

        /* redzone */
        if (IS_ENABLED(CONFIG_X86_64))
                sp -= 128;

        /* This is the X/Open sanctioned signal stack switching.  */
        if (ka->sa.sa_flags & SA_ONSTACK) {
                /*
                 * This checks nested_altstack via sas_ss_flags(). Sensible
                 * programs use SS_AUTODISARM, which disables that check, and
                 * programs that don't use SS_AUTODISARM get compatible.
                 */
                if (sas_ss_flags(sp) == 0) {
                        sp = current->sas_ss_sp + current->sas_ss_size;
                        entering_altstack = true;
                }
        } else if (IS_ENABLED(CONFIG_X86_32) &&
                   !nested_altstack &&
                   regs->ss != __USER_DS &&
                   !(ka->sa.sa_flags & SA_RESTORER) &&
                   ka->sa.sa_restorer) {
                /* This is the legacy signal stack switching. */
                sp = (unsigned long) ka->sa.sa_restorer;
                entering_altstack = true;
        }

        sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
                                  &buf_fx, &math_size);
        *fpstate = (void __user *)sp;

        sp = align_sigframe(sp - frame_size);

        /*
         * If we are on the alternate signal stack and would overflow it, don't.
         * Return an always-bogus address instead so we will die with SIGSEGV.
         */
        if (unlikely((nested_altstack || entering_altstack) &&
                     !__on_sig_stack(sp))) {

                if (show_unhandled_signals && printk_ratelimit())
                        pr_info("%s[%d] overflowed sigaltstack\n",
                                current->comm, task_pid_nr(current));

                return (void __user *)-1L;
        }

        /* save i387 and extended state */
        ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size);
        if (ret < 0)
                return (void __user *)-1L;

        return (void __user *)sp;
}

#ifdef CONFIG_X86_32
static const struct {
        u16 poplmovl;
        u32 val;
        u16 int80;
} __attribute__((packed)) retcode = {
        0xb858,         /* popl %eax; movl $..., %eax */
        __NR_sigreturn,
        0x80cd,         /* int $0x80 */
};

static const struct {
        u8  movl;
        u32 val;
        u16 int80;
        u8  pad;
} __attribute__((packed)) rt_retcode = {
        0xb8,           /* movl $..., %eax */
        __NR_rt_sigreturn,
        0x80cd,         /* int $0x80 */
        0
};

static int
__setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
              struct pt_regs *regs)
{
        struct sigframe __user *frame;
        void __user *restorer;
        void __user *fp = NULL;

        frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);

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

        unsafe_put_user(sig, &frame->sig, Efault);
        unsafe_put_sigcontext(&frame->sc, fp, regs, set, Efault);
        unsafe_put_user(set->sig[1], &frame->extramask[0], Efault);
        if (current->mm->context.vdso)
                restorer = current->mm->context.vdso +
                        vdso_image_32.sym___kernel_sigreturn;
        else
                restorer = &frame->retcode;
        if (ksig->ka.sa.sa_flags & SA_RESTORER)
                restorer = ksig->ka.sa.sa_restorer;

        /* Set up to return from userspace.  */
        unsafe_put_user(restorer, &frame->pretcode, Efault);

        /*
         * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
         *
         * WE DO NOT USE IT ANY MORE! It's only left here for historical
         * reasons and because gdb uses it as a signature to notice
         * signal handler stack frames.
         */
        unsafe_put_user(*((u64 *)&retcode), (u64 *)frame->retcode, Efault);
        user_access_end();

        /* Set up registers for signal handler */
        regs->sp = (unsigned long)frame;
        regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
        regs->ax = (unsigned long)sig;
        regs->dx = 0;
        regs->cx = 0;

        regs->ds = __USER_DS;
        regs->es = __USER_DS;
        regs->ss = __USER_DS;
        regs->cs = __USER_CS;

        return 0;

Efault:
        user_access_end();
        return -EFAULT;
}

static int __setup_rt_frame(int sig, struct ksignal *ksig,
                            sigset_t *set, struct pt_regs *regs)
{
        struct rt_sigframe __user *frame;
        void __user *restorer;
        void __user *fp = NULL;

        frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);

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

        unsafe_put_user(sig, &frame->sig, Efault);
        unsafe_put_user(&frame->info, &frame->pinfo, Efault);
        unsafe_put_user(&frame->uc, &frame->puc, Efault);

        /* Create the ucontext.  */
        if (static_cpu_has(X86_FEATURE_XSAVE))
                unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
        else
                unsafe_put_user(0, &frame->uc.uc_flags, Efault);
        unsafe_put_user(0, &frame->uc.uc_link, Efault);
        unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);

        /* Set up to return from userspace.  */
        restorer = current->mm->context.vdso +
                vdso_image_32.sym___kernel_rt_sigreturn;
        if (ksig->ka.sa.sa_flags & SA_RESTORER)
                restorer = ksig->ka.sa.sa_restorer;
        unsafe_put_user(restorer, &frame->pretcode, Efault);

        /*
         * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
         *
         * WE DO NOT USE IT ANY MORE! It's only left here for historical
         * reasons and because gdb uses it as a signature to notice
         * signal handler stack frames.
         */
        unsafe_put_user(*((u64 *)&rt_retcode), (u64 *)frame->retcode, Efault);
        unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
        unsafe_put_sigmask(set, frame, Efault);
        user_access_end();
        
        if (copy_siginfo_to_user(&frame->info, &ksig->info))
                return -EFAULT;

        /* Set up registers for signal handler */
        regs->sp = (unsigned long)frame;
        regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
        regs->ax = (unsigned long)sig;
        regs->dx = (unsigned long)&frame->info;
        regs->cx = (unsigned long)&frame->uc;

        regs->ds = __USER_DS;
        regs->es = __USER_DS;
        regs->ss = __USER_DS;
        regs->cs = __USER_CS;

        return 0;
Efault:
        user_access_end();
        return -EFAULT;
}
#else /* !CONFIG_X86_32 */
static unsigned long frame_uc_flags(struct pt_regs *regs)
{
        unsigned long flags;

        if (boot_cpu_has(X86_FEATURE_XSAVE))
                flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
        else
                flags = UC_SIGCONTEXT_SS;

        if (likely(user_64bit_mode(regs)))
                flags |= UC_STRICT_RESTORE_SS;

        return flags;
}

static int __setup_rt_frame(int sig, struct ksignal *ksig,
                            sigset_t *set, struct pt_regs *regs)
{
        struct rt_sigframe __user *frame;
        void __user *fp = NULL;
        unsigned long uc_flags;

        /* x86-64 should always use SA_RESTORER. */
        if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
                return -EFAULT;

        frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
        uc_flags = frame_uc_flags(regs);

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

        /* Create the ucontext.  */
        unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault);
        unsafe_put_user(0, &frame->uc.uc_link, Efault);
        unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);

        /* Set up to return from userspace.  If provided, use a stub
           already in userspace.  */
        unsafe_put_user(ksig->ka.sa.sa_restorer, &frame->pretcode, Efault);
        unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
        unsafe_put_sigmask(set, frame, Efault);
        user_access_end();

        if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
                if (copy_siginfo_to_user(&frame->info, &ksig->info))
                        return -EFAULT;
        }

        /* Set up registers for signal handler */
        regs->di = sig;
        /* In case the signal handler was declared without prototypes */
        regs->ax = 0;

        /* This also works for non SA_SIGINFO handlers because they expect the
           next argument after the signal number on the stack. */
        regs->si = (unsigned long)&frame->info;
        regs->dx = (unsigned long)&frame->uc;
        regs->ip = (unsigned long) ksig->ka.sa.sa_handler;

        regs->sp = (unsigned long)frame;

        /*
         * Set up the CS and SS registers to run signal handlers in
         * 64-bit mode, even if the handler happens to be interrupting
         * 32-bit or 16-bit code.
         *
         * SS is subtle.  In 64-bit mode, we don't need any particular
         * SS descriptor, but we do need SS to be valid.  It's possible
         * that the old SS is entirely bogus -- this can happen if the
         * signal we're trying to deliver is #GP or #SS caused by a bad
         * SS value.  We also have a compatibility issue here: DOSEMU
         * relies on the contents of the SS register indicating the
         * SS value at the time of the signal, even though that code in
         * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
         * avoids relying on sigreturn to restore SS; instead it uses
         * a trampoline.)  So we do our best: if the old SS was valid,
         * we keep it.  Otherwise we replace it.
         */
        regs->cs = __USER_CS;

        if (unlikely(regs->ss != __USER_DS))
                force_valid_ss(regs);

        return 0;

Efault:
        user_access_end();
        return -EFAULT;
}
#endif /* CONFIG_X86_32 */

#ifdef CONFIG_X86_X32_ABI
static int x32_copy_siginfo_to_user(struct compat_siginfo __user *to,
                const struct kernel_siginfo *from)
{
        struct compat_siginfo new;

        copy_siginfo_to_external32(&new, from);
        if (from->si_signo == SIGCHLD) {
                new._sifields._sigchld_x32._utime = from->si_utime;
                new._sifields._sigchld_x32._stime = from->si_stime;
        }
        if (copy_to_user(to, &new, sizeof(struct compat_siginfo)))
                return -EFAULT;
        return 0;
}

int copy_siginfo_to_user32(struct compat_siginfo __user *to,
                           const struct kernel_siginfo *from)
{
        if (in_x32_syscall())
                return x32_copy_siginfo_to_user(to, from);
        return __copy_siginfo_to_user32(to, from);
}
#endif /* CONFIG_X86_X32_ABI */

static int x32_setup_rt_frame(struct ksignal *ksig,
                              compat_sigset_t *set,
                              struct pt_regs *regs)
{
#ifdef CONFIG_X86_X32_ABI
        struct rt_sigframe_x32 __user *frame;
        unsigned long uc_flags;
        void __user *restorer;
        void __user *fp = NULL;

        if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
                return -EFAULT;

        frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);

        uc_flags = frame_uc_flags(regs);

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

        /* Create the ucontext.  */
        unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault);
        unsafe_put_user(0, &frame->uc.uc_link, Efault);
        unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
        unsafe_put_user(0, &frame->uc.uc__pad0, Efault);
        restorer = ksig->ka.sa.sa_restorer;
        unsafe_put_user(restorer, (unsigned long __user *)&frame->pretcode, Efault);
        unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
        unsafe_put_sigmask(set, frame, Efault);
        user_access_end();

        if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
                if (x32_copy_siginfo_to_user(&frame->info, &ksig->info))
                        return -EFAULT;
        }

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

        /* We use the x32 calling convention here... */
        regs->di = ksig->sig;
        regs->si = (unsigned long) &frame->info;
        regs->dx = (unsigned long) &frame->uc;

        loadsegment(ds, __USER_DS);
        loadsegment(es, __USER_DS);

        regs->cs = __USER_CS;
        regs->ss = __USER_DS;
#endif  /* CONFIG_X86_X32_ABI */

        return 0;
#ifdef CONFIG_X86_X32_ABI
Efault:
        user_access_end();
        return -EFAULT;
#endif
}

/*
 * Do a signal return; undo the signal stack.
 */
#ifdef CONFIG_X86_32
SYSCALL_DEFINE0(sigreturn)
{
        struct pt_regs *regs = current_pt_regs();
        struct sigframe __user *frame;
        sigset_t set;

        frame = (struct sigframe __user *)(regs->sp - 8);

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

        set_current_blocked(&set);

        /*
         * x86_32 has no uc_flags bits relevant to restore_sigcontext.
         * Save a few cycles by skipping the __get_user.
         */
        if (restore_sigcontext(regs, &frame->sc, 0))
                goto badframe;
        return regs->ax;

badframe:
        signal_fault(regs, frame, "sigreturn");

        return 0;
}
#endif /* CONFIG_X86_32 */

SYSCALL_DEFINE0(rt_sigreturn)
{
        struct pt_regs *regs = current_pt_regs();
        struct rt_sigframe __user *frame;
        sigset_t set;
        unsigned long uc_flags;

        frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
        if (!access_ok(frame, sizeof(*frame)))
                goto badframe;
        if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask))
                goto badframe;
        if (__get_user(uc_flags, &frame->uc.uc_flags))
                goto badframe;

        set_current_blocked(&set);

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

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

        return regs->ax;

badframe:
        signal_fault(regs, frame, "rt_sigreturn");
        return 0;
}

/*
 * There are four different struct types for signal frame: sigframe_ia32,
 * rt_sigframe_ia32, rt_sigframe_x32, and rt_sigframe. Use the worst case
 * -- the largest size. It means the size for 64-bit apps is a bit more
 * than needed, but this keeps the code simple.
 */
#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
# define MAX_FRAME_SIGINFO_UCTXT_SIZE   sizeof(struct sigframe_ia32)
#else
# define MAX_FRAME_SIGINFO_UCTXT_SIZE   sizeof(struct rt_sigframe)
#endif

/*
 * The FP state frame contains an XSAVE buffer which must be 64-byte aligned.
 * If a signal frame starts at an unaligned address, extra space is required.
 * This is the max alignment padding, conservatively.
 */
#define MAX_XSAVE_PADDING       63UL

/*
 * The frame data is composed of the following areas and laid out as:
 *
 * -------------------------
 * | alignment padding     |
 * -------------------------
 * | (f)xsave frame        |
 * -------------------------
 * | fsave header          |
 * -------------------------
 * | alignment padding     |
 * -------------------------
 * | siginfo + ucontext    |
 * -------------------------
 */

/* max_frame_size tells userspace the worst case signal stack size. */
static unsigned long __ro_after_init max_frame_size;

void __init init_sigframe_size(void)
{
        max_frame_size = MAX_FRAME_SIGINFO_UCTXT_SIZE + MAX_FRAME_PADDING;

        max_frame_size += fpu__get_fpstate_size() + MAX_XSAVE_PADDING;

        /* Userspace expects an aligned size. */
        max_frame_size = round_up(max_frame_size, FRAME_ALIGNMENT);

        pr_info("max sigframe size: %lu\n", max_frame_size);
}

unsigned long get_sigframe_size(void)
{
        return max_frame_size;
}

static inline int is_ia32_compat_frame(struct ksignal *ksig)
{
        return IS_ENABLED(CONFIG_IA32_EMULATION) &&
                ksig->ka.sa.sa_flags & SA_IA32_ABI;
}

static inline int is_ia32_frame(struct ksignal *ksig)
{
        return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
}

static inline int is_x32_frame(struct ksignal *ksig)
{
        return IS_ENABLED(CONFIG_X86_X32_ABI) &&
                ksig->ka.sa.sa_flags & SA_X32_ABI;
}

static int
setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
{
        int usig = ksig->sig;
        sigset_t *set = sigmask_to_save();
        compat_sigset_t *cset = (compat_sigset_t *) set;

        /* Perform fixup for the pre-signal frame. */
        rseq_signal_deliver(ksig, regs);

        /* Set up the stack frame */
        if (is_ia32_frame(ksig)) {
                if (ksig->ka.sa.sa_flags & SA_SIGINFO)
                        return ia32_setup_rt_frame(usig, ksig, cset, regs);
                else
                        return ia32_setup_frame(usig, ksig, cset, regs);
        } else if (is_x32_frame(ksig)) {
                return x32_setup_rt_frame(ksig, cset, regs);
        } else {
                return __setup_rt_frame(ksig->sig, ksig, set, regs);
        }
}

static void
handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
        bool stepping, failed;
        struct fpu *fpu = &current->thread.fpu;

        if (v8086_mode(regs))
                save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);

        /* Are we from a system call? */
        if (syscall_get_nr(current, regs) != -1) {
                /* If so, check system call restarting.. */
                switch (syscall_get_error(current, regs)) {
                case -ERESTART_RESTARTBLOCK:
                case -ERESTARTNOHAND:
                        regs->ax = -EINTR;
                        break;

                case -ERESTARTSYS:
                        if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
                                regs->ax = -EINTR;
                                break;
                        }
                        fallthrough;
                case -ERESTARTNOINTR:
                        regs->ax = regs->orig_ax;
                        regs->ip -= 2;
                        break;
                }
        }

        /*
         * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
         * so that register information in the sigcontext is correct and
         * then notify the tracer before entering the signal handler.
         */
        stepping = test_thread_flag(TIF_SINGLESTEP);
        if (stepping)
                user_disable_single_step(current);

        failed = (setup_rt_frame(ksig, regs) < 0);
        if (!failed) {
                /*
                 * Clear the direction flag as per the ABI for function entry.
                 *
                 * Clear RF when entering the signal handler, because
                 * it might disable possible debug exception from the
                 * signal handler.
                 *
                 * Clear TF for the case when it wasn't set by debugger to
                 * avoid the recursive send_sigtrap() in SIGTRAP handler.
                 */
                regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
                /*
                 * Ensure the signal handler starts with the new fpu state.
                 */
                fpu__clear_user_states(fpu);
        }
        signal_setup_done(failed, ksig, stepping);
}

static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
{
#ifdef CONFIG_IA32_EMULATION
        if (current->restart_block.arch_data & TS_COMPAT)
                return __NR_ia32_restart_syscall;
#endif
#ifdef CONFIG_X86_X32_ABI
        return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
#else
        return __NR_restart_syscall;
#endif
}

/*
 * Note that 'init' is a special process: it doesn't get signals it doesn't
 * want to handle. Thus you cannot kill init even with a SIGKILL even by
 * mistake.
 */
void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal)
{
        struct ksignal ksig;

        if (has_signal && get_signal(&ksig)) {
                /* Whee! Actually deliver the signal.  */
                handle_signal(&ksig, regs);
                return;
        }

        /* Did we come from a system call? */
        if (syscall_get_nr(current, regs) != -1) {
                /* Restart the system call - no handlers present */
                switch (syscall_get_error(current, regs)) {
                case -ERESTARTNOHAND:
                case -ERESTARTSYS:
                case -ERESTARTNOINTR:
                        regs->ax = regs->orig_ax;
                        regs->ip -= 2;
                        break;

                case -ERESTART_RESTARTBLOCK:
                        regs->ax = get_nr_restart_syscall(regs);
                        regs->ip -= 2;
                        break;
                }
        }

        /*
         * If there's no signal to deliver, we just put the saved sigmask
         * back.
         */
        restore_saved_sigmask();
}

void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
{
        struct task_struct *me = current;

        if (show_unhandled_signals && printk_ratelimit()) {
                printk("%s"
                       "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
                       task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
                       me->comm, me->pid, where, frame,
                       regs->ip, regs->sp, regs->orig_ax);
                print_vma_addr(KERN_CONT " in ", regs->ip);
                pr_cont("\n");
        }

        force_sig(SIGSEGV);
}

#ifdef CONFIG_X86_X32_ABI
COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn)
{
        struct pt_regs *regs = current_pt_regs();
        struct rt_sigframe_x32 __user *frame;
        sigset_t set;
        unsigned long uc_flags;

        frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);

        if (!access_ok(frame, sizeof(*frame)))
                goto badframe;
        if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask))
                goto badframe;
        if (__get_user(uc_flags, &frame->uc.uc_flags))
                goto badframe;

        set_current_blocked(&set);

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

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

        return regs->ax;

badframe:
        signal_fault(regs, frame, "x32 rt_sigreturn");
        return 0;
}
#endif