root/arch/sparc/kernel/signal_32.c 
// SPDX-License-Identifier: GPL-2.0
/*  linux/arch/sparc/kernel/signal.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
 *  Copyright (C) 1996 Miguel de Icaza (miguel@nuclecu.unam.mx)
 *  Copyright (C) 1997 Eddie C. Dost   (ecd@skynet.be)
 */

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/mm.h>
#include <linux/tty.h>
#include <linux/smp.h>
#include <linux/binfmts.h>      /* do_coredum */
#include <linux/bitops.h>
#include <linux/resume_user_mode.h>

#include <linux/uaccess.h>
#include <asm/ptrace.h>
#include <asm/cacheflush.h>     /* flush_sig_insns */
#include <asm/switch_to.h>

#include "sigutil.h"
#include "kernel.h"

extern void fpsave(unsigned long *fpregs, unsigned long *fsr,
                   void *fpqueue, unsigned long *fpqdepth);
extern void fpload(unsigned long *fpregs, unsigned long *fsr);

struct signal_frame {
        struct sparc_stackf     ss;
        __siginfo32_t           info;
        __siginfo_fpu_t __user  *fpu_save;
        unsigned long           insns[2] __attribute__ ((aligned (8)));
        unsigned int            extramask[_NSIG_WORDS - 1];
        unsigned int            extra_size; /* Should be 0 */
        __siginfo_rwin_t __user *rwin_save;
} __attribute__((aligned(8)));

struct rt_signal_frame {
        struct sparc_stackf     ss;
        siginfo_t               info;
        struct pt_regs          regs;
        sigset_t                mask;
        __siginfo_fpu_t __user  *fpu_save;
        unsigned int            insns[2];
        stack_t                 stack;
        unsigned int            extra_size; /* Should be 0 */
        __siginfo_rwin_t __user *rwin_save;
} __attribute__((aligned(8)));

/* Align macros */
#define SF_ALIGNEDSZ  (((sizeof(struct signal_frame) + 7) & (~7)))
#define RT_ALIGNEDSZ  (((sizeof(struct rt_signal_frame) + 7) & (~7)))

/* Checks if the fp is valid.  We always build signal frames which are
 * 16-byte aligned, therefore we can always enforce that the restore
 * frame has that property as well.
 */
static inline bool invalid_frame_pointer(void __user *fp, int fplen)
{
        if ((((unsigned long) fp) & 15) || !access_ok(fp, fplen))
                return true;

        return false;
}

asmlinkage void do_sigreturn(struct pt_regs *regs)
{
        unsigned long up_psr, pc, npc, ufp;
        struct signal_frame __user *sf;
        sigset_t set;
        __siginfo_fpu_t __user *fpu_save;
        __siginfo_rwin_t __user *rwin_save;
        int err;

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

        synchronize_user_stack();

        sf = (struct signal_frame __user *) regs->u_regs[UREG_FP];

        /* 1. Make sure we are not getting garbage from the user */
        if (invalid_frame_pointer(sf, sizeof(*sf)))
                goto segv_and_exit;

        if (get_user(ufp, &sf->info.si_regs.u_regs[UREG_FP]))
                goto segv_and_exit;

        if (ufp & 0x7)
                goto segv_and_exit;

        err = __get_user(pc,  &sf->info.si_regs.pc);
        err |= __get_user(npc, &sf->info.si_regs.npc);

        if ((pc | npc) & 3)
                goto segv_and_exit;

        /* 2. Restore the state */
        up_psr = regs->psr;
        err |= __copy_from_user(regs, &sf->info.si_regs, sizeof(struct pt_regs));

        /* User can only change condition codes and FPU enabling in %psr. */
        regs->psr = (up_psr & ~(PSR_ICC | PSR_EF))
                  | (regs->psr & (PSR_ICC | PSR_EF));

        /* Prevent syscall restart.  */
        pt_regs_clear_syscall(regs);

        err |= __get_user(fpu_save, &sf->fpu_save);
        if (fpu_save)
                err |= restore_fpu_state(regs, fpu_save);
        err |= __get_user(rwin_save, &sf->rwin_save);
        if (rwin_save)
                err |= restore_rwin_state(rwin_save);

        /* This is pretty much atomic, no amount locking would prevent
         * the races which exist anyways.
         */
        err |= __get_user(set.sig[0], &sf->info.si_mask);
        err |= __copy_from_user(&set.sig[1], &sf->extramask,
                                (_NSIG_WORDS-1) * sizeof(unsigned int));
                           
        if (err)
                goto segv_and_exit;

        set_current_blocked(&set);
        return;

segv_and_exit:
        force_sig(SIGSEGV);
}

asmlinkage void do_rt_sigreturn(struct pt_regs *regs)
{
        struct rt_signal_frame __user *sf;
        unsigned int psr, pc, npc, ufp;
        __siginfo_fpu_t __user *fpu_save;
        __siginfo_rwin_t __user *rwin_save;
        sigset_t set;
        int err;

        synchronize_user_stack();
        sf = (struct rt_signal_frame __user *) regs->u_regs[UREG_FP];
        if (invalid_frame_pointer(sf, sizeof(*sf)))
                goto segv;

        if (get_user(ufp, &sf->regs.u_regs[UREG_FP]))
                goto segv;

        if (ufp & 0x7)
                goto segv;

        err = __get_user(pc, &sf->regs.pc);
        err |= __get_user(npc, &sf->regs.npc);
        err |= ((pc | npc) & 0x03);

        err |= __get_user(regs->y, &sf->regs.y);
        err |= __get_user(psr, &sf->regs.psr);

        err |= __copy_from_user(&regs->u_regs[UREG_G1],
                                &sf->regs.u_regs[UREG_G1], 15 * sizeof(u32));

        regs->psr = (regs->psr & ~PSR_ICC) | (psr & PSR_ICC);

        /* Prevent syscall restart.  */
        pt_regs_clear_syscall(regs);

        err |= __get_user(fpu_save, &sf->fpu_save);
        if (!err && fpu_save)
                err |= restore_fpu_state(regs, fpu_save);
        err |= __copy_from_user(&set, &sf->mask, sizeof(sigset_t));
        err |= restore_altstack(&sf->stack);
        
        if (err)
                goto segv;
                
        regs->pc = pc;
        regs->npc = npc;
        
        err |= __get_user(rwin_save, &sf->rwin_save);
        if (!err && rwin_save) {
                if (restore_rwin_state(rwin_save))
                        goto segv;
        }

        set_current_blocked(&set);
        return;
segv:
        force_sig(SIGSEGV);
}

static inline void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs, unsigned long framesize)
{
        unsigned long sp = regs->u_regs[UREG_FP];

        /*
         * 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 (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
                return (void __user *) -1L;

        /* This is the X/Open sanctioned signal stack switching.  */
        sp = sigsp(sp, ksig) - framesize;

        /* Always align the stack frame.  This handles two cases.  First,
         * sigaltstack need not be mindful of platform specific stack
         * alignment.  Second, if we took this signal because the stack
         * is not aligned properly, we'd like to take the signal cleanly
         * and report that.
         */
        sp &= ~15UL;

        return (void __user *) sp;
}

static int setup_frame(struct ksignal *ksig, struct pt_regs *regs,
                       sigset_t *oldset)
{
        struct signal_frame __user *sf;
        int sigframe_size, err, wsaved;
        void __user *tail;

        /* 1. Make sure everything is clean */
        synchronize_user_stack();

        wsaved = current_thread_info()->w_saved;

        sigframe_size = sizeof(*sf);
        if (used_math())
                sigframe_size += sizeof(__siginfo_fpu_t);
        if (wsaved)
                sigframe_size += sizeof(__siginfo_rwin_t);

        sf = (struct signal_frame __user *)
                get_sigframe(ksig, regs, sigframe_size);

        if (invalid_frame_pointer(sf, sigframe_size)) {
                force_exit_sig(SIGILL);
                return -EINVAL;
        }

        tail = sf + 1;

        /* 2. Save the current process state */
        err = __copy_to_user(&sf->info.si_regs, regs, sizeof(struct pt_regs));
        
        err |= __put_user(0, &sf->extra_size);

        if (used_math()) {
                __siginfo_fpu_t __user *fp = tail;
                tail += sizeof(*fp);
                err |= save_fpu_state(regs, fp);
                err |= __put_user(fp, &sf->fpu_save);
        } else {
                err |= __put_user(0, &sf->fpu_save);
        }
        if (wsaved) {
                __siginfo_rwin_t __user *rwp = tail;
                tail += sizeof(*rwp);
                err |= save_rwin_state(wsaved, rwp);
                err |= __put_user(rwp, &sf->rwin_save);
        } else {
                err |= __put_user(0, &sf->rwin_save);
        }

        err |= __put_user(oldset->sig[0], &sf->info.si_mask);
        err |= __copy_to_user(sf->extramask, &oldset->sig[1],
                              (_NSIG_WORDS - 1) * sizeof(unsigned int));
        if (!wsaved) {
                err |= __copy_to_user(sf, (char *) regs->u_regs[UREG_FP],
                                      sizeof(struct reg_window32));
        } else {
                struct reg_window32 *rp;

                rp = &current_thread_info()->reg_window[wsaved - 1];
                err |= __copy_to_user(sf, rp, sizeof(struct reg_window32));
        }
        if (err)
                return err;
        
        /* 3. signal handler back-trampoline and parameters */
        regs->u_regs[UREG_FP] = (unsigned long) sf;
        regs->u_regs[UREG_I0] = ksig->sig;
        regs->u_regs[UREG_I1] = (unsigned long) &sf->info;
        regs->u_regs[UREG_I2] = (unsigned long) &sf->info;

        /* 4. signal handler */
        regs->pc = (unsigned long) ksig->ka.sa.sa_handler;
        regs->npc = (regs->pc + 4);

        /* 5. return to kernel instructions */
        if (ksig->ka.ka_restorer)
                regs->u_regs[UREG_I7] = (unsigned long)ksig->ka.ka_restorer;
        else {
                regs->u_regs[UREG_I7] = (unsigned long)(&(sf->insns[0]) - 2);

                /* mov __NR_sigreturn, %g1 */
                err |= __put_user(0x821020d8, &sf->insns[0]);

                /* t 0x10 */
                err |= __put_user(0x91d02010, &sf->insns[1]);
                if (err)
                        return err;

                /* Flush instruction space. */
                flush_sig_insns(current->mm, (unsigned long) &(sf->insns[0]));
        }
        return 0;
}

static int setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs,
                          sigset_t *oldset)
{
        struct rt_signal_frame __user *sf;
        int sigframe_size, wsaved;
        void __user *tail;
        unsigned int psr;
        int err;

        synchronize_user_stack();
        wsaved = current_thread_info()->w_saved;
        sigframe_size = sizeof(*sf);
        if (used_math())
                sigframe_size += sizeof(__siginfo_fpu_t);
        if (wsaved)
                sigframe_size += sizeof(__siginfo_rwin_t);
        sf = (struct rt_signal_frame __user *)
                get_sigframe(ksig, regs, sigframe_size);
        if (invalid_frame_pointer(sf, sigframe_size)) {
                force_exit_sig(SIGILL);
                return -EINVAL;
        }

        tail = sf + 1;
        err  = __put_user(regs->pc, &sf->regs.pc);
        err |= __put_user(regs->npc, &sf->regs.npc);
        err |= __put_user(regs->y, &sf->regs.y);
        psr = regs->psr;
        if (used_math())
                psr |= PSR_EF;
        err |= __put_user(psr, &sf->regs.psr);
        err |= __copy_to_user(&sf->regs.u_regs, regs->u_regs, sizeof(regs->u_regs));
        err |= __put_user(0, &sf->extra_size);

        if (psr & PSR_EF) {
                __siginfo_fpu_t __user *fp = tail;
                tail += sizeof(*fp);
                err |= save_fpu_state(regs, fp);
                err |= __put_user(fp, &sf->fpu_save);
        } else {
                err |= __put_user(0, &sf->fpu_save);
        }
        if (wsaved) {
                __siginfo_rwin_t __user *rwp = tail;
                tail += sizeof(*rwp);
                err |= save_rwin_state(wsaved, rwp);
                err |= __put_user(rwp, &sf->rwin_save);
        } else {
                err |= __put_user(0, &sf->rwin_save);
        }
        err |= __copy_to_user(&sf->mask, &oldset->sig[0], sizeof(sigset_t));
        
        /* Setup sigaltstack */
        err |= __save_altstack(&sf->stack, regs->u_regs[UREG_FP]);
        
        if (!wsaved) {
                err |= __copy_to_user(sf, (char *) regs->u_regs[UREG_FP],
                                      sizeof(struct reg_window32));
        } else {
                struct reg_window32 *rp;

                rp = &current_thread_info()->reg_window[wsaved - 1];
                err |= __copy_to_user(sf, rp, sizeof(struct reg_window32));
        }

        err |= copy_siginfo_to_user(&sf->info, &ksig->info);

        if (err)
                return err;

        regs->u_regs[UREG_FP] = (unsigned long) sf;
        regs->u_regs[UREG_I0] = ksig->sig;
        regs->u_regs[UREG_I1] = (unsigned long) &sf->info;
        regs->u_regs[UREG_I2] = (unsigned long) &sf->regs;

        regs->pc = (unsigned long) ksig->ka.sa.sa_handler;
        regs->npc = (regs->pc + 4);

        if (ksig->ka.ka_restorer)
                regs->u_regs[UREG_I7] = (unsigned long)ksig->ka.ka_restorer;
        else {
                regs->u_regs[UREG_I7] = (unsigned long)(&(sf->insns[0]) - 2);

                /* mov __NR_rt_sigreturn, %g1 */
                err |= __put_user(0x82102065, &sf->insns[0]);

                /* t 0x10 */
                err |= __put_user(0x91d02010, &sf->insns[1]);
                if (err)
                        return err;

                /* Flush instruction space. */
                flush_sig_insns(current->mm, (unsigned long) &(sf->insns[0]));
        }
        return 0;
}

static inline void
handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
        sigset_t *oldset = sigmask_to_save();
        int err;

        if (ksig->ka.sa.sa_flags & SA_SIGINFO)
                err = setup_rt_frame(ksig, regs, oldset);
        else
                err = setup_frame(ksig, regs, oldset);
        signal_setup_done(err, ksig, 0);
}

static inline void syscall_restart(unsigned long orig_i0, struct pt_regs *regs,
                                   struct sigaction *sa)
{
        switch(regs->u_regs[UREG_I0]) {
        case ERESTART_RESTARTBLOCK:
        case ERESTARTNOHAND:
        no_system_call_restart:
                regs->u_regs[UREG_I0] = EINTR;
                regs->psr |= PSR_C;
                break;
        case ERESTARTSYS:
                if (!(sa->sa_flags & SA_RESTART))
                        goto no_system_call_restart;
                fallthrough;
        case ERESTARTNOINTR:
                regs->u_regs[UREG_I0] = orig_i0;
                regs->pc -= 4;
                regs->npc -= 4;
        }
}

/* 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.
 */
static void do_signal(struct pt_regs *regs, unsigned long orig_i0)
{
        struct ksignal ksig;
        int restart_syscall;
        bool has_handler;

        /* It's a lot of work and synchronization to add a new ptrace
         * register for GDB to save and restore in order to get
         * orig_i0 correct for syscall restarts when debugging.
         *
         * Although it should be the case that most of the global
         * registers are volatile across a system call, glibc already
         * depends upon that fact that we preserve them.  So we can't
         * just use any global register to save away the orig_i0 value.
         *
         * In particular %g2, %g3, %g4, and %g5 are all assumed to be
         * preserved across a system call trap by various pieces of
         * code in glibc.
         *
         * %g7 is used as the "thread register".   %g6 is not used in
         * any fixed manner.  %g6 is used as a scratch register and
         * a compiler temporary, but its value is never used across
         * a system call.  Therefore %g6 is usable for orig_i0 storage.
         */
        if (pt_regs_is_syscall(regs) && (regs->psr & PSR_C))
                regs->u_regs[UREG_G6] = orig_i0;

        has_handler = get_signal(&ksig);

        /* If the debugger messes with the program counter, it clears
         * the software "in syscall" bit, directing us to not perform
         * a syscall restart.
         */
        restart_syscall = 0;
        if (pt_regs_is_syscall(regs) && (regs->psr & PSR_C)) {
                restart_syscall = 1;
                orig_i0 = regs->u_regs[UREG_G6];
        }

        if (has_handler) {
                if (restart_syscall)
                        syscall_restart(orig_i0, regs, &ksig.ka.sa);
                handle_signal(&ksig, regs);
        } else {
                if (restart_syscall) {
                        switch (regs->u_regs[UREG_I0]) {
                        case ERESTARTNOHAND:
                        case ERESTARTSYS:
                        case ERESTARTNOINTR:
                                /* replay the system call when we are done */
                                regs->u_regs[UREG_I0] = orig_i0;
                                regs->pc -= 4;
                                regs->npc -= 4;
                                pt_regs_clear_syscall(regs);
                                fallthrough;
                        case ERESTART_RESTARTBLOCK:
                                regs->u_regs[UREG_G1] = __NR_restart_syscall;
                                regs->pc -= 4;
                                regs->npc -= 4;
                                pt_regs_clear_syscall(regs);
                        }
                }
                restore_saved_sigmask();
        }
}

void do_notify_resume(struct pt_regs *regs, unsigned long orig_i0,
                      unsigned long thread_info_flags)
{
        if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
                do_signal(regs, orig_i0);
        if (thread_info_flags & _TIF_NOTIFY_RESUME)
                resume_user_mode_work(regs);
}

asmlinkage int do_sys_sigstack(struct sigstack __user *ssptr,
                               struct sigstack __user *ossptr,
                               unsigned long sp)
{
        int ret = -EFAULT;

        /* First see if old state is wanted. */
        if (ossptr) {
                if (put_user(current->sas_ss_sp + current->sas_ss_size,
                             &ossptr->the_stack) ||
                    __put_user(on_sig_stack(sp), &ossptr->cur_status))
                        goto out;
        }

        /* Now see if we want to update the new state. */
        if (ssptr) {
                char *ss_sp;

                if (get_user(ss_sp, &ssptr->the_stack))
                        goto out;
                /* If the current stack was set with sigaltstack, don't
                   swap stacks while we are on it.  */
                ret = -EPERM;
                if (current->sas_ss_sp && on_sig_stack(sp))
                        goto out;

                /* Since we don't know the extent of the stack, and we don't
                   track onstack-ness, but rather calculate it, we must
                   presume a size.  Ho hum this interface is lossy.  */
                current->sas_ss_sp = (unsigned long)ss_sp - SIGSTKSZ;
                current->sas_ss_size = SIGSTKSZ;
        }
        ret = 0;
out:
        return ret;
}