signal_64.c

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/*
 *  PowerPC version 
 *    Copyright (C) 1995-1996 Gary Thomas ([email protected])
 *
 *  Derived from "arch/i386/kernel/signal.c"
 *    Copyright (C) 1991, 1992 Linus Torvalds
 *    1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <linux/sched.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/unistd.h>
#include <linux/stddef.h>
#include <linux/elf.h>
#include <linux/ptrace.h>
#include <linux/ratelimit.h>

#include <asm/sigcontext.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/unistd.h>
#include <asm/cacheflush.h>
#include <asm/syscalls.h>
#include <asm/vdso.h>
#include <asm/switch_to.h>

#include "signal.h"

#define DEBUG_SIG 0

#define GP_REGS_SIZE    min(sizeof(elf_gregset_t), sizeof(struct pt_regs))
#define FP_REGS_SIZE    sizeof(elf_fpregset_t)

#define TRAMP_TRACEBACK 3
#define TRAMP_SIZE  6

/*
 * When we have signals to deliver, we set up on the user stack,
 * going down from the original stack pointer:
 *  1) a rt_sigframe struct which contains the ucontext 
 *  2) a gap of __SIGNAL_FRAMESIZE bytes which acts as a dummy caller
 *     frame for the signal handler.
 */

struct rt_sigframe {
    /* sys_rt_sigreturn requires the ucontext be the first field */
    struct ucontext uc;
    unsigned long _unused[2];
    unsigned int tramp[TRAMP_SIZE];
    struct siginfo __user *pinfo;
    void __user *puc;
    struct siginfo info;
    /* 64 bit ABI allows for 288 bytes below sp before decrementing it. */
    char abigap[288];
} __attribute__ ((aligned (16)));

static const char fmt32[] = KERN_INFO \
    "%s[%d]: bad frame in %s: %08lx nip %08lx lr %08lx\n";
static const char fmt64[] = KERN_INFO \
    "%s[%d]: bad frame in %s: %016lx nip %016lx lr %016lx\n";

/*
 * Set up the sigcontext for the signal frame.
 */

static long setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
         int signr, sigset_t *set, unsigned long handler,
         int ctx_has_vsx_region)
{
    /* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the
     * process never used altivec yet (MSR_VEC is zero in pt_regs of
     * the context). This is very important because we must ensure we
     * don't lose the VRSAVE content that may have been set prior to
     * the process doing its first vector operation
     * Userland shall check AT_HWCAP to know wether it can rely on the
     * v_regs pointer or not
     */
#ifdef CONFIG_ALTIVEC
    elf_vrreg_t __user *v_regs = (elf_vrreg_t __user *)(((unsigned long)sc->vmx_reserve + 15) & ~0xful);
#endif
    unsigned long msr = regs->msr;
    long err = 0;

    flush_fp_to_thread(current);

#ifdef CONFIG_ALTIVEC
    err |= __put_user(v_regs, &sc->v_regs);

    /* save altivec registers */
    if (current->thread.used_vr) {
        flush_altivec_to_thread(current);
        /* Copy 33 vec registers (vr0..31 and vscr) to the stack */
        err |= __copy_to_user(v_regs, current->thread.vr, 33 * sizeof(vector128));
        /* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg)
         * contains valid data.
         */
        msr |= MSR_VEC;
    }
    /* We always copy to/from vrsave, it's 0 if we don't have or don't
     * use altivec.
     */
    err |= __put_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
#else /* CONFIG_ALTIVEC */
    err |= __put_user(0, &sc->v_regs);
#endif /* CONFIG_ALTIVEC */
    flush_fp_to_thread(current);
    /* copy fpr regs and fpscr */
    err |= copy_fpr_to_user(&sc->fp_regs, current);
#ifdef CONFIG_VSX
    /*
     * Copy VSX low doubleword to local buffer for formatting,
     * then out to userspace.  Update v_regs to point after the
     * VMX data.
     */
    if (current->thread.used_vsr && ctx_has_vsx_region) {
        __giveup_vsx(current);
        v_regs += ELF_NVRREG;
        err |= copy_vsx_to_user(v_regs, current);
        /* set MSR_VSX in the MSR value in the frame to
         * indicate that sc->vs_reg) contains valid data.
         */
        msr |= MSR_VSX;
    }
#endif /* CONFIG_VSX */
    err |= __put_user(&sc->gp_regs, &sc->regs);
    WARN_ON(!FULL_REGS(regs));
    err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE);
    err |= __put_user(msr, &sc->gp_regs[PT_MSR]);
    err |= __put_user(signr, &sc->signal);
    err |= __put_user(handler, &sc->handler);
    if (set != NULL)
        err |=  __put_user(set->sig[0], &sc->oldmask);

    return err;
}

/*
 * Restore the sigcontext from the signal frame.
 */

static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
                  struct sigcontext __user *sc)
{
#ifdef CONFIG_ALTIVEC
    elf_vrreg_t __user *v_regs;
#endif
    unsigned long err = 0;
    unsigned long save_r13 = 0;
    unsigned long msr;
#ifdef CONFIG_VSX
    int i;
#endif

    /* If this is not a signal return, we preserve the TLS in r13 */
    if (!sig)
        save_r13 = regs->gpr[13];

    /* copy the GPRs */
    err |= __copy_from_user(regs->gpr, sc->gp_regs, sizeof(regs->gpr));
    err |= __get_user(regs->nip, &sc->gp_regs[PT_NIP]);
    /* get MSR separately, transfer the LE bit if doing signal return */
    err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
    if (sig)
        regs->msr = (regs->msr & ~MSR_LE) | (msr & MSR_LE);
    err |= __get_user(regs->orig_gpr3, &sc->gp_regs[PT_ORIG_R3]);
    err |= __get_user(regs->ctr, &sc->gp_regs[PT_CTR]);
    err |= __get_user(regs->link, &sc->gp_regs[PT_LNK]);
    err |= __get_user(regs->xer, &sc->gp_regs[PT_XER]);
    err |= __get_user(regs->ccr, &sc->gp_regs[PT_CCR]);
    /* skip SOFTE */
    regs->trap = 0;
    err |= __get_user(regs->dar, &sc->gp_regs[PT_DAR]);
    err |= __get_user(regs->dsisr, &sc->gp_regs[PT_DSISR]);
    err |= __get_user(regs->result, &sc->gp_regs[PT_RESULT]);

    if (!sig)
        regs->gpr[13] = save_r13;
    if (set != NULL)
        err |=  __get_user(set->sig[0], &sc->oldmask);

    /*
     * Do this before updating the thread state in
     * current->thread.fpr/vr.  That way, if we get preempted
     * and another task grabs the FPU/Altivec, it won't be
     * tempted to save the current CPU state into the thread_struct
     * and corrupt what we are writing there.
     */
    discard_lazy_cpu_state();

    /*
     * Force reload of FP/VEC.
     * This has to be done before copying stuff into current->thread.fpr/vr
     * for the reasons explained in the previous comment.
     */
    regs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1 | MSR_VEC | MSR_VSX);

#ifdef CONFIG_ALTIVEC
    err |= __get_user(v_regs, &sc->v_regs);
    if (err)
        return err;
    if (v_regs && !access_ok(VERIFY_READ, v_regs, 34 * sizeof(vector128)))
        return -EFAULT;
    /* Copy 33 vec registers (vr0..31 and vscr) from the stack */
    if (v_regs != 0 && (msr & MSR_VEC) != 0)
        err |= __copy_from_user(current->thread.vr, v_regs,
                    33 * sizeof(vector128));
    else if (current->thread.used_vr)
        memset(current->thread.vr, 0, 33 * sizeof(vector128));
    /* Always get VRSAVE back */
    if (v_regs != 0)
        err |= __get_user(current->thread.vrsave, (u32 __user *)&v_regs[33]);
    else
        current->thread.vrsave = 0;
#endif /* CONFIG_ALTIVEC */
    /* restore floating point */
    err |= copy_fpr_from_user(current, &sc->fp_regs);
#ifdef CONFIG_VSX
    /*
     * Get additional VSX data. Update v_regs to point after the
     * VMX data.  Copy VSX low doubleword from userspace to local
     * buffer for formatting, then into the taskstruct.
     */
    v_regs += ELF_NVRREG;
    if ((msr & MSR_VSX) != 0)
        err |= copy_vsx_from_user(current, v_regs);
    else
        for (i = 0; i < 32 ; i++)
            current->thread.fpr[i][TS_VSRLOWOFFSET] = 0;
#endif
    return err;
}

/*
 * Setup the trampoline code on the stack
 */
static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
{
    int i;
    long err = 0;

    /* addi r1, r1, __SIGNAL_FRAMESIZE  # Pop the dummy stackframe */
    err |= __put_user(0x38210000UL | (__SIGNAL_FRAMESIZE & 0xffff), &tramp[0]);
    /* li r0, __NR_[rt_]sigreturn| */
    err |= __put_user(0x38000000UL | (syscall & 0xffff), &tramp[1]);
    /* sc */
    err |= __put_user(0x44000002UL, &tramp[2]);

    /* Minimal traceback info */
    for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
        err |= __put_user(0, &tramp[i]);

    if (!err)
        flush_icache_range((unsigned long) &tramp[0],
               (unsigned long) &tramp[TRAMP_SIZE]);

    return err;
}

/*
 * Userspace code may pass a ucontext which doesn't include VSX added
 * at the end.  We need to check for this case.
 */
#define UCONTEXTSIZEWITHOUTVSX \
        (sizeof(struct ucontext) - 32*sizeof(long))

/*
 * Handle {get,set,swap}_context operations
 */
int sys_swapcontext(struct ucontext __user *old_ctx,
            struct ucontext __user *new_ctx,
            long ctx_size, long r6, long r7, long r8, struct pt_regs *regs)
{
    unsigned char tmp;
    sigset_t set;
    unsigned long new_msr = 0;
    int ctx_has_vsx_region = 0;

    if (new_ctx &&
        get_user(new_msr, &new_ctx->uc_mcontext.gp_regs[PT_MSR]))
        return -EFAULT;
    /*
     * Check that the context is not smaller than the original
     * size (with VMX but without VSX)
     */
    if (ctx_size < UCONTEXTSIZEWITHOUTVSX)
        return -EINVAL;
    /*
     * If the new context state sets the MSR VSX bits but
     * it doesn't provide VSX state.
     */
    if ((ctx_size < sizeof(struct ucontext)) &&
        (new_msr & MSR_VSX))
        return -EINVAL;
    /* Does the context have enough room to store VSX data? */
    if (ctx_size >= sizeof(struct ucontext))
        ctx_has_vsx_region = 1;

    if (old_ctx != NULL) {
        if (!access_ok(VERIFY_WRITE, old_ctx, ctx_size)
            || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0,
                    ctx_has_vsx_region)
            || __copy_to_user(&old_ctx->uc_sigmask,
                      &current->blocked, sizeof(sigset_t)))
            return -EFAULT;
    }
    if (new_ctx == NULL)
        return 0;
    if (!access_ok(VERIFY_READ, new_ctx, ctx_size)
        || __get_user(tmp, (u8 __user *) new_ctx)
        || __get_user(tmp, (u8 __user *) new_ctx + ctx_size - 1))
        return -EFAULT;

    /*
     * If we get a fault copying the context into the kernel's
     * image of the user's registers, we can't just return -EFAULT
     * because the user's registers will be corrupted.  For instance
     * the NIP value may have been updated but not some of the
     * other registers.  Given that we have done the access_ok
     * and successfully read the first and last bytes of the region
     * above, this should only happen in an out-of-memory situation
     * or if another thread unmaps the region containing the context.
     * We kill the task with a SIGSEGV in this situation.
     */

    if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
        do_exit(SIGSEGV);
    set_current_blocked(&set);
    if (restore_sigcontext(regs, NULL, 0, &new_ctx->uc_mcontext))
        do_exit(SIGSEGV);

    /* This returns like rt_sigreturn */
    set_thread_flag(TIF_RESTOREALL);
    return 0;
}


/*
 * Do a signal return; undo the signal stack.
 */

int sys_rt_sigreturn(unsigned long r3, unsigned long r4, unsigned long r5,
             unsigned long r6, unsigned long r7, unsigned long r8,
             struct pt_regs *regs)
{
    struct ucontext __user *uc = (struct ucontext __user *)regs->gpr[1];
    sigset_t set;

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

    if (!access_ok(VERIFY_READ, uc, sizeof(*uc)))
        goto badframe;

    if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
        goto badframe;
    set_current_blocked(&set);
    if (restore_sigcontext(regs, NULL, 1, &uc->uc_mcontext))
        goto badframe;

    /* do_sigaltstack expects a __user pointer and won't modify
     * what's in there anyway
     */
    do_sigaltstack(&uc->uc_stack, NULL, regs->gpr[1]);

    set_thread_flag(TIF_RESTOREALL);
    return 0;

badframe:
#if DEBUG_SIG
    printk("badframe in sys_rt_sigreturn, regs=%p uc=%p &uc->uc_mcontext=%p\n",
           regs, uc, &uc->uc_mcontext);
#endif
    if (show_unhandled_signals)
        printk_ratelimited(regs->msr & MSR_64BIT ? fmt64 : fmt32,
                   current->comm, current->pid, "rt_sigreturn",
                   (long)uc, regs->nip, regs->link);

    force_sig(SIGSEGV, current);
    return 0;
}

int handle_rt_signal64(int signr, struct k_sigaction *ka, siginfo_t *info,
        sigset_t *set, struct pt_regs *regs)
{
    /* Handler is *really* a pointer to the function descriptor for
     * the signal routine.  The first entry in the function
     * descriptor is the entry address of signal and the second
     * entry is the TOC value we need to use.
     */
    func_descr_t __user *funct_desc_ptr;
    struct rt_sigframe __user *frame;
    unsigned long newsp = 0;
    long err = 0;

    frame = get_sigframe(ka, regs, sizeof(*frame), 0);
    if (unlikely(frame == NULL))
        goto badframe;

    err |= __put_user(&frame->info, &frame->pinfo);
    err |= __put_user(&frame->uc, &frame->puc);
    err |= copy_siginfo_to_user(&frame->info, info);
    if (err)
        goto badframe;

    /* Create the ucontext.  */
    err |= __put_user(0, &frame->uc.uc_flags);
    err |= __put_user(0, &frame->uc.uc_link);
    err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
    err |= __put_user(sas_ss_flags(regs->gpr[1]),
              &frame->uc.uc_stack.ss_flags);
    err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
    err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, signr, NULL,
                (unsigned long)ka->sa.sa_handler, 1);
    err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
    if (err)
        goto badframe;

    /* Make sure signal handler doesn't get spurious FP exceptions */
    current->thread.fpscr.val = 0;

    /* Set up to return from userspace. */
    if (vdso64_rt_sigtramp && current->mm->context.vdso_base) {
        regs->link = current->mm->context.vdso_base + vdso64_rt_sigtramp;
    } else {
        err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
        if (err)
            goto badframe;
        regs->link = (unsigned long) &frame->tramp[0];
    }
    funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;

    /* Allocate a dummy caller frame for the signal handler. */
    newsp = ((unsigned long)frame) - __SIGNAL_FRAMESIZE;
    err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);

    /* Set up "regs" so we "return" to the signal handler. */
    err |= get_user(regs->nip, &funct_desc_ptr->entry);
    /* enter the signal handler in big-endian mode */
    regs->msr &= ~MSR_LE;
    regs->gpr[1] = newsp;
    err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
    regs->gpr[3] = signr;
    regs->result = 0;
    if (ka->sa.sa_flags & SA_SIGINFO) {
        err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
        err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);
        regs->gpr[6] = (unsigned long) frame;
    } else {
        regs->gpr[4] = (unsigned long)&frame->uc.uc_mcontext;
    }
    if (err)
        goto badframe;

    return 1;

badframe:
#if DEBUG_SIG
    printk("badframe in setup_rt_frame, regs=%p frame=%p newsp=%lx\n",
           regs, frame, newsp);
#endif
    if (show_unhandled_signals)
        printk_ratelimited(regs->msr & MSR_64BIT ? fmt64 : fmt32,
                   current->comm, current->pid, "setup_rt_frame",
                   (long)frame, regs->nip, regs->link);

    force_sigsegv(signr, current);
    return 0;
}