ptrace.c

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/*
 * Kernel support for the ptrace() and syscall tracing interfaces.
 *
 * Copyright (C) 2000 Hewlett-Packard Co, Linuxcare Inc.
 * Copyright (C) 2000 Matthew Wilcox <[email protected]>
 * Copyright (C) 2000 David Huggins-Daines <[email protected]>
 * Copyright (C) 2008 Helge Deller <[email protected]>
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/tracehook.h>
#include <linux/user.h>
#include <linux/personality.h>
#include <linux/security.h>
#include <linux/compat.h>
#include <linux/signal.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/asm-offsets.h>

/* PSW bits we allow the debugger to modify */
#define USER_PSW_BITS   (PSW_N | PSW_V | PSW_CB)

/*
 * Called by kernel/ptrace.c when detaching..
 *
 * Make sure single step bits etc are not set.
 */
void ptrace_disable(struct task_struct *task)
{
    clear_tsk_thread_flag(task, TIF_SINGLESTEP);
    clear_tsk_thread_flag(task, TIF_BLOCKSTEP);

    /* make sure the trap bits are not set */
    pa_psw(task)->r = 0;
    pa_psw(task)->t = 0;
    pa_psw(task)->h = 0;
    pa_psw(task)->l = 0;
}

/*
 * The following functions are called by ptrace_resume() when
 * enabling or disabling single/block tracing.
 */
void user_disable_single_step(struct task_struct *task)
{
    ptrace_disable(task);
}

void user_enable_single_step(struct task_struct *task)
{
    clear_tsk_thread_flag(task, TIF_BLOCKSTEP);
    set_tsk_thread_flag(task, TIF_SINGLESTEP);

    if (pa_psw(task)->n) {
        struct siginfo si;

        /* Nullified, just crank over the queue. */
        task_regs(task)->iaoq[0] = task_regs(task)->iaoq[1];
        task_regs(task)->iasq[0] = task_regs(task)->iasq[1];
        task_regs(task)->iaoq[1] = task_regs(task)->iaoq[0] + 4;
        pa_psw(task)->n = 0;
        pa_psw(task)->x = 0;
        pa_psw(task)->y = 0;
        pa_psw(task)->z = 0;
        pa_psw(task)->b = 0;
        ptrace_disable(task);
        /* Don't wake up the task, but let the
           parent know something happened. */
        si.si_code = TRAP_TRACE;
        si.si_addr = (void __user *) (task_regs(task)->iaoq[0] & ~3);
        si.si_signo = SIGTRAP;
        si.si_errno = 0;
        force_sig_info(SIGTRAP, &si, task);
        /* notify_parent(task, SIGCHLD); */
        return;
    }

    /* Enable recovery counter traps.  The recovery counter
     * itself will be set to zero on a task switch.  If the
     * task is suspended on a syscall then the syscall return
     * path will overwrite the recovery counter with a suitable
     * value such that it traps once back in user space.  We
     * disable interrupts in the tasks PSW here also, to avoid
     * interrupts while the recovery counter is decrementing.
     */
    pa_psw(task)->r = 1;
    pa_psw(task)->t = 0;
    pa_psw(task)->h = 0;
    pa_psw(task)->l = 0;
}

void user_enable_block_step(struct task_struct *task)
{
    clear_tsk_thread_flag(task, TIF_SINGLESTEP);
    set_tsk_thread_flag(task, TIF_BLOCKSTEP);

    /* Enable taken branch trap. */
    pa_psw(task)->r = 0;
    pa_psw(task)->t = 1;
    pa_psw(task)->h = 0;
    pa_psw(task)->l = 0;
}

long arch_ptrace(struct task_struct *child, long request,
         unsigned long addr, unsigned long data)
{
    unsigned long tmp;
    long ret = -EIO;

    switch (request) {

    /* Read the word at location addr in the USER area.  For ptraced
       processes, the kernel saves all regs on a syscall. */
    case PTRACE_PEEKUSR:
        if ((addr & (sizeof(unsigned long)-1)) ||
             addr >= sizeof(struct pt_regs))
            break;
        tmp = *(unsigned long *) ((char *) task_regs(child) + addr);
        ret = put_user(tmp, (unsigned long __user *) data);
        break;

    /* Write the word at location addr in the USER area.  This will need
       to change when the kernel no longer saves all regs on a syscall.
       FIXME.  There is a problem at the moment in that r3-r18 are only
       saved if the process is ptraced on syscall entry, and even then
       those values are overwritten by actual register values on syscall
       exit. */
    case PTRACE_POKEUSR:
        /* Some register values written here may be ignored in
         * entry.S:syscall_restore_rfi; e.g. iaoq is written with
         * r31/r31+4, and not with the values in pt_regs.
         */
        if (addr == PT_PSW) {
            /* Allow writing to Nullify, Divide-step-correction,
             * and carry/borrow bits.
             * BEWARE, if you set N, and then single step, it won't
             * stop on the nullified instruction.
             */
            data &= USER_PSW_BITS;
            task_regs(child)->gr[0] &= ~USER_PSW_BITS;
            task_regs(child)->gr[0] |= data;
            ret = 0;
            break;
        }

        if ((addr & (sizeof(unsigned long)-1)) ||
             addr >= sizeof(struct pt_regs))
            break;
        if ((addr >= PT_GR1 && addr <= PT_GR31) ||
                addr == PT_IAOQ0 || addr == PT_IAOQ1 ||
                (addr >= PT_FR0 && addr <= PT_FR31 + 4) ||
                addr == PT_SAR) {
            *(unsigned long *) ((char *) task_regs(child) + addr) = data;
            ret = 0;
        }
        break;

    default:
        ret = ptrace_request(child, request, addr, data);
        break;
    }

    return ret;
}


#ifdef CONFIG_COMPAT

/* This function is needed to translate 32 bit pt_regs offsets in to
 * 64 bit pt_regs offsets.  For example, a 32 bit gdb under a 64 bit kernel
 * will request offset 12 if it wants gr3, but the lower 32 bits of
 * the 64 bit kernels view of gr3 will be at offset 28 (3*8 + 4).
 * This code relies on a 32 bit pt_regs being comprised of 32 bit values
 * except for the fp registers which (a) are 64 bits, and (b) follow
 * the gr registers at the start of pt_regs.  The 32 bit pt_regs should
 * be half the size of the 64 bit pt_regs, plus 32*4 to allow for fr[]
 * being 64 bit in both cases.
 */

static compat_ulong_t translate_usr_offset(compat_ulong_t offset)
{
    if (offset < 0)
        return sizeof(struct pt_regs);
    else if (offset <= 32*4)    /* gr[0..31] */
        return offset * 2 + 4;
    else if (offset <= 32*4+32*8)   /* gr[0..31] + fr[0..31] */
        return offset + 32*4;
    else if (offset < sizeof(struct pt_regs)/2 + 32*4)
        return offset * 2 + 4 - 32*8;
    else
        return sizeof(struct pt_regs);
}

long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
            compat_ulong_t addr, compat_ulong_t data)
{
    compat_uint_t tmp;
    long ret = -EIO;

    switch (request) {

    case PTRACE_PEEKUSR:
        if (addr & (sizeof(compat_uint_t)-1))
            break;
        addr = translate_usr_offset(addr);
        if (addr >= sizeof(struct pt_regs))
            break;

        tmp = *(compat_uint_t *) ((char *) task_regs(child) + addr);
        ret = put_user(tmp, (compat_uint_t *) (unsigned long) data);
        break;

    /* Write the word at location addr in the USER area.  This will need
       to change when the kernel no longer saves all regs on a syscall.
       FIXME.  There is a problem at the moment in that r3-r18 are only
       saved if the process is ptraced on syscall entry, and even then
       those values are overwritten by actual register values on syscall
       exit. */
    case PTRACE_POKEUSR:
        /* Some register values written here may be ignored in
         * entry.S:syscall_restore_rfi; e.g. iaoq is written with
         * r31/r31+4, and not with the values in pt_regs.
         */
        if (addr == PT_PSW) {
            /* Since PT_PSW==0, it is valid for 32 bit processes
             * under 64 bit kernels as well.
             */
            ret = arch_ptrace(child, request, addr, data);
        } else {
            if (addr & (sizeof(compat_uint_t)-1))
                break;
            addr = translate_usr_offset(addr);
            if (addr >= sizeof(struct pt_regs))
                break;
            if (addr >= PT_FR0 && addr <= PT_FR31 + 4) {
                /* Special case, fp regs are 64 bits anyway */
                *(__u64 *) ((char *) task_regs(child) + addr) = data;
                ret = 0;
            }
            else if ((addr >= PT_GR1+4 && addr <= PT_GR31+4) ||
                    addr == PT_IAOQ0+4 || addr == PT_IAOQ1+4 ||
                    addr == PT_SAR+4) {
                /* Zero the top 32 bits */
                *(__u32 *) ((char *) task_regs(child) + addr - 4) = 0;
                *(__u32 *) ((char *) task_regs(child) + addr) = data;
                ret = 0;
            }
        }
        break;

    default:
        ret = compat_ptrace_request(child, request, addr, data);
        break;
    }

    return ret;
}
#endif

long do_syscall_trace_enter(struct pt_regs *regs)
{
    if (test_thread_flag(TIF_SYSCALL_TRACE) &&
        tracehook_report_syscall_entry(regs))
        return -1L;

    return regs->gr[20];
}

void do_syscall_trace_exit(struct pt_regs *regs)
{
    int stepping = test_thread_flag(TIF_SINGLESTEP) ||
        test_thread_flag(TIF_BLOCKSTEP);

    if (stepping || test_thread_flag(TIF_SYSCALL_TRACE))
        tracehook_report_syscall_exit(regs, stepping);
}