ptrace.c

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/*
 * `ptrace' system call
 *
 * Copyright (C) 2008-2009 Michal Simek <[email protected]>
 * Copyright (C) 2007-2009 PetaLogix
 * Copyright (C) 2004-2007 John Williams <[email protected]>
 *
 * derived from arch/v850/kernel/ptrace.c
 *
 * Copyright (C) 2002,03 NEC Electronics Corporation
 * Copyright (C) 2002,03 Miles Bader <[email protected]>
 *
 * Derived from arch/mips/kernel/ptrace.c:
 *
 * Copyright (C) 1992 Ross Biro
 * Copyright (C) Linus Torvalds
 * Copyright (C) 1994, 95, 96, 97, 98, 2000 Ralf Baechle
 * Copyright (C) 1996 David S. Miller
 * Kevin D. Kissell, [email protected] and Carsten Langgaard, [email protected]
 * Copyright (C) 1999 MIPS Technologies, Inc.
 *
 * This file is subject to the terms and conditions of the GNU General
 * Public License. See the file COPYING in the main directory of this
 * archive for more details.
 */

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/signal.h>
#include <linux/elf.h>
#include <linux/audit.h>
#include <linux/seccomp.h>
#include <linux/tracehook.h>

#include <linux/errno.h>
#include <asm/processor.h>
#include <linux/uaccess.h>
#include <asm/asm-offsets.h>
#include <asm/cacheflush.h>
#include <asm/syscall.h>
#include <asm/io.h>

/* Returns the address where the register at REG_OFFS in P is stashed away. */
static microblaze_reg_t *reg_save_addr(unsigned reg_offs,
                    struct task_struct *t)
{
    struct pt_regs *regs;

    /*
     * Three basic cases:
     *
     * (1)  A register normally saved before calling the scheduler, is
     *  available in the kernel entry pt_regs structure at the top
     *  of the kernel stack. The kernel trap/irq exit path takes
     *  care to save/restore almost all registers for ptrace'd
     *  processes.
     *
     * (2)  A call-clobbered register, where the process P entered the
     *  kernel via [syscall] trap, is not stored anywhere; that's
     *  OK, because such registers are not expected to be preserved
     *  when the trap returns anyway (so we don't actually bother to
     *  test for this case).
     *
     * (3)  A few registers not used at all by the kernel, and so
     *  normally never saved except by context-switches, are in the
     *  context switch state.
     */

    /* Register saved during kernel entry (or not available). */
    regs = task_pt_regs(t);

    return (microblaze_reg_t *)((char *)regs + reg_offs);
}

long arch_ptrace(struct task_struct *child, long request,
         unsigned long addr, unsigned long data)
{
    int rval;
    unsigned long val = 0;

    switch (request) {
    /* Read/write the word at location ADDR in the registers. */
    case PTRACE_PEEKUSR:
    case PTRACE_POKEUSR:
        pr_debug("PEEKUSR/POKEUSR : 0x%08lx\n", addr);
        rval = 0;
        if (addr >= PT_SIZE && request == PTRACE_PEEKUSR) {
            /*
             * Special requests that don't actually correspond
             * to offsets in struct pt_regs.
             */
            if (addr == PT_TEXT_ADDR) {
                val = child->mm->start_code;
            } else if (addr == PT_DATA_ADDR) {
                val = child->mm->start_data;
            } else if (addr == PT_TEXT_LEN) {
                val = child->mm->end_code
                    - child->mm->start_code;
            } else {
                rval = -EIO;
            }
        } else if (addr < PT_SIZE && (addr & 0x3) == 0) {
            microblaze_reg_t *reg_addr = reg_save_addr(addr, child);
            if (request == PTRACE_PEEKUSR)
                val = *reg_addr;
            else {
#if 1
                *reg_addr = data;
#else
                /* MS potential problem on WB system
                 * Be aware that reg_addr is virtual address
                 * virt_to_phys conversion is necessary.
                 * This could be sensible solution.
                 */
                u32 paddr = virt_to_phys((u32)reg_addr);
                invalidate_icache_range(paddr, paddr + 4);
                *reg_addr = data;
                flush_dcache_range(paddr, paddr + 4);
#endif
            }
        } else
            rval = -EIO;

        if (rval == 0 && request == PTRACE_PEEKUSR)
            rval = put_user(val, (unsigned long __user *)data);
        break;
    default:
        rval = ptrace_request(child, request, addr, data);
    }
    return rval;
}

asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
{
    long ret = 0;

    secure_computing_strict(regs->r12);

    if (test_thread_flag(TIF_SYSCALL_TRACE) &&
        tracehook_report_syscall_entry(regs))
        /*
         * Tracing decided this syscall should not happen.
         * We'll return a bogus call number to get an ENOSYS
         * error, but leave the original number in regs->regs[0].
         */
        ret = -1L;

    audit_syscall_entry(EM_MICROBLAZE, regs->r12, regs->r5, regs->r6,
                regs->r7, regs->r8);

    return ret ?: regs->r12;
}

asmlinkage void do_syscall_trace_leave(struct pt_regs *regs)
{
    int step;

    audit_syscall_exit(regs);

    step = test_thread_flag(TIF_SINGLESTEP);
    if (step || test_thread_flag(TIF_SYSCALL_TRACE))
        tracehook_report_syscall_exit(regs, step);
}

#if 0
static asmlinkage void syscall_trace(void)
{
    if (!test_thread_flag(TIF_SYSCALL_TRACE))
        return;
    if (!(current->ptrace & PT_PTRACED))
        return;
    /* The 0x80 provides a way for the tracing parent to distinguish
     between a syscall stop and SIGTRAP delivery */
    ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
                ? 0x80 : 0));
    /*
     * this isn't the same as continuing with a signal, but it will do
     * for normal use. strace only continues with a signal if the
     * stopping signal is not SIGTRAP. -brl
     */
    if (current->exit_code) {
        send_sig(current->exit_code, current, 1);
        current->exit_code = 0;
    }
}
#endif

void ptrace_disable(struct task_struct *child)
{
    /* nothing to do */
}