runtime/linux/itrace.c - systemtap

Global variables defined

Data types defined

Functions defined

Macros defined

Source code

/*
 * user space instruction tracing
 * Copyright (C) 2005, 2006, 2007, 2008, 2009 IBM Corp.
 * Copyright (C) 2009 Red Hat Inc.
 *
 * This file is part of systemtap, and is free software.  You can
 * redistribute it and/or modify it under the terms of the GNU General
 * Public License (GPL); either version 2, or (at your option) any
 * later version.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/rcupdate.h>
#include <linux/utrace.h>
#include "ptrace_compatibility.h"

/* PR10171: To avoid ia64 lockups, disable itrace on ia64. */
#if defined(__ia64__)
#error "Unsupported itrace architecture"
#endif

/* PR9974: Adapt to struct renaming. */
#ifdef UTRACE_API_VERSION
‌#define utrace_attached_engine utrace_engine
#endif

#include <asm/string.h>
#include "uprobes/uprobes.h"
#include "utrace_compatibility.h"

#ifndef put_task_struct
‌#define put_task_struct(t)    \
    BUG_ON(atomic_dec_and_test(&tsk->usage))
#endif

#ifdef CONFIG_PPC
‌struct bpt_info {
        unsigned long addr;
        unsigned int instr;
};

‌struct atomic_ss_info {
        int step_over_atomic;
        struct bpt_info end_bpt;
        struct bpt_info br_bpt;
};

static int handle_ppc_atomic_seq(struct task_struct *tsk, struct pt_regs *regs,
    struct atomic_ss_info *ss_info);
static void remove_atomic_ss_breakpoint (struct task_struct *tsk,
    struct bpt_info *bpt);
#endif

‌struct itrace_info {
    u32 step_flag;
    struct stap_itrace_probe *itrace_probe;
#ifdef CONFIG_PPC
    struct atomic_ss_info ppc_atomic_ss;
#endif
    struct task_struct *tsk;
    struct utrace_attached_engine *engine;
    struct list_head link;
};

‌static u32 debug = 0 /* 1 */;

static LIST_HEAD(usr_itrace_info);
‌static spinlock_t itrace_lock;
static struct itrace_info *create_itrace_info(
    struct task_struct *tsk, u32 step_flag,
    struct stap_itrace_probe *itrace_probe);


/* Note: __access_process_vm moved to access_process_vm.h */

#ifdef UTRACE_ORIG_VERSION
‌static u32 usr_itrace_report_quiesce(struct utrace_attached_engine *engine,
                    struct task_struct *tsk)
#else
#if defined(UTRACE_API_VERSION) && (UTRACE_API_VERSION >= 20091216)
static u32 usr_itrace_report_quiesce(u32 action,
                struct utrace_attached_engine *engine,
                unsigned long event)
#else
static u32 usr_itrace_report_quiesce(enum utrace_resume_action action,
                struct utrace_attached_engine *engine,
                struct task_struct *tsk,
                unsigned long event)
#endif
#endif
{
    int status;
    struct itrace_info *ui;

    rcu_read_lock();
    ui = rcu_dereference(engine->data);
    rcu_read_unlock();
    WARN_ON(!ui);

#ifdef UTRACE_ORIG_VERSION
    return (ui->step_flag | UTRACE_ACTION_NEWSTATE);
#else
    return (event == 0 ? ui->step_flag : UTRACE_RESUME);
#endif
}


#ifdef UTRACE_ORIG_VERSION
‌static u32 usr_itrace_report_signal(
                 struct utrace_attached_engine *engine,
                 struct task_struct *tsk,
                 struct pt_regs *regs,
                             u32 action, siginfo_t *info,
                 const struct k_sigaction *orig_ka,
                 struct k_sigaction *return_ka)
#else
#if defined(UTRACE_API_VERSION) && (UTRACE_API_VERSION >= 20091216)
static u32 usr_itrace_report_signal(u32 action,
                 struct utrace_attached_engine *engine,
                 struct pt_regs *regs,
                 siginfo_t *info,
                 const struct k_sigaction *orig_ka,
                 struct k_sigaction *return_ka)
#else
static u32 usr_itrace_report_signal(u32 action,
                 struct utrace_attached_engine *engine,
                 struct task_struct *tsk,
                 struct pt_regs *regs,
                 siginfo_t *info,
                 const struct k_sigaction *orig_ka,
                 struct k_sigaction *return_ka)
#endif
#endif
{
#if defined(UTRACE_API_VERSION) && (UTRACE_API_VERSION >= 20091216)
    struct task_struct *tsk = current;
#endif
    struct itrace_info *ui;
    u32 return_flags;
    unsigned long data = 0;
#ifdef CONFIG_PPC
    data = mfspr(SPRN_SDAR);
#endif

    rcu_read_lock();
    ui = rcu_dereference(engine->data);
    rcu_read_unlock();
    WARN_ON(!ui);

#if defined(UTRACE_ORIG_VERSION)
        if (info->si_signo != SIGTRAP || !ui)
      return UTRACE_RESUME;
#else
    if (utrace_signal_action(action) == UTRACE_SIGNAL_HANDLER ||
            utrace_signal_action(action) == UTRACE_SIGNAL_REPORT ||
        info->si_signo != SIGTRAP || !ui)
      return UTRACE_RESUME | utrace_signal_action(action);
#endif

#if defined(UTRACE_ORIG_VERSION) && defined(CONFIG_PPC)
    /* Because of a ppc utrace bug, we need to stop the task here.
       usr_itrace_report_quiesce() will continue stepping the task. */
    return_flags = UTRACE_SIGNAL_IGN | UTRACE_STOP | UTRACE_ACTION_NEWSTATE;
#else
    /* normal case: continue stepping */
    return_flags =  ui->step_flag | UTRACE_SIGNAL_IGN;
#endif
#ifdef CONFIG_PPC
    if (ui->ppc_atomic_ss.step_over_atomic) {
        remove_atomic_ss_breakpoint(tsk, &ui->ppc_atomic_ss.end_bpt);
        if (ui->ppc_atomic_ss.br_bpt.addr)
            remove_atomic_ss_breakpoint(tsk,
                &ui->ppc_atomic_ss.br_bpt);
        ui->ppc_atomic_ss.step_over_atomic = 0;
    }

    if (handle_ppc_atomic_seq(tsk, regs, &ui->ppc_atomic_ss))
        return_flags = UTRACE_RESUME | UTRACE_SIGNAL_IGN;
#endif

    enter_itrace_probe(ui->itrace_probe, regs, (void *)&data);

    return return_flags;
}



#ifdef UTRACE_ORIG_VERSION
‌static u32 usr_itrace_report_clone(
        struct utrace_attached_engine *engine,
        struct task_struct *parent,
                unsigned long clone_flags,
        struct task_struct *child)
#else
#if defined(UTRACE_API_VERSION) && (UTRACE_API_VERSION >= 20091216)
static u32 usr_itrace_report_clone(u32 action,
        struct utrace_attached_engine *engine,
        unsigned long clone_flags,
        struct task_struct *child)
#else
static u32 usr_itrace_report_clone(enum utrace_resume_action action,
        struct utrace_attached_engine *engine,
        struct task_struct *parent, unsigned long clone_flags,
        struct task_struct *child)
#endif
#endif
{
    return UTRACE_RESUME;
}

#ifdef UTRACE_ORIG_VERSION
‌static u32 usr_itrace_report_death(struct utrace_attached_engine *e,
                                   struct task_struct *tsk)
#else
#if defined(UTRACE_API_VERSION) && (UTRACE_API_VERSION >= 20091216)
static u32 usr_itrace_report_death(struct utrace_attached_engine *e,
    bool group_dead, int signal)
#else
static u32 usr_itrace_report_death(struct utrace_attached_engine *e,
    struct task_struct *tsk, bool group_dead, int signal)
#endif
#endif
{
    struct itrace_info *ui;
    rcu_read_lock();
    ui = rcu_dereference(e->data);
    rcu_read_unlock();
    WARN_ON(!ui);

    return (UTRACE_DETACH);
}

‌static const struct utrace_engine_ops utrace_ops =
{
    .report_quiesce = usr_itrace_report_quiesce,
    .report_signal = usr_itrace_report_signal,
    .report_clone = usr_itrace_report_clone,
    .report_death = usr_itrace_report_death
};


‌static struct itrace_info *create_itrace_info(
    struct task_struct *tsk, u32 step_flag,
    struct stap_itrace_probe *itrace_probe)
{
    struct itrace_info *ui;
    int status;

    if (debug)
        printk(KERN_INFO "create_itrace_info: tid=%d\n", tsk->pid);
    /* initialize ui */
    ui = _stp_kzalloc(sizeof(struct itrace_info));
    if (ui == NULL) {
        printk(KERN_ERR "%s:%d: Unable to allocate memory\n",
               __FUNCTION__, __LINE__);
        return NULL;
    }
    ui->tsk = tsk;
    ui->step_flag = step_flag;
    ui->itrace_probe = itrace_probe;
#ifdef CONFIG_PPC
    ui->ppc_atomic_ss.step_over_atomic = 0;
#endif
    INIT_LIST_HEAD(&ui->link);

    /* push ui onto usr_itrace_info */
    spin_lock(&itrace_lock);
    list_add(&ui->link, &usr_itrace_info);
    spin_unlock(&itrace_lock);

    /* attach a single stepping engine.  create_itrace_info is called
       under rcu read lock, so needs atomic.  */
    ui->engine = utrace_attach_task(ui->tsk,
                    (UTRACE_ATTACH_CREATE
                     | UTRACE_ATTACH_ATOMIC),
                    &utrace_ops, ui);
    if (IS_ERR(ui->engine)) {
        printk(KERN_ERR "utrace_attach returns %ld\n",
            PTR_ERR(ui->engine));
        return NULL;
    }
    status = utrace_set_events(tsk, ui->engine, ui->engine->flags |
        UTRACE_EVENT(QUIESCE) |
        UTRACE_EVENT(CLONE) | UTRACE_EVENT_SIGNAL_ALL |
        UTRACE_EVENT(DEATH));
    if (status < 0) {
        printk(KERN_ERR "utrace_attach returns %d\n", status);
        utrace_engine_put(ui->engine);
        return NULL;
    }

    status = utrace_control(tsk, ui->engine, UTRACE_STOP);
    if (status == 0) {
        status = utrace_control(tsk, ui->engine, step_flag);
        if (status < 0) {
            printk(KERN_ERR "utrace_control(%d) returns %d\n",
                step_flag, status);
            utrace_engine_put(ui->engine);
            return NULL;
        }
    }

    utrace_engine_put(ui->engine);
    return ui;
}

‌static struct itrace_info *find_itrace_info(struct task_struct *tsk)
{
    struct itrace_info *ui = NULL;

    spin_lock(&itrace_lock);
    list_for_each_entry(ui, &usr_itrace_info, link) {
        if (ui->tsk == tsk)
            goto done;
    }
    ui = NULL;
done:
    spin_unlock(&itrace_lock);
    return ui;
}


‌static int usr_itrace_init(int single_step, struct task_struct *tsk, struct stap_itrace_probe *p)
{
    struct itrace_info *ui;

    spin_lock_init(&itrace_lock);
    rcu_read_lock();
    if (tsk == NULL) {
        printk(KERN_ERR "usr_itrace_init: Invalid task\n");
        rcu_read_unlock();
        return 1;
    }

    get_task_struct(tsk);
    ui = create_itrace_info(tsk,
        (single_step ?
            UTRACE_SINGLESTEP : UTRACE_BLOCKSTEP), p);
    if (!ui)
        return 1;

    put_task_struct(tsk);
    rcu_read_unlock();

        if (debug)
        printk(KERN_INFO "usr_itrace_init: completed for tid = %d\n",
               tsk->pid);

    return 0;
}

‌void static remove_usr_itrace_info(struct itrace_info *ui)
{
    struct itrace_info *tmp;
    int status;

    if (!ui)
        return;

    if (debug)
        printk(KERN_INFO "remove_usr_itrace_info: tid=%d\n",
               (ui->tsk ? ui->tsk->pid : -1));

    if (ui->tsk && ui->engine) {
        status = utrace_control(ui->tsk, ui->engine, UTRACE_DETACH);
        if (status == -EINPROGRESS) {
            do {
                status = utrace_barrier(ui->tsk, ui->engine);
            } while (status == -ERESTARTSYS);
        }
        if (status < 0 && status != -ESRCH && status != -EALREADY)
            printk(KERN_ERR
                   "utrace_control(UTRACE_DETACH) returns %d\n",
                   status);
    }
    spin_lock(&itrace_lock);
    list_del(&ui->link);
    spin_unlock(&itrace_lock);
    _stp_kfree(ui);
}

‌void static cleanup_usr_itrace(void)
{
    struct itrace_info *tmp;
    struct itrace_info *ui;

    if (debug)
        printk(KERN_INFO "cleanup_usr_itrace called\n");

    list_for_each_entry_safe(ui, tmp, &usr_itrace_info, link) {
        remove_usr_itrace_info(ui);
    }
}


#ifdef CONFIG_PPC
‌#define PPC_INSTR_SIZE 4
‌#define TEXT_SEGMENT_BASE 1

/* Instruction masks used during single-stepping of atomic sequences.  */
‌#define LWARX_MASK 0xfc0007fe
‌#define LWARX_INSTR 0x7c000028
‌#define LDARX_INSTR 0x7c0000A8
‌#define STWCX_MASK 0xfc0007ff
‌#define STWCX_INSTR 0x7c00012d
‌#define STDCX_INSTR 0x7c0001ad
‌#define BC_MASK 0xfc000000
‌#define BC_INSTR 0x40000000
‌#define ATOMIC_SEQ_LENGTH 16
‌#define BPT_TRAP 0x7fe00008
‌#define INSTR_SZ sizeof(int)

‌static int get_instr(unsigned long addr, char *msg)
{
    unsigned int instr;

    if (copy_from_user(&instr, (const void __user *) addr,
            sizeof(instr))) {
        printk(KERN_ERR "get_instr failed: %s\n", msg);
        WARN_ON(1);
    }
    return instr;

}

‌static void insert_atomic_ss_breakpoint (struct task_struct *tsk,
    struct bpt_info *bpt)
{
    unsigned int bp_instr = BPT_TRAP;
    unsigned int cur_instr;

    cur_instr = get_instr(bpt->addr, "insert_atomic_ss_breakpoint");
    if (cur_instr != BPT_TRAP) {
        bpt->instr = cur_instr;
        WARN_ON(__access_process_vm(tsk, bpt->addr, &bp_instr, INSTR_SZ, 1) !=
            INSTR_SZ);
    }
}

‌static void remove_atomic_ss_breakpoint (struct task_struct *tsk,
    struct bpt_info *bpt)
{
    WARN_ON(__access_process_vm(tsk, bpt->addr, &bpt->instr, INSTR_SZ, 1) !=
        INSTR_SZ);
}

/* locate the branch destination.  Return -1 if not a branch.  */
static unsigned long
‌branch_dest (int opcode, int instr, struct pt_regs *regs, unsigned long pc)
{
    unsigned long dest;
    int immediate;
    int absolute;
    int ext_op;

    absolute = (int) ((instr >> 1) & 1);

    switch (opcode) {
    case 18:
        immediate = ((instr & ~3) << 6) >> 6;    /* br unconditional */
        if (absolute)
            dest = immediate;
        else
            dest = pc + immediate;
        break;

    case 16:
        immediate = ((instr & ~3) << 16) >> 16;    /* br conditional */
        if (absolute)
            dest = immediate;
        else
            dest = pc + immediate;
        break;

    case 19:
        ext_op = (instr >> 1) & 0x3ff;

        if (ext_op == 16) {
            /* br conditional register */
            dest = regs->link & ~3;
            /* FIX: we might be in a signal handler */
            WARN_ON(dest > 0);
        } else if (ext_op == 528) {
            /* br cond to ctr reg */
            dest = regs->ctr & ~3;

            /* for system call dest < TEXT_SEGMENT_BASE */
            if (dest < TEXT_SEGMENT_BASE)
                dest = regs->link & ~3;
        } else
            return -1;
        break;

    default:
        return -1;
    }
    return dest;
}

/* Checks for an atomic sequence of instructions beginning with a LWARX/LDARX
   instruction and ending with a STWCX/STDCX instruction.  If such a sequence
   is found, attempt to step through it.  A breakpoint is placed at the end of
   the sequence.  */

‌static int handle_ppc_atomic_seq(struct task_struct *tsk, struct pt_regs *regs,
    struct atomic_ss_info *ss_info)
{
    unsigned long ip = regs->nip;
    unsigned long start_addr;
    unsigned int instr;
    int got_stx = 0;
    int i;
    int ret;

    unsigned long br_dest; /* bpt at branch instr's destination */
    int bc_instr_count = 0; /* conditional branch instr count  */

    instr = get_instr(regs->nip, "handle_ppc_atomic_seq:1");
    /* Beginning of atomic sequence starts with lwarx/ldarx instr */
    if ((instr & LWARX_MASK) != LWARX_INSTR
        && (instr & LWARX_MASK) != LDARX_INSTR)
        return 0;

    start_addr = regs->nip;
    for (i = 0; i < ATOMIC_SEQ_LENGTH; ++i) {
        ip += INSTR_SZ;
        instr = get_instr(ip, "handle_ppc_atomic_seq:2");

        /* look for at most one conditional branch in the sequence
         * and put a bpt at it's destination address
         */
        if ((instr & BC_MASK) == BC_INSTR) {
            if (bc_instr_count >= 1)
                return 0; /* only handle a single branch */

            br_dest = branch_dest (BC_INSTR >> 26, instr, regs, ip);

            if (br_dest != -1 &&
                br_dest >= TEXT_SEGMENT_BASE) {
                ss_info->br_bpt.addr = br_dest;
                bc_instr_count++;
            }
        }

        if ((instr & STWCX_MASK) == STWCX_INSTR
            || (instr & STWCX_MASK) == STDCX_INSTR) {
            got_stx = 1;
            break;
        }
    }

    /* Atomic sequence ends with a stwcx/stdcx instr */
    if (!got_stx)
        return 0;

    ip += INSTR_SZ;
    instr = get_instr(ip, "handle_ppc_atomic_seq:3");
    if ((instr & BC_MASK) == BC_INSTR) {
        ip += INSTR_SZ;
        instr = get_instr(ip, "handle_ppc_atomic_seq:4");
    }

    /* Insert a breakpoint right after the end of the atomic sequence.  */
    ss_info->end_bpt.addr = ip;

    /* Check for duplicate bpts */
    if (bc_instr_count && (ss_info->br_bpt.addr >= start_addr &&
        ss_info->br_bpt.addr <= ss_info->end_bpt.addr))
        ss_info->br_bpt.addr = 0;

    insert_atomic_ss_breakpoint (tsk, &ss_info->end_bpt);
    if (ss_info->br_bpt.addr)
        insert_atomic_ss_breakpoint (tsk, &ss_info->br_bpt);

    ss_info->step_over_atomic = 1;
    return 1;
}
#endif