fnrec.c

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/*
 * Copyright (C) 2010 Stefan Hajnoczi <stefanha@gmail.com>.
 *
 * 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 any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ipxe/init.h>
#include <ipxe/uaccess.h>
#include <ipxe/io.h>

/** @file
 *
 * Function trace recorder for crash and hang debugging
 *
 */

/** Constant for identifying valid trace buffers */
#define FNREC_MAGIC ( 'f' << 24 | 'n' << 16 | 'r' << 8 | 'e' )

/** Number of trace buffer entries */
#define FNREC_NUM_ENTRIES 4096

/** Trace buffer physical address
 *
 * Fixed at 17MB
 */
#define FNREC_PHYS_ADDRESS ( 17 * 1024 * 1024 )

/** A trace buffer entry */
struct fnrec_entry {
        /** Called function address */
        void *called_fn;
        /** Call site */
        void *call_site;
        /** Entry count */
        uint16_t entry_count;
        /** Exit count */
        uint16_t exit_count;
        /** Checksum */
        unsigned long checksum;
};

/** A trace buffer */
struct fnrec_buffer {
        /** Constant for identifying valid trace buffers */
        uint32_t magic;

        /** Next trace buffer entry to fill */
        unsigned int idx;

        /** Trace buffer */
        struct fnrec_entry data[FNREC_NUM_ENTRIES]
                __attribute__ (( aligned ( 64 ) ));
};

/** The trace buffer */
static struct fnrec_buffer *fnrec_buffer;

/**
 * Test whether the trace buffer is valid
 *
 * @ret is_valid        Buffer is valid
 */
static int fnrec_is_valid ( void ) {
        return ( fnrec_buffer && ( fnrec_buffer->magic == FNREC_MAGIC ) );
}

/**
 * Invalidate the trace buffer
 *
 */
static void fnrec_invalidate ( void ) {
        fnrec_buffer->magic = 0;
}

/**
 * Reset the trace buffer and clear entries
 */
static void fnrec_reset ( void ) {
        memset ( fnrec_buffer, 0, sizeof ( *fnrec_buffer ) );
        fnrec_buffer->magic = FNREC_MAGIC;
}

/**
 * Append an entry to the trace buffer
 *
 * @v called_fn         Called function
 * @v call_site         Call site
 * @ret entry           Trace buffer entry
 */
static struct fnrec_entry * fnrec_append ( void *called_fn, void *call_site ) {
        struct fnrec_entry *entry;

        /* Re-use existing entry, if possible */
        entry = &fnrec_buffer->data[ fnrec_buffer->idx ];
        if ( ( entry->called_fn == called_fn ) &&
             ( entry->call_site == call_site ) &&
             ( entry->entry_count >= entry->exit_count ) ) {
                return entry;
        }

        /* Otherwise, create a new entry */
        fnrec_buffer->idx = ( ( fnrec_buffer->idx + 1 ) % FNREC_NUM_ENTRIES );
        entry = &fnrec_buffer->data[ fnrec_buffer->idx ];
        entry->called_fn = called_fn;
        entry->call_site = call_site;
        entry->entry_count = 0;
        entry->exit_count = 0;
        entry->checksum = ( ( ( unsigned long ) called_fn ) ^
                            ( ( unsigned long ) call_site ) );
        return entry;
}

/**
 * Print the contents of the trace buffer in chronological order
 */
static void fnrec_dump ( void ) {
        struct fnrec_entry *entry;
        unsigned int i;
        unsigned int idx;
        unsigned long checksum;

        printf ( "fnrec buffer dump:\n" );
        for ( i = 1 ; i <= FNREC_NUM_ENTRIES ; i++ ) {
                idx = ( ( fnrec_buffer->idx + i ) % FNREC_NUM_ENTRIES );
                entry = &fnrec_buffer->data[idx];
                if ( ( entry->entry_count == 0 ) && ( entry->exit_count == 0 ) )
                        continue;
                checksum = ( ( ( ( unsigned long ) entry->called_fn ) ^
                               ( ( unsigned long ) entry->call_site ) ) +
                             entry->entry_count + entry->exit_count );
                printf ( "%p %p %d %d", entry->called_fn, entry->call_site,
                         entry->entry_count, entry->exit_count );
                if ( entry->checksum != checksum ) {
                        printf ( " (checksum wrong at phys %08lx)",
                                 virt_to_phys ( entry ) );
                }
                printf ( "\n");
        }
}

/**
 * Function tracer initialisation function
 */
static void fnrec_init ( void ) {

        fnrec_buffer = phys_to_virt ( FNREC_PHYS_ADDRESS );
        if ( fnrec_is_valid() ) {
                fnrec_invalidate();
                fnrec_dump();
        } else {
                printf ( "fnrec buffer not found\n" );
        }
        fnrec_reset();
}

struct init_fn fnrec_init_fn __init_fn ( INIT_NORMAL ) = {
        .initialise = fnrec_init,
};

/*
 * These functions are called from every C function.  The compiler inserts
 * these calls when -finstrument-functions is used.
 */
void __cyg_profile_func_enter ( void *called_fn, void *call_site ) {
        struct fnrec_entry *entry;

        if ( fnrec_is_valid() ) {
                entry = fnrec_append ( called_fn, call_site );
                entry->entry_count++;
                entry->checksum++;
                mb();
        }
}

void __cyg_profile_func_exit ( void *called_fn, void *call_site ) {
        struct fnrec_entry *entry;

        if ( fnrec_is_valid() ) {
                entry = fnrec_append ( called_fn, call_site );
                entry->exit_count++;
                entry->checksum++;
                mb();
        }
}