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[fnrec] Enhance function recording
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Enhance the information collected by the function recorder to include
the call site and entry/exit counts.  This allows fnrec.pl to produce
a call tree such as:

    step (from core/getkey.c:46 = 0x17e90) {
      ref_increment (from core/process.c:93 = 0x73ec) { }
      net_step (from core/process.c:96 = 0x73f1) {
        net_poll (from net/netdevice.c:741 = 0xbce6) {
          netdev_poll (from net/netdevice.c:700 = 0xbc58) { }
          netdev_rx_dequeue (from net/netdevice.c:709 = 0xbc65) { }
        }
      }
      ref_decrement (from core/process.c:96 = 0x73f9) { }
    }

Note that inlined functions are reported, confusingly, as extra calls
to the *containing* function.  Minimise this confusion by adding the
attribute "no_instrument_function" to all functions declared as
inline.  (Static functions that have been inlined autonomously by gcc
will still be problematic, but these are far fewer in number.)

Signed-off-by: Michael Brown <mcb30@ipxe.org>
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@mcb30
mcb30 committed Dec 9, 2010
1 parent f8a82c7 commit ea0fcb9
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Showing 4 changed files with 265 additions and 71 deletions.
146 changes: 107 additions & 39 deletions src/core/fnrec.c
View file
Expand Up @@ -23,19 +23,38 @@ FILE_LICENCE ( GPL2_OR_LATER );
#include <string.h>
#include <ipxe/init.h>
#include <ipxe/uaccess.h>
#include <ipxe/io.h>

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

enum {
/** Constant for identifying valid trace buffers */
fnrec_magic = 'f' << 24 | 'n' << 16 | 'r' << 8 | 'e',
/** 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 length */
fnrec_buffer_length = 4096 / sizeof ( unsigned long ),
/** 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 */
Expand All @@ -44,10 +63,11 @@ struct fnrec_buffer {
uint32_t magic;

/** Next trace buffer entry to fill */
uint32_t idx;
unsigned int idx;

/** Function address trace buffer */
unsigned long data[fnrec_buffer_length];
/** Trace buffer */
struct fnrec_entry data[FNREC_NUM_ENTRIES]
__attribute__ (( aligned ( 64 ) ));
};

/** The trace buffer */
Expand All @@ -59,61 +79,95 @@ static struct fnrec_buffer *fnrec_buffer;
* @ret is_valid Buffer is valid
*/
static int fnrec_is_valid ( void ) {
return fnrec_buffer && fnrec_buffer->magic == fnrec_magic;
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;
fnrec_buffer->magic = FNREC_MAGIC;
}

/**
* Write a value to the end of the buffer if it is not a repetition
* Append an entry to the trace buffer
*
* @v l Value to append
* @v called_fn Called function
* @v call_site Call site
* @ret entry Trace buffer entry
*/
static void fnrec_append_unique ( unsigned long l ) {
static unsigned long lastval;
uint32_t idx = fnrec_buffer->idx;

/* Avoid recording the same value repeatedly */
if ( l == lastval )
return;
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;
}

fnrec_buffer->data[idx] = l;
fnrec_buffer->idx = ( idx + 1 ) % fnrec_buffer_length;
lastval = l;
/* 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 ) {
size_t i;

if ( !fnrec_is_valid() ) {
printf ( "fnrec buffer not found\n" );
return;
}
struct fnrec_entry *entry;
unsigned int i;
unsigned int idx;
unsigned long checksum;

printf ( "fnrec buffer dump:\n" );
for ( i = 0; i < fnrec_buffer_length; i++ ) {
unsigned long l = fnrec_buffer->data[
( fnrec_buffer->idx + i ) % fnrec_buffer_length];
printf ( "%08lx%c", l, i % 8 == 7 ? '\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 ) {
/* Hardcoded to 17 MB */
fnrec_buffer = phys_to_virt ( 17 * 1024 * 1024 );
fnrec_dump();

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();
}

Expand All @@ -125,10 +179,24 @@ struct init_fn fnrec_init_fn __init_fn ( INIT_NORMAL ) = {
* 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 __unused ) {
if ( fnrec_is_valid() )
fnrec_append_unique ( ( unsigned long ) called_fn );
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 __unused, void *call_site __unused ) {
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();
}
}
13 changes: 13 additions & 0 deletions src/include/compiler.h
View file
Expand Up @@ -537,6 +537,19 @@ int __debug_disable;
/** Declare a function to be always inline */
#define __always_inline __attribute__ (( always_inline ))

/* Force all inline functions to not be instrumented
*
* This is required to cope with what seems to be a long-standing gcc
* bug, in which -finstrument-functions will cause instances of
* inlined functions to be reported as further calls to the
* *containing* function. This makes instrumentation very difficult
* to use.
*
* Work around this problem by adding the no_instrument_function
* attribute to all inlined functions.
*/
#define inline inline __attribute__ (( no_instrument_function ))

/**
* Shared data.
*
Expand Down
145 changes: 145 additions & 0 deletions src/util/fnrec.pl
View file
@@ -0,0 +1,145 @@
#!/usr/bin/perl -w
#
# Copyright (C) 2010 Michael Brown <mbrown@fensystems.co.uk>.
#
# 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., 675 Mass Ave, Cambridge, MA 02139, USA.

=head1 NAME
fnrec.pl
=head1 SYNOPSIS
fnrec.pl [options] bin/image.xxx < logfile
Decode a function trace produced by building with FNREC=1
Options:
-m,--max-depth=N Set maximum displayed function depth
=cut

use IPC::Open2;
use Getopt::Long;
use Pod::Usage;
use strict;
use warnings;

use constant MAX_OPEN_BRACE => 10;
use constant MAX_COMMON_BRACE => 3;
use constant MAX_CLOSE_BRACE => 10;

# Parse command-line options
my $max_depth = 16;
Getopt::Long::Configure ( 'bundling', 'auto_abbrev' );
GetOptions (
'help|h' => sub { pod2usage ( 1 ); },
'max-depth|m=i' => sub { shift; $max_depth = shift; },
) or die "Could not parse command-line options\n";
pod2usage ( 1 ) unless @ARGV == 1;
my $image = shift;
my $elf = $image.".tmp";
die "ELF file ".$elf." not found\n" unless -e $elf;

# Start up addr2line
my $addr2line_pid = open2 ( my $addr2line_out, my $addr2line_in,
"addr2line", "-f", "-e", $elf )
or die "Could not start addr2line: $!\n";

# Translate address using addr2line
sub addr2line {
my $address = shift;

print $addr2line_in $address."\n";
chomp ( my $name = <$addr2line_out> );
chomp ( my $file_line = <$addr2line_out> );
( my $file, my $line ) = ( $file_line =~ /^(.*):(\d+)$/ );
$file =~ s/^.*\/src\///;
my $location = ( $line ? $file.":".$line." = ".$address : $address );
return ( $name, $location );
}

# Parse logfile
my $depth = 0;
my $depths = [];
while ( my $line = <> ) {
chomp $line;
$line =~ s/\r//g;
( my $called_fn, my $call_site, my $entry_count, my $exit_count ) =
( $line =~ /^(0x[0-9a-f]+)\s+(0x[0-9a-f]+)\s+([0-9]+)\s+([0-9]+)$/ )
or print $line."\n" and next;

( my $called_fn_name, undef ) = addr2line ( $called_fn );
( undef, my $call_site_location ) = addr2line ( $call_site );
$entry_count = ( $entry_count + 0 );
$exit_count = ( $exit_count + 0 );

if ( $entry_count >= $exit_count ) {
#
# Function entry
#
my $text = "";
$text .= $called_fn_name." (from ".$call_site_location.")";
if ( $exit_count <= MAX_COMMON_BRACE ) {
$text .= " { }" x $exit_count;
} else {
$text .= " { } x ".$exit_count;
}
$entry_count -= $exit_count;
if ( $entry_count <= MAX_OPEN_BRACE ) {
$text .= " {" x $entry_count;
} else {
$text .= " { x ".$entry_count;
}
my $indent = " " x $depth;
print $indent.$text."\n";
$depth += $entry_count;
$depth = $max_depth if ( $depth > $max_depth );
push @$depths, ( { called_fn => $called_fn, call_site => $call_site } ) x
( $depth - @$depths );
} else {
#
# Function exit
#
my $text = "";
if ( $entry_count <= MAX_COMMON_BRACE ) {
$text .= " { }" x $entry_count;
} else {
$text .= " { } x ".$entry_count;
}
$exit_count -= $entry_count;
if ( $exit_count <= MAX_CLOSE_BRACE ) {
$text .= " }" x $exit_count;
} else {
$text .= " } x ".$exit_count;
}
$depth -= $exit_count;
$depth = 0 if ( $depth < 0 );
if ( ( @$depths == 0 ) ||
( $depths->[$depth]->{called_fn} ne $called_fn ) ||
( $depths->[$depth]->{call_site} ne $call_site ) ) {
$text .= " (from ".$called_fn_name." to ".$call_site_location.")";
}
splice ( @$depths, $depth );
my $indent = " " x $depth;
print substr ( $indent.$text, 1 )."\n";
}
}

# Clean up addr2line
close $addr2line_in;
close $addr2line_out;
waitpid ( $addr2line_pid, 0 );

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