#
# This file contains a few gdb macros (user defined commands) to extract
# useful information from kernel crashdump (kdump) like stack traces of
# all the processes or a particular process and trapinfo.
#
# These macros can be used by copying this file in .gdbinit (put in home
# directory or current directory) or by invoking gdb command with
# --command=<command-file-name> option
#
# Credits:
# Alexander Nyberg <[email protected]>
# V Srivatsa <[email protected]>
# Maneesh Soni <[email protected]>
#
define bttnobp
set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
set $init_t=&init_task
set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
set var $stacksize = sizeof(union thread_union)
while ($next_t != $init_t)
set $next_t=(struct task_struct *)$next_t
printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
printf "===================\n"
set var $stackp = $next_t.thread.sp
set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
while ($stackp < $stack_top)
if (*($stackp) > _stext && *($stackp) < _sinittext)
info symbol *($stackp)
end
set $stackp += 4
end
set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
while ($next_th != $next_t)
set $next_th=(struct task_struct *)$next_th
printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
printf "===================\n"
set var $stackp = $next_t.thread.sp
set var $stack_top = ($stackp & ~($stacksize - 1)) + stacksize
while ($stackp < $stack_top)
if (*($stackp) > _stext && *($stackp) < _sinittext)
info symbol *($stackp)
end
set $stackp += 4
end
set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
end
set $next_t=(char *)($next_t->tasks.next) - $tasks_off
end
end
document bttnobp
dump all thread stack traces on a kernel compiled with !CONFIG_FRAME_POINTER
end
define btthreadstack
set var $pid_task = $arg0
printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm
printf "task struct: "
print $pid_task
printf "===================\n"
set var $stackp = $pid_task.thread.sp
set var $stacksize = sizeof(union thread_union)
set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
set var $stack_bot = ($stackp & ~($stacksize - 1))
set $stackp = *((unsigned long *) $stackp)
while (($stackp < $stack_top) && ($stackp > $stack_bot))
set var $addr = *(((unsigned long *) $stackp) + 1)
info symbol $addr
set $stackp = *((unsigned long *) $stackp)
end
end
document btthreadstack
dump a thread stack using the given task structure pointer
end
define btt
set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
set $init_t=&init_task
set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
while ($next_t != $init_t)
set $next_t=(struct task_struct *)$next_t
btthreadstack $next_t
set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
while ($next_th != $next_t)
set $next_th=(struct task_struct *)$next_th
btthreadstack $next_th
set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
end
set $next_t=(char *)($next_t->tasks.next) - $tasks_off
end
end
document btt
dump all thread stack traces on a kernel compiled with CONFIG_FRAME_POINTER
end
define btpid
set var $pid = $arg0
set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
set $init_t=&init_task
set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
set var $pid_task = 0
while ($next_t != $init_t)
set $next_t=(struct task_struct *)$next_t
if ($next_t.pid == $pid)
set $pid_task = $next_t
end
set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
while ($next_th != $next_t)
set $next_th=(struct task_struct *)$next_th
if ($next_th.pid == $pid)
set $pid_task = $next_th
end
set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
end
set $next_t=(char *)($next_t->tasks.next) - $tasks_off
end
btthreadstack $pid_task
end
document btpid
backtrace of pid
end
define trapinfo
set var $pid = $arg0
set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
set $init_t=&init_task
set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
set var $pid_task = 0
while ($next_t != $init_t)
set $next_t=(struct task_struct *)$next_t
if ($next_t.pid == $pid)
set $pid_task = $next_t
end
set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
while ($next_th != $next_t)
set $next_th=(struct task_struct *)$next_th
if ($next_th.pid == $pid)
set $pid_task = $next_th
end
set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
end
set $next_t=(char *)($next_t->tasks.next) - $tasks_off
end
printf "Trapno %ld, cr2 0x%lx, error_code %ld\n", $pid_task.thread.trap_no, \
$pid_task.thread.cr2, $pid_task.thread.error_code
end
document trapinfo
Run info threads and lookup pid of thread #1
'trapinfo <pid>' will tell you by which trap & possibly
address the kernel panicked.
end
define dump_record
set var $desc = $arg0
set var $info = $arg1
if ($argc > 2)
set var $prev_flags = $arg2
else
set var $prev_flags = 0
end
set var $prefix = 1
set var $newline = 1
set var $begin = $desc->text_blk_lpos.begin % (1U << prb->text_data_ring.size_bits)
set var $next = $desc->text_blk_lpos.next % (1U << prb->text_data_ring.size_bits)
# handle data-less record
if ($begin & 1)
set var $text_len = 0
set var $log = ""
else
# handle wrapping data block
if ($begin > $next)
set var $begin = 0
end
# skip over descriptor id
set var $begin = $begin + sizeof(long)
# handle truncated message
if ($next - $begin < $info->text_len)
set var $text_len = $next - $begin
else
set var $text_len = $info->text_len
end
set var $log = &prb->text_data_ring.data[$begin]
end
# prev & LOG_CONT && !(info->flags & LOG_PREIX)
if (($prev_flags & 8) && !($info->flags & 4))
set var $prefix = 0
end
# info->flags & LOG_CONT
if ($info->flags & 8)
# (prev & LOG_CONT && !(prev & LOG_NEWLINE))
if (($prev_flags & 8) && !($prev_flags & 2))
set var $prefix = 0
end
# (!(info->flags & LOG_NEWLINE))
if (!($info->flags & 2))
set var $newline = 0
end
end
if ($prefix)
printf "[%5lu.%06lu] ", $info->ts_nsec / 1000000000, $info->ts_nsec % 1000000000
end
if ($text_len)
eval "printf \"%%%d.%ds\", $log", $text_len, $text_len
end
if ($newline)
printf "\n"
end
# handle dictionary data
set var $dict = &$info->dev_info.subsystem[0]
set var $dict_len = sizeof($info->dev_info.subsystem)
if ($dict[0] != '\0')
printf " SUBSYSTEM="
set var $idx = 0
while ($idx < $dict_len)
set var $c = $dict[$idx]
if ($c == '\0')
loop_break
else
if ($c < ' ' || $c >= 127 || $c == '\\')
printf "\\x%02x", $c
else
printf "%c", $c
end
end
set var $idx = $idx + 1
end
printf "\n"
end
set var $dict = &$info->dev_info.device[0]
set var $dict_len = sizeof($info->dev_info.device)
if ($dict[0] != '\0')
printf " DEVICE="
set var $idx = 0
while ($idx < $dict_len)
set var $c = $dict[$idx]
if ($c == '\0')
loop_break
else
if ($c < ' ' || $c >= 127 || $c == '\\')
printf "\\x%02x", $c
else
printf "%c", $c
end
end
set var $idx = $idx + 1
end
printf "\n"
end
end
document dump_record
Dump a single record. The first parameter is the descriptor,
the second parameter is the info, the third parameter is
optional and specifies the previous record's flags, used for
properly formatting continued lines.
end
define dmesg
# definitions from kernel/printk/printk_ringbuffer.h
set var $desc_committed = 1
set var $desc_finalized = 2
set var $desc_sv_bits = sizeof(long) * 8
set var $desc_flags_shift = $desc_sv_bits - 2
set var $desc_flags_mask = 3 << $desc_flags_shift
set var $id_mask = ~$desc_flags_mask
set var $desc_count = 1U << prb->desc_ring.count_bits
set var $prev_flags = 0
set var $id = prb->desc_ring.tail_id.counter
set var $end_id = prb->desc_ring.head_id.counter
while (1)
set var $desc = &prb->desc_ring.descs[$id % $desc_count]
set var $info = &prb->desc_ring.infos[$id % $desc_count]
# skip non-committed record
set var $state = 3 & ($desc->state_var.counter >> $desc_flags_shift)
if ($state == $desc_committed || $state == $desc_finalized)
dump_record $desc $info $prev_flags
set var $prev_flags = $info->flags
end
if ($id == $end_id)
loop_break
end
set var $id = ($id + 1) & $id_mask
end
end
document dmesg
print the kernel ring buffer
end
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