[PATCH] kdump: Documentation for Kdump
This patch contains the documentation for the kexec based crash dump tool.
Quick kdump-howto
================================================================
1) Download and build kexec-tools.
2) Download and build the latest kexec/kdump (-mm) kernel patchset.
Two kernels need to be built in order to get this feature working.
A) First kernel:
a) Enable "kexec system call" feature:
CONFIG_KEXEC=y
b) Physical load address (use default):
CONFIG_PHYSICAL_START=0x100000
c) Enable "sysfs file system support":
CONFIG_SYSFS=y
d) Boot into first kernel with the command line parameter "crashkernel=Y@X":
For example: "crashkernel=64M@16M".
B) Second kernel:
a) Enable "kernel crash dumps" feature:
CONFIG_CRASH_DUMP=y
b) Physical load addreess, use same load address as X in "crashkernel"
kernel parameter in d) above, e.g., 16 MB or 0x1000000.
CONFIG_PHYSICAL_START=0x1000000
c) Enable "/proc/vmcore support" (Optional, in Pseudo filesystems).
CONFIG_PROC_VMCORE=y
3) Boot into the first kernel.
4) Load the second kernel to be booted using:
kexec -p <second-kernel> --crash-dump --args-linux --append="root=<root-dev>
maxcpus=1 init 1"
5) System reboots into the second kernel when a panic occurs. A module can be
written to force the panic, for testing purposes.
6) See Documentation/kdump.txt for how to read the first kernel's
memory image and how to analyze it.
Signed-off-by: Hariprasad Nellitheertha <hari@in.ibm.com>
Signed-off-by: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: randy_dunlap <rdunlap@xenotime.net>
Signed-off-by: Maneesh Soni <maneesh@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/Documentation/kdump/gdbmacros.txt b/Documentation/kdump/gdbmacros.txt
new file mode 100644
index 0000000..bc1b9eb
--- /dev/null
+++ b/Documentation/kdump/gdbmacros.txt
@@ -0,0 +1,179 @@
+#
+# 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 <alexn@telia.com>
+# V Srivatsa <vatsa@in.ibm.com>
+# Maneesh Soni <maneesh@in.ibm.com>
+#
+
+define bttnobp
+ set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+ set $pid_off=((size_t)&((struct task_struct *)0)->pids[1].pid_list.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
+ printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
+ printf "===================\n"
+ set var $stackp = $next_t.thread.esp
+ set var $stack_top = ($stackp & ~4095) + 4096
+
+ while ($stackp < $stack_top)
+ if (*($stackp) > _stext && *($stackp) < _sinittext)
+ info symbol *($stackp)
+ end
+ set $stackp += 4
+ end
+ set $next_th=(((char *)$next_t->pids[1].pid_list.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.esp
+ set var $stack_top = ($stackp & ~4095) + 4096
+
+ while ($stackp < $stack_top)
+ if (*($stackp) > _stext && *($stackp) < _sinittext)
+ info symbol *($stackp)
+ end
+ set $stackp += 4
+ end
+ set $next_th=(((char *)$next_th->pids[1].pid_list.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 btt
+ set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+ set $pid_off=((size_t)&((struct task_struct *)0)->pids[1].pid_list.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
+ printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
+ printf "===================\n"
+ set var $stackp = $next_t.thread.esp
+ set var $stack_top = ($stackp & ~4095) + 4096
+ set var $stack_bot = ($stackp & ~4095)
+
+ set $stackp = *($stackp)
+ while (($stackp < $stack_top) && ($stackp > $stack_bot))
+ set var $addr = *($stackp + 4)
+ info symbol $addr
+ set $stackp = *($stackp)
+ end
+
+ set $next_th=(((char *)$next_t->pids[1].pid_list.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.esp
+ set var $stack_top = ($stackp & ~4095) + 4096
+ set var $stack_bot = ($stackp & ~4095)
+
+ set $stackp = *($stackp)
+ while (($stackp < $stack_top) && ($stackp > $stack_bot))
+ set var $addr = *($stackp + 4)
+ info symbol $addr
+ set $stackp = *($stackp)
+ end
+ set $next_th=(((char *)$next_th->pids[1].pid_list.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)->pids[1].pid_list.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->pids[1].pid_list.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->pids[1].pid_list.next) - $pid_off)
+ end
+ set $next_t=(char *)($next_t->tasks.next) - $tasks_off
+ end
+
+ printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm
+ printf "===================\n"
+ set var $stackp = $pid_task.thread.esp
+ set var $stack_top = ($stackp & ~4095) + 4096
+ set var $stack_bot = ($stackp & ~4095)
+
+ set $stackp = *($stackp)
+ while (($stackp < $stack_top) && ($stackp > $stack_bot))
+ set var $addr = *($stackp + 4)
+ info symbol $addr
+ set $stackp = *($stackp)
+ end
+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)->pids[1].pid_list.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->pids[1].pid_list.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->pids[1].pid_list.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
+ addresthe kernel paniced.
+end