[Crash-utility] kmem command problem (bug of dump_mem_map_SPARSEMEM?)
Hi,
I used crash-4.0-3.18 and found a problem.
When I used kmem command to get information of
virtual address e000000105090000, which is page ptr,
segmentation fault occurred.
-----------------------------------------------------------------------
KERNEL: /usr/lib/debug/lib/modules/2.6.18-8.el5/vmlinux
DUMPFILE: /dev/mem
CPUS: 4
DATE: Tue Feb 6 15:53:25 2007
UPTIME: 01:12:05
LOAD AVERAGE: 0.55, 0.56, 0.30
TASKS: 185
NODENAME: build.fujitsu.com
RELEASE: 2.6.18-8.el5
VERSION: #1 SMP Fri Jan 26 14:16:09 EST 2007
MACHINE: ia64 (1600 Mhz)
MEMORY: 31.2 GB
PID: 16173
COMMAND: "crash"
TASK: e0000040b2660000 [THREAD_INFO: e0000040b2661040]
CPU: 1
STATE: TASK_RUNNING (ACTIVE)
crash> kmem -p | grep e000000105090000
e000000105090000 180000000 ------- ----- 0 600200080000
crash> kmem -p e000000105090000
Segmentation fault (core dumped)
-----------------------------------------------------------------------
This is a backtrace.
#0 0x40000000000faa20 in nr_to_section (nr=15032385540) at memory.c:11897
#1 0x40000000000fb360 in valid_section_nr (nr=15032385540) at memory.c:11966
#2 0x40000000000ab000 in dump_mem_map_SPARSEMEM (mi=0x60000fffffd88370)
at memory.c:3754
#3 0x40000000000b00c0 in dump_mem_map (mi=0x60000fffffd88370) at memory.c:4120
#4 0x40000000000a7b70 in cmd_kmem () at memory.c:3345
#5 0x400000000005ad20 in exec_command () at main.c:528
#6 0x400000000005a900 in main_loop () at main.c:487
It seems that there is a problem in dump_mem_map_SPARSEMEM.
Here is a part of it.
switch (mi->flags)
{
case ADDRESS_SPECIFIED:
switch (mi->memtype)
{
case KVADDR:
1) if (is_page_ptr(mi->spec_addr, NULL))
pg_spec = TRUE;
else {
if (kvtop(NULL, mi->spec_addr, &phys, 0)) {
2) mi->spec_addr = phys;
phys_spec = TRUE;
}
else
return;
}
break;
(snipped)
if (mi->flags & ADDRESS_SPECIFIED) {
3) ulong pfn = mi->spec_addr >> PAGESHIFT();
section_nr = pfn_to_section_nr(pfn);
}
4) if (!(section = valid_section_nr(section_nr))) {
1) e000000105090000 is a page pointer, so is_page_ptr returns TRUE.
2) mi->spec_addr is converted to physical addr here, but, this
code does not be executed in this case.
3) mi->spec_addr is converted to pfn, but mi->spec_addr has
virtual address in this case, so this conversion fails.
4) section_nr has invalid section number and it causes fault.
I have yet to find how to fix it.
Any idea?
Takao Indoh