Re: [Crash-utility] Kernel Crash Analysis on Android
by Shankar, AmarX
Hi Dave,
Thanks for your info regarding kexec tool.
I am unable to download kexec from below link.
http://www.kernel.org/pub/linux/kernel/people/horms/kexec-tools/kexec-too...
It says HTTP 404 Page Not Found.
Could you please guide me on this?
Thanks & Regards,
Amar Shankar
> On Wed, Mar 21, 2012 at 06:00:00PM +0000, Shankar, AmarX wrote:
>
> > I want to do kernel crash Analysis on Android Merrifield Target.
> >
> > Could someone please help me how to do it?
>
> Merrifield is pretty much similar than Medfield, e.g it has x86 core. So I
> guess you can follow the instructions how to setup kdump on x86 (see
> Documentation/kdump/kdump.txt) unless you already have that configured.
>
> crash should support this directly presuming you have vmlinux/vmcore files to
> feed it. You can configure crash to support x86 on x86_64 host by running:
>
> % make target=X86
> & make
>
> (or something along those lines).
Right -- just the first make command will suffice, i.e., when running
on an x86_64 host:
$ wget http://people.redhat.com/anderson/crash-6.0.4.tar.gz
$ tar xzf crash-6.0.4.tar.gz
...
$ cd crash-6.0.4
$ make target=X86
...
$ ./crash <path-to>/vmlinux <path-to>/vmcore
Dave
From: Shankar, AmarX
Sent: Wednesday, March 21, 2012 11:30 PM
To: 'crash-utility(a)redhat.com'
Subject: Kernel Crash Analysis on Android
Hi,
I want to do kernel crash Analysis on Android Merrifield Target.
Could someone please help me how to do it?
Thanks & Regards,
Amar Shankar
1 year
[PATCH] kmem, snap: iomem/ioport display and vmcore snapshot support
by HATAYAMA Daisuke
Some days ago I was in a situation that I had to convert vmcore in
kvmdump format into ELF since some extension module we have locally
can be used only on relatively old crash utility, around version 4,
but such old crash utility cannot handle kvmdump format.
To do the conversion in handy, I used snap command with some modifications
so that it tries to use iomem information in vmcore instead of host's
/proc/iomem. This patch is its cleaned-up version.
In this development, I naturally got down to also making an interface
for an access to resource objects, and so together with the snap
command's patch, I also extended kmem command for iomem/ioport
support. Actually:
kmem -r displays /proc/iomem
crash> kmem -r
00000000-0000ffff : reserved
00010000-0009dbff : System RAM
0009dc00-0009ffff : reserved
000c0000-000c7fff : Video ROM
...
and kmem -R displays /proc/ioport
crash> kmem -R
0000-001f : dma1
0020-0021 : pic1
0040-0043 : timer0
0050-0053 : timer1
...
Looking into old version of kernel source code back, resource structure
has been unchanged since linux-2.4.0. I borrowed the way of walking on
resouce tree in this patch from the lastest v3.3-rc series, but I
guess the logic is also applicable to old kernels. I expect Dave's
regression testsuite.
Also, there would be another command more sutable for iomem/ioport.
If necessay, I'll repost the patch.
---
HATAYAMA Daisuke (4):
Add vmcore snapshot support
Add kmem -r and -R options
Add dump iomem/ioport functions; a helper for resource objects
Add a helper function for iterating resource objects
defs.h | 9 ++++
extensions/snap.c | 54 ++++++++++++++++++++++-
help.c | 2 +
memory.c | 122 +++++++++++++++++++++++++++++++++++++++++++++++++++--
4 files changed, 180 insertions(+), 7 deletions(-)
--
Thanks.
HATAYAMA Daisuke
1 year
Re: [Crash-utility] question about phys_base
by Dave Anderson
----- Original Message -----
> >
> > OK, so then I don't understand what you mean by "may be the same"?
> >
> > You didn't answer my original question, but if I understand you correctly,
> > it would be impossible for the qemu host to create a PT_LOAD segment that
> > describes an x86_64 guest's __START_KERNEL_map region, because the host
> > doesn't know that what kind of kernel the guest is running.
>
> Yes. Even if the guest is linux, it is still impossible to do it. Because
> the guest maybe in the second kernel.
>
> qemu-dump walks all guest's page table and collect virtual address and
> physical address mapping. If the page is not used by guest, the virtual is set
> to 0. I create PT_LOAD according to such mapping. So if the guest is linux,
> there may be a PT_LOAD segment that describes __START_KERNEL_map region.
> But the information stored in PT_LOAD maybe for the second kernel. If crash
> uses it, crash will see the second kernel, not the first kernel.
Just to be clear -- what do you mean by the "second" kernel? Do you
mean that a guest kernel crashed guest, and did a kdump operation,
and that second kdump kernel failed somehow, and now you're trying
to do a "virsh dump" on the kdump kernel?
Dave
1 year
question about phys_base
by Wen Congyang
Hi, Dave
I am implementing a new dump command in the qemu. The vmcore's
format is elf(like kdump). And I try to provide phys_base in
the PT_LOAD. But if the os uses the first vcpu do kdump, the
value of phys_base is wrong.
I find a function x86_64_virt_phys_base() in crash's code.
Is it OK to call this function first? If the function
successes, we do not calculate phys_base according to PT_LOAD.
Thanks
Wen Congyang
1 year
[PATCH] runq: search current task's runqueue explicitly
by HATAYAMA Daisuke
Currently, runq sub-command doesn't consider CFS runqueue's current
task removed from CFS runqueue. Due to this, the remaining CFS
runqueus that follow the current task's is not displayed. This patch
fixes this by making runq sub-command search current task's runqueue
explicitly.
Note that CFS runqueue exists for each task group, and so does CFS
runqueue's current task, and the above search needs to be done
recursively.
Test
====
On vmcore I made 7 task groups:
root group --- A --- AA --- AAA
+ +- AAB
|
+- AB --- ABA
+- ABB
and then I ran three CPU bound tasks, which is exactly the same as
int main(void) { for (;;) continue; return 0; }
for each task group, including root group; so total 24 tasks. For
readability, I annotated each task name with its belonging group name.
For example, loop.ABA belongs to task group ABA.
Look at CPU0 collumn below. [before] lacks 8 tasks and [after]
successfully shows all tasks on the runqueue, which is identical to
the result of [sched debug] that is expected to ouput correct result.
I'll send this vmcore later.
[before]
crash> runq | cat
CPU 0 RUNQUEUE: ffff88000a215f80
CURRENT: PID: 28263 TASK: ffff880037aaa040 COMMAND: "loop.ABA"
RT PRIO_ARRAY: ffff88000a216098
[no tasks queued]
CFS RB_ROOT: ffff88000a216010
[120] PID: 28262 TASK: ffff880037cc40c0 COMMAND: "loop.ABA"
<cut>
[after]
crash_fix> runq
CPU 0 RUNQUEUE: ffff88000a215f80
CURRENT: PID: 28263 TASK: ffff880037aaa040 COMMAND: "loop.ABA"
RT PRIO_ARRAY: ffff88000a216098
[no tasks queued]
CFS RB_ROOT: ffff88000a216010
[120] PID: 28262 TASK: ffff880037cc40c0 COMMAND: "loop.ABA"
[120] PID: 28271 TASK: ffff8800787a8b40 COMMAND: "loop.ABB"
[120] PID: 28272 TASK: ffff880037afd580 COMMAND: "loop.ABB"
[120] PID: 28245 TASK: ffff8800785e8b00 COMMAND: "loop.AB"
[120] PID: 28246 TASK: ffff880078628ac0 COMMAND: "loop.AB"
[120] PID: 28241 TASK: ffff880078616b40 COMMAND: "loop.AA"
[120] PID: 28239 TASK: ffff8800785774c0 COMMAND: "loop.AA"
[120] PID: 28240 TASK: ffff880078617580 COMMAND: "loop.AA"
[120] PID: 28232 TASK: ffff880079b5d4c0 COMMAND: "loop.A"
<cut>
[sched debug]
crash> runq -d
CPU 0
[120] PID: 28232 TASK: ffff880079b5d4c0 COMMAND: "loop.A"
[120] PID: 28239 TASK: ffff8800785774c0 COMMAND: "loop.AA"
[120] PID: 28240 TASK: ffff880078617580 COMMAND: "loop.AA"
[120] PID: 28241 TASK: ffff880078616b40 COMMAND: "loop.AA"
[120] PID: 28245 TASK: ffff8800785e8b00 COMMAND: "loop.AB"
[120] PID: 28246 TASK: ffff880078628ac0 COMMAND: "loop.AB"
[120] PID: 28262 TASK: ffff880037cc40c0 COMMAND: "loop.ABA"
[120] PID: 28263 TASK: ffff880037aaa040 COMMAND: "loop.ABA"
[120] PID: 28271 TASK: ffff8800787a8b40 COMMAND: "loop.ABB"
[120] PID: 28272 TASK: ffff880037afd580 COMMAND: "loop.ABB"
<cut>
Diff stat
=========
defs.h | 1 +
task.c | 37 +++++++++++++++++--------------------
2 files changed, 18 insertions(+), 20 deletions(-)
Thanks.
HATAYAMA, Daisuke
1 year
[RFC] makedumpfile, crash: LZO compression support
by HATAYAMA Daisuke
Hello,
This is a RFC patch set that adds LZO compression support to
makedumpfile and crash utility. LZO is as good as in size but by far
better in speed than ZLIB, leading to reducing down time during
generation of crash dump and refiltering.
How to build:
1. Get LZO library, which is provided as lzo-devel package on recent
linux distributions, and is also available on author's website:
http://www.oberhumer.com/opensource/lzo/.
2. Apply the patch set to makedumpfile v1.4.0 and crash v6.0.0.
3. Build both using make. But for crash, do the following now:
$ make CFLAGS="-llzo2"
How to use:
I've newly used -l option for lzo compression in this patch. So for
example, do as follows:
$ makedumpfile -l vmcore dumpfile
$ crash vmlinux dumpfile
Request of configure-like feature for crash utility:
I would like configure-like feature on crash utility for users to
select wheather to add LZO feature actually or not in build-time,
that is: ./configure --enable-lzo or ./configure --disable-lzo.
The reason is that support staff often downloads and installs the
latest version of crash utility on machines where lzo library is not
provided.
Looking at the source code, it looks to me that crash does some kind
of configuration processing in a local manner, around configure.c,
and I guess it's difficult to use autoconf tools directly.
Or is there another better way?
Performance Comparison:
Sample Data
Ideally, I must have measured the performance for many enough
vmcores generated from machines that was actually running, but now
I don't have enough sample vmcores, I couldn't do so. So this
comparison doesn't answer question on I/O time improvement. This
is TODO for now.
Instead, I choosed worst and best cases regarding compression
ratio and speed only. Specifically, the former is /dev/urandom and
the latter is /dev/zero.
I get the sample data of 10MB, 100MB and 1GB by doing like this:
$ dd bs=4096 count=$((1024*1024*1024/4096)) if=/dev/urandom of=urandom.1GB
How to measure
Then I performed compression for each block, 4096 bytes, and
measured total compression time and output size. See attached
mycompress.c.
Result
See attached file result.txt.
Discussion
For both kinds of data, lzo's compression was considerably quicker
than zlib's. Compression ratio is about 37% for urandom data, and
about 8.5% for zero data. Actual situation of physical memory
would be in between the two cases, and so I guess average
compression time ratio is between 37% and 8.5%.
Although beyond the topic of this patch set, we can estimate worst
compression time on more data size since compression is performed
block size wise and the compression time increases
linearly. Estimated worst time on 2TB memory is about 15 hours for
lzo and about 40 hours for zlib. In this case, compressed data
size is larger than the original, so they are really not used,
compression time is fully meaningless. I think compression must be
done in parallel, and I'll post such patch later.
Diffstat
* makedumpfile
diskdump_mod.h | 3 +-
makedumpfile.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++------
makedumpfile.h | 12 +++++++
3 files changed, 101 insertions(+), 12 deletions(-)
* crash
defs.h | 1 +
diskdump.c | 20 +++++++++++++++++++-
diskdump.h | 3 ++-
3 files changed, 22 insertions(+), 2 deletions(-)
TODO
* evaluation including I/O time using actual vmcores
Thanks.
HATAYAMA, Daisuke
1 year
Re: [Crash-utility] [RFI] Support Fujitsu's sadump dump format
by tachibana＠mxm.nes.nec.co.jp
Hi Hatayama-san,
On 2011/06/29 12:12:18 +0900, HATAYAMA Daisuke <d.hatayama(a)jp.fujitsu.com> wrote:
> From: Dave Anderson <anderson(a)redhat.com>
> Subject: Re: [Crash-utility] [RFI] Support Fujitsu's sadump dump format
> Date: Tue, 28 Jun 2011 08:57:42 -0400 (EDT)
>
> >
> >
> > ----- Original Message -----
> >> Fujitsu has stand-alone dump mechanism based on firmware level
> >> functionality, which we call SADUMP, in short.
> >>
> >> We've maintained utility tools internally but now we're thinking that
> >> the best is crash utility and makedumpfile supports the sadump format
> >> for the viewpoint of both portability and maintainability.
> >>
> >> We'll be of course responsible for its maintainance in a continuous
> >> manner. The sadump dump format is very similar to diskdump format and
> >> so kdump (compressed) format, so we estimate patch set would be a
> >> relatively small size.
> >>
> >> Could you tell me whether crash utility and makedumpfile can support
> >> the sadump format? If OK, we'll start to make patchset.
I think it's not bad to support sadump by makedumpfile. However I have
several questions.
- Do you want to use makedumpfile to make an existing file that sadump has
dumped small?
- It isn't possible to support the same form as kdump-compressed format
now, is it?
- When the information that makedumpfile reads from a note of /proc/vmcore
(or a header of kdump-compressed format) is added by an extension of
makedumpfile, do you need to modify sadump?
Thanks
tachibana
> >
> > Sure, yes, the crash utility can always support another dumpfile format.
> >
>
> Thanks. It helps a lot.
>
> > It's unclear to me how similar SADUMP is to diskdump/compressed-kdump.
> > Does your internal version patch diskdump.c, or do you maintain your
> > own "sadump.c"? I ask because if your patchset is at all intrusive,
> > I'd prefer it be kept in its own file, primarily for maintainability,
> > but also because SADUMP is essentially a black-box to anybody outside
> > Fujitsu.
>
> What I meant when I used ``similar'' is both literally and
> logically. The format consists of diskdump header-like header, two
> kinds of bitmaps used for the same purpose as those in diskump format,
> and memory data. They can be handled in common with the existing data
> structure, diskdump_data, non-intrusively, so I hope they are placed
> in diskdump.c.
>
> On the other hand, there's a code to be placed at such specific
> area. sadump is triggered depending on kdump's progress and so
> register values to be contained in vmcore varies according to the
> progress: If crash_notes has been initialized when sadump is
> triggered, sadump packs the register values in crash_notes; if not
> yet, packs registers gathered by firmware. This is sadump specific
> processing, so I think putting it in specific sadump.c file is a
> natural and reasonable choise.
>
> Anyway, I have not made any patch set for this. I'll post a patch set
> when I complete.
>
> Again, thanks a lot for the positive answer.
>
> Thanks.
> HATAYAMA, Daisuke
>
>
> _______________________________________________
> kexec mailing list
> kexec(a)lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
1 year
[PATCH v3] Add support for kASLR for offline vmcore files
by Andy Honig
This patch adds a --kaslr command line parameter for loading x86_64
crash dumps with kaslr enabled. This reuses the code from 32-bit
x86 relocations with some small changes. The ASLR offset is postive
instead of negative. Also had to move the code to traverse the
kernel section before the symbol storing code to figure out which
symbols were outside any sections and therefore were not relocated.
Also made a very small change in search_for_switch_to it was
searching through gdb command output for a slightly incorrect syntax.
Tested: Tested by loading kdump files from kernels with aslr enabled
and not enabled. Ran bt, files, and struct file 0xXXXXXX.
Signed-off-by: Andy Honig <ahonig(a)google.com>
---
defs.h | 2 ++
main.c | 8 ++++++--
symbols.c | 69 +++++++++++++++++++++++++++++++++++++++++++++------------------
x86_64.c | 20 ++++++++++++------
4 files changed, 72 insertions(+), 27 deletions(-)
diff --git a/defs.h b/defs.h
index 83a4402..8de1fa4 100755
--- a/defs.h
+++ b/defs.h
@@ -2394,6 +2394,8 @@ struct symbol_table_data {
ulong __per_cpu_end;
off_t dwarf_debug_frame_file_offset;
ulong dwarf_debug_frame_size;
+ ulong first_section_start;
+ ulong last_section_end;
};
/* flags for st */
diff --git a/main.c b/main.c
index 3b469e3..5a41c1a 100755
--- a/main.c
+++ b/main.c
@@ -57,6 +57,7 @@ static struct option long_options[] = {
{"CRASHPAGER", 0, 0, 0},
{"no_scroll", 0, 0, 0},
{"reloc", required_argument, 0, 0},
+ {"kaslr", required_argument, 0, 0},
{"active", 0, 0, 0},
{"minimal", 0, 0, 0},
{"mod", required_argument, 0, 0},
@@ -216,12 +217,15 @@ main(int argc, char **argv)
else if (STREQ(long_options[option_index].name, "mod"))
kt->module_tree = optarg;
- else if (STREQ(long_options[option_index].name, "reloc")) {
+ else if (STREQ(long_options[option_index].name, "reloc") ||
+ STREQ(long_options[option_index].name, "kaslr")) {
if (!calculate(optarg, &kt->relocate, NULL, 0)) {
error(INFO, "invalid --reloc argument: %s\n",
optarg);
program_usage(SHORT_FORM);
- }
+ } else if (STREQ(long_options[option_index].name, "kaslr")) {
+ kt->relocate *= -1;
+ }
kt->flags |= RELOC_SET;
}
diff --git a/symbols.c b/symbols.c
index 93d9c8c..5a22d1a 100755
--- a/symbols.c
+++ b/symbols.c
@@ -192,22 +192,6 @@ symtab_init(void)
if (!check_gnu_debuglink(st->bfd))
no_debugging_data(FATAL);
}
-
- symcount = bfd_read_minisymbols(st->bfd, FALSE, &minisyms, &size);
-
- if (symcount <= 0)
- no_debugging_data(FATAL);
-
- sort_x = bfd_make_empty_symbol(st->bfd);
- sort_y = bfd_make_empty_symbol(st->bfd);
- if (sort_x == NULL || sort_y == NULL)
- error(FATAL, "bfd_make_empty_symbol() failed\n");
-
- gnu_qsort(st->bfd, minisyms, symcount, size, sort_x, sort_y);
-
- store_symbols(st->bfd, FALSE, minisyms, symcount, size);
-
- free(minisyms);
/*
* Gather references to the kernel sections.
@@ -217,6 +201,7 @@ symtab_init(void)
error(FATAL, "symbol table section array malloc: %s\n",
strerror(errno));
BZERO(st->sections, st->bfd->section_count * sizeof(struct sec *));
+ st->first_section_start = st->last_section_end = 0;
bfd_map_over_sections(st->bfd, section_header_info, KERNEL_SECTIONS);
if ((st->flags & (NO_SEC_LOAD|NO_SEC_CONTENTS)) ==
@@ -227,6 +212,23 @@ symtab_init(void)
error(FATAL, DEBUGINFO_ERROR_MESSAGE2);
}
}
+
+ symcount = bfd_read_minisymbols(st->bfd, FALSE, &minisyms, &size);
+
+ if (symcount <= 0)
+ no_debugging_data(FATAL);
+
+ sort_x = bfd_make_empty_symbol(st->bfd);
+ sort_y = bfd_make_empty_symbol(st->bfd);
+ if (sort_x == NULL || sort_y == NULL)
+ error(FATAL, "bfd_make_empty_symbol() failed\n");
+
+ gnu_qsort(st->bfd, minisyms, symcount, size, sort_x, sort_y);
+
+ store_symbols(st->bfd, FALSE, minisyms, symcount, size);
+
+ free(minisyms);
+
symname_hash_init();
symval_hash_init();
@@ -585,7 +587,7 @@ store_symbols(bfd *abfd, int dynamic, void *minisyms, long symcount,
st->symcnt = 0;
sp = st->symtable;
- if (machine_type("X86")) {
+ if (machine_type("X86") || machine_type("X86_64")) {
if (!(kt->flags & RELOC_SET))
kt->flags |= RELOC_FORCE;
} else
@@ -658,7 +660,7 @@ store_sysmap_symbols(void)
error(FATAL, "symbol table namespace malloc: %s\n",
strerror(errno));
- if (!machine_type("X86"))
+ if (!machine_type("X86") && !machine_type("X86_64"))
kt->flags &= ~RELOC_SET;
first = 0;
@@ -730,7 +732,20 @@ relocate(ulong symval, char *symname, int first_symbol)
break;
}
- return (symval - kt->relocate);
+ if (machine_type("X86_64")) {
+ /*
+ * There are some symbols which are outside of any section
+ * either because they are offsets or because they are absolute
+ * addresses. These should not be relocated.
+ */
+ if (symval >= st->first_section_start &&
+ symval <= st->last_section_end) {
+ return (symval - kt->relocate);
+ } else {
+ return symval;
+ }
+ } else
+ return symval - kt->relocate;
}
/*
@@ -9506,6 +9521,7 @@ section_header_info(bfd *bfd, asection *section, void *reqptr)
struct load_module *lm;
ulong request;
asection **sec;
+ ulong section_end_address;
request = ((ulong)reqptr);
@@ -9524,6 +9540,12 @@ section_header_info(bfd *bfd, asection *section, void *reqptr)
kt->etext_init = kt->stext_init +
(ulong)bfd_section_size(bfd, section);
}
+
+ if (STREQ(bfd_get_section_name(bfd, section), ".text")) {
+ st->first_section_start = (ulong)
+ bfd_get_section_vma(bfd, section);
+ }
+
if (STREQ(bfd_get_section_name(bfd, section), ".text") ||
STREQ(bfd_get_section_name(bfd, section), ".data")) {
if (!(bfd_get_section_flags(bfd, section) & SEC_LOAD))
@@ -9540,6 +9562,15 @@ section_header_info(bfd *bfd, asection *section, void *reqptr)
st->dwarf_debug_frame_file_offset = (off_t)section->filepos;
st->dwarf_debug_frame_size = (ulong)bfd_section_size(bfd, section);
}
+
+ if (st->first_section_start != 0) {
+ section_end_address =
+ (ulong) bfd_get_section_vma(bfd, section) +
+ (ulong) bfd_section_size(bfd, section);
+ if (section_end_address > st->last_section_end)
+ st->last_section_end = section_end_address;
+ }
+
break;
case (ulong)MODULE_SECTIONS:
diff --git a/x86_64.c b/x86_64.c
index 1d915b1..0c22ee1 100755
--- a/x86_64.c
+++ b/x86_64.c
@@ -5382,16 +5382,22 @@ search_for_switch_to(ulong start, ulong end)
{
ulong max_instructions, address;
char buf1[BUFSIZE];
- char buf2[BUFSIZE];
+ char search_string1[BUFSIZE];
+ char search_string2[BUFSIZE];
int found;
max_instructions = end - start;
found = FALSE;
sprintf(buf1, "x/%ldi 0x%lx", max_instructions, start);
- if (symbol_exists("__switch_to"))
- sprintf(buf2, "callq 0x%lx", symbol_value("__switch_to"));
- else
- buf2[0] = NULLCHAR;
+ if (symbol_exists("__switch_to")) {
+ sprintf(search_string1,
+ "call 0x%lx", symbol_value("__switch_to"));
+ sprintf(search_string2,
+ "callq 0x%lx", symbol_value("__switch_to"));
+ } else {
+ search_string1[0] = NULLCHAR;
+ search_string2[0] = NULLCHAR;
+ }
open_tmpfile();
@@ -5404,7 +5410,9 @@ search_for_switch_to(ulong start, ulong end)
break;
if (strstr(buf1, "<__switch_to>"))
found = TRUE;
- if (strlen(buf2) && strstr(buf1, buf2))
+ if (strlen(search_string1) && strstr(buf1, search_string1))
+ found = TRUE;
+ if (strlen(search_string2) && strstr(buf1, search_string2))
found = TRUE;
}
close_tmpfile();
--
1.8.4
10 years, 10 months
HEADS-UP: Linux 3.13-rc1 failures with CONFIG_MAXSMP and CONFIG_SLAB
by Dave Anderson
Just a heads-up if you are attempting to use crash with the
recently-released 3.13-rc1 kernel that is configured with either:
CONFIG_MAXSMP=y (x86_64 kernels)
CONFIG_SLAB=y
If CONFIG_MAXSMP is configured, the CONFIG_NR_CPUS value is
overridden, and will be changed to be 8192. This is from the
3.13-rc1 arch/x86/Kconfig:
config NR_CPUS
int "Maximum number of CPUs" if SMP && !MAXSMP
range 2 8 if SMP && X86_32 && !X86_BIGSMP
range 2 512 if SMP && !MAXSMP && !CPUMASK_OFFSTACK
range 2 8192 if SMP && !MAXSMP && CPUMASK_OFFSTACK && X86_64
default "1" if !SMP
default "8192" if MAXSMP
default "32" if SMP && (X86_NUMAQ || X86_SUMMIT || X86_BIGSMP || X86_ES7000)
default "8" if SMP
---help---
This allows you to specify the maximum number of CPUs which this
kernel will support. If CPUMASK_OFFSTACK is enabled, the maximum
supported value is 4096, otherwise the maximum value is 512. The
minimum value which makes sense is 2.
This is purely to save memory - each supported CPU adds
approximately eight kilobytes to the kernel image.
That is beyond the current crash limit of 5120, and as a result the crash
session will fail like so:
# crash vmlinux vmcore
crash 7.0.3-1.fc20
Copyright (C) 2002-2013 Red Hat, Inc.
Copyright (C) 2004, 2005, 2006, 2010 IBM Corporation
Copyright (C) 1999-2006 Hewlett-Packard Co
Copyright (C) 2005, 2006, 2011, 2012 Fujitsu Limited
Copyright (C) 2006, 2007 VA Linux Systems Japan K.K.
Copyright (C) 2005, 2011 NEC Corporation
Copyright (C) 1999, 2002, 2007 Silicon Graphics, Inc.
Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc.
This program is free software, covered by the GNU General Public License,
and you are welcome to change it and/or distribute copies of it under
certain conditions. Enter "help copying" to see the conditions.
This program has absolutely no warranty. Enter "help warranty" for details.
GNU gdb (GDB) 7.6
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu"...
WARNING: kernel-configured NR_CPUS (8192) greater than compiled-in NR_CPUS (5120)
crash: recompile crash with larger NR_CPUS
#
As the message indicates, the X86_64 NR_CPUS value in "defs.h"
must be bumped from 5120 up to 8192, and the crash binary rebuilt.
Secondly, if the 3.11-rc1 kernel is configured with CONFIG_SLAB, the crash
session will fail with a segmentation violation. Here is an example with a
crash version that has a bumped-up NR_CPUS and configured to use CONFIG_SLAB:
# crash vmlinux vmcore
crash 7.0.4rc17
Copyright (C) 2002-2013 Red Hat, Inc.
Copyright (C) 2004, 2005, 2006, 2010 IBM Corporation
Copyright (C) 1999-2006 Hewlett-Packard Co
Copyright (C) 2005, 2006, 2011, 2012 Fujitsu Limited
Copyright (C) 2006, 2007 VA Linux Systems Japan K.K.
Copyright (C) 2005, 2011 NEC Corporation
Copyright (C) 1999, 2002, 2007 Silicon Graphics, Inc.
Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc.
This program is free software, covered by the GNU General Public License,
and you are welcome to change it and/or distribute copies of it under
certain conditions. Enter "help copying" to see the conditions.
This program has absolutely no warranty. Enter "help warranty" for details.
GNU gdb (GDB) 7.6
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu"...
please wait... (gathering kmem slab cache data)Segmentation fault
Although I haven't tested recent CONFIG_SLAB kernels (Fedora and RHEL use CONFIG_SLUB
by default) I believe this is related to this patch-set that was pulled into Linux 3.13:
https://lkml.org/lkml/2013/10/16/155
From: Joonsoo Kim <>
Subject: [PATCH v2 00/15] slab: overload struct slab over struct page to reduce memory usage
Date: Wed, 16 Oct 2013 17:43:57 +0900
There is two main topics in this patchset. One is to reduce memory usage
and the other is to change a management method of free objects of a slab.
The SLAB allocate a struct slab for each slab. The size of this structure
except bufctl array is 40 bytes on 64 bits machine. We can reduce memory
waste and cache footprint if we overload struct slab over struct page.
And this patchset change a management method of free objects of a slab.
Current free objects management method of the slab is weird, because
it touch random position of the array of kmem_bufctl_t when we try to
get free object. See following example.
struct slab's free = 6
kmem_bufctl_t array: 1 END 5 7 0 4 3 2
To get free objects, we access this array with following index pattern.
6 -> 3 -> 7 -> 2 -> 5 -> 4 -> 0 -> 1 -> END
If we have many objects, this array would be larger and be not in the same
cache line. It is not good for performance.
We can do same thing through more easy way, like as the stack.
This patchset implement it and remove complex code for above algorithm.
This makes slab code much cleaner.
...
And even if it's not the direct cause of the segmentation violation, that patchset
completely changes the slab object bookkeeping, and will require a significant
change to the crash utility to support CONFIG_SLAB kernels.
I am starting to work on the CONFIG_SLAB issue, but in the meantime, you can use
the --no_kmem_cache command-line workaround:
# crash --no_kmem_cache vmlinux vmcore
crash 7.0.4rc17
Copyright (C) 2002-2013 Red Hat, Inc.
Copyright (C) 2004, 2005, 2006, 2010 IBM Corporation
Copyright (C) 1999-2006 Hewlett-Packard Co
Copyright (C) 2005, 2006, 2011, 2012 Fujitsu Limited
Copyright (C) 2006, 2007 VA Linux Systems Japan K.K.
Copyright (C) 2005, 2011 NEC Corporation
Copyright (C) 1999, 2002, 2007 Silicon Graphics, Inc.
Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc.
This program is free software, covered by the GNU General Public License,
and you are welcome to change it and/or distribute copies of it under
certain conditions. Enter "help copying" to see the conditions.
This program has absolutely no warranty. Enter "help warranty" for details.
GNU gdb (GDB) 7.6
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu"...
KERNEL: vmlinux
DUMPFILE: vmcore
CPUS: 2
DATE: Wed Nov 27 11:46:03 2013
UPTIME: 00:11:55
LOAD AVERAGE: 0.50, 0.35, 0.20
TASKS: 103
NODENAME: hp-xw4550-02.ml3.eng.bos.redhat.com
RELEASE: 3.13.0-0.rc1.git2.1.fc20.x86_64
VERSION: #1 SMP Tue Nov 26 14:42:45 EST 2013
MACHINE: x86_64 (2194 Mhz)
MEMORY: 1.9 GB
PANIC: "Oops: 0002 [#1] SMP " (check log for details)
PID: 663
COMMAND: "bash"
TASK: ffff88006ba70650 [THREAD_INFO: ffff88006ba34000]
CPU: 0
STATE: TASK_RUNNING (PANIC)
crash>
If that option is used, any command that tries to access the slab cache data
will not execute:
crash> kmem -s
kmem: kmem cache slab subsystem not available
crash>
When I get CONFIG_SLAB support functional again, I'll release crash-7.0.4.
Thanks,
Dave
11 years
