6:06 p.m.
Hi Dave,
With 7.1.7, crash is working for MIPS when all drivers are embedded
inside kernel.
When I make the driver loadable and panic the kernel, crash doesn't
locate some symbols correctly.
please wait... (gathering module symbol data)
crash: invalid size request: 0 type: "pgd page"
debugged further and find that PGD_ORDER provides incorrect number
due to which the PGD_SIZE macro results in 0.
Just for fun, I replaced PGD_ORDER with 0(I know its incorrect) and it
went ahead but couldn't run "mod" command successfully as it threw
following error
crash> mod
mod: cannot access vmalloc'd module memory
Any idea?
Thanks
Sagar
9:45 p.m.
----- Original Message -----
Hi Dave,
With 7.1.7, crash is working for MIPS when all drivers are embedded
inside kernel.
When I make the driver loadable and panic the kernel, crash doesn't
locate some symbols correctly.
please wait... (gathering module symbol data)
crash: invalid size request: 0 type: "pgd page"
debugged further and find that PGD_ORDER provides incorrect number
due to which the PGD_SIZE macro results in 0.
Just for fun, I replaced PGD_ORDER with 0(I know its incorrect) and it
went ahead but couldn't run "mod" command successfully as it threw
following error
crash> mod
mod: cannot access vmalloc'd module memory
Any idea?
Clearly it's failing to translate any kernel virtual address that is
not unity-mapped. I have 3 sample 3.19-based MIPS vmcores on hand,
and crash-7.1.7 can translate both mapped user-space and vmalloc'd module
addresses. But I am completely unfamiliar with the particulars of the MIPS
architecture. MIPS support in the crash utility was written by, and its
maintenance is done by, Rabin Vincent. He is a member of this list, but
just in case he missed your post, I've cc'd this message to both of his
registered email addresses.
Dave
Thanks
Sagar
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3:59 a.m.
On Fri, Dec 02, 2016 at 04:06:20PM -0800, Sagar Borikar wrote:
With 7.1.7, crash is working for MIPS when all drivers are embedded
inside kernel.
When I make the driver loadable and panic the kernel, crash doesn't
locate some symbols correctly.
please wait... (gathering module symbol data)
crash: invalid size request: 0 type: "pgd page"
debugged further and find that PGD_ORDER provides incorrect number
due to which the PGD_SIZE macro results in 0.
Just for fun, I replaced PGD_ORDER with 0(I know its incorrect) and it
went ahead but couldn't run "mod" command successfully as it threw
following error
crash> mod
mod: cannot access vmalloc'd module memory
In order to access vmalloc'd memory we need interpret the page tables
correctly. This isn't needed when the modules are built in since then
the memory will be in the direct-mapped kseg0 segment. So the "mod"
failure is just a consequence of replacing PGD_ORDER with 0.
So the first error should be fixed properly before attempting "mod". What
kernel version is this and what page size do to use?
Try running the "help -m" and "mach" commands (you can skip module
loading with
--no_modules to get to the crash> prompt) and check if the values for the
various page table sizes and bits match what your kernel is using.
crash> help -m
...
pagesize: 4096
pageshift: 12
pagemask: fffffffffffff000
pageoffset: fff
pgdir_shift: 22
ptrs_per_pgd: 1024
ptrs_per_pte: 1024
...
crash-mips> mach
PAGE SIZE: 4096
_PAGE_PRESENT: 00000001
_PAGE_READ: 00000002
_PAGE_WRITE: 00000004
_PAGE_ACCESSED: 00000008
_PAGE_MODIFIED: 00000010
_PAGE_GLOBAL: 00000020
_PAGE_VALID: 00000040
_PAGE_DIRTY: 00000080
3:15 p.m.
On Sat, Dec 3, 2016 at 1:59 AM, Rabin Vincent <rabin(a)rab.in> wrote:
On Fri, Dec 02, 2016 at 04:06:20PM -0800, Sagar Borikar wrote:
> With 7.1.7, crash is working for MIPS when all drivers are embedded
> inside kernel.
> When I make the driver loadable and panic the kernel, crash doesn't
> locate some symbols correctly.
>
> please wait... (gathering module symbol data)
> crash: invalid size request: 0 type: "pgd page"
>
> debugged further and find that PGD_ORDER provides incorrect number
> due to which the PGD_SIZE macro results in 0.
>
> Just for fun, I replaced PGD_ORDER with 0(I know its incorrect) and it
> went ahead but couldn't run "mod" command successfully as it threw
> following error
>
> crash> mod
> mod: cannot access vmalloc'd module memory
In order to access vmalloc'd memory we need interpret the page tables
correctly. This isn't needed when the modules are built in since then
the memory will be in the direct-mapped kseg0 segment. So the "mod"
failure is just a consequence of replacing PGD_ORDER with 0.
Yes, mod will not work as I said earlier. Crash was exiting hence I
wanted to have quick workaround.
So the first error should be fixed properly before attempting
"mod". What
kernel version is this and what page size do to use?
4.4.20 kernel and page size is 16K
Try running the "help -m" and "mach" commands (you can skip module
loading with
--no_modules to get to the crash> prompt) and check if the values for the
various page table sizes and bits match what your kernel is using.
crash> help -m
...
pagesize: 4096
pageshift: 12
pagemask: fffffffffffff000
pageoffset: fff
pgdir_shift: 22
ptrs_per_pgd: 1024
ptrs_per_pte: 1024
...
crash-mips> mach
PAGE SIZE: 4096
_PAGE_PRESENT: 00000001
_PAGE_READ: 00000002
_PAGE_WRITE: 00000004
_PAGE_ACCESSED: 00000008
_PAGE_MODIFIED: 00000010
_PAGE_GLOBAL: 00000020
_PAGE_VALID: 00000040
_PAGE_DIRTY: 00000080
This appears to be correct info for my platform.
Thanks
Sagar
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7:17 a.m.
----- Original Message -----
On Sat, Dec 3, 2016 at 1:59 AM, Rabin Vincent <rabin(a)rab.in>
wrote:
> On Fri, Dec 02, 2016 at 04:06:20PM -0800, Sagar Borikar wrote:
>> With 7.1.7, crash is working for MIPS when all drivers are embedded
>> inside kernel.
>> When I make the driver loadable and panic the kernel, crash doesn't
>> locate some symbols correctly.
>>
>> please wait... (gathering module symbol data)
>> crash: invalid size request: 0 type: "pgd page"
>>
>> debugged further and find that PGD_ORDER provides incorrect number
>> due to which the PGD_SIZE macro results in 0.
>>
>> Just for fun, I replaced PGD_ORDER with 0(I know its incorrect) and it
>> went ahead but couldn't run "mod" command successfully as it
threw
>> following error
>>
>> crash> mod
>> mod: cannot access vmalloc'd module memory
>
> In order to access vmalloc'd memory we need interpret the page tables
> correctly. This isn't needed when the modules are built in since then
> the memory will be in the direct-mapped kseg0 segment. So the "mod"
> failure is just a consequence of replacing PGD_ORDER with 0.
Yes, mod will not work as I said earlier. Crash was exiting hence I
wanted to have quick workaround.
> So the first error should be fixed properly before attempting "mod".
What
> kernel version is this and what page size do to use?
4.4.20 kernel and page size is 16K
>
> Try running the "help -m" and "mach" commands (you can skip
module loading
> with
> --no_modules to get to the crash> prompt) and check if the values for the
> various page table sizes and bits match what your kernel is using.
>
> crash> help -m
> ...
> pagesize: 4096
> pageshift: 12
> pagemask: fffffffffffff000
> pageoffset: fff
> pgdir_shift: 22
> ptrs_per_pgd: 1024
> ptrs_per_pte: 1024
> ...
>
>
> crash-mips> mach
> PAGE SIZE: 4096
>
> _PAGE_PRESENT: 00000001
> _PAGE_READ: 00000002
> _PAGE_WRITE: 00000004
> _PAGE_ACCESSED: 00000008
> _PAGE_MODIFIED: 00000010
> _PAGE_GLOBAL: 00000020
> _PAGE_VALID: 00000040
> _PAGE_DIRTY: 00000080
This appears to be correct info for my platform.
Thanks
If your kernel has a 16k page size and "help -m" shows 4096 as above,
then there's one major problem. The calculation of page size in mips.c
is based upon the difference between the the "swapper_pg_dir" symbol
and the next symbol above it:
crash> sym -n swapper_pg_dir
806d0000 (B) swapper_pg_dir
806d1000 (B) invalid_pte_table
crash>
What does the command above on your kernel show?
Dave
Sagar
>
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8:05 a.m.
On Sat, Dec 03, 2016 at 01:15:23PM -0800, Sagar Borikar wrote:
> So the first error should be fixed properly before attempting
"mod". What
> kernel version is this and what page size do to use?
4.4.20 kernel and page size is 16K
I'd only tested 4K pages before but I've now provisioned a QEMU Malta machine
with 16K pages. I've now sent a patch to the list which fixes the
definition of __PGD_ORDER. With only that patch, the pgd size errors
are gone and "mod" works for my 16K kernel/dump:
crash> sym -n swapper_pg_dir
80540000 (B) swapper_pg_dir
80544000 (B) invalid_pte_table
crash> sys
KERNEL: vmlinux-16k-unload
DUMPFILES: /var/tmp/ramdump_elf_wZxP65 [temporary ELF header]
rawdump-16k-unload
CPUS: 1
DATE: Sun Dec 4 14:46:08 2016
UPTIME: 00:00:21
LOAD AVERAGE: 0.31, 0.07, 0.02
TASKS: 54
NODENAME: buildroot
RELEASE: 4.4.27-dirty
VERSION: #12 SMP Sun Dec 4 14:45:32 CET 2016
MACHINE: mips (unknown Mhz)
MEMORY: 128 MB
PANIC: "Kernel panic - not syncing: Fatal exception"
crash> help -m | grep -A7 pagesize
pagesize: 16384
pageshift: 14
pagemask: ffffffffffffc000
pageoffset: 3fff
pgdir_shift: 26
ptrs_per_pgd: 64
ptrs_per_pte: 4096
stacksize: 16384
crash> mod
MODULE NAME SIZE OBJECT FILE
c01050c0 null_blk 5333 (not loaded) [CONFIG_KALLSYMS]
With the fixed __PGD_ORDER, PGD_ORDER gets the value zero and that is
correct for my kernel. __PGD_ORDER isn't used anywhere else that in
PGD_ORDER, so even your hack of forcing PGD_ORDER to zero would have
fixed "mod" for me.
So there could be some other additional problem in your case besides the
incorrect __PGD_ORDER. Could you please apply the fix and run crash
with the -d8 argument and post the full log? Thanks.
9:10 a.m.
On Sun, Dec 4, 2016 at 6:05 AM, Rabin Vincent <rabin(a)rab.in> wrote:
On Sat, Dec 03, 2016 at 01:15:23PM -0800, Sagar Borikar wrote:
> > So the first error should be fixed properly before attempting "mod".
What
> > kernel version is this and what page size do to use?
>
> 4.4.20 kernel and page size is 16K
I'd only tested 4K pages before but I've now provisioned a QEMU Malta machine
with 16K pages. I've now sent a patch to the list which fixes the
definition of __PGD_ORDER. With only that patch, the pgd size errors
are gone and "mod" works for my 16K kernel/dump:
crash> sym -n swapper_pg_dir
80540000 (B) swapper_pg_dir
80544000 (B) invalid_pte_table
crash> sys
KERNEL: vmlinux-16k-unload
DUMPFILES: /var/tmp/ramdump_elf_wZxP65 [temporary ELF header]
rawdump-16k-unload
CPUS: 1
DATE: Sun Dec 4 14:46:08 2016
UPTIME: 00:00:21
LOAD AVERAGE: 0.31, 0.07, 0.02
TASKS: 54
NODENAME: buildroot
RELEASE: 4.4.27-dirty
VERSION: #12 SMP Sun Dec 4 14:45:32 CET 2016
MACHINE: mips (unknown Mhz)
MEMORY: 128 MB
PANIC: "Kernel panic - not syncing: Fatal exception"
crash> help -m | grep -A7 pagesize
pagesize: 16384
pageshift: 14
pagemask: ffffffffffffc000
pageoffset: 3fff
pgdir_shift: 26
ptrs_per_pgd: 64
ptrs_per_pte: 4096
stacksize: 16384
crash> mod
MODULE NAME SIZE OBJECT FILE
c01050c0 null_blk 5333 (not loaded) [CONFIG_KALLSYMS]
With the fixed __PGD_ORDER, PGD_ORDER gets the value zero and that is
correct for my kernel. __PGD_ORDER isn't used anywhere else that in
PGD_ORDER, so even your hack of forcing PGD_ORDER to zero would have
fixed "mod" for me.
So there could be some other additional problem in your case besides the
incorrect __PGD_ORDER. Could you please apply the fix and run crash
with the -d8 argument and post the full log? Thanks.
With your earlier patches, its same result as I was getting. i.e
please wait... (gathering module symbol data)
WARNING: cannot access vmalloc'd module memory
crash> mod
mod: cannot access vmalloc'd module memory
Here is detailed info of the help -m and mach output
flags: 1 (KSYMS_START)
[0/153]
kvbase: 80000000
identity_map_base: 80000000
pagesize: 16384
pageshift: 14
pagemask: ffffffffffffc000
pageoffset: 3fff
pgdir_shift: 26
ptrs_per_pgd: 64
ptrs_per_pte: 4096
stacksize: 16384
hz: 1000
memsize: 261865472 (0xf9bc000)
bits: 32
nr_irqs: 360
eframe_search: mips_eframe_search()
back_trace: mips_back_trace_cmd()
processor_speed: mips_processor_speed()
uvtop: mips_uvtop()
kvtop: mips_kvtop()
get_task_pgd: mips_get_task_pgd()
dump_irq: generic_dump_irq()
show_interrupts: generic_show_interrupts()
get_irq_affinity: generic_get_irq_affinity()
get_stack_frame: mips_get_stack_frame()
get_stackbase: generic_get_stackbase()
get_stacktop: generic_get_stacktop()
translate_pte: mips_translate_pte()
memory_size: generic_memory_size()
vmalloc_start: mips_vmalloc_start()
is_task_addr: mips_is_task_addr()
verify_symbol: mips_verify_symbol()
dis_filter: generic_dis_filter()
cmd_mach: mips_cmd_mach()
get_smp_cpus: mips_get_smp_cpus()
is_kvaddr: generic_is_kvaddr()
is_uvaddr: generic_is_uvaddr()
verify_paddr: generic_verify_paddr()
init_kernel_pgd: NULL
value_to_symbol: generic_machdep_value_to_symbol()
line_number_hooks: NULL
last_pgd_read: 82c30000
last_pmd_read: 0
last_ptbl_read: 3018000
pgd: 8a71b70
pmd: 0
ptbl: 8a75b78
section_size_bits: 26
max_physmem_bits: 32
sections_per_root: 0
machspec: 8696240
crash> mach
HZ: 1000
PAGE SIZE: 16384
_PAGE_PRESENT: 00000001
_PAGE_READ: 00000020
_PAGE_WRITE: 00000002
_PAGE_ACCESSED: 00000004
_PAGE_MODIFIED: 00000008
_PAGE_GLOBAL: 00000040
_PAGE_VALID: 00000080
_PAGE_NO_READ: 00000020
_PAGE_NO_EXEC: 00000010
_PAGE_DIRTY: 00000100
Please find the attached log with -d8 output.
Thanks
Sagar
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10:16 a.m.
On Sun, Dec 04, 2016 at 07:10:38AM -0800, Sagar Borikar wrote:
<readmem: 806d2c68, KVADDR, "modules", 4, (FOE),
868e5ec>
<read_kdump: addr: 806d2c68 paddr: 6d2c68 cnt: 4>
read_netdump: addr: 806d2c68 paddr: 6d2c68 cnt: 4 offset: 5dac68
GETBUF(416 -> 0)
please wait... (gathering module symbol data)module: c0bc9cc0
<readmem: c0bc9cc0, KVADDR, "module struct", 416,
(ROE|Q), 86b25e0>
<readmem: 82c30000, KVADDR, "pgd page", 16384, (FOE), 948a2a0>
<read_kdump: addr: 82c30000 paddr: 2c30000 cnt: 16384>
read_netdump: addr: 82c30000 paddr: 2c30000 cnt: 16384 offset: 31f8000
<readmem: 3018000, PHYSADDR, "page table", 16384, (FOE), 948e2a8>
<read_kdump: addr: 3018000 paddr: 3018000 cnt: 16384>
read_netdump: addr: 0 paddr: 3018000 cnt: 16384 offset: 35e0000
<read_kdump: addr: c0bc9cc0 paddr: 271e9cc0 cnt: 416>
read_netdump: READ_ERROR: offset not found for paddr: 271e9cc0
crash: read error: kernel virtual address: c0bc9cc0 type: "module struct"
Here's the error. Either 271e9cc0 is a valid physical address and the dump is
incomplete, or it's not and the page table translation is returning a bogus
physical address for c0bc9cc0.
To check the page table translation, use "vtop <addr>" (example below)
to see how crash comes to its result. You'll have to then manually walk
the page tables for this particular virtual address and verify that the
correct PGD and PTE entries are being read. It could be easier if use
vmalloc_to_page() and page_address() first in your kernel to print out
the correct physical address for some known vmalloc'd address.
crash> vtop c01050c0
VIRTUAL PHYSICAL
c01050c0 71550c0
SEGMENT: ksseg
PAGE DIRECTORY: 80540000
PGD: 805400c0 => 872b0000
PTE: 072b0104 => 071545ef
PAGE: 07154000
PTE PHYSICAL FLAGS
71545ef 7154000 (PRESENT|READ|WRITE|ACCESSED|MODIFIED|GLOBAL|VALID|NO_READ|DIRTY)
PAGE PHYSICAL MAPPING INDEX CNT FLAGS
81038e60 7154000 0 0 1 40000000
3:07 p.m.
On Sun, Dec 4, 2016 at 8:16 AM, Rabin Vincent <rabin(a)rab.in> wrote:
On Sun, Dec 04, 2016 at 07:10:38AM -0800, Sagar Borikar wrote:
> <readmem: 806d2c68, KVADDR, "modules", 4, (FOE), 868e5ec>
> <read_kdump: addr: 806d2c68 paddr: 6d2c68 cnt: 4>
> read_netdump: addr: 806d2c68 paddr: 6d2c68 cnt: 4 offset: 5dac68
> GETBUF(416 -> 0)
>
please wait... (gathering module symbol data)module: c0bc9cc0
> <readmem: c0bc9cc0, KVADDR, "module struct", 416, (ROE|Q), 86b25e0>
> <readmem: 82c30000, KVADDR, "pgd page", 16384, (FOE), 948a2a0>
> <read_kdump: addr: 82c30000 paddr: 2c30000 cnt: 16384>
> read_netdump: addr: 82c30000 paddr: 2c30000 cnt: 16384 offset: 31f8000
> <readmem: 3018000, PHYSADDR, "page table", 16384, (FOE), 948e2a8>
> <read_kdump: addr: 3018000 paddr: 3018000 cnt: 16384>
> read_netdump: addr: 0 paddr: 3018000 cnt: 16384 offset: 35e0000
> <read_kdump: addr: c0bc9cc0 paddr: 271e9cc0 cnt: 416>
> read_netdump: READ_ERROR: offset not found for paddr: 271e9cc0
>
> crash: read error: kernel virtual address: c0bc9cc0 type: "module struct"
Here's the error. Either 271e9cc0 is a valid physical address and the dump is
incomplete, or it's not and the page table translation is returning a bogus
physical address for c0bc9cc0.
crash> vtop c0bc9cc0
VIRTUAL PHYSICAL
c0bc9cc0 271e9cc0
SEGMENT: ksseg
PAGE DIRECTORY: 82c30000
PGD: 82c300c0 => 83018000
PTE: 03018bc8 => 271e87cf
PAGE: 271e8000
PTE PHYSICAL FLAGS
271e87cf 271e8000 (PRESENT|WRITE|ACCESSED|MODIFIED|GLOBAL|VALID|DIRTY)
PAGE PHYSICAL MAPPING INDEX CNT FLAGS
82dc0f40 271e8000 0 0 1 40000000
0x271e9cc0 is a valid address but it belongs to high mem(0x20000000
onwards for this platform). Also I don't think there is any problem in
dump as I have done several testing of crash without modules and every
time I have got correct result.
Are you accounting for high memory?
To check the page table translation, use "vtop <addr>" (example below)
to see how crash comes to its result. You'll have to then manually walk
the page tables for this particular virtual address and verify that the
correct PGD and PTE entries are being read. It could be easier if use
vmalloc_to_page() and page_address() first in your kernel to print out
the correct physical address for some known vmalloc'd address.
As the driver works fine, I think kernel translation looks ok. Wrong
physical address translation would have failed the nvme driver to run.
Stress testing with the driver is fine. But still would go through the
PTE entries.
Dave,
crash> sym -n swapper_pg_dir
806d0000 (B) swapper_pg_dir
806d1000 (B) invalid_pte_table
crash>
What does the command above on your kernel show?
crash> sym -n swapper_pg_dir
82c30000 (B) swapper_pg_dir
82c34000 (B) invalid_pte_table
Thanks
Sagar
crash> vtop c01050c0
VIRTUAL PHYSICAL
c01050c0 71550c0
SEGMENT: ksseg
PAGE DIRECTORY: 80540000
PGD: 805400c0 => 872b0000
PTE: 072b0104 => 071545ef
PAGE: 07154000
PTE PHYSICAL FLAGS
71545ef 7154000 (PRESENT|READ|WRITE|ACCESSED|MODIFIED|GLOBAL|VALID|NO_READ|DIRTY)
PAGE PHYSICAL MAPPING INDEX CNT FLAGS
81038e60 7154000 0 0 1 40000000
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3:47 p.m.
On Sun, Dec 04, 2016 at 01:07:03PM -0800, Sagar Borikar wrote:
On Sun, Dec 4, 2016 at 8:16 AM, Rabin Vincent <rabin(a)rab.in>
wrote:
>> read_netdump: READ_ERROR: offset not found for paddr: 271e9cc0
>>
>> crash: read error: kernel virtual address: c0bc9cc0 type: "module
struct"
>
> Here's the error. Either 271e9cc0 is a valid physical address and the dump is
> incomplete, or it's not and the page table translation is returning a bogus
> physical address for c0bc9cc0.
crash> vtop c0bc9cc0
VIRTUAL PHYSICAL
c0bc9cc0 271e9cc0
SEGMENT: ksseg
PAGE DIRECTORY: 82c30000
PGD: 82c300c0 => 83018000
PTE: 03018bc8 => 271e87cf
PAGE: 271e8000
PTE PHYSICAL FLAGS
271e87cf 271e8000 (PRESENT|WRITE|ACCESSED|MODIFIED|GLOBAL|VALID|DIRTY)
PAGE PHYSICAL MAPPING INDEX CNT FLAGS
82dc0f40 271e8000 0 0 1 40000000
0x271e9cc0 is a valid address but it belongs to high mem(0x20000000
onwards for this platform). Also I don't think there is any problem in
dump as I have done several testing of crash without modules and every
time I have got correct result.
Have a look at the segments at the start of the log. The 271e9cc0
physical address is apparently not included in the dump:
pt_load_segment[0]:
file_offset: 8000
phys_start: 100000
phys_end: 703fff
zero_fill: 0
pt_load_segment[1]:
file_offset: 60c000
phys_start: 44000
phys_end: 144000
zero_fill: 0
pt_load_segment[2]:
file_offset: 70c000
phys_start: 144000
phys_end: 4300000
zero_fill: 0
pt_load_segment[3]:
file_offset: 48c8000
phys_start: d200000
phys_end: d200000
> To check the page table translation, use "vtop
<addr>" (example below)
> to see how crash comes to its result. You'll have to then manually walk
> the page tables for this particular virtual address and verify that the
> correct PGD and PTE entries are being read. It could be easier if use
> vmalloc_to_page() and page_address() first in your kernel to print out
> the correct physical address for some known vmalloc'd address.
As the driver works fine, I think kernel translation looks ok. Wrong
physical address translation would have failed the nvme driver to run.
Stress testing with the driver is fine. But still would go through the
PTE entries.
I wasn't implying that the kernel's virt-to-phys translation was wrong,
but rather that the crash utility's translation might be. But if
271e9cc0 is a valid physical address on your platform then the
translation itself is probably fine.
4:24 p.m.
On Sun, Dec 4, 2016 at 1:47 PM, Rabin Vincent <rabin(a)rab.in> wrote:
On Sun, Dec 04, 2016 at 01:07:03PM -0800, Sagar Borikar wrote:
> On Sun, Dec 4, 2016 at 8:16 AM, Rabin Vincent <rabin(a)rab.in> wrote:
> >> read_netdump: READ_ERROR: offset not found for paddr: 271e9cc0
> >>
> >> crash: read error: kernel virtual address: c0bc9cc0 type: "module
struct"
> >
> > Here's the error. Either 271e9cc0 is a valid physical address and the dump
is
> > incomplete, or it's not and the page table translation is returning a bogus
> > physical address for c0bc9cc0.
>
> crash> vtop c0bc9cc0
> VIRTUAL PHYSICAL
> c0bc9cc0 271e9cc0
>
> SEGMENT: ksseg
> PAGE DIRECTORY: 82c30000
> PGD: 82c300c0 => 83018000
> PTE: 03018bc8 => 271e87cf
> PAGE: 271e8000
>
> PTE PHYSICAL FLAGS
> 271e87cf 271e8000 (PRESENT|WRITE|ACCESSED|MODIFIED|GLOBAL|VALID|DIRTY)
>
> PAGE PHYSICAL MAPPING INDEX CNT FLAGS
> 82dc0f40 271e8000 0 0 1 40000000
>
> 0x271e9cc0 is a valid address but it belongs to high mem(0x20000000
> onwards for this platform). Also I don't think there is any problem in
> dump as I have done several testing of crash without modules and every
> time I have got correct result.
Have a look at the segments at the start of the log. The 271e9cc0
physical address is apparently not included in the dump:
pt_load_segment[0]:
file_offset: 8000
phys_start: 100000
phys_end: 703fff
zero_fill: 0
pt_load_segment[1]:
file_offset: 60c000
phys_start: 44000
phys_end: 144000
zero_fill: 0
pt_load_segment[2]:
file_offset: 70c000
phys_start: 144000
phys_end: 4300000
zero_fill: 0
pt_load_segment[3]:
file_offset: 48c8000
phys_start: d200000
phys_end: d200000
Right. Looked at it in more detail. kexec looks for "System RAM" under
/proc/iomem to build the memory segments which are passed to crash
notes.
But for some reason MIPS kernel doesn't add high mem in /proc/iomem
resource list.
Refer to arch/mips/kernel/setup.c resource_init() function
729
730 start = boot_mem_map.map[i].addr;
731 end = boot_mem_map.map[i].addr + boot_mem_map.map[i].size - 1;
732 if (start >= HIGHMEM_START)
733 continue;
734 if (end >= HIGHMEM_START)
735 end = HIGHMEM_START - 1;
736
Because of which highmem segment is not passed by kexec.
Sagar
> > To check the page table translation, use "vtop <addr>" (example
below)
> > to see how crash comes to its result. You'll have to then manually walk
> > the page tables for this particular virtual address and verify that the
> > correct PGD and PTE entries are being read. It could be easier if use
> > vmalloc_to_page() and page_address() first in your kernel to print out
> > the correct physical address for some known vmalloc'd address.
>
> As the driver works fine, I think kernel translation looks ok. Wrong
> physical address translation would have failed the nvme driver to run.
> Stress testing with the driver is fine. But still would go through the
> PTE entries.
I wasn't implying that the kernel's virt-to-phys translation was wrong,
but rather that the crash utility's translation might be. But if
271e9cc0 is a valid physical address on your platform then the
translation itself is probably fine.
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Dave Anderson -
Rabin Vincent -
Sagar Borikar