EXT: RE: crash: read error on type: "memory section root table"
Agrain Patrick
patrick.agrain at al-enterprise.com
Tue Apr 5 01:53:57 PDT 2022
Hello,
Some news about the issue described below.
I'm facing very strange behavior from one day to the other.
On Friday, I was able to get readable crash dump files after excluding all (-d31 on makedumpfile).
That results in crash dump files of ~17MB.
This morning, same process (sysrq-trigger crash) and file size is ~5MB and crash is failing on page_offset_base reading.
Note 1: I had the same behavior using makedumpfile from CentOS 8 kexec-tools package or a compiled-by-myself makedumpfile from github.
Note 2: The debug message of makedumpfile report 'Write bytes : 17364943', but the file is ~5MB for '-d 31' opton. The same message reports 'Write bytes : 183719992' For a file size of 183MB with '-d 0' option.
Does it make sense ?
Thanks.
Best regards,
Patrick Agrain
-----Message d'origine-----
De : Crash-utility <crash-utility-bounces at redhat.com> De la part de Agrain Patrick
Envoyé : vendredi 1 avril 2022 14:22
À : Discussion list for crash utility usage, maintenance and development <crash-utility at redhat.com>
Objet : Re: [Crash-utility] EXT: RE: crash: read error on type: "memory section root table"
-----Message d'origine-----
De : HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab at nec.com> Envoyé : mercredi 30 mars 2022 04:05 À : Agrain Patrick <patrick.agrain at al-enterprise.com>
Cc : Discussion list for crash utility usage, maintenance and development <crash-utility at redhat.com>; kexec at lists.infradead.org Objet : EXT: RE: crash: read error on type: "memory section root table"
** External email - Please consider with caution **
-----Original Message-----
> Hello,
>
> Sorry to cross post on both ML, I'm not sure which one would be the most suitable.
>
> Issue on analysis with crash-7.3.1 on a Centos 8 machine:
> crash: read error: kernel virtual address: ffff8f4fff7fc000 type: "memory section root table"
>
> Crash machine has a Rocky Linux 8.5 based kernel with following config options:
> - CONFIG_RANDOMIZE_BASE=y
> - CONFIG_RANDOMIZE_MEMORY=y
> - CONFIG_SPARSEMEM_MANUAL=y
> - CONFIG_SPARSEMEM=y
> - CONFIG_SPARSEMEM_EXTREME=y
> - CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y
> - CONFIG_KEXEC_CORE=y
> - CONFIG_KEXEC=y
> - CONFIG_KEXEC_FILE=y
>
> Kexec-tools package is from Centos Stream repo:
> kexec-tools-2.0.20-68.el8.2.5ale.x86_64
>
> /proc/vmcore is packaged with :
> /sbin/makedumpfile -D -d 0 -c --message-level 15 /proc/vmcore
> /tmpd/crashdump-${linux_ver}-${date_time}
>
> At kernel panic, I get:
> Dumping memory to crash partition
> This may take a while, please wait...
> makedumpfile: version 1.7.0 (released on 8 Nov 2021) command line:
> /sbin/makedumpfile -D -d 0 -c --message-level 15 /proc/vmcore
> /tmpd/crashdump--20220329-1538
>
> sadump: does not have partition header
> sadump: read dump device as unknown format
> sadump: unknown format
> phys_start phys_end virt_start virt_end
> LOAD[ 0] 8000000 9a2c000 ffffffff8a400000 ffffffff8be2c000
> LOAD[ 1] 100000 3b000000 ffff8f4fc0100000 ffff8f4ffb000000
> LOAD[ 2] 3d800000 3e341000 ffff8f4ffd800000 ffff8f4ffe341000
> LOAD[ 3] 3ed7b000 3eee2000 ffff8f4ffed7b000 ffff8f4ffeee2000
> LOAD[ 4] 3f63a000 3f800000 ffff8f4fff63a000 ffff8f4fff800000
> Linux kdump
> VMCOREINFO :
> OSRELEASE=4.18.0-348.12.2.el8_5-ale
> PAGESIZE=4096
> page_size : 4096
> SYMBOL(init_uts_ns)=ffffffff8b653600
> SYMBOL(node_online_map)=ffffffff8b7630a8
> SYMBOL(swapper_pg_dir)=ffffffff8b64c000
> SYMBOL(_stext)=ffffffff8a400000
> SYMBOL(vmap_area_list)=ffffffff8b6a47a0
> SYMBOL(mem_map)=ffffffff8bd25828
> SYMBOL(contig_page_data)=ffffffff8b726600
> SYMBOL(mem_section)=ffff8f4fff7fc000
hm, probably I've never seen a system that has both mem_map and mem_section, but it looks like makedumpfile works fine.. i.e. recognizes it as SPARSEMEM_EXTREME correctly.
> LENGTH(mem_section)=2048
> SIZE(mem_section)=16
> OFFSET(mem_section.section_mem_map)=0
> SIZE(page)=64
> SIZE(pglist_data)=5696
> SIZE(zone)=1216
> SIZE(free_area)=72
> SIZE(list_head)=16
> SIZE(nodemask_t)=8
> OFFSET(page.flags)=0
> OFFSET(page._refcount)=52
> OFFSET(page.mapping)=24
> OFFSET(page.lru)=8
> OFFSET(page._mapcount)=48
> OFFSET(page.private)=40
> OFFSET(page.compound_dtor)=16
> OFFSET(page.compound_order)=17
> OFFSET(page.compound_head)=8
> OFFSET(pglist_data.node_zones)=0
> OFFSET(pglist_data.nr_zones)=4944
> OFFSET(pglist_data.node_start_pfn)=4952
> OFFSET(pglist_data.node_spanned_pages)=4968
> OFFSET(pglist_data.node_id)=4976
> OFFSET(zone.free_area)=192
> OFFSET(zone.vm_stat)=1104
> OFFSET(zone.spanned_pages)=96
> OFFSET(free_area.free_list)=0
> OFFSET(list_head.next)=0
> OFFSET(list_head.prev)=8
> OFFSET(vmap_area.va_start)=0
> OFFSET(vmap_area.list)=40
> LENGTH(zone.free_area)=11
> SYMBOL(log_buf)=ffffffff8b67d3c0
> SYMBOL(log_buf_len)=ffffffff8b67d3bc
> SYMBOL(log_first_idx)=ffffffff8bd1a3d8
> SYMBOL(clear_idx)=ffffffff8bd1a3a4
> SYMBOL(log_next_idx)=ffffffff8bd1a3c8
> SIZE(printk_log)=16
> OFFSET(printk_log.ts_nsec)=0
> OFFSET(printk_log.len)=8
> OFFSET(printk_log.text_len)=10
> OFFSET(printk_log.dict_len)=12
> LENGTH(free_area.free_list)=4
> NUMBER(NR_FREE_PAGES)=0
> NUMBER(PG_lru)=5
> NUMBER(PG_private)=12
> NUMBER(PG_swapcache)=9
> NUMBER(PG_swapbacked)=18
> NUMBER(PG_slab)=8
> NUMBER(PG_head_mask)=32768
> NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE)=-129
> NUMBER(HUGETLB_PAGE_DTOR)=2
> NUMBER(PAGE_OFFLINE_MAPCOUNT_VALUE)=-257
> SYMBOL(alcatel_dump_info)=ffffffff8b647000
> NUMBER(phys_base)=-37748736
> SYMBOL(init_top_pgt)=ffffffff8b64c000
> NUMBER(pgtable_l5_enabled)=0
> KERNELOFFSET=9400000
> NUMBER(KERNEL_IMAGE_SIZE)=1073741824
> NUMBER(sme_mask)=0
> CRASHTIME=1648561077
>
> phys_base : fffffffffdc00000 (vmcoreinfo)
>
> max_mapnr : 3f800
> There is enough free memory to be done in one cycle.
>
> Buffer size for the cyclic mode: 65024 page_offset : ffff8f4fc0000000
> (pt_load) num of NODEs : 1 Memory type : SPARSEMEM_EX
>
> mem_map pfn_start pfn_end
> mem_map[ 0] ffff8f4ffa000000 0 8000
> mem_map[ 1] ffff8f4ffa200000 8000 10000
> mem_map[ 2] ffff8f4ffa400000 10000 18000
> mem_map[ 3] ffff8f4ffa600000 18000 20000
> mem_map[ 4] ffff8f4ffa800000 20000 28000
> mem_map[ 5] ffff8f4ffaa00000 28000 30000
> mem_map[ 6] ffff8f4ffac00000 30000 38000
> mem_map[ 7] ffff8f4ffae00000 38000 3f800
> mmap() is available on the kernel.
> Copying data : [100.0 %] | eta: 0s
> Writing erase info...
> offset_eraseinfo: ca157f3, size_eraseinfo: 0
>
> The dumpfile is saved to /tmpd/crashdump--20220329-1538.
>
> makedumpfile Completed.
> Rebooting the system...
>
> And latest logs from a 'crash -d 7' command are:
> <.>
> kernel NR_CPUS: 2
> <readmem: ffffffff8bd25820, KVADDR, "high_memory", 8, (FOE),
> 55e05ecb3608>
> <read_diskdump: addr: ffffffff8bd25820 paddr: 9925820 cnt: 8>
> PAGESIZE=4096
> mem_section_size = 16384
> NR_SECTION_ROOTS = 2048
> NR_MEM_SECTIONS = 524288
> SECTIONS_PER_ROOT = 256
> SECTION_ROOT_MASK = 0xff
> PAGES_PER_SECTION = 32768
> <readmem: ffffffff8bd26db0, KVADDR, "mem_section", 8, (FOE),
> 7ffdbf96a440>
> <read_diskdump: addr: ffffffff8bd26db0 paddr: 9926db0 cnt: 8>
> <readmem: ffff8f4fff7fc000, KVADDR, "memory section root table",
> 16384, (FOE), 55e06391b840>
> <read_diskdump: addr: ffff8f4fff7fc000 paddr: 3f7fc000 cnt: 4096>
> crash: read error: kernel virtual address: ffff8f4fff7fc000 type: "memory section root table"
>
> The address (ffff8f4fff7fc000) seems to be inside the LOAD[4] range
> and is recorded as 'mem_section' with VMCOREINFO.
Yes, this says it's sane, and its paddr also looks sane..
So I'm not sure why read_diskdump() returns READ_ERROR, could you debug it?
I'm suspecting the read() below in cache_page() returns something, e.g.
--- a/diskdump.c
+++ b/diskdump.c
@@ -1189,10 +1189,13 @@ cache_page(physaddr_t paddr)
return PAGE_INCOMPLETE;
}
} else {
+ ssize_t r;
if (lseek(dd->dfd, pd.offset, SEEK_SET) == failed)
return SEEK_ERROR;
- if (read(dd->dfd, dd->compressed_page, pd.size) != pd.size)
+ if ((r = read(dd->dfd, dd->compressed_page, pd.size)) != pd.size) {
+ error(INFO, "errno=%d r=%ld pd.size=%u\n",
+ errno, r, pd.size);
return READ_ERROR;
+ }
}
if (pd.flags & DUMP_DH_COMPRESSED_ZLIB) {
although another path may be returning it.
Thanks,
Kazu
Hello,
Suggested trace above gives following information after a crash -d 8 command:
<...>
kernel NR_CPUS: 2
<readmem: ffffffffa4925820, KVADDR, "high_memory", 8, (FOE), 56017b542648>
<read_diskdump: addr: ffffffffa4925820 paddr: 12925820 cnt: 8>
read_diskdump: paddr/pfn: 12925820/12925 -> cache physical page: 12925000
GETBUF(328 -> 0)
FREEBUF(0)
GETBUF(328 -> 0)
FREEBUF(0)
PAGESIZE=4096
mem_section_size = 16384
NR_SECTION_ROOTS = 2048
NR_MEM_SECTIONS = 524288
SECTIONS_PER_ROOT = 256
SECTION_ROOT_MASK = 0xff
PAGES_PER_SECTION = 32768
<readmem: ffffffffa4926db0, KVADDR, "mem_section", 8, (FOE), 7ffd1b6bb000>
<read_diskdump: addr: ffffffffa4926db0 paddr: 12926db0 cnt: 8>
read_diskdump: paddr/pfn: 12926db0/12926 -> cache physical page: 12926000
<readmem: ffff904c7f7fc000, KVADDR, "memory section root table", 16384, (FOE), 56017da26fd0>
<read_diskdump: addr: ffff904c7f7fc000 paddr: 3f7fc000 cnt: 4096>
read_diskdump: paddr/pfn: 3f7fc000/3f7fc -> cache physical page: 3f7fc000
crash: PAG3 - errno=2 r=0 pd.size=49
read_diskdump: READ_ERROR: cannot cache page: 3f7fc000
crash: read error: kernel virtual address: ffff904c7f7fc000 type: "memory section root table"
What could be done now ?
Thanks.
Best regards,
Patrick
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