Whoops! Important typo.... "other than that it involves network traffic and should NOT be causing any funky behavior here" -Kevin -----Original Message----- From: crash-utility-bounces@xxxxxxxxxx [mailto:crash-utility-bounces@xxxxxxxxxx] On Behalf Of Worth, Kevin Sent: Saturday, October 04, 2008 10:35 AM To: Discussion list for crash utility usage, maintenance and development; kexec-ml Subject: RE: "cannot access vmalloc'd module memory" when loading kdump'ed vmcore in crash Hi Dave (and kexec list), Including kexec list in this email because Dave mentioned: "Show the outputs of the live system and the subsequent dumpfile. If they both end up resolving to the same physical address, then there's an issue with the dumpfile." Things appear to be resolving to the same address (though I suspect Dave can confirm). Please see below. I did have to censor one of the lines a bit- I do have a proprietary kernel module that I'm not able to discuss much about other than that it involves network traffic and should be causing any funky behavior here (the ext3 module seems to behave the same way). I just changed its name to "custom_lkm". One additional note, although my "running system" kernel has the modified 3G kernel / 1G user split, my "capture kernel" is just the standard Ubuntu kernel (with 1G kernel / 3G user). The system panic'ed immediately if I tried to use my modified kernel as the "capture kernel". I figured this was outside the norm so I've been using the standard kernel to perform the capture. First I ran through some commands Dave suggested on the live system (my contexts for the live system and dump were different, but what might be more important is that "vm -p" on a live system produced errors, while on the dump it did not): crash> vm PID: 32227 TASK: 47bc8030 CPU: 0 COMMAND: "crash" MM PGD RSS TOTAL_VM f7e67040 5fddfe00 63336k 67412k VMA START END FLAGS FILE f3ed61d4 8048000 83e5000 1875 /root/crash f3ed6d84 83e5000 83fc000 101877 /root/crash .... crash> vm -p PID: 32227 TASK: 47bc8030 CPU: 0 COMMAND: "crash" MM PGD RSS TOTAL_VM f7e67040 5fddfe00 63336k 67412k VMA START END FLAGS FILE f3ed61d4 8048000 83e5000 1875 /root/crash VIRTUAL PHYSICAL vm: read error: physical address: 10b60b000 type: "page table" crash> p modules modules = $2 = { next = 0xf9088284, prev = 0xf8842104 } crash> module 0xf9088280 struct module { state = MODULE_STATE_LIVE, list = { next = 0xf8ff9d84, prev = 0x403c63a4 }, name = "custom_lkm\000\000\000\000\000\000\000\000\000\000\000\000\000\000\00 0\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\00 0\000\000\000\000\000\000\000\000\000\000\000\000\000", mkobj = { kobj = { k_name = 0xf90882cc "custom_lkm", name = "custom_lkm\000\000\000\000\000\000\000\000", kref = { refcount = { counter = 3 } }, entry = { next = 0x403c6068, prev = 0xf8ff9de4 }, ... crash> vtop 0xf9088280 VIRTUAL PHYSICAL f9088280 119b98280 PAGE DIRECTORY: 4044b000 PGD: 4044b018 => 6001 PMD: 6e40 => 1d515067 PTE: 1d515440 => 119b98163 PAGE: 119b98000 PTE PHYSICAL FLAGS 119b98163 119b98000 (PRESENT|RW|ACCESSED|DIRTY|GLOBAL) crash> mod | grep ext3 f88c8000 ext3 132616 (not loaded) [CONFIG_KALLSYMS] crash> module 0xf88c8000 struct module { state = MODULE_STATE_LIVE, list = { next = 0xf88a6604, prev = 0xf885d584 }, name = "ext3\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 00\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 00\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000", mkobj = { kobj = { k_name = 0xf88c804c "ext3", name = "ext3\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000", kref = { refcount = { counter = 3 } }, entry = { next = 0xf885d5e4, prev = 0xf88a6664 }, ... (Realized afterward that I forgot to vtop ext3. Let me know if it's needed and I can repeat this procedure) >From dump file: crash> vm PID: 4323 TASK: 47be0a90 CPU: 0 COMMAND: "bash" MM PGD RSS TOTAL_VM 5d683580 5d500dc0 2616k 3968k VMA START END FLAGS FILE 5fc2aac4 8048000 80ee000 1875 /bin/bash 5fe5f0cc 80ee000 80f3000 101877 /bin/bash ... crash> vm -p PID: 4323 TASK: 47be0a90 CPU: 0 COMMAND: "bash" MM PGD RSS TOTAL_VM 5d683580 5d500dc0 2616k 3968k VMA START END FLAGS FILE 5fc2aac4 8048000 80ee000 1875 /bin/bash VIRTUAL PHYSICAL 8048000 FILE: /bin/bash OFFSET: 0 8049000 FILE: /bin/bash OFFSET: 1000 804a000 FILE: /bin/bash OFFSET: 2000 ...no errors, lots of output crash> modules modules = $2 = { next = 0xf9088284, prev = 0xf8842104 } crash> module 0xf9088280 struct module { state = MODULE_STATE_LIVE, list = { next = 0x0, prev = 0x0 }, name = "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 00\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 00\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 00\000", mkobj = { kobj = { k_name = 0x0, name = "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 00\000\000", kref = { refcount = { counter = 0 } }, entry = { next = 0x0, prev = 0x0 ... crash> vtop 0xf9088280 VIRTUAL PHYSICAL f9088280 119b98280 PAGE DIRECTORY: 4044b000 PGD: 4044b018 => 6001 PMD: 6e40 => 1d515067 PTE: 1d515440 => 119b98163 PAGE: 119b98000 PTE PHYSICAL FLAGS 119b98163 119b98000 (PRESENT|RW|ACCESSED|DIRTY|GLOBAL) PAGE PHYSICAL MAPPING INDEX CNT FLAGS 47337300 119b98000 0 0 1 80000000 crash> mod | grep ext3 mod: cannot access vmalloc'd module memory (using the same address that ext3 had in a running system) crash> module 0xf88c8000 struct module { state = MODULE_STATE_LIVE, list = { next = 0x0, prev = 0x0 }, name = "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 00\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 00\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 00\000", mkobj = { kobj = { k_name = 0x0, name = "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 00\000\000", kref = { refcount = { counter = 0 } }, entry = { next = 0x0, prev = 0x0 ... crash> vtop 0xf88c8000 VIRTUAL PHYSICAL f88c8000 13905f000 PAGE DIRECTORY: 4044b000 PGD: 4044b018 => 6001 PMD: 6e20 => 1d5fc067 PTE: 1d5fc640 => 13905f163 PAGE: 13905f000 PTE PHYSICAL FLAGS 13905f163 13905f000 (PRESENT|RW|ACCESSED|DIRTY|GLOBAL) PAGE PHYSICAL MAPPING INDEX CNT FLAGS Thanks again for your continued assistance. I hope this is helpful information. -Kevin -----Original Message----- From: crash-utility-bounces@xxxxxxxxxx [mailto:crash-utility-bounces@xxxxxxxxxx] On Behalf Of Dave Anderson Sent: Friday, October 03, 2008 8:44 AM To: Discussion list for crash utility usage, maintenance and development; kexec@xxxxxxxxxxxxxxxxxxx Subject: Re: "cannot access vmalloc'd module memory" when loading kdump'ed vmcore in crash NOTE: I've restored the kexec list to this discussion because this 1G/3G issue does have ramifications w/respect to kexec-tools. I'm first going to ramble on about crash utility debugging for a bit here, but for the kexec/kdump masters in the audience, please at least take a look at the end of this message (do a "find in this message" for "KEXEC-KDUMP") where I discuss the kexec-tools hardwiring of the x86 PAGE_OFFSET to c000000, and whether it could screw up the dumpfile contents for Kevin's 1G/3G split where his PAGE_OFFSET is 40000000. First, the crash discussion... Worth, Kevin wrote: > Yep, I can run mod commands on a live system just fine. > > Looks like "next" doesn't point to fffffffc... > No, but it's 0x0, and therefore the "next" module in the list gets calculated as 0 - offset-of-list-member, or fffffffc. And "MODULE_STATE_LIVE" is being shown by dumb luck because its enumerator value is 0: > crash> module f9088280 > struct module { > state = MODULE_STATE_LIVE, > list = { > next = 0x0, > prev = 0x0 > }, > name = "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 > 00\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 > 00\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 > 00\000", > mkobj = { > kobj = { > k_name = 0x0, > name = "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\0 > 00\000\000", > kref = { > refcount = { > counter = 0 ... > > ...and all the rest of the struct is zeros too... Right, so we know bogus data is being read from the dumpfile. The question is: (1) whether the virtual-to-physical address translation is failing somehow, or (2) the dumpfile is screwed up. > Does the following mean that user virtual address translations are failing too? > > crash> set > PID: 4304 > COMMAND: "bash" > TASK: 5d7e9030 [THREAD_INFO: f4b70000] > CPU: 0 > STATE: TASK_RUNNING (SYSRQ) > crash> vm > PID: 4304 TASK: 5d7e9030 CPU: 0 COMMAND: "bash" > MM PGD RSS TOTAL_VM > f7e7f040 5d5002c0 2616k 3972k > VMA START END FLAGS FILE > 5fe454ec 8048000 80ee000 1875 /bin/bash > 5fe45e34 80ee000 80f3000 101877 /bin/bash > ... > > crash> rd 8048000 > rd: invalid kernel virtual address: 8048000 type: "32-bit KVADDR" > crash> rd -u 8048000 > rd: invalid user virtual address: 8048000 type: "32-bit UVADDR" > crash> rd 80ee000 > rd: invalid kernel virtual address: 80ee000 type: "32-bit KVADDR" > crash> rd -u 80ee000 > rd: invalid user virtual address: 80ee000 type: "32-bit UVADDR" > The fact that crash initially presumes that 8048000 and 80ee000 are kernel virtual addresses can be explained by this part of "help -v" debug output: flags: 515a (NODES_ONLINE|ZONES|PERCPU_KMALLOC_V2|COMMON_VADDR|KMEM_CACHE_INIT|FLATMEM|PERCPU_KMALLOC_V2_NODES) The "COMMON_VADDR" flag should *only* be set in the case of the Red Hat hugemem 4G/4G split kernel. However, I believe that crash should be able to continue even if the bit is set, as is the case when you run live. It is a crash issue having to do with your 4000000 PAGE_OFFSET, but I think it's benign, especially if user virtual address accesses run OK on your live system. That's one thing that needs verification. The "invalid user virtual address" messages above that you get *even* when you use "-u" would typically be generated as a result of the user virtual-to-physical address translation. However, they also could be generated if the virtual page being accessed has been swapped out. A better test would be translate all virtual address in the user address space in one fell swoop with "vm -p". It's a verbose command, but for each user virtual page in the current context, it will translate it to: (1) the current physical address location, or (2) if it's not in memory, but is backed by a file, it will show what file it comes from, or (3) if it's been swapped out, what swapfile location is has been swapped out to, or (4) if it's an anonymous page (with no file backing) that hasn't been touched yet, it will show "(not mapped)" Here's a truncated example: PID: 19839 TASK: f7b03000 CPU: 1 COMMAND: "bash" MM PGD RSS TOTAL_VM f6dc5740 f745c9c0 1392k 4532k VMA START END FLAGS FILE f69019bc 6fa000 703000 75 /lib/libnss_files-2.5.so VIRTUAL PHYSICAL 6fa000 12fdba000 6fb000 12fdbb000 6fc000 FILE: /lib/libnss_files-2.5.so OFFSET: 2000 6fd000 FILE: /lib/libnss_files-2.5.so OFFSET: 3000 6fe000 12f660000 6ff000 12f2cf000 700000 FILE: /lib/libnss_files-2.5.so OFFSET: 6000 701000 FILE: /lib/libnss_files-2.5.so OFFSET: 7000 702000 12fc6f000 VMA START END FLAGS FILE f69013e4 703000 704000 100071 /lib/libnss_files-2.5.so VIRTUAL PHYSICAL 703000 54791000 VMA START END FLAGS FILE f6901d84 704000 705000 100073 /lib/libnss_files-2.5.so VIRTUAL PHYSICAL 704000 12450d000 VMA START END FLAGS FILE f6901284 a7c000 a96000 875 /lib/ld-2.5.so VIRTUAL PHYSICAL a7c000 6ea28000 a7d000 101f62000 a7e000 6e6f3000 a7f000 6e07e000 a80000 6e084000 a81000 114c8e000 ... Run the command above on a "bash" context on *both* the live system and the dumpfile -- they should behave in a similar manner, but I'm guessing you may get some bizarre errors when you run it on the dumpfile. Getting back to the base problem with the bogus module read, here'a suggestion for debugging this. It requires that you run the live system, gather some basic data with the crash utility, and then enter "alt-sysrq-c". What we want to see is a virtual-to-physical translation of the first module in the module list on the live system. Then crash the system. Then we want to do the same thing on the subsequent vmcore to see if the same physical address references are made during the translation. So for example, on my live system, the "/dev/crash" kernel module is the last module entered, and therefore is pointed to by the base kernel's "modules" list_head: crash> p modules modules = $2 = { next = 0xf8bd0904, prev = 0xf882b104 } Subtract 4 from the "next" pointer, and display the module: crash> module 0xf8bd0900 struct module { state = MODULE_STATE_LIVE, list = { next = 0xf8caf984, prev = 0xc06787b0 }, name = "crash", mkobj = { kobj = { k_name = 0xf8bd094c "crash", name = "crash", kref = { refcount = { counter = 2 } }, ... Then translate it: crash> vtop 0xf8bd0900 VIRTUAL PHYSICAL f8bd0900 48ba1900 PAGE DIRECTORY: c0724000 PGD: c0724018 => 4001 PMD: 4e28 => 37ae067 PTE: 37aee80 => 48ba1163 PAGE: 48ba1000 PTE PHYSICAL FLAGS 48ba1163 48ba1000 (PRESENT|RW|ACCESSED|DIRTY|GLOBAL) PAGE PHYSICAL MAPPING INDEX CNT FLAGS c1917420 48ba1000 0 785045 1 c0000000 crash> Do the same type of thing on your live system (where you'll have a different module), and save the output in a file. Then immediately enter "alt-sysrq-c". With the resultant dumpfile, perform the same "p modules", "module <next-address-4>", and "vtop <next-address-4> steps as done above. The output *should* be identical, although we're primarily interested in the vtop output given that the "module <next-address-4>" will probably show garbage. (BTW, this presumes that the first module in the kernel list will still return bogus data like your current dumpfile. That may not be the case, and if so, we'll need to do something similar but different. For example, on the live system, capture the address of the "ext3" module, vtop it, crash the system, and then do the same thing in the dumpfile. You might want to do that anyway, just in case the default behavior is different. Then again, maybe it will work both live and in the dumpfile for the ext3 module address, in which case we'll need to go in a different debug-direction...) Show the outputs of the live system and the subsequent dumpfile. If they both end up resolving to the same physical address, then there's an issue with the dumpfile. KEXEC-KDUMP: I talked to Vivek Goyal, who originally wrote the kexec-tools facility, and he pointed me to this in the kexec-tools package's "kexec/arch/i386/crashdump-x86.h" file: #define PAGE_OFFSET 0xc0000000 #define __pa(x) ((unsigned long)(x)-PAGE_OFFSET) #define __VMALLOC_RESERVE (128 << 20) #define MAXMEM (-PAGE_OFFSET-__VMALLOC_RESERVE) where for x86, it hard-wires the x86 PAGE_OFFSET to c0000000, and will certainly result in a bogus MAXMEM given that your PAGE_OFFSET is 40000000. I don't know if that is related to the problem, but if you do a "readelf -a" of your vmcore file, you'll see some funky virtual address values for each PT_LOAD segment. They were dumped in the crash.log you sent me. Note that the virtual address regions (p_vaddr) are c0000000, c0100000, c5000000, ffffffffffffffff and ffffffffffffffff, all of which are incorrect or nonsensical w/respect to your 1G/3G split: Elf64_Phdr: p_type: 1 (PT_LOAD) p_offset: 728 (2d8) p_vaddr: c0000000 p_paddr: 0 p_filesz: 655360 (a0000) p_memsz: 655360 (a0000) p_flags: 7 (PF_X|PF_W|PF_R) p_align: 0 Elf64_Phdr: p_type: 1 (PT_LOAD) p_offset: 656088 (a02d8) p_vaddr: c0100000 p_paddr: 100000 p_filesz: 15728640 (f00000) p_memsz: 15728640 (f00000) p_flags: 7 (PF_X|PF_W|PF_R) p_align: 0 Elf64_Phdr: p_type: 1 (PT_LOAD) p_offset: 16384728 (fa02d8) p_vaddr: c5000000 p_paddr: 5000000 p_filesz: 855638016 (33000000) p_memsz: 855638016 (33000000) p_flags: 7 (PF_X|PF_W|PF_R) p_align: 0 Elf64_Phdr: p_type: 1 (PT_LOAD) p_offset: 872022744 (33fa02d8) p_vaddr: ffffffffffffffff p_paddr: 38000000 p_filesz: 2272854016 (87790000) p_memsz: 2272854016 (87790000) p_flags: 7 (PF_X|PF_W|PF_R) p_align: 0 Elf64_Phdr: p_type: 1 (PT_LOAD) p_offset: 3144876760 (bb7302d8) p_vaddr: ffffffffffffffff p_paddr: 100000000 p_filesz: 1073741824 (40000000) p_memsz: 1073741824 (40000000) p_flags: 7 (PF_X|PF_W|PF_R) p_align: 0 Now, the crash utility only uses the p_paddr physical address fields for x86 dumpfiles, so that shouldn't be a problem. But I wonder whether when the /proc/vmcore is put together that there isn't some problem with the data that it accesses? Thanks, Dave -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/crash-utility -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/crash-utility -- Crash-utility mailing list Crash-utility@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/crash-utility
