Recent testing on very large memory systems dictates that an update is required for the compressed kdump header generated by makedumpfile. The dumpfile header has this field, which was inherited from the old "diskdump" facility: struct disk_dump_header { ... unsigned int max_mapnr; /* = max_mapnr */ ... and which, among other things, is used by the crash utility as a delimiter to determine whether a physical address read request is legitimate. And obviously the field cannot handle PFN values greater than 32-bits. The makedumpfile source code does have its own max_mapnr representation in its DumpInfo structure in "makedumpfile.h": struct DumpInfo { ... unsigned long long max_mapnr; /* number of page descriptor */ ... But in its "diskdump_mod.h" file, it carries forward the old diskdump header format, which has the 32-bit field: struct disk_dump_header { ... unsigned int max_mapnr; /* = max_mapnr */ ... And here in "makedumpfile.c", the inadvertent truncation occurs when the PFN is greater than 32-bits: int write_kdump_header(void) { ... dh->max_mapnr = info->max_mapnr; ... The 32-bit field has also been carried forward into the SADUMP header as well, which has this in "sadump_mod.h": struct sadump_header { ... uint32_t max_mapnr; /* = max_mapnr */ ... And when these header structures change, the crash utility will need to be changed accordingly. Preferably for backwards-compatibility, a new header_version can be created, with the new expanded field located in the kdump_sub_header so that the original base structure can remain as-is. But I leave that up to the maintainers. Thanks, Dave _______________________________________________ kexec mailing list kexec(a)lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec

(2013/09/17 13:36), Jingbai Ma wrote: <cut> >> >> And when these header structures change, the crash utility will need >> to be changed accordingly. >> >> Preferably for backwards-compatibility, a new header_version can be >> created, with the new expanded field located in the kdump_sub_header >> so that the original base structure can remain as-is. But I leave that >> up to the maintainers. >> >> Thanks, >> Dave >> >> _______________________________________________ >> kexec mailing list >> kexec(a)lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/kexec >> > > For the persistent data structures, we should use more precision > declaration int32_t, int64_t, uint64_t instead of ambiguous int, long > int, long long int. > For example, we can change structure disk_dump_header as below: > struct disk_dump_header { > char signature[SIG_LEN]; /* = "KDUMP " */ > int32_t header_version; /* Dump header version */ > struct new_utsname utsname; /* copy of system_utsname */ > struct timeval timestamp; /* Time stamp */ > uint32_t status; /* Above flags */ > int32_t block_size; /* Size of a block in byte */ > int32_t sub_hdr_size; /* Size of arch dependent > header in blocks */ > uint32_t bitmap_blocks; /* Size of Memory bitmap in > block */ > uint64_t max_mapnr; /* = max_mapnr */ > uint32_t total_ram_blocks;/* Number of blocks should be > written */ > uint32_t device_blocks; /* Number of total blocks in > * the dump device */ > uint32_t written_blocks; /* Number of written blocks */ > uint32_t current_cpu; /* CPU# which handles dump */ > int32_t nr_cpus; /* Number of CPUs */ > struct task_struct *tasks[0]; > }; > > Looking at arch directory, this structure is used on x86, x86_64, ppc, ppc64, s390 and ia64. Does this definition work well on all the architectures? tasks member has obviously different length in each architecture but this member is never used now. More worse is kdump_sub_header structure. Obviously, unsigned long has different length on x86 and x86_64, though you have already noticed this. I don't know ABI on other architectures. Sorry. /* * Sub header for KDUMP * But Common header of KDUMP is disk_dump_header of diskdump. */ struct kdump_sub_header { unsigned long phys_base; int dump_level; /* header_version 1 and later */ int split; /* header_version 2 and later */ unsigned long start_pfn; /* header_version 2 and later */ unsigned long end_pfn; /* header_version 2 and later */ off_t offset_vmcoreinfo;/* header_version 3 and later */ unsigned long size_vmcoreinfo; /* header_version 3 and later */ off_t offset_note; /* header_version 4 and later */ unsigned long size_note; /* header_version 4 and later */ off_t offset_eraseinfo; /* header_version 5 and later */ unsigned long size_eraseinfo; /* header_version 5 and later */ };

(2013/09/17 16:12), Jingbai Ma wrote: > On 09/17/2013 02:55 PM, HATAYAMA Daisuke wrote: > > int32_t, int64_t, uint64_t, etc ... are parts of C99 standard: > http://en.wikipedia.org/wiki/C_data_types > All there types have been supported by GCC, so them should work on all > the architectures. > > Although change these persistent data structure will affect both > makedumpfile and crash utility, but we will benefit from the > consistent data structures independent from architectures. We can > analyze a dumpfile on a OS with different architecture than the > crashed OS. > > I know stdint.h things and usefulness if we can use crash and makedumpfile for a multiple architectures on single arch. In fact, crash already supports cross platform build among some architectures thanks to Dave. My question came from the fact that it looks like you introduced a single modified kdump_sub_header structure for all the architectures. They might have different combination of length between int and long and maybe also have other each architecture specific incompatibility. It wouldn't work well. But from your reply, I think you mean a fully new header for kdump-compressed format, right? If so, it must work well. But of course you need to modify both of makedumpfile and crash utility to support it.

----- Original Message ----- > On 09/17/2013 03:33 PM, HATAYAMA Daisuke wrote: >> (2013/09/17 16:12), Jingbai Ma wrote: >>> On 09/17/2013 02:55 PM, HATAYAMA Daisuke wrote: >>> >>> int32_t, int64_t, uint64_t, etc ... are parts of C99 standard: >>> http://en.wikipedia.org/wiki/C_data_types >>> All there types have been supported by GCC, so them should work on all >>> the architectures. >>> >>> Although change these persistent data structure will affect both >>> makedumpfile and crash utility, but we will benefit from the >>> consistent data structures independent from architectures. We can >>> analyze a dumpfile on a OS with different architecture than the >>> crashed OS. >>> >>> >> >> I know stdint.h things and usefulness if we can use crash and makedumpfile >> for a multiple architectures on single arch. In fact, crash already supports >> cross platform build among some architectures thanks to Dave. But only if the host and target architectures have the same endian-ness and whose data type sizes match.

The only problem that has ever been seen with the current header declarations is if an x86 crash binary is built to support the 32-bit ARM architecture. For x86, the 64-bit off_t variables can start on a 4-byte boundary, but on ARM, they have to start on an 8-byte boundary. That being the case, the off_t offset_vmcoreinfo is at offset 20 when built on an x86, and at offset 24 when built on ARM:

struct kdump_sub_header { unsigned long phys_base; int dump_level; /* header_version 1 and later */ int split; /* header_version 2 and later */ unsigned long start_pfn; /* header_version 2 and later */ unsigned long end_pfn; /* header_version 2 and later */ off_t offset_vmcoreinfo; /* header_version 3 and later */ unsigned long size_vmcoreinfo; /* header_version 3 and later */ off_t offset_note; /* header_version 4 and later */ unsigned long size_note; /* header_version 4 and later */ off_t offset_eraseinfo; /* header_version 5 and later */ unsigned long size_eraseinfo; /* header_version 5 and later */ };

So for that anomoly, crash has to support a kdump_sub_header_ARM_target structure that has a pad integer after the end_pfn variable. >> >> My question came from the fact that it looks like you introduced a single >> modified kdump_sub_header structure for all the architectures. They might >> have different combination of length between int and long and maybe >> also have other each architecture specific incompatibility. It wouldn't >> work well. >> >> But from your reply, I think you mean a fully new header for >> kdump-compressed >> format, right? If so, it must work well. But of course you need to modify >> both of makedumpfile and crash utility to support it. >> > > Yes, I would like to have a new header for kdump-compressed format. But > I'm not sure how much code will be affected in makedumpfile and crash utility. > I'm still under investigating, any ideas would be appreciated. The challenging part will be the requirement to maintain backwards-compatibility, at least in the crash utility. And backwards-compatibility would also be required in makedumpfile, right? For example, if you want to re-filter an older compressed kdump.

But if -- as has been done so far -- an increment of the header_version in the disk_dump_header to signal an additional field in the kdump_sub_header would be trivial to implement.

Dave

----- Original Message ----- > On 09/17/2013 09:23 PM, Dave Anderson wrote: > > > > > > ----- Original Message ----- > >> On 09/17/2013 03:33 PM, HATAYAMA Daisuke wrote: > >>> (2013/09/17 16:12), Jingbai Ma wrote: > >>>> On 09/17/2013 02:55 PM, HATAYAMA Daisuke wrote: > >>>> > >>>> int32_t, int64_t, uint64_t, etc ... are parts of C99 standard: > >>>> http://en.wikipedia.org/wiki/C_data_types > >>>> All there types have been supported by GCC, so them should work on >all > >>>> the architectures. > >>>> > >>>> Although change these persistent data structure will affect both > >>>> makedumpfile and crash utility, but we will benefit from the > >>>> consistent data structures independent from architectures. We can > >>>> analyze a dumpfile on a OS with different architecture than the > >>>> crashed OS. > >>>> > >>>> > >>> > >>> I know stdint.h things and usefulness if we can use crash and >makedumpfile > >>> for a multiple architectures on single arch. In fact, crash already >supports > >>> cross platform build among some architectures thanks to Dave. > > > > But only if the host and target architectures have the same >endian-ness and > > whose data type sizes match. > > > > If we have a standard for the dump file format, we can handle all the >endian-ness issues. > I know it may affect the dumping speed on the platform that has to > convert the byte order. But at least we can specify the byte order for > dump file header. It won't cost too much. > > > The only problem that has ever been seen with the current header >declarations > > is if an x86 crash binary is built to support the 32-bit ARM >architecture. > > For x86, the 64-bit off_t variables can start on a 4-byte boundary, >but on ARM, > > they have to start on an 8-byte boundary. That being the case, the >off_t > > offset_vmcoreinfo is at offset 20 when built on an x86, and at offset >24 > > when built on ARM: > > This could be addressed through compiler attributes: > off_t offset_vmcoreinfo __atttribute__ ((aligned(8)); > offset_vmcoreinfo will be the same 8-byte boundary on x86 as same as ARM > > > > > struct kdump_sub_header { > > unsigned long phys_base; > > int dump_level; /* header_version 1 and >later */ > > int split; /* header_version 2 and >later */ > > unsigned long start_pfn; /* header_version 2 and >later */ > > unsigned long end_pfn; /* header_version 2 and >later */ > > off_t offset_vmcoreinfo; /* header_version 3 and >later */ > > unsigned long size_vmcoreinfo; /* header_version 3 and >later */ > > off_t offset_note; /* header_version 4 and >later */ > > unsigned long size_note; /* header_version 4 and >later */ > > off_t offset_eraseinfo; /* header_version 5 and >later */ > > unsigned long size_eraseinfo; /* header_version 5 and >later */ > > }; > > > > Do you like this change? > struct kdump_sub_header { > unsigned long phys_base; > int dump_level; > int split; > unsigned long start_pfn; > unsigned long end_pfn; > off_t offset_vmcoreinfo __atttribute__ ((aligned(8)); > unsigned long size_vmcoreinfo; > off_t offset_note __atttribute__ ((aligned(8)); > unsigned long size_note; > off_t offset_eraseinfo __atttribute__ ((aligned(8)); > unsigned long size_eraseinfo; > }; > > Then you can get rid of the padded struct kdump_sub_header_ARM_target in > crash utility. Adding the aligned(8) attribute to the kdump_sub_header would break compatibility with all of the old/current 32-bit x86 dumpfiles that have it aligned on an 4-byte boundary. How do you propose working around that? > > Or we can go further, redefine whole structure and set all fields with > specific bit width. > > struct kdump_sub_header { > uint64_t phys_base; > int32_t dump_level; > int32_t split; > uint64_t start_pfn; > uint64_t end_pfn; > uint64_t offset_vmcoreinfo; > uint64_t size_vmcoreinfo; > uint64_t offset_note; > uint64_t size_note; > uint64_t offset_eraseinfo; > uint64_t size_eraseinfo; > }; > > I have checked the code of crash utility, it shouldn't affect too much, > only in diskdump.c and diskdump.h. > > > So for that anomoly, crash has to support a >kdump_sub_header_ARM_target > > structure that has a pad integer after the end_pfn variable. > > > >>> > >>> My question came from the fact that it looks like you introduced a >single > >>> modified kdump_sub_header structure for all the architectures. They >might > >>> have different combination of length between int and long and maybe > >>> also have other each architecture specific incompatibility. It >wouldn't > >>> work well. > >>> > >>> But from your reply, I think you mean a fully new header for >kdump-compressed > >>> format, right? If so, it must work well. But of course you need to >modify > >>> both of makedumpfile and crash utility to support it. > >>> > >> > >> Yes, I would like to have a new header for kdump-compressed format. >But > >> I'm not sure how much code will be affected in makedumpfile and >crash utility. > >> I'm still under investigating, any ideas would be appreciated. > > > > The challenging part will be the requirement to maintain >backwards-compatibility, > > at least in the crash utility. And backwards-compatibility would >also be required > > in makedumpfile, right? For example, if you want to re-filter an >older compressed > > kdump. > > > > It's not a big deal, we can check the header_version to decide treat it > as traditional format or new format. > We can preserve the current structures as kdump_sub_header_v5 , > kdump_sub_header_v5, etc... in both makedumpfile and crash utility. OK, but I still don't see how to avoid carrying two versions of kdump_sub_header_v5 to handle the current ARM-on-x86 support. Or doing some kind of similar kludge... Supporting both a kdump_sub_header and a kdump_sub_header_v5 is going to make read_dump_header() a bit tricky. I suppose after reading the raw kdump_sub_header block (of either type), if it's v5 or less you could copy the individual fields from the kdump_sub_header_v5 to the new kdump_sub_header before referencing them? > > But if -- as has been done so far -- an increment of the >header_version in the > > disk_dump_header to signal an additional field in the >kdump_sub_header would be > > trivial to implement. > > Yes, this approach is more simpler, but the drawback is we have to add a > new 64bit max_mapnr_64 to disk_dump_header, then we will have two > max_mapnr* fields, not very nice. And when we add more platforms, we > still have to take care of the bit width and alignment. > Should we fix it in this version or just leave it as it used to be? Note that I suggested above that the 64-bit max_mapnr be added to the kdump_sub_header, so that the disk_dump_header itself can remain backwards-compatible. Dave

The 32-bit field has also been carried forward into the SADUMP header as well, which has this in "sadump_mod.h": struct sadump_header { ... uint32_t max_mapnr; /* = max_mapnr */ ... And when these header structures change, the crash utility will need to be changed accordingly. Preferably for backwards-compatibility, a new header_version can be created, with the new expanded field located in the kdump_sub_header so that the original base structure can remain as-is. But I leave that up to the maintainers. Thanks, Dave