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Re: [Xen-devel] [PATCH] Support cross-bitness guest when core-dumping

 On 1/14/2009 at 10:08 PM, Isaku Yamahata <yamahata@xxxxxxxxxxxxx> wrote:
> On Wed, Jan 14, 2009 at 09:00:38PM -0700, Bruce Rogers wrote:
>> The "change" to the format is as follows:  Now the file format for a 
> cross-bit configuration will be the same as would have been produced by a 
> same-bitness configuration, which crash of course already handles.  So crash 
> should be fine with this change. In fact that was part of how I determined 
> that it was working right.
>> I consider that the cross-bitness format was simply not valid as there is no 
> reason for there to be a different format for the file simply because the 
> host was a different bitsize than the guest (and it didn't work with crash & 
> gdb-xenserver as it was).
>> 
> 
> Yes, I agree with you. However for FV case, e_ident[EI_DATA] is set
> according to the host configuration because XEN_DOMCTL_[sg]et_address_bits
> doesn't make sense. And there is no easy way to determine the guest OS mode.
> The following patch looks okay?
> 
Right - thanks for pointing that out.  The doc change looks good to me.
Bruce

> dump-core: update the documentation
> 
> This patch updates the document on dump-core file format.
> 
> Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
> 
> diff --git a/docs/misc/dump-core-format.txt b/docs/misc/dump-core-format.txt
> --- a/docs/misc/dump-core-format.txt
> +++ b/docs/misc/dump-core-format.txt
> @@ -30,8 +30,13 @@ The elf header members are set as follow
>          e_ident[EI_OSABI] = ELFOSABI_SYSV = 0
>          e_type = ET_CORE = 4
>  ELFCLASS64 is always used independent of architecture.
> -e_ident[EI_DATA] and e_flags are set according to the dumping system's
> -architecture. Other members are set as usual.
> +e_ident[EI_DATA] is set as follows
> +  For x86 PV domain case, it is set according to the guest configuration
> +  (i.e. if guest is 32bit it is set to EM_386 even when the dom0 is 64 
> bit.)
> +  For other domain case (x86 HVM domain case and ia64 domain case),
> +  it is set according to the dumping system's architecture.
> +e_flags is set according to the dumping system's architecture.
> +Other members are set as usual.
>  
>  Sections
>  --------
> @@ -241,3 +246,7 @@ Currently only (major, minor) = (0, 1) i
>    The format version isn't bumped because analysis tools can distinguish 
> it.
>  - .xen_ia64_mapped_regs section was made only for ia64 PV domain.
>    In case of IA64 HVM domain, this section doesn't exist.
> +- elf header e_ident[EI_DATA]
> +  On x86 PV domain case, it is set according to the guest configuration.
> +  I.e. 32-on-64 case, the file will be set EM_386 instead of EM_X86_64.
> +  This is the same as 32-on-32 case, so there is no impact on analysis tools.
> 
> 
>> - Bruce
>> 
>> >>> Isaku Yamahata <yamahata@xxxxxxxxxxxxx> 01/14/09 8:17 PM >>>
>> [CCed to Anderson, Oda and crash-utility ml]
>> Hi Bruce. Nice patch.
>> 
>> Could you please update the documentation about its format too?
>>   docs/misc/dump-core-format.txt
>>   - Elf header section, and
>>   - revision history at the end of the file.
>> 
>> And what is the impact on the crash utility?
>> 
>> thanks,
>> 
>> On Wed, Jan 14, 2009 at 04:47:41PM -0700, Bruce Rogers wrote:
>> > This patch allows core-dumping to work on a cross-bit host/guest 
> configuration, whereas previously that was not supported.  It supports both 
> PV and FV guests. The core file format generated by the host, needs to match 
> that of the guest, so an alignment issue is addressed, along with the p2m 
> frame list handling being done according to the guest size.
>> > 
>> > Signed-off-by: Bruce Rogers <brogers@xxxxxxxxxx>
>> > 
>> 
>> > diff -r 77476eeb8c42 tools/libxc/xc_core.c
>> > --- a/tools/libxc/xc_core.c    Wed Jan 14 11:39:01 2009 +0000
>> > +++ b/tools/libxc/xc_core.c    Wed Jan 14 16:40:17 2009 -0700
>> > @@ -57,9 +57,6 @@
>> >  
>> >  /* number of pages to write at a time */
>> >  #define DUMP_INCREMENT (4 * 1024)
>> > -
>> > -/* Don't yet support cross-address-size core dump */
>> > -#define guest_width (sizeof (unsigned long))
>> >  
>> >  /* string table */
>> >  struct xc_core_strtab {
>> > @@ -240,7 +237,7 @@ xc_core_ehdr_init(Elf64_Ehdr *ehdr)
>> >      ehdr->e_ident[EI_ABIVERSION] = EV_CURRENT;
>> >  
>> >      ehdr->e_type = ET_CORE;
>> > -    ehdr->e_machine = ELF_ARCH_MACHINE;
>> > +    /* e_machine will be filled in later */
>> >      ehdr->e_version = EV_CURRENT;
>> >      ehdr->e_entry = 0;
>> >      ehdr->e_phoff = 0;
>> > @@ -359,7 +356,8 @@ elfnote_dump_core_header(
>> >  }
>> >  
>> >  static int
>> > -elfnote_dump_xen_version(void *args, dumpcore_rtn_t dump_rtn, int 
> xc_handle)
>> > +elfnote_dump_xen_version(void *args, dumpcore_rtn_t dump_rtn, int 
> xc_handle,
>> > +                         unsigned int guest_width)
>> >  {
>> >      int sts;
>> >      struct elfnote elfnote;
>> > @@ -371,6 +369,12 @@ elfnote_dump_xen_version(void *args, dum
>> >      elfnote.descsz = sizeof(xen_version);
>> >      elfnote.type = XEN_ELFNOTE_DUMPCORE_XEN_VERSION;
>> >      elfnote_fill_xen_version(xc_handle, &xen_version);
>> > +    if (guest_width < sizeof(unsigned long))
>> > +    {
>> > +        // 32 bit elf file format differs in pagesize's alignment
>> > +        char *p = (char *)&xen_version.pagesize;
>> > +        memmove(p - 4, p, sizeof(xen_version.pagesize));
>> > +    }
>> >      sts = dump_rtn(args, (char*)&elfnote, sizeof(elfnote));
>> >      if ( sts != 0 )
>> >          return sts;
>> > @@ -396,6 +400,24 @@ elfnote_dump_format_version(void *args, 
>> >      return dump_rtn(args, (char*)&format_version, sizeof(format_version));
>> >  }
>> >  
>> > +static int
>> > +get_guest_width(int xc_handle,
>> > +                uint32_t domid,
>> > +                unsigned int *guest_width)
>> > +{
>> > +    DECLARE_DOMCTL;
>> > +
>> > +    memset(&domctl, 0, sizeof(domctl));
>> > +    domctl.domain = domid;
>> > +    domctl.cmd = XEN_DOMCTL_get_address_size;
>> > +
>> > +    if ( do_domctl(xc_handle, &domctl) != 0 )
>> > +        return 1;
>> > +        
>> > +    *guest_width = domctl.u.address_size.size / 8;
>> > +    return 0;
>> > +}
>> > +
>> >  int
>> >  xc_domain_dumpcore_via_callback(int xc_handle,
>> >                                  uint32_t domid,
>> > @@ -403,7 +425,8 @@ xc_domain_dumpcore_via_callback(int xc_h
>> >                                  dumpcore_rtn_t dump_rtn)
>> >  {
>> >      xc_dominfo_t info;
>> > -    shared_info_t *live_shinfo = NULL;
>> > +    shared_info_any_t *live_shinfo = NULL;
>> > +    unsigned int guest_width; 
>> >  
>> >      int nr_vcpus = 0;
>> >      char *dump_mem, *dump_mem_start = NULL;
>> > @@ -437,6 +460,12 @@ xc_domain_dumpcore_via_callback(int xc_h
>> >      uint16_t strtab_idx;
>> >      struct xc_core_section_headers *sheaders = NULL;
>> >      Elf64_Shdr *shdr;
>> > + 
>> > +    if ( get_guest_width(xc_handle, domid, &guest_width) != 0 )
>> > +    {
>> > +        PERROR("Could not get address size for domain");
>> > +        return sts;
>> > +    }
>> >  
>> >      xc_core_arch_context_init(&arch_ctxt);
>> >      if ( (dump_mem_start = malloc(DUMP_INCREMENT*PAGE_SIZE)) == NULL )
>> > @@ -500,7 +529,7 @@ xc_domain_dumpcore_via_callback(int xc_h
>> >              goto out;
>> >          }
>> >  
>> > -        sts = xc_core_arch_map_p2m(xc_handle, &info, live_shinfo,
>> > +        sts = xc_core_arch_map_p2m(xc_handle, guest_width, &info, 
> live_shinfo,
>> >                                     &p2m, &p2m_size);
>> >          if ( sts != 0 )
>> >              goto out;
>> > @@ -676,6 +705,7 @@ xc_domain_dumpcore_via_callback(int xc_h
>> >      /* write out elf header */
>> >      ehdr.e_shnum = sheaders->num;
>> >      ehdr.e_shstrndx = strtab_idx;
>> > +    ehdr.e_machine = ELF_ARCH_MACHINE;
>> >      sts = dump_rtn(args, (char*)&ehdr, sizeof(ehdr));
>> >      if ( sts != 0 )
>> >          goto out;
>> > @@ -697,7 +727,7 @@ xc_domain_dumpcore_via_callback(int xc_h
>> >          goto out;
>> >  
>> >      /* elf note section: xen version */
>> > -    sts = elfnote_dump_xen_version(args, dump_rtn, xc_handle);
>> > +    sts = elfnote_dump_xen_version(args, dump_rtn, xc_handle, 
> guest_width);
>> >      if ( sts != 0 )
>> >          goto out;
>> >  
>> > @@ -757,9 +787,21 @@ xc_domain_dumpcore_via_callback(int xc_h
>> >  
>> >              if ( !auto_translated_physmap )
>> >              {
>> > -                gmfn = p2m[i];
>> > -                if ( gmfn == INVALID_P2M_ENTRY )
>> > -                    continue;
>> > +                if ( guest_width >= sizeof(unsigned long) )
>> > +                {
>> > +                    if ( guest_width == sizeof(unsigned long) )
>> > +                        gmfn = p2m[i];
>> > +                    else
>> > +                        gmfn = ((uint64_t *)p2m)[i];
>> > +                    if ( gmfn == INVALID_P2M_ENTRY )
>> > +                        continue;
>> > +                }
>> > +                else
>> > +                {
>> > +                    gmfn = ((uint32_t *)p2m)[i];
>> > +                    if ( gmfn == (uint32_t)INVALID_P2M_ENTRY )
>> > +                       continue;
>> > +                }
>> >  
>> >                  p2m_array[j].pfn = i;
>> >                  p2m_array[j].gmfn = gmfn;
>> > @@ -802,7 +844,7 @@ copy_done:
>> >          /* When live dump-mode (-L option) is specified,
>> >           * guest domain may reduce memory. pad with zero pages.
>> >           */
>> > -        IPRINTF("j (%ld) != nr_pages (%ld)", j , nr_pages);
>> > +        IPRINTF("j (%ld) != nr_pages (%ld)", j, nr_pages);
>> >          memset(dump_mem_start, 0, PAGE_SIZE);
>> >          for (; j < nr_pages; j++) {
>> >              sts = dump_rtn(args, dump_mem_start, PAGE_SIZE);
>> > @@ -891,7 +933,7 @@ xc_domain_dumpcore(int xc_handle,
>> >      struct dump_args da;
>> >      int sts;
>> >  
>> > -    if ( (da.fd = open(corename, O_CREAT|O_RDWR, S_IWUSR|S_IRUSR)) < 0 )
>> > +    if ( (da.fd = open(corename, O_CREAT|O_RDWR|O_TRUNC, 
>> > S_IWUSR|S_IRUSR)) 
> < 0 )
>> >      {
>> >          PERROR("Could not open corefile %s", corename);
>> >          return -errno;
>> > diff -r 77476eeb8c42 tools/libxc/xc_core.h
>> > --- a/tools/libxc/xc_core.h    Wed Jan 14 11:39:01 2009 +0000
>> > +++ b/tools/libxc/xc_core.h    Wed Jan 14 16:40:17 2009 -0700
>> > @@ -136,12 +136,12 @@ struct xc_core_arch_context;
>> >  struct xc_core_arch_context;
>> >  int xc_core_arch_memory_map_get(int xc_handle,
>> >                                  struct xc_core_arch_context *arch_ctxt,
>> > -                                xc_dominfo_t *info, shared_info_t 
> *live_shinfo,
>> > +                                xc_dominfo_t *info, shared_info_any_t 
> *live_shinfo,
>> >                                  xc_core_memory_map_t **mapp,
>> >                                  unsigned int *nr_entries);
>> > -int xc_core_arch_map_p2m(int xc_handle, xc_dominfo_t *info,
>> > -                         shared_info_t *live_shinfo, xen_pfn_t **live_p2m,
>> > -                         unsigned long *pfnp);
>> > +int xc_core_arch_map_p2m(int xc_handle, unsigned int guest_width,
>> > +                         xc_dominfo_t *info, shared_info_any_t 
> *live_shinfo,
>> > +                         xen_pfn_t **live_p2m, unsigned long *pfnp);
>> >  
>> >  
>> >  #if defined (__i386__) || defined (__x86_64__)
>> > diff -r 77476eeb8c42 tools/libxc/xc_core_ia64.c
>> > --- a/tools/libxc/xc_core_ia64.c    Wed Jan 14 11:39:01 2009 +0000
>> > +++ b/tools/libxc/xc_core_ia64.c    Wed Jan 14 16:40:17 2009 -0700
>> > @@ -235,7 +235,7 @@ old:
>> >  }
>> >  
>> >  int
>> > -xc_core_arch_map_p2m(int xc_handle, xc_dominfo_t *info,
>> > +xc_core_arch_map_p2m(int xc_handle, unsigned int guest_width, 
>> > xc_dominfo_t 
> *info,
>> >                       shared_info_t *live_shinfo, xen_pfn_t **live_p2m,
>> >                       unsigned long *pfnp)
>> >  {
>> > diff -r 77476eeb8c42 tools/libxc/xc_core_x86.c
>> > --- a/tools/libxc/xc_core_x86.c    Wed Jan 14 11:39:01 2009 +0000
>> > +++ b/tools/libxc/xc_core_x86.c    Wed Jan 14 16:40:17 2009 -0700
>> > @@ -20,9 +20,25 @@
>> >  
>> >  #include "xg_private.h"
>> >  #include "xc_core.h"
>> > +#include "xc_e820.h"
>> >  
>> > -/* Don't yet support cross-address-size core dump */
>> > -#define guest_width (sizeof (unsigned long))
>> > +#define GET_FIELD(_p, _f) ((guest_width==8) ? ((_p)->x64._f) : 
>> > ((_p)->x32._f))
>> > +
>> > +#ifndef MAX
>> > +#define MAX(_a, _b) ((_a) >= (_b) ? (_a) : (_b))
>> > +#endif
>> > +
>> > +int
>> > +xc_core_arch_gpfn_may_present(struct xc_core_arch_context *arch_ctxt,
>> > +                              unsigned long pfn)
>> > +{
>> > +    if ((pfn >= 0xa0 && pfn < 0xc0) /* VGA hole */
>> > +        || (pfn >= (HVM_BELOW_4G_MMIO_START >> PAGE_SHIFT)
>> > +            && pfn < (1ULL<<32) >> PAGE_SHIFT)) /* MMIO */
>> > +        return 0;
>> > +    return 1;
>> > +}
>> > +
>> >  
>> >  static int nr_gpfns(int xc_handle, domid_t domid)
>> >  {
>> > @@ -37,7 +53,7 @@ xc_core_arch_auto_translated_physmap(con
>> >  
>> >  int
>> >  xc_core_arch_memory_map_get(int xc_handle, struct xc_core_arch_context 
> *unused,
>> > -                            xc_dominfo_t *info, shared_info_t 
>> > *live_shinfo,
>> > +                            xc_dominfo_t *info, shared_info_any_t 
> *live_shinfo,
>> >                              xc_core_memory_map_t **mapp,
>> >                              unsigned int *nr_entries)
>> >  {
>> > @@ -60,17 +76,22 @@ xc_core_arch_memory_map_get(int xc_handl
>> >  }
>> >  
>> >  int
>> > -xc_core_arch_map_p2m(int xc_handle, xc_dominfo_t *info,
>> > -                     shared_info_t *live_shinfo, xen_pfn_t **live_p2m,
>> > +xc_core_arch_map_p2m(int xc_handle, unsigned int guest_width, 
>> > xc_dominfo_t 
> *info,
>> > +                     shared_info_any_t *live_shinfo, xen_pfn_t **live_p2m,
>> >                       unsigned long *pfnp)
>> >  {
>> >      /* Double and single indirect references to the live P2M table */
>> >      xen_pfn_t *live_p2m_frame_list_list = NULL;
>> >      xen_pfn_t *live_p2m_frame_list = NULL;
>> > +    /* Copies of the above. */
>> > +    xen_pfn_t *p2m_frame_list_list = NULL;
>> > +    xen_pfn_t *p2m_frame_list = NULL;
>> > +
>> >      uint32_t dom = info->domid;
>> >      unsigned long p2m_size = nr_gpfns(xc_handle, info->domid);
>> >      int ret = -1;
>> >      int err;
>> > +    int i;
>> >  
>> >      if ( p2m_size < info->nr_pages  )
>> >      {
>> > @@ -80,7 +101,7 @@ xc_core_arch_map_p2m(int xc_handle, xc_d
>> >  
>> >      live_p2m_frame_list_list =
>> >          xc_map_foreign_range(xc_handle, dom, PAGE_SIZE, PROT_READ,
>> > -                             
>> > live_shinfo->arch.pfn_to_mfn_frame_list_list);
>> > +                             GET_FIELD(live_shinfo, 
> arch.pfn_to_mfn_frame_list_list));
>> >  
>> >      if ( !live_p2m_frame_list_list )
>> >      {
>> > @@ -88,9 +109,28 @@ xc_core_arch_map_p2m(int xc_handle, xc_d
>> >          goto out;
>> >      }
>> >  
>> > +    /* Get a local copy of the live_P2M_frame_list_list */
>> > +    if ( !(p2m_frame_list_list = malloc(PAGE_SIZE)) )
>> > +    {
>> > +        ERROR("Couldn't allocate p2m_frame_list_list array");
>> > +        goto out;
>> > +    }
>> > +    memcpy(p2m_frame_list_list, live_p2m_frame_list_list, PAGE_SIZE);
>> > +
>> > +    /* Canonicalize guest's unsigned long vs ours */
>> > +    if ( guest_width > sizeof(unsigned long) )
>> > +        for ( i = 0; i < PAGE_SIZE/sizeof(unsigned long); i++ )
>> > +            if ( i < PAGE_SIZE/guest_width )
>> > +                p2m_frame_list_list[i] = ((uint64_t 
> *)p2m_frame_list_list)[i];
>> > +            else
>> > +                p2m_frame_list_list[i] = 0;
>> > +    else if ( guest_width < sizeof(unsigned long) )
>> > +        for ( i = PAGE_SIZE/sizeof(unsigned long) - 1; i >= 0; i-- )
>> > +            p2m_frame_list_list[i] = ((uint32_t *)p2m_frame_list_list)[i];
>> > +
>> >      live_p2m_frame_list =
>> >          xc_map_foreign_pages(xc_handle, dom, PROT_READ,
>> > -                             live_p2m_frame_list_list,
>> > +                             p2m_frame_list_list,
>> >                               P2M_FLL_ENTRIES);
>> >  
>> >      if ( !live_p2m_frame_list )
>> > @@ -99,8 +139,25 @@ xc_core_arch_map_p2m(int xc_handle, xc_d
>> >          goto out;
>> >      }
>> >  
>> > +    /* Get a local copy of the live_P2M_frame_list */
>> > +    if ( !(p2m_frame_list = malloc(P2M_TOOLS_FL_SIZE)) )
>> > +    {
>> > +        ERROR("Couldn't allocate p2m_frame_list array");
>> > +        goto out;
>> > +    }
>> > +    memset(p2m_frame_list, 0, P2M_TOOLS_FL_SIZE);
>> > +    memcpy(p2m_frame_list, live_p2m_frame_list, P2M_GUEST_FL_SIZE);
>> > +
>> > +    /* Canonicalize guest's unsigned long vs ours */
>> > +    if ( guest_width > sizeof(unsigned long) )
>> > +        for ( i = 0; i < P2M_FL_ENTRIES; i++ )
>> > +            p2m_frame_list[i] = ((uint64_t *)p2m_frame_list)[i];
>> > +    else if ( guest_width < sizeof(unsigned long) )
>> > +        for ( i = P2M_FL_ENTRIES - 1; i >= 0; i-- )
>> > +            p2m_frame_list[i] = ((uint32_t *)p2m_frame_list)[i];
>> > +
>> >      *live_p2m = xc_map_foreign_pages(xc_handle, dom, PROT_READ,
>> > -                                    live_p2m_frame_list,
>> > +                                    p2m_frame_list,
>> >                                      P2M_FL_ENTRIES);
>> >  
>> >      if ( !*live_p2m )
>> > @@ -122,6 +179,12 @@ out:
>> >      if ( live_p2m_frame_list )
>> >          munmap(live_p2m_frame_list, P2M_FLL_ENTRIES * PAGE_SIZE);
>> >  
>> > +    if ( p2m_frame_list_list )
>> > +        free(p2m_frame_list_list);
>> > +
>> > +    if ( p2m_frame_list )
>> > +        free(p2m_frame_list);
>> > +
>> >      errno = err;
>> >      return ret;
>> >  }
>> > diff -r 77476eeb8c42 tools/libxc/xc_core_x86.h
>> > --- a/tools/libxc/xc_core_x86.h    Wed Jan 14 11:39:01 2009 +0000
>> > +++ b/tools/libxc/xc_core_x86.h    Wed Jan 14 16:40:17 2009 -0700
>> > @@ -21,15 +21,8 @@
>> >  #ifndef XC_CORE_X86_H
>> >  #define XC_CORE_X86_H
>> >  
>> > -#if defined(__i386__) || defined(__x86_64__)
>> >  #define ELF_ARCH_DATA           ELFDATA2LSB
>> > -#if defined (__i386__)
>> > -# define ELF_ARCH_MACHINE       EM_386
>> > -#else
>> > -# define ELF_ARCH_MACHINE       EM_X86_64
>> > -#endif
>> > -#endif /* __i386__ or __x86_64__ */
>> > -
>> > +#define ELF_ARCH_MACHINE       (guest_width == 8 ? EM_X86_64 : EM_386)
>> >  
>> >  struct xc_core_arch_context {
>> >      /* nothing */
>> > @@ -40,8 +33,10 @@ struct xc_core_arch_context {
>> >  #define xc_core_arch_context_get(arch_ctxt, ctxt, xc_handle, domid) \
>> >                                                                  (0)
>> >  #define xc_core_arch_context_dump(arch_ctxt, args, dump_rtn)    (0)
>> > -#define xc_core_arch_gpfn_may_present(arch_ctxt, i)             (1)
>> >  
>> > +int
>> > +xc_core_arch_gpfn_may_present(struct xc_core_arch_context *arch_ctxt,
>> > +                              unsigned long pfn);
>> >  static inline int
>> >  xc_core_arch_context_get_shdr(struct xc_core_arch_context *arch_ctxt, 
>> >                                struct xc_core_section_headers *sheaders,
>> 
>> > _______________________________________________
>> > Xen-devel mailing list
>> > Xen-devel@xxxxxxxxxxxxxxxxxxx 
>> > http://lists.xensource.com/xen-devel 
>> 
>> 




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