[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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



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?

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
> 
> 

-- 
yamahata

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.