libxc: Support cross-bitness guest when core-dumping

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@novell.com>

1 files changed, 55 insertions, 13 deletions

diff --git a/tools/libxc/xc_core.c b/tools/libxc/xc_core.c
index 9ee3981040..a7fd1647f3 100644
--- a/tools/libxc/xc_core.c
+++ b/tools/libxc/xc_core.c
@@ -58,9 +58,6 @@
 /* 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 {
     char       *strings;
@@ -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, dumpcore_rtn_t dump_rtn, int xc_handle)
     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, dumpcore_rtn_t dump_rtn)
     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_handle,
                                 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_handle,
     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_handle,
             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_handle,
     /* 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_handle,
         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_handle,
 
             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;