libelf: improve PVH elfnote parsing

Pass an hvm boolean parameter to the elf note checking routines, so that
better checking can be done in case libelf is dealing with an hvm
container.

elf_xen_note_check shouldn't return early unless PHYS32_ENTRY is set
and the container is of type HVM, or else the loader and version
checks would be avoided for kernels intended to be booted as PV but
that also have PHYS32_ENTRY set.

Adjust elf_xen_addr_calc_check so that the virtual addresses are
actually physical ones (by setting virt_base and elf_paddr_offset to
zero) when the container is of type HVM, as that container is always
started with paging disabled.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/common/libelf/libelf-dominfo.c b/xen/common/libelf/libelf-dominfo.c
index bd295a9b7e65d17871989b37fce1df78505c9dd7..24d1371dd7a95d8d8f199ddd24f7d3fd0df398ea 100644 (file)
--- a/xen/common/libelf/libelf-dominfo.c
+++ b/xen/common/libelf/libelf-dominfo.c
@@ -360,7 +360,7 @@ elf_errorstatus elf_xen_parse_guest_info(struct elf_binary *elf,
 /* sanity checks                                                            */
 
 static elf_errorstatus elf_xen_note_check(struct elf_binary *elf,
-                              struct elf_dom_parms *parms)
+                              struct elf_dom_parms *parms, bool hvm)
 {
     if ( (ELF_PTRVAL_INVALID(parms->elf_note_start)) &&
          (ELF_PTRVAL_INVALID(parms->guest_info)) )
@@ -382,7 +382,7 @@ static elf_errorstatus elf_xen_note_check(struct elf_binary *elf,
     }
 
     /* PVH only requires one ELF note to be set */
-    if ( parms->phys_entry != UNSET_ADDR32 )
+    if ( parms->phys_entry != UNSET_ADDR32 && hvm )
     {
         elf_msg(elf, "ELF: Found PVH image\n");
         return 0;
@@ -414,7 +414,7 @@ static elf_errorstatus elf_xen_note_check(struct elf_binary *elf,
 }
 
 static elf_errorstatus elf_xen_addr_calc_check(struct elf_binary *elf,
-                                   struct elf_dom_parms *parms)
+                                   struct elf_dom_parms *parms, bool hvm)
 {
     uint64_t virt_offset;
 
@@ -425,12 +425,15 @@ static elf_errorstatus elf_xen_addr_calc_check(struct elf_binary *elf,
         return -1;
     }
 
-    /* Initial guess for virt_base is 0 if it is not explicitly defined. */
-    if ( parms->virt_base == UNSET_ADDR )
+    /*
+     * Initial guess for virt_base is 0 if it is not explicitly defined in the
+     * PV case. For PVH virt_base is forced to 0 because paging is disabled.
+     */
+    if ( parms->virt_base == UNSET_ADDR || hvm )
     {
         parms->virt_base = 0;
-        elf_msg(elf, "ELF: VIRT_BASE unset, using %#" PRIx64 "\n",
-                parms->virt_base);
+        if ( !hvm )
+            elf_msg(elf, "ELF: VIRT_BASE unset, using 0\n");
     }
 
     /*
@@ -441,23 +444,31 @@ static elf_errorstatus elf_xen_addr_calc_check(struct elf_binary *elf,
      *
      * If we are using the modern ELF notes interface then the default
      * is 0.
+     *
+     * For PVH this is forced to 0, as it's already a legacy option for PV.
      */
-    if ( parms->elf_paddr_offset == UNSET_ADDR )
+    if ( parms->elf_paddr_offset == UNSET_ADDR || hvm )
     {
-        if ( parms->elf_note_start )
+        if ( parms->elf_note_start || hvm )
             parms->elf_paddr_offset = 0;
         else
             parms->elf_paddr_offset = parms->virt_base;
-        elf_msg(elf, "ELF_PADDR_OFFSET unset, using %#" PRIx64 "\n",
-                parms->elf_paddr_offset);
+        if ( !hvm )
+            elf_msg(elf, "ELF_PADDR_OFFSET unset, using %#" PRIx64 "\n",
+                    parms->elf_paddr_offset);
     }
 
     virt_offset = parms->virt_base - parms->elf_paddr_offset;
     parms->virt_kstart = elf->pstart + virt_offset;
     parms->virt_kend   = elf->pend   + virt_offset;
 
-    if ( parms->virt_entry == UNSET_ADDR )
-        parms->virt_entry = elf_uval(elf, elf->ehdr, e_entry);
+    if ( parms->virt_entry == UNSET_ADDR || hvm )
+    {
+        if ( parms->phys_entry != UNSET_ADDR32 && hvm )
+            parms->virt_entry = parms->phys_entry;
+        else
+            parms->virt_entry = elf_uval(elf, elf->ehdr, e_entry);
+    }
 
     if ( parms->bsd_symtab )
     {
@@ -592,9 +603,9 @@ elf_errorstatus elf_xen_parse(struct elf_binary *elf,
         }
     }
 
-    if ( elf_xen_note_check(elf, parms) != 0 )
+    if ( elf_xen_note_check(elf, parms, hvm) != 0 )
         return -1;
-    if ( elf_xen_addr_calc_check(elf, parms) != 0 )
+    if ( elf_xen_addr_calc_check(elf, parms, hvm) != 0 )
         return -1;
     return 0;
 }