[Xen-devel] [PATCH 1/2] guest/pvh: fix handling of multiboot info and module list

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

When booting Xen as a PVH guest the data in the PVH start info
structure is copied over to a multiboot structure and a module list
array that resides in the .init section of the Xen image. The
resulting multiboot structures are then handled to the generic boot
process using their physical address.

This works fine as long as the Xen image doesn't relocate itself, if
there's such a relocation the physical addresses of the multiboot
structure and the module array are no longer valid.

Fix this by handling the virtual address of the multiboot structure
and module array to the generic boot process instead of it's physical
address.

Reported-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 xen/arch/x86/guest/pvh-boot.c        | 20 ++++++++++----------
 xen/arch/x86/setup.c                 |  7 ++++---
 xen/include/asm-x86/guest/pvh-boot.h |  5 ++---
 3 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/xen/arch/x86/guest/pvh-boot.c b/xen/arch/x86/guest/pvh-boot.c
index 6e81b32b92..544775eeb4 100644
--- a/xen/arch/x86/guest/pvh-boot.c
+++ b/xen/arch/x86/guest/pvh-boot.c
@@ -35,11 +35,11 @@ static multiboot_info_t __initdata pvh_mbi;
 static module_t __initdata pvh_mbi_mods[8];
 static const char *__initdata pvh_loader = "PVH Directboot";
 
-static void __init convert_pvh_info(void)
+static void __init convert_pvh_info(multiboot_info_t **mbi,
+                                    module_t **mod)
 {
     const struct hvm_start_info *pvh_info = __va(pvh_start_info_pa);
     const struct hvm_modlist_entry *entry;
-    module_t *mod;
     unsigned int i;
 
     if ( pvh_info->magic != XEN_HVM_START_MAGIC_VALUE )
@@ -68,20 +68,22 @@ static void __init convert_pvh_info(void)
     pvh_mbi.mods_count = pvh_info->nr_modules;
     pvh_mbi.mods_addr = __pa(pvh_mbi_mods);
 
-    mod = pvh_mbi_mods;
     entry = __va(pvh_info->modlist_paddr);
     for ( i = 0; i < pvh_info->nr_modules; i++ )
     {
         BUG_ON(entry[i].paddr >> 32);
         BUG_ON(entry[i].cmdline_paddr >> 32);
 
-        mod[i].mod_start = entry[i].paddr;
-        mod[i].mod_end   = entry[i].paddr + entry[i].size;
-        mod[i].string    = entry[i].cmdline_paddr;
+        pvh_mbi_mods[i].mod_start = entry[i].paddr;
+        pvh_mbi_mods[i].mod_end   = entry[i].paddr + entry[i].size;
+        pvh_mbi_mods[i].string    = entry[i].cmdline_paddr;
     }
 
     BUG_ON(!pvh_info->rsdp_paddr);
     rsdp_hint = pvh_info->rsdp_paddr;
+
+    *mbi = &pvh_mbi;
+    *mod = pvh_mbi_mods;
 }
 
 static void __init get_memory_map(void)
@@ -98,16 +100,14 @@ static void __init get_memory_map(void)
     sanitize_e820_map(e820_raw.map, &e820_raw.nr_map);
 }
 
-multiboot_info_t *__init pvh_init(void)
+void __init pvh_init(multiboot_info_t **mbi, module_t **mod)
 {
-    convert_pvh_info();
+    convert_pvh_info(mbi, mod);
 
     probe_hypervisor();
     ASSERT(xen_guest);
 
     get_memory_map();
-
-    return &pvh_mbi;
 }
 
 void __init pvh_print_info(void)
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 55a288f332..9cbff22fb3 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -719,12 +719,13 @@ void __init noreturn __start_xen(unsigned long mbi_p)
          */
         opt_console_xen = -1;
         ASSERT(mbi_p == 0);
-        mbi = pvh_init();
+        pvh_init(&mbi, &mod);
     }
     else
+    {
         mbi = __va(mbi_p);
-
-    mod = __va(mbi->mods_addr);
+        mod = __va(mbi->mods_addr);
+    }
 
     loader = (mbi->flags & MBI_LOADERNAME)
         ? (char *)__va(mbi->boot_loader_name) : "unknown";
diff --git a/xen/include/asm-x86/guest/pvh-boot.h 
b/xen/include/asm-x86/guest/pvh-boot.h
index 1b429f9401..922b6e68c5 100644
--- a/xen/include/asm-x86/guest/pvh-boot.h
+++ b/xen/include/asm-x86/guest/pvh-boot.h
@@ -25,17 +25,16 @@
 
 extern bool pvh_boot;
 
-multiboot_info_t *pvh_init(void);
+void pvh_init(multiboot_info_t **mbi, module_t **mod);
 void pvh_print_info(void);
 
 #else
 
 #define pvh_boot 0
 
-static inline multiboot_info_t *pvh_init(void)
+static inline void *pvh_init(multiboot_info_t **mbi, module_t **mod)
 {
     ASSERT_UNREACHABLE();
-    return NULL;
 }
 
 static inline void pvh_print_info(void)
-- 
2.19.1


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