x86/boot: introduce module release

A precarious approach was used to release the pages used to hold a boot module.
The precariousness stemmed from the fact that in the case of PV dom0, the
initrd module pages may be either mapped or copied into the dom0 address space.
In the former case, the PV dom0 construction code will set the size of the
module to zero, relying on discard_initial_images() to skip any modules with a
size of zero. In the latter case, the pages are freed by the PV dom0
construction code. This freeing of pages is done so that in either case, the
initrd variable can be reused for tracking the initrd location in dom0 memory
through the remaining dom0 construction code.

To encapsulate the logical action of releasing a boot module, the function
release_boot_module() is introduced along with the `released` flag added to
boot module. The boot module flag `released` allows the tracking of when a boot
module has been released by release_boot_module().

As part of adopting release_boot_module() the function discard_initial_images()
is renamed to free_boot_modules(), a name that better reflects the functions
actions.

Signed-off-by: Daniel P. Smith <dpsmith@apertussolutions.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/xen/arch/x86/hvm/dom0_build.c b/xen/arch/x86/hvm/dom0_build.c
index 35d8d6a070853aa0898cd214a8b1f4c93bc253ee..b4433bed30844a5e1dad5e4e1bb7d0fb53d156ed 100644 (file)
--- a/xen/arch/x86/hvm/dom0_build.c
+++ b/xen/arch/x86/hvm/dom0_build.c
@@ -755,7 +755,7 @@ static int __init pvh_load_kernel(
     }
 
     /* Free temporary buffers. */
-    discard_initial_images();
+    free_boot_modules();
 
     if ( cmdline != NULL )
     {

diff --git a/xen/arch/x86/include/asm/bootinfo.h b/xen/arch/x86/include/asm/bootinfo.h
index b9c94b370d57736c18621c7f0dc9f8c0ee2314b8..f76876386763efeeb4bdf9746344706948440ae6 100644 (file)
--- a/xen/arch/x86/include/asm/bootinfo.h
+++ b/xen/arch/x86/include/asm/bootinfo.h
@@ -34,8 +34,10 @@ struct boot_module {
     /*
      * Module State Flags:
      *   relocated: indicates module has been relocated in memory.
+     *   released:  indicates module's pages have been freed.
      */
     bool relocated:1;
+    bool released:1;
 
     /*
      * A boot module may need decompressing by Xen.  Headroom is an estimate of

diff --git a/xen/arch/x86/include/asm/setup.h b/xen/arch/x86/include/asm/setup.h
index 8a415087e9a401b2c548a884a11b9bae92aa7f94..4ad4936378928189cdd99bb7ead841acc2575210 100644 (file)
--- a/xen/arch/x86/include/asm/setup.h
+++ b/xen/arch/x86/include/asm/setup.h
@@ -34,13 +34,15 @@ void setup_io_bitmap(struct domain *d);
 extern struct boot_info xen_boot_info;
 
 unsigned long initial_images_nrpages(nodeid_t node);
-void discard_initial_images(void);
+void free_boot_modules(void);
 
 struct boot_module;
 void *bootstrap_map_bm(const struct boot_module *bm);
 void *bootstrap_map(const module_t *mod);
 void bootstrap_unmap(void);
 
+void release_boot_module(struct boot_module *bm);
+
 struct rangeset;
 int remove_xen_ranges(struct rangeset *r);
 

diff --git a/xen/arch/x86/pv/dom0_build.c b/xen/arch/x86/pv/dom0_build.c
index 9cf4519111b5341c1872bdcf1af5bdd8ede0b678..f52ede1786eab3908d10879331f2113b779c19f2 100644 (file)
--- a/xen/arch/x86/pv/dom0_build.c
+++ b/xen/arch/x86/pv/dom0_build.c
@@ -649,9 +649,12 @@ static int __init dom0_construct(struct boot_info *bi, struct domain *d)
                 }
             memcpy(page_to_virt(page), mfn_to_virt(initrd->mod->mod_start),
                    initrd_len);
-            mpt_alloc = pfn_to_paddr(initrd->mod->mod_start);
-            init_domheap_pages(mpt_alloc,
-                               mpt_alloc + PAGE_ALIGN(initrd_len));
+            /*
+             * The initrd was copied but the initrd variable is reused in the
+             * calculations below. As to not leak the memory used for the
+             * module free at this time.
+             */
+            release_boot_module(initrd);
             initrd_mfn = mfn_x(page_to_mfn(page));
             initrd->mod->mod_start = initrd_mfn;
         }
@@ -660,18 +663,14 @@ static int __init dom0_construct(struct boot_info *bi, struct domain *d)
             while ( count-- )
                 if ( assign_pages(mfn_to_page(_mfn(mfn++)), 1, d, 0) )
                     BUG();
+            /*
+             * We have mapped the initrd directly into dom0, and assigned the
+             * pages. Tell the boot_module handling that we've freed it, so the
+             * memory is left alone.
+             */
+            initrd->released = true;
         }
 
-        /*
-         * We have either:
-         * - Mapped the initrd directly into dom0, or
-         * - Copied it and freed the module.
-         *
-         * Either way, tell discard_initial_images() to not free it a second
-         * time.
-         */
-        initrd->mod->mod_end = 0;
-
         iommu_memory_setup(d, "initrd", mfn_to_page(_mfn(initrd_mfn)),
                            PFN_UP(initrd_len), &flush_flags);
     }
@@ -875,7 +874,7 @@ static int __init dom0_construct(struct boot_info *bi, struct domain *d)
     }
 
     /* Free temporary buffers. */
-    discard_initial_images();
+    free_boot_modules();
 
     /* Set up start info area. */
     si = (start_info_t *)vstartinfo_start;

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 302ff61e2b27140301ced94ca57490d321ebef71..a3b4d59e8069b569f34223d970ed4339066ac480 100644 (file)
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -346,27 +346,30 @@ unsigned long __init initial_images_nrpages(nodeid_t node)
     return nr;
 }
 
-void __init discard_initial_images(void) /* a.k.a. Free boot modules */
+void __init release_boot_module(struct boot_module *bm)
+{
+    uint64_t start = pfn_to_paddr(bm->mod->mod_start);
+    uint64_t size  = bm->mod->mod_end;
+
+    ASSERT(!bm->released);
+
+    init_domheap_pages(start, start + PAGE_ALIGN(size));
+
+    bm->released = true;
+}
+
+void __init free_boot_modules(void)
 {
     struct boot_info *bi = &xen_boot_info;
     unsigned int i;
 
     for ( i = 0; i < bi->nr_modules; ++i )
     {
-        uint64_t start = pfn_to_paddr(bi->mods[i].mod->mod_start);
-        uint64_t size  = bi->mods[i].mod->mod_end;
-
-        /*
-         * Sometimes the initrd is mapped, rather than copied, into dom0.
-         * Size being 0 is how we're instructed to leave the module alone.
-         */
-        if ( size == 0 )
+        if ( bi->mods[i].released )
             continue;
 
-        init_domheap_pages(start, start + PAGE_ALIGN(size));
+        release_boot_module(&bi->mods[i]);
     }
-
-    bi->nr_modules = 0;
 }
 
 static void __init init_idle_domain(void)