[Xen-devel] [PATCH v2 20/22] libxc/xen: introduce HVM_PARAM_MODLIST_PFN

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

This HVM parameter is used to pass a list of loaded modules to the guest.
Right now the number of loaded modules is limited to 1 by the current
implementation, but this interface allows passing more than one module.

Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
Cc: Keir Fraser <keir@xxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 tools/libxc/xc_dom_x86.c        | 24 +++++++++++++++++++++++-
 xen/arch/x86/hvm/hvm.c          |  1 +
 xen/include/public/hvm/params.h | 23 ++++++++++++++++++++++-
 3 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
index 74c3819..71b353e 100644
--- a/tools/libxc/xc_dom_x86.c
+++ b/tools/libxc/xc_dom_x86.c
@@ -58,7 +58,8 @@
 #define SPECIALPAGE_IDENT_PT 6
 #define SPECIALPAGE_CONSOLE  7
 #define SPECIALPAGE_CMDLINE  8
-#define NR_SPECIAL_PAGES     9
+#define SPECIALPAGE_MODLIST  9
+#define NR_SPECIAL_PAGES     10
 #define LAST_SPECIAL_PFN     0xff000u
 
 #define NR_IOREQ_SERVER_PAGES 8
@@ -533,6 +534,7 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
     xen_pfn_t ioreq_server_array[NR_IOREQ_SERVER_PAGES];
     xc_interface *xch = dom->xch;
     char *cmdline;
+    uint64_t *modlist;
 
     if ( dom->emulation )
     {
@@ -621,6 +623,26 @@ static int alloc_magic_pages_hvm(struct xc_dom_image *dom)
                          NR_IOREQ_SERVER_PAGES);
     }
 
+    if ( dom->ramdisk_blob )
+    {
+        modlist = xc_map_foreign_range(
+                  xch, domid, PAGE_SIZE, PROT_READ | PROT_WRITE,
+                  special_pfn(SPECIALPAGE_MODLIST, dom));
+        if ( modlist == NULL ) {
+            DOMPRINTF("Unable to map module list page");
+            goto error_out;
+        }
+
+        /* This is currently limited to only one module. */
+        modlist[0] = dom->ramdisk_seg.vstart - dom->parms.virt_base;
+        modlist[1] = dom->ramdisk_seg.vend - dom->ramdisk_seg.vstart;
+        modlist[2] = 0;
+        modlist[3] = 0;
+        munmap(modlist, PAGE_SIZE);
+        xc_hvm_param_set(xch, domid, HVM_PARAM_MODLIST_PFN,
+                     special_pfn(SPECIALPAGE_MODLIST, dom));
+    }
+
     /*
      * Identity-map page table is required for running with CR0.PG=0 when
      * using Intel EPT. Create a 32-bit non-PAE page directory of superpages.
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index b7b1300..293e740 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -5902,6 +5902,7 @@ static int hvm_allow_get_param(struct domain *d,
     case HVM_PARAM_CONSOLE_EVTCHN:
     case HVM_PARAM_CMDLINE_PFN:
     case HVM_PARAM_FIRST_FREE_PFN:
+    case HVM_PARAM_MODLIST_PFN:
         break;
     /*
      * The following parameters must not be read by the guest
diff --git a/xen/include/public/hvm/params.h b/xen/include/public/hvm/params.h
index 47e38a8..86cc15b 100644
--- a/xen/include/public/hvm/params.h
+++ b/xen/include/public/hvm/params.h
@@ -193,6 +193,27 @@
 /* First free PFN after the special pages. */
 #define HVM_PARAM_FIRST_FREE_PFN 36
 
-#define HVM_NR_PARAMS          37
+/*
+ * List of modules passed to the kernel.
+ *
+ * The PFN returned by this HVM_PARAM points to a page that contains an
+ * array of unsigned 64bit integers encoded in little endian.
+ *
+ * The first integer contains the address where the module has been loaded,
+ * while the second contains the size of the module in bytes. The last element
+ * in the array is a module with address 0 and length 0:
+ *
+ * module[0] = <address of 1st module>
+ * module[1] = <size of 1st module>
+ * [...]
+ * module[N/2] = <address of module N>
+ * module[N/2+1] = <size of module N>
+ * [...]
+ * module[M] = 0
+ * module[M+1] = 0
+ */
+#define HVM_PARAM_MODLIST_PFN 37
+
+#define HVM_NR_PARAMS          38
 
 #endif /* __XEN_PUBLIC_HVM_PARAMS_H__ */
-- 
1.9.5 (Apple Git-50.3)


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