[Xen-devel] [PATCH v4] arch/x86: Add registers to vm_event

[Alexandru Stefan ISAILA <aisaila@xxxxxxxxxxxxxxx>]

This patch adds a couple of regs to the vm_event that are used by
the introspection. The base, limit and ar
bits are compressed into a uint64_t union so as not to enlarge the
vm_event.

Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>

---
Changes since V3:
        - Remove union from x86_selector_reg
        - Split x86_selector_reg into 32/64 bit
        - Add comment for the shifting of the limit field
        - Add ASSERT_UNREACHABLE() on default case
        - Add blank lines before case.
---
 xen/arch/x86/vm_event.c       | 71 +++++++++++++++++++++++++++++++----
 xen/include/public/vm_event.h | 33 ++++++++++++++--
 2 files changed, 92 insertions(+), 12 deletions(-)

diff --git a/xen/arch/x86/vm_event.c b/xen/arch/x86/vm_event.c
index 15de43c3e6..ac977064fb 100644
--- a/xen/arch/x86/vm_event.c
+++ b/xen/arch/x86/vm_event.c
@@ -122,11 +122,66 @@ void vm_event_monitor_next_interrupt(struct vcpu *v)
     v->arch.monitor.next_interrupt_enabled = true;
 }
 
+static void vm_event_pack_segment_register(enum x86_segment segment,
+                                           struct vm_event_regs_x86 *reg)
+{
+    struct segment_register seg;
+
+    hvm_get_segment_register(current, segment, &seg);
+
+    switch ( segment )
+    {
+    case x86_seg_ss:
+        reg->ss.base = seg.base;
+        reg->ss.limit = seg.g ? seg.limit >> 12 : seg.limit;
+        reg->ss.ar = seg.attr;
+        reg->ss_sel = seg.sel;
+        break;
+
+    case x86_seg_fs:
+        reg->fs.base = seg.base;
+        reg->fs.limit = seg.g ? seg.limit >> 12 : seg.limit;
+        reg->fs.ar = seg.attr;
+        reg->fs_sel = seg.sel;
+        break;
+
+    case x86_seg_gs:
+        reg->gs.base = seg.base;
+        reg->gs.limit = seg.g ? seg.limit >> 12 : seg.limit;
+        reg->gs.ar = seg.attr;
+        reg->gs_sel = seg.sel;
+        break;
+
+    case x86_seg_cs:
+        reg->cs.base = seg.base;
+        reg->cs.limit = seg.g ? seg.limit >> 12 : seg.limit;
+        reg->cs.ar = seg.attr;
+        reg->cs_sel = seg.sel;
+        break;
+
+    case x86_seg_ds:
+        reg->ds.base = seg.base;
+        reg->ds.limit = seg.g ? seg.limit >> 12 : seg.limit;
+        reg->ds.ar = seg.attr;
+        reg->ds_sel = seg.sel;
+        break;
+
+    case x86_seg_es:
+        reg->es.base = seg.base;
+        reg->es.limit = seg.g ? seg.limit >> 12 : seg.limit;
+        reg->es.ar = seg.attr;
+        reg->es_sel = seg.sel;
+        break;
+
+    default:
+        ASSERT_UNREACHABLE();
+    }
+}
+
 void vm_event_fill_regs(vm_event_request_t *req)
 {
 #ifdef CONFIG_HVM
     const struct cpu_user_regs *regs = guest_cpu_user_regs();
-    struct segment_register seg;
     struct hvm_hw_cpu ctxt = {};
     struct vcpu *curr = current;
 
@@ -170,14 +225,14 @@ void vm_event_fill_regs(vm_event_request_t *req)
     req->data.regs.x86.msr_star = ctxt.msr_star;
     req->data.regs.x86.msr_lstar = ctxt.msr_lstar;
 
-    hvm_get_segment_register(curr, x86_seg_fs, &seg);
-    req->data.regs.x86.fs_base = seg.base;
-
-    hvm_get_segment_register(curr, x86_seg_gs, &seg);
-    req->data.regs.x86.gs_base = seg.base;
+    vm_event_pack_segment_register(x86_seg_fs, &req->data.regs.x86);
+    vm_event_pack_segment_register(x86_seg_gs, &req->data.regs.x86);
+    vm_event_pack_segment_register(x86_seg_cs, &req->data.regs.x86);
+    vm_event_pack_segment_register(x86_seg_ss, &req->data.regs.x86);
+    vm_event_pack_segment_register(x86_seg_ds, &req->data.regs.x86);
+    vm_event_pack_segment_register(x86_seg_es, &req->data.regs.x86);
 
-    hvm_get_segment_register(curr, x86_seg_cs, &seg);
-    req->data.regs.x86.cs_arbytes = seg.attr;
+    req->data.regs.x86.shadow_gs = ctxt.shadow_gs;
 #endif
 }
 
diff --git a/xen/include/public/vm_event.h b/xen/include/public/vm_event.h
index 36e3f4685d..27d19220de 100644
--- a/xen/include/public/vm_event.h
+++ b/xen/include/public/vm_event.h
@@ -29,7 +29,7 @@
 
 #include "xen.h"
 
-#define VM_EVENT_INTERFACE_VERSION 0x00000003
+#define VM_EVENT_INTERFACE_VERSION 0x00000004
 
 #if defined(__XEN__) || defined(__XEN_TOOLS__)
 
@@ -157,6 +157,21 @@
 #define VM_EVENT_X86_CR4    2
 #define VM_EVENT_X86_XCR0   3
 
+/*
+ * The limit field is right-shifted by 12 bits if .ar.g is set.
+ */
+struct x86_selector_reg_64 {
+    uint64_t base;
+    uint32_t limit  :    20;
+    uint32_t ar     :    12;
+};
+
+struct x86_selector_reg_32 {
+    uint32_t base;
+    uint32_t limit  :    20;
+    uint32_t ar     :    12;
+};
+
 /*
  * Using custom vCPU structs (i.e. not hvm_hw_cpu) for both x86 and ARM
  * so as to not fill the vm_event ring buffer too quickly.
@@ -191,9 +206,19 @@ struct vm_event_regs_x86 {
     uint64_t msr_efer;
     uint64_t msr_star;
     uint64_t msr_lstar;
-    uint64_t fs_base;
-    uint64_t gs_base;
-    uint32_t cs_arbytes;
+    struct x86_selector_reg_32 cs;
+    struct x86_selector_reg_32 ss;
+    struct x86_selector_reg_32 ds;
+    struct x86_selector_reg_32 es;
+    struct x86_selector_reg_64 fs;
+    struct x86_selector_reg_64 gs;
+    uint64_t shadow_gs;
+    uint16_t cs_sel;
+    uint16_t ss_sel;
+    uint16_t ds_sel;
+    uint16_t es_sel;
+    uint16_t fs_sel;
+    uint16_t gs_sel;
     uint32_t _pad;
 };
 
-- 
2.17.1


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