[Xen-devel] [PATCH v2] 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 V1:
        - Add helper function for packing
        - Change packing logic
        - Add sel to x86_selector_reg.
---
 xen/arch/x86/vm_event.c       | 30 ++++++++++++++++++++++--------
 xen/include/public/vm_event.h | 26 ++++++++++++++++++++++----
 2 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/xen/arch/x86/vm_event.c b/xen/arch/x86/vm_event.c
index 15de43c3e6..3a29441c84 100644
--- a/xen/arch/x86/vm_event.c
+++ b/xen/arch/x86/vm_event.c
@@ -122,11 +122,25 @@ 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 x86_selector_reg *reg)
+{
+    struct segment_register seg;
+
+    hvm_get_segment_register(current, segment, &seg);
+    reg->fields.base = seg.base;
+    if ( seg.g )
+        reg->fields.limit = seg.limit >> 12;
+    else
+        reg->fields.limit = seg.limit;
+    reg->fields.ar = seg.attr;
+    reg->sel = seg.sel;
+}
+
 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 +184,14 @@ 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.fs);
+    vm_event_pack_segment_register(x86_seg_gs, &req->data.regs.x86.gs);
+    vm_event_pack_segment_register(x86_seg_cs, &req->data.regs.x86.cs);
+    vm_event_pack_segment_register(x86_seg_ss, &req->data.regs.x86.ss);
+    vm_event_pack_segment_register(x86_seg_ds, &req->data.regs.x86.ds);
+    vm_event_pack_segment_register(x86_seg_es, &req->data.regs.x86.es);
 
-    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..705e6f8a1c 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 +157,20 @@
 #define VM_EVENT_X86_CR4    2
 #define VM_EVENT_X86_XCR0   3
 
+struct __attribute__((__packed__)) x86_selector_reg {
+    uint16_t sel;
+    union
+    {
+        uint64_t bytes;
+        struct
+        {
+            uint64_t base   :    32;
+            uint64_t limit  :    20;
+            uint64_t ar     :    12;
+        } fields;
+    };
+};
+
 /*
  * 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 +205,13 @@ 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 cs;
+    struct x86_selector_reg ss;
+    struct x86_selector_reg ds;
+    struct x86_selector_reg es;
+    struct x86_selector_reg fs;
+    struct x86_selector_reg gs;
+    uint64_t shadow_gs;
     uint32_t _pad;
 };
 
-- 
2.17.1


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