x86/event: correct debug event generation

RIP is not a linear address, and hence should not on its own be subject
to GVA -> GFN translation. Once at it, move all of the (perhaps
expensive) operations in the two functions into their main if()'s body,
and improve the error code passed to the translation function.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/hvm/event.c
+++ b/xen/arch/x86/hvm/event.c
@@ -144,36 +144,59 @@ void hvm_event_guest_request(void)
     }
 }
 
-int hvm_event_int3(unsigned long gla)
+int hvm_event_int3(unsigned long rip)
 {
     int rc = 0;
-    uint32_t pfec = PFEC_page_present;
     struct vcpu *curr = current;
-    vm_event_request_t req = {
-        .reason = VM_EVENT_REASON_SOFTWARE_BREAKPOINT,
-        .vcpu_id = curr->vcpu_id,
-        .u.software_breakpoint.gfn = paging_gva_to_gfn(curr, gla, &pfec)
-    };
 
     if ( curr->domain->arch.monitor.software_breakpoint_enabled )
+    {
+        struct segment_register sreg;
+        uint32_t pfec = PFEC_page_present | PFEC_insn_fetch;
+        vm_event_request_t req = {
+            .reason = VM_EVENT_REASON_SOFTWARE_BREAKPOINT,
+            .vcpu_id = curr->vcpu_id,
+        };
+
+        hvm_get_segment_register(curr, x86_seg_ss, &sreg);
+        if ( sreg.attr.fields.dpl == 3 )
+            pfec |= PFEC_user_mode;
+
+        hvm_get_segment_register(curr, x86_seg_cs, &sreg);
+        req.u.software_breakpoint.gfn = paging_gva_to_gfn(curr,
+                                                          sreg.base + rip,
+                                                          &pfec);
+
         rc = hvm_event_traps(1, &req);
+    }
 
     return rc;
 }
 
-int hvm_event_single_step(unsigned long gla)
+int hvm_event_single_step(unsigned long rip)
 {
     int rc = 0;
-    uint32_t pfec = PFEC_page_present;
     struct vcpu *curr = current;
-    vm_event_request_t req = {
-        .reason = VM_EVENT_REASON_SINGLESTEP,
-        .vcpu_id = curr->vcpu_id,
-        .u.singlestep.gfn = paging_gva_to_gfn(curr, gla, &pfec)
-    };
 
     if ( curr->domain->arch.monitor.singlestep_enabled )
+    {
+        struct segment_register sreg;
+        uint32_t pfec = PFEC_page_present | PFEC_insn_fetch;
+        vm_event_request_t req = {
+            .reason = VM_EVENT_REASON_SINGLESTEP,
+            .vcpu_id = curr->vcpu_id,
+        };
+
+        hvm_get_segment_register(curr, x86_seg_ss, &sreg);
+        if ( sreg.attr.fields.dpl == 3 )
+            pfec |= PFEC_user_mode;
+
+        hvm_get_segment_register(curr, x86_seg_cs, &sreg);
+        req.u.singlestep.gfn = paging_gva_to_gfn(curr, sreg.base + rip,
+                                                 &pfec);
+
         rc = hvm_event_traps(1, &req);
+    }
 
     return rc;
 }
--- a/xen/include/asm-x86/hvm/event.h
+++ b/xen/include/asm-x86/hvm/event.h
@@ -28,8 +28,8 @@ bool_t hvm_event_cr(unsigned int index,
     hvm_event_cr(VM_EVENT_X86_##what, new, old)
 void hvm_event_msr(unsigned int msr, uint64_t value);
 /* Called for current VCPU: returns -1 if no listener */
-int hvm_event_int3(unsigned long gla);
-int hvm_event_single_step(unsigned long gla);
+int hvm_event_int3(unsigned long rip);
+int hvm_event_single_step(unsigned long rip);
 void hvm_event_guest_request(void);
 
 #endif /* __ASM_X86_HVM_EVENT_H__ */