Xen devel - May 2005 - [PATCH] vmx-gdbserver-sstep.patch

This patch enables single stepping a VMX domain using the gdbserver.

Signed-Off-By: Leendert van Doorn <leendert@watson.ibm.com>
Signed-off-by: Arun Sharma <arun.sharma@intel.com>

--- 1.190/xen/arch/x86/domain.c	2005-05-12 06:58:45 -07:00
+++ edited/xen/arch/x86/domain.c	2005-05-17 15:55:28 -07:00
@@ -417,6 +417,12 @@
 
         /* Ensure real hardware interrupts are enabled. */
         ed->arch.guest_context.user_regs.eflags |= EF_IE;
+    } else {
+        __vmwrite(GUEST_EFLAGS, ed->arch.guest_context.user_regs.eflags);
+        if (ed->arch.guest_context.user_regs.eflags & EF_TF)
+                __vm_set_bit(EXCEPTION_BITMAP, EXCEPTION_BITMAP_DB);
+        else 
+                __vm_clear_bit(EXCEPTION_BITMAP, EXCEPTION_BITMAP_DB);
     }
 
     if ( test_bit(_VCPUF_initialised, &ed->vcpu_flags) )
===== xen/arch/x86/vmx.c 1.50 vs edited ====--- 1.50/xen/arch/x86/vmx.c
2005-05-12 06:58:45 -07:00
+++ edited/xen/arch/x86/vmx.c	2005-05-17 15:29:07 -07:00
@@ -166,7 +166,7 @@
         cr0 &= ~X86_CR0_TS;
         __vmwrite(GUEST_CR0, cr0);
     }
-    __vmwrite(EXCEPTION_BITMAP, MONITOR_DEFAULT_EXCEPTION_BITMAP);
+    __vm_clear_bit(EXCEPTION_BITMAP, EXCEPTION_BITMAP_NM);
 }
 
 static void vmx_do_general_protection_fault(struct cpu_user_regs *regs) 
@@ -1108,6 +1108,21 @@
             save_cpu_user_regs(&regs);
             pdb_handle_exception(3, &regs, 1);
             restore_cpu_user_regs(&regs);
+            break;
+        }
+#else
+        case TRAP_debug:
+        {
+            void store_cpu_user_regs(struct cpu_user_regs *regs);
+            long do_sched_op(unsigned long op);
+
+
+            store_cpu_user_regs(&regs);
+            __vm_clear_bit(GUEST_PENDING_DBG_EXCEPTIONS, PENDING_DEBUG_EXC_BS);
+
+            set_bit(_VCPUF_ctrl_pause, &current->vcpu_flags);
+            do_sched_op(SCHEDOP_yield);
+
             break;
         }
 #endif
===== xen/arch/x86/vmx_platform.c 1.15 vs edited ====---
1.15/xen/arch/x86/vmx_platform.c	2005-04-28 07:04:10 -07:00
+++ edited/xen/arch/x86/vmx_platform.c	2005-05-17 15:15:24 -07:00
@@ -49,7 +49,7 @@
     return 0;
 }
 #elif defined (__i386__)
-static void store_cpu_user_regs(struct cpu_user_regs *regs)
+void store_cpu_user_regs(struct cpu_user_regs *regs)
 {
     __vmread(GUEST_SS_SELECTOR, &regs->ss);
     __vmread(GUEST_ESP, &regs->esp);
===== xen/include/asm-x86/vmx.h 1.7 vs edited ====---
1.7/xen/include/asm-x86/vmx.h	2005-05-11 13:20:21 -07:00
+++ edited/xen/include/asm-x86/vmx.h	2005-05-17 15:28:11 -07:00
@@ -131,6 +131,11 @@
 #define EXCEPTION_BITMAP_MC     (1 << 18)       /* Machine Check */
 #define EXCEPTION_BITMAP_XF     (1 << 19)       /* SIMD Floating-Point
Exception */
 
+/* Pending Debug exceptions */
+
+#define PENDING_DEBUG_EXC_BP    (1 << 12)       /* break point */
+#define PENDING_DEBUG_EXC_BS    (1 << 14)       /* Single step */
+
 #ifdef XEN_DEBUGGER
 #define MONITOR_DEFAULT_EXCEPTION_BITMAP        \
     ( EXCEPTION_BITMAP_PG |                     \
@@ -231,6 +236,30 @@
     return 0;
 }
 
+static inline int __vm_set_bit(unsigned long field, unsigned long mask)
+{
+        unsigned long tmp;
+        int err = 0;
+
+        err |= __vmread(field, &tmp);
+        tmp |= mask;
+        err |= __vmwrite(field, tmp);
+
+        return err;
+}
+
+static inline int __vm_clear_bit(unsigned long field, unsigned long mask)
+{
+        unsigned long tmp;
+        int err = 0;
+
+        err |= __vmread(field, &tmp);
+        tmp &= ~mask;
+        err |= __vmwrite(field, tmp);
+
+        return err;
+}
+
 static inline void __vmxoff (void)
 {
     __asm__ __volatile__ ( VMXOFF_OPCODE 
@@ -263,8 +292,7 @@
 
     __vmread(CR0_READ_SHADOW, &cr0);
     if (!(cr0 & X86_CR0_TS))
-       __vmwrite(EXCEPTION_BITMAP, MONITOR_DEFAULT_EXCEPTION_BITMAP | 
-                                   EXCEPTION_BITMAP_NM);
+       __vm_set_bit(EXCEPTION_BITMAP, EXCEPTION_BITMAP_NM);
 }
  

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Arun Sharma wrote:
> +static inline int __vm_set_bit(unsigned long field, unsigned long mask)
> +{
> +        unsigned long tmp;
> +        int err = 0;
> +
> +        err |= __vmread(field, &tmp);
> +        tmp |= mask;
> +        err |= __vmwrite(field, tmp);
Wouldn''t this be better:

   err = __vmread(field, &tmp);
   tmp |= mask;
   if (err == 0) err = __vmwrite(field, tmp);

(and similarly for __vm_clear_bit)?

-- 
David Hopwood <david.nospam.hopwood@blueyonder.co.uk>


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