New subject: [v4 1/4] ntdll: Proper handling of debug regs on x86-64.

13 Feb 2017

On 12.02.2017 23:41, Andrew Wesie wrote:
...
Based on existing code for i386. Code is shared when possible to avoid too
much duplication, even though this leads to more ifdefs.
Signed-off-by: Andrew Wesie <awesie(a)gmail.com>
---
 dlls/ntdll/ntdll_misc.h    | 28 ++++++++++----------
 dlls/ntdll/signal_x86_64.c | 64 +++++++++++++++++++++++++++++++++++++++++++---
 dlls/ntdll/thread.c        | 12 +++++++--
 3 files changed, 85 insertions(+), 19 deletions(-)

diff --git a/dlls/ntdll/ntdll_misc.h b/dlls/ntdll/ntdll_misc.h
index 5e4c39e..5c5cbd2 100644
--- a/dlls/ntdll/ntdll_misc.h
+++ b/dlls/ntdll/ntdll_misc.h
@@ -215,25 +215,27 @@ struct debug_info
 /* thread private data, stored in NtCurrentTeb()->SpareBytes1 */
 struct ntdll_thread_data
 {
+#if defined(__i386__) || defined(__x86_64__)
+    DWORD_PTR          dr0;           /* 1bc/2e8 Debug registers */
+    DWORD_PTR          dr1;           /* 1c0/2f0 */
+    DWORD_PTR          dr2;           /* 1c4/2f8 */
+    DWORD_PTR          dr3;           /* 1c8/300 */
+    DWORD_PTR          dr6;           /* 1cc/308 */
+    DWORD_PTR          dr7;           /* 1d0/310 */
+#endif
 #ifdef __i386__
-    DWORD              dr0;           /* 1bc Debug registers */
-    DWORD              dr1;           /* 1c0 */
-    DWORD              dr2;           /* 1c4 */
-    DWORD              dr3;           /* 1c8 */
-    DWORD              dr6;           /* 1cc */
-    DWORD              dr7;           /* 1d0 */
     DWORD              fs;            /* 1d4 TEB selector */
     DWORD              gs;            /* 1d8 libc selector; update winebuild if you move this! */
     void              *vm86_ptr;      /* 1dc data for vm86 mode */
 #else
-    void              *exit_frame;    /*    /2e8 exit frame pointer */
+    void              *exit_frame;    /*    /318 exit frame pointer */
 #endif
-    struct debug_info *debug_info;    /* 1e0/2f0 info for debugstr functions */
-    int                request_fd;    /* 1e4/2f8 fd for sending server requests */
-    int                reply_fd;      /* 1e8/2fc fd for receiving server replies */
-    int                wait_fd[2];    /* 1ec/300 fd for sleeping server requests */
-    BOOL               wow64_redir;   /* 1f4/308 Wow64 filesystem redirection flag */
-    pthread_t          pthread_id;    /* 1f8/310 pthread thread id */
+    struct debug_info *debug_info;    /* 1e0/320 info for debugstr functions */
+    int                request_fd;    /* 1e4/328 fd for sending server requests */
+    int                reply_fd;      /* 1e8/32c fd for receiving server replies */
+    int                wait_fd[2];    /* 1ec/330 fd for sleeping server requests */
+    BOOL               wow64_redir;   /* 1f4/338 Wow64 filesystem redirection flag */
+    pthread_t          pthread_id;    /* 1f8/340 pthread thread id */
 #ifdef __i386__
     WINE_VM86_TEB_INFO vm86;          /* 1fc vm86 private data */
     void              *exit_frame;    /* 204 exit frame pointer */
Adding those fields should work, but it is a bit dangerous because we only have
limited space. I would suggest adding asserts to ensure we never make this struct
too big. Something like this should work:

C_ASSERT( FIELD_OFFSET(TEB, SpareBytes1) + sizeof(struct ntdll_thread_data) <=
          FIELD_OFFSET(TEB, GdiTebBatch) + sizeof(((TEB *)0)->GdiTebBatch) );

Probably we should also use it for important i386 fields, to ensure they are not
moved.

#ifdef __i386__
C_ASSERT( FIELD_OFFSET(TEB, SpareBytes1) + FIELD_OFFSET(struct ntdll_thread_data, vm86) == FIELD_OFFSET(TEB, GdiTebBatch) );
C_ASSERT( FIELD_OFFSET(TEB, SpareBytes1) + FIELD_OFFSET(struct ntdll_thread_data, vm86) == 0x1fc );
C_ASSERT( FIELD_OFFSET(TEB, SpareBytes1) + FIELD_OFFSET(struct ntdll_thread_data, gs)   == 0x1d8 );
#endif
...
diff --git a/dlls/ntdll/signal_x86_64.c b/dlls/ntdll/signal_x86_64.c
index f33fe4c..d2b040e 100644
--- a/dlls/ntdll/signal_x86_64.c
+++ b/dlls/ntdll/signal_x86_64.c
@@ -1649,7 +1649,9 @@ static inline BOOL is_inside_signal_stack( void *ptr )
  */
 static void save_context( CONTEXT *context, const ucontext_t *sigcontext )
 {
-    context->ContextFlags = CONTEXT_CONTROL | CONTEXT_INTEGER | CONTEXT_SEGMENTS;
+    struct ntdll_thread_data * const regs = ntdll_get_thread_data();
+
+    context->ContextFlags = CONTEXT_CONTROL | CONTEXT_INTEGER | CONTEXT_SEGMENTS | CONTEXT_DEBUG_REGISTERS;
     context->Rax    = RAX_sig(sigcontext);
     context->Rcx    = RCX_sig(sigcontext);
     context->Rdx    = RDX_sig(sigcontext);
@@ -1686,6 +1688,12 @@ static void save_context( CONTEXT *context, const ucontext_t *sigcontext )
 #else
     __asm__("movw %%ss,%0" : "=m" (context->SegSs));
 #endif
+    context->Dr0          = regs->dr0;
+    context->Dr1          = regs->dr1;
+    context->Dr2          = regs->dr2;
+    context->Dr3          = regs->dr3;
+    context->Dr6          = regs->dr6;
+    context->Dr7          = regs->dr7;
     if (FPU_sig(sigcontext))
     {
         context->ContextFlags |= CONTEXT_FLOATING_POINT;
@@ -1702,6 +1710,14 @@ static void save_context( CONTEXT *context, const ucontext_t *sigcontext )
  */
 static void restore_context( const CONTEXT *context, ucontext_t *sigcontext )
 {
+    struct ntdll_thread_data * const regs = ntdll_get_thread_data();
+
+    regs->dr0 = context->Dr0;
+    regs->dr1 = context->Dr1;
+    regs->dr2 = context->Dr2;
+    regs->dr3 = context->Dr3;
+    regs->dr6 = context->Dr6;
+    regs->dr7 = context->Dr7;
     RAX_sig(sigcontext) = context->Rax;
     RCX_sig(sigcontext) = context->Rcx;
     RDX_sig(sigcontext) = context->Rdx;
@@ -1861,6 +1877,16 @@ __ASM_GLOBAL_FUNC( set_full_cpu_context,
 void set_cpu_context( const CONTEXT *context )
 {
     DWORD flags = context->ContextFlags & ~CONTEXT_AMD64;
+
+    if (flags & CONTEXT_DEBUG_REGISTERS)
+    {
+        ntdll_get_thread_data()->dr0 = context->Dr0;
+        ntdll_get_thread_data()->dr1 = context->Dr1;
+        ntdll_get_thread_data()->dr2 = context->Dr2;
+        ntdll_get_thread_data()->dr3 = context->Dr3;
+        ntdll_get_thread_data()->dr6 = context->Dr6;
+        ntdll_get_thread_data()->dr7 = context->Dr7;
+    }
     if (flags & CONTEXT_FULL)
     {
         if (!(flags & CONTEXT_CONTROL))
@@ -2559,7 +2585,7 @@ static void raise_segv_exception( EXCEPTION_RECORD *rec, CONTEXT *context )
         }
         break;
     }
-    status = raise_exception( rec, context, TRUE );
+    status = NtRaiseException( rec, context, TRUE );
     if (status) raise_status( status, rec );
NtRaiseException will always return a status != 0, so there
is no need for the check anymore.
...
done:
     set_cpu_context( context );
@@ -2567,13 +2593,43 @@ done:
/**********************************************************************
+ *		raise_trap_exception
+ */
+static void raise_trap_exception( EXCEPTION_RECORD *rec, CONTEXT *context )
+{
+    NTSTATUS status;
+
+    if (rec->ExceptionCode == EXCEPTION_SINGLE_STEP)
+    {
+        /* when single stepping can't tell whether this is a hw bp or a
+         * single step interrupt. try to avoid as much overhead as possible
+         * and only do a server call if there is any hw bp enabled. */
+
+        if( !(context->EFlags & 0x100) || (ntdll_get_thread_data()->dr7 & 0xff) )
+        {
+            /* (possible) hardware breakpoint, fetch the debug registers */
+            DWORD saved_flags = context->ContextFlags;
+            context->ContextFlags = CONTEXT_DEBUG_REGISTERS;
+            NtGetContextThread(GetCurrentThread(), context);
+            context->ContextFlags |= saved_flags;  /* restore flags */
+        }
+
+        context->EFlags &= ~0x100;  /* clear single-step flag */
+    }
+
+    status = NtRaiseException( rec, context, TRUE );
+    raise_status( status, rec );
+}
+
+
+/**********************************************************************
  *		raise_generic_exception
  *
  * Generic raise function for exceptions that don't need special treatment.
  */
 static void raise_generic_exception( EXCEPTION_RECORD *rec, CONTEXT *context )
 {
-    NTSTATUS status = raise_exception( rec, context, TRUE );
+    NTSTATUS status = NtRaiseException( rec, context, TRUE );
     if (status) raise_status( status, rec );
     set_cpu_context( context );
Similar to above, this can be simplified because status is always != 0.
...
}
@@ -2684,7 +2740,7 @@ static void segv_handler( int signal, siginfo_t *siginfo, void *sigcontext )
  */
 static void trap_handler( int signal, siginfo_t *siginfo, void *sigcontext )
 {
-    EXCEPTION_RECORD *rec = setup_exception( sigcontext, raise_generic_exception );
+    EXCEPTION_RECORD *rec = setup_exception( sigcontext, raise_trap_exception );
switch (siginfo->si_code)
     {
diff --git a/dlls/ntdll/thread.c b/dlls/ntdll/thread.c
index c9a5da6..934ada1 100644
--- a/dlls/ntdll/thread.c
+++ b/dlls/ntdll/thread.c
@@ -744,10 +744,14 @@ NTSTATUS WINAPI NtSetContextThread( HANDLE handle, const CONTEXT *context )
     DWORD dummy, i;
     BOOL self;
-#ifdef __i386__
+#if defined(__i386__) || defined(__x86_64__)
     /* on i386 debug registers always require a server call */
     self = (handle == GetCurrentThread());
+#ifdef __i386__
     if (self && (context->ContextFlags & (CONTEXT_DEBUG_REGISTERS & ~CONTEXT_i386)))
+#elif defined(__x86_64__)
+    if (self && (context->ContextFlags & (CONTEXT_DEBUG_REGISTERS & ~CONTEXT_AMD64)))
+#endif
     {
         self = (ntdll_get_thread_data()->dr0 == context->Dr0 &&
                 ntdll_get_thread_data()->dr1 == context->Dr1 &&
@@ -903,9 +907,13 @@ NTSTATUS WINAPI NtGetContextThread( HANDLE handle, CONTEXT *context )
             copy_context( context, &ctx, ctx.ContextFlags & needed_flags );
             context->ContextFlags |= ctx.ContextFlags & needed_flags;
         }
-#ifdef __i386__
+#if defined(__i386__) || defined(__x86_64__)
         /* update the cached version of the debug registers */
+#ifdef __i386__
         if (context->ContextFlags & (CONTEXT_DEBUG_REGISTERS & ~CONTEXT_i386))
+#elif defined(__x86_64__)
+        if (context->ContextFlags & (CONTEXT_DEBUG_REGISTERS & ~CONTEXT_AMD64))
+#endif
         {
             ntdll_get_thread_data()->dr0 = context->Dr0;
             ntdll_get_thread_data()->dr1 = context->Dr1;
-- 2.7.4


    

Re: [v4 1/4] ntdll: Proper handling of debug regs on x86-64.

Sebastian Lackner

Andrew Wesie

Sebastian Lackner

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