Handle 64bit breakpoints of WOW64 processes as SIGINT

When a WOW64 process triggers a breakpoint exception in 64bit code (which
happens when a 64bit gdb calls DebugBreakProcess for a 32bit target),
gdb ignores the breakpoint (because Wow64GetThreadContext can only report
the pc of 32bit code, and there is not int3 at this location).

But if these 64bit breakpoint exceptions are handled as SIGINT, gdb
doesn't check for int3, and always stops the target.

gdb/ChangeLog:

2020-09-23  Hannes Domani  <ssbssa@yahoo.de>

	* nat/windows-nat.c (handle_exception): Handle 64bit breakpoints
	in WOW64 processes as SIGINT.
	* nat/windows-nat.h: Make wow64_process a shared variable.
	* windows-nat.c: Remove static wow64_process variable.

gdbserver/ChangeLog:

2020-09-23  Hannes Domani  <ssbssa@yahoo.de>

	* win32-low.cc: Remove local wow64_process variable.
	* win32-low.h: Remove local wow64_process variable.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 241f3e7027195dc79e006a49ba690eb9371919ed..3b851dba41ece1d4696d0f1b1b7b267cd007bfac 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2020-09-23  Hannes Domani  <ssbssa@yahoo.de>
+
+       * nat/windows-nat.c (handle_exception): Handle 64bit breakpoints
+       in WOW64 processes as SIGINT.
+       * nat/windows-nat.h: Make wow64_process a shared variable.
+       * windows-nat.c: Remove static wow64_process variable.
+
 2020-09-23  Tom Tromey  <tom@tromey.com>
 
        PR symtab/25470:

diff --git a/gdb/nat/windows-nat.c b/gdb/nat/windows-nat.c
index be6db9719a0b37b8ad4db089ac70bf626fd592ef..2cbbc0f2ccb03f3c6e5073cce5d960afbbe7e359 100644 (file)
--- a/gdb/nat/windows-nat.c
+++ b/gdb/nat/windows-nat.c
@@ -41,6 +41,7 @@ std::vector<pending_stop> pending_stops;
 EXCEPTION_RECORD siginfo_er;
 
 #ifdef __x86_64__
+bool wow64_process = false;
 bool ignore_first_breakpoint = false;
 #endif
 
@@ -240,6 +241,20 @@ handle_exception (struct target_waitstatus *ourstatus, bool debug_exceptions)
          ourstatus->kind = TARGET_WAITKIND_SPURIOUS;
          ignore_first_breakpoint = false;
        }
+      else if (wow64_process)
+       {
+         /* This breakpoint exception is triggered for WOW64 processes when
+            reaching an int3 instruction in 64bit code.
+            gdb checks for int3 in case of SIGTRAP, this fails because
+            Wow64GetThreadContext can only report the pc of 32bit code, and
+            gdb lets the target process continue.
+            So handle it as SIGINT instead, then the target is stopped
+            unconditionally.  */
+         DEBUG_EXCEPTION_SIMPLE ("EXCEPTION_BREAKPOINT");
+         rec->ExceptionCode = DBG_CONTROL_C;
+         ourstatus->value.sig = GDB_SIGNAL_INT;
+         break;
+       }
 #endif
       /* FALLTHROUGH */
     case STATUS_WX86_BREAKPOINT:

diff --git a/gdb/nat/windows-nat.h b/gdb/nat/windows-nat.h
index f742db2acc8e71167075ae4716c1dfa3041bd585..9bfcb16865c471a51d6694f6ddf4d4e2c84e4e6a 100644 (file)
--- a/gdb/nat/windows-nat.h
+++ b/gdb/nat/windows-nat.h
@@ -215,6 +215,8 @@ extern std::vector<pending_stop> pending_stops;
 extern EXCEPTION_RECORD siginfo_er;
 
 #ifdef __x86_64__
+/* The target is a WOW64 process */
+extern bool wow64_process;
 /* Ignore first breakpoint exception of WOW64 process */
 extern bool ignore_first_breakpoint;
 #endif

diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index ba88c33cac3835d2d66852872ce3d3b31810016e..7fff41de760a32a0b7c13bf84c95c72af3ddfef0 100644 (file)
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -235,7 +235,6 @@ static std::vector<windows_thread_info *> thread_list;
 static int saw_create;
 static int open_process_used = 0;
 #ifdef __x86_64__
-static bool wow64_process = false;
 static void *wow64_dbgbreak;
 #endif
 

diff --git a/gdbserver/ChangeLog b/gdbserver/ChangeLog
index d47fcfd300aeaf465ef97444792bd43b0ed6c36a..c97d4b1d28440e53d7449e2cb8e00c798acac8c9 100644 (file)
--- a/gdbserver/ChangeLog
+++ b/gdbserver/ChangeLog
@@ -1,3 +1,8 @@
+2020-09-23  Hannes Domani  <ssbssa@yahoo.de>
+
+       * win32-low.cc: Remove local wow64_process variable.
+       * win32-low.h: Remove local wow64_process variable.
+
 2020-09-18  Tom Tromey  <tromey@adacore.com>
 
        * netbsd-low.h (class netbsd_process_target) <wait>: Update.

diff --git a/gdbserver/win32-low.cc b/gdbserver/win32-low.cc
index 9980986c739229eacf100c3c6b45f66c4c3517df..e5f85a1a22fa65ccb5c7ca527ad7326e4f5d5a72 100644 (file)
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -91,10 +91,6 @@ static int faked_breakpoint = 0;
 /* True if current_process_handle needs to be closed.  */
 static bool open_process_used = false;
 
-#ifdef __x86_64__
-bool wow64_process = false;
-#endif
-
 const struct target_desc *win32_tdesc;
 #ifdef __x86_64__
 const struct target_desc *wow64_win32_tdesc;

diff --git a/gdbserver/win32-low.h b/gdbserver/win32-low.h
index d4ad5d83d29185458828861132edc7d82e57ba3d..8c113f86c77226df17233a624ce0a3895b1b1206 100644 (file)
--- a/gdbserver/win32-low.h
+++ b/gdbserver/win32-low.h
@@ -30,8 +30,6 @@ extern const struct target_desc *win32_tdesc;
 #ifdef __x86_64__
 extern const struct target_desc *wow64_win32_tdesc;
 
-extern bool wow64_process;
-
 typedef BOOL (WINAPI *winapi_Wow64GetThreadContext) (HANDLE, PWOW64_CONTEXT);
 extern winapi_Wow64GetThreadContext win32_Wow64GetThreadContext;
 #endif