[PATCH] Fix ctrl-c when debugging WOW64 processes
Hannes Domani
ssbssa@yahoo.de
Thu Sep 17 18:03:37 GMT 2020
DebugBreakProcess starts a new thread in the target process with the
entry point DbgUiRemoteBreakin, where an int3 triggers a breakpoint
exception for gdb.
But this uses DbgUiRemoteBreakin of the 64bit ntdll.dll even for
WOW64 processes.
It stops in 64bit code, Wow64GetThreadContext reports a wrong pc without
the int3, and gdb lets the target process continue.
So this uses DbgUiRemoteBreakin of the 32bit ntdll.dll as the thread
entry point for WOW64 processes instead.
gdb/ChangeLog:
2020-09-17 Hannes Domani <ssbssa@yahoo.de>
* windows-nat.c (ctrl_c_handler): Use 32bit DbgUiRemoteBreakin
for WOW64 processes.
---
gdb/windows-nat.c | 35 ++++++++++++++++++++++++++++++++---
1 file changed, 32 insertions(+), 3 deletions(-)
diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index 188a920cbb..284c529b9c 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -71,6 +71,7 @@
#include "gdbsupport/pathstuff.h"
#include "gdbsupport/gdb_wait.h"
#include "nat/windows-nat.h"
+#include "gdbsupport/symbol.h"
using namespace windows_nat;
@@ -235,6 +236,7 @@ static int saw_create;
static int open_process_used = 0;
#ifdef __x86_64__
static bool wow64_process = false;
+static void *wow64_dbgbreak;
#endif
/* User options. */
@@ -1522,9 +1524,36 @@ ctrl_c_handler (DWORD event_type)
if (!new_console && !attach_flag)
return TRUE;
- if (!DebugBreakProcess (current_process_handle))
- warning (_("Could not interrupt program. "
- "Press Ctrl-c in the program console."));
+#ifdef __x86_64__
+ if (wow64_process)
+ {
+ /* Call DbgUiRemoteBreakin of the 32bit ntdll.dll in the target process.
+ DebugBreakProcess would call the one of the 64bit ntdll.dll, which
+ can't be correctly handled by gdb. */
+ if (!wow64_dbgbreak)
+ {
+ CORE_ADDR addr;
+ if (!find_minimal_symbol_address ("ntdll!DbgUiRemoteBreakin",
+ &addr, 0))
+ wow64_dbgbreak = (void *) addr;
+ }
+
+ if (wow64_dbgbreak)
+ {
+ HANDLE thread = CreateRemoteThread (current_process_handle, NULL,
+ 0, (LPTHREAD_START_ROUTINE)
+ wow64_dbgbreak, NULL, 0, NULL);
+ if (thread)
+ CloseHandle (thread);
+ }
+ }
+ else
+#endif
+ {
+ if (!DebugBreakProcess (current_process_handle))
+ warning (_("Could not interrupt program. "
+ "Press Ctrl-c in the program console."));
+ }
/* Return true to tell that Ctrl-C has been handled. */
return TRUE;
--
2.27.0
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