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Fix watchpoints with multiple threads on Windows

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A recent internal change pointed out that watchpoints were not working
on Windows when the inferior was multi-threaded.  This happened
because the debug registers were only updated for certain threads --
in particular, those that were being resumed and that were not marked
as suspended.  In the case of single-stepping, the need to update the
debug registers in other threads could also be "forgotten".

This patch changes windows-nat.c to mark all threads needing a debug
register update.  This brings the code closer to what gdbserver does
(though, unfortunately, it still seems more complicated than needed).
This commit is contained in:
Tom Tromey 2021-10-04 14:38:23 -04:00
parent 35da8c6140
commit 296d3d2e15
1 changed files with 20 additions and 51 deletions
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71
gdb/windows-nat.c
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@ -123,8 +123,6 @@ enum
| CONTEXT_EXTENDED_REGISTERS
static uintptr_t dr[8];
static int debug_registers_changed;
static int debug_registers_used;
static int windows_initialization_done;
#define DR6_CLEAR_VALUE 0xffff0ff0
@ -386,40 +384,10 @@ windows_add_thread (ptid_t ptid, HANDLE h, void *tlb, bool main_thread_p)
else
add_thread (&the_windows_nat_target, ptid);
/* Set the debug registers for the new thread if they are used. */
if (debug_registers_used)
{
#ifdef __x86_64__
if (wow64_process)
{
/* Only change the value of the debug registers. */
th->wow64_context.ContextFlags = CONTEXT_DEBUG_REGISTERS;
CHECK (Wow64GetThreadContext (th->h, &th->wow64_context));
th->wow64_context.Dr0 = dr[0];
th->wow64_context.Dr1 = dr[1];
th->wow64_context.Dr2 = dr[2];
th->wow64_context.Dr3 = dr[3];
th->wow64_context.Dr6 = DR6_CLEAR_VALUE;
th->wow64_context.Dr7 = dr[7];
CHECK (Wow64SetThreadContext (th->h, &th->wow64_context));
th->wow64_context.ContextFlags = 0;
}
else
#endif
{
/* Only change the value of the debug registers. */
th->context.ContextFlags = CONTEXT_DEBUG_REGISTERS;
CHECK (GetThreadContext (th->h, &th->context));
th->context.Dr0 = dr[0];
th->context.Dr1 = dr[1];
th->context.Dr2 = dr[2];
th->context.Dr3 = dr[3];
th->context.Dr6 = DR6_CLEAR_VALUE;
th->context.Dr7 = dr[7];
CHECK (SetThreadContext (th->h, &th->context));
th->context.ContextFlags = 0;
}
}
/* It's simplest to always set this and update the debug
registers. */
th->debug_registers_changed = true;
return th;
}
@ -593,7 +561,7 @@ windows_nat_target::fetch_registers (struct regcache *regcache, int r)
/* Copy dr values from that thread.
But only if there were not modified since last stop.
PR gdb/2388 */
if (!debug_registers_changed)
if (!th->debug_registers_changed)
{
dr[0] = th->wow64_context.Dr0;
dr[1] = th->wow64_context.Dr1;
@ -611,7 +579,7 @@ windows_nat_target::fetch_registers (struct regcache *regcache, int r)
/* Copy dr values from that thread.
But only if there were not modified since last stop.
PR gdb/2388 */
if (!debug_registers_changed)
if (!th->debug_registers_changed)
{
dr[0] = th->context.Dr0;
dr[1] = th->context.Dr1;
@ -1193,12 +1161,10 @@ windows_continue (DWORD continue_status, int id, int killed)
for (windows_thread_info *th : thread_list)
if (id == -1 || id == (int) th->tid)
{
if (!th->suspended)
continue;
#ifdef __x86_64__
if (wow64_process)
{
if (debug_registers_changed)
if (th->debug_registers_changed)
{
th->wow64_context.ContextFlags |= CONTEXT_DEBUG_REGISTERS;
th->wow64_context.Dr0 = dr[0];
@ -1207,6 +1173,7 @@ windows_continue (DWORD continue_status, int id, int killed)
th->wow64_context.Dr3 = dr[3];
th->wow64_context.Dr6 = DR6_CLEAR_VALUE;
th->wow64_context.Dr7 = dr[7];
th->debug_registers_changed = false;
}
if (th->wow64_context.ContextFlags)
{
@ -1227,7 +1194,7 @@ windows_continue (DWORD continue_status, int id, int killed)
else
#endif
{
if (debug_registers_changed)
if (th->debug_registers_changed)
{
th->context.ContextFlags |= CONTEXT_DEBUG_REGISTERS;
th->context.Dr0 = dr[0];
@ -1236,6 +1203,7 @@ windows_continue (DWORD continue_status, int id, int killed)
th->context.Dr3 = dr[3];
th->context.Dr6 = DR6_CLEAR_VALUE;
th->context.Dr7 = dr[7];
th->debug_registers_changed = false;
}
if (th->context.ContextFlags)
{
@ -1268,7 +1236,6 @@ windows_continue (DWORD continue_status, int id, int killed)
" (ContinueDebugEvent failed, error %u)"),
(unsigned int) GetLastError ());
debug_registers_changed = 0;
return res;
}
@ -1365,7 +1332,7 @@ windows_nat_target::resume (ptid_t ptid, int step, enum gdb_signal sig)
if (th->wow64_context.ContextFlags)
{
if (debug_registers_changed)
if (th->debug_registers_changed)
{
th->wow64_context.Dr0 = dr[0];
th->wow64_context.Dr1 = dr[1];
@ -1373,6 +1340,7 @@ windows_nat_target::resume (ptid_t ptid, int step, enum gdb_signal sig)
th->wow64_context.Dr3 = dr[3];
th->wow64_context.Dr6 = DR6_CLEAR_VALUE;
th->wow64_context.Dr7 = dr[7];
th->debug_registers_changed = false;
}
CHECK (Wow64SetThreadContext (th->h, &th->wow64_context));
th->wow64_context.ContextFlags = 0;
@ -1392,7 +1360,7 @@ windows_nat_target::resume (ptid_t ptid, int step, enum gdb_signal sig)
if (th->context.ContextFlags)
{
if (debug_registers_changed)
if (th->debug_registers_changed)
{
th->context.Dr0 = dr[0];
th->context.Dr1 = dr[1];
@ -1400,6 +1368,7 @@ windows_nat_target::resume (ptid_t ptid, int step, enum gdb_signal sig)
th->context.Dr3 = dr[3];
th->context.Dr6 = DR6_CLEAR_VALUE;
th->context.Dr7 = dr[7];
th->debug_registers_changed = false;
}
CHECK (SetThreadContext (th->h, &th->context));
th->context.ContextFlags = 0;
@ -1798,8 +1767,6 @@ windows_nat_target::do_initial_windows_stuff (DWORD pid, bool attaching)
last_sig = GDB_SIGNAL_0;
open_process_used = 0;
debug_registers_changed = 0;
debug_registers_used = 0;
for (i = 0; i < sizeof (dr) / sizeof (dr[0]); i++)
dr[i] = 0;
#ifdef __CYGWIN__
@ -3203,8 +3170,9 @@ cygwin_set_dr (int i, CORE_ADDR addr)
internal_error (__FILE__, __LINE__,
_("Invalid register %d in cygwin_set_dr.\n"), i);
dr[i] = addr;
debug_registers_changed = 1;
debug_registers_used = 1;
for (windows_thread_info *th : thread_list)
th->debug_registers_changed = true;
}
/* Pass the value VAL to the inferior in the DR7 debug control
@ -3214,8 +3182,9 @@ static void
cygwin_set_dr7 (unsigned long val)
{
dr[7] = (CORE_ADDR) val;
debug_registers_changed = 1;
debug_registers_used = 1;
for (windows_thread_info *th : thread_list)
th->debug_registers_changed = true;
}
/* Get the value of debug register I from the inferior. */