[PATCH v2 30/47] Windows gdb+gdbserver: Share $_siginfo reading code

Pedro Alves
2025-05-19T13:33:46Z

Both GDB and GDBserver have similar code to read the $_siginfo data.
This patch moves the bulk of it to gdb/nat/windows-nat.c so it can be
shared.

Approved-By: Tom Tromey <tom@tromey.com>
Change-Id: I58f9074caf6362274453c78ed1fc9e31249f6854
---
gdb/nat/windows-nat.c | 49 ++++++++++++++++++++++++++++++++++++++++++
gdb/nat/windows-nat.h | 9 ++++++++
gdb/windows-nat.c | 40 +++-------------------------------
gdbserver/win32-low.cc | 42 ++++--------------------------------
4 files changed, 65 insertions(+), 75 deletions(-)

diff --git a/gdb/nat/windows-nat.c b/gdb/nat/windows-nat.c
index 6128b83bea4..a548acc97d3 100644
--- a/gdb/nat/windows-nat.c
+++ b/gdb/nat/windows-nat.c
@@ -153,6 +153,55 @@ windows_thread_info::thread_name ()
return name.get ();
}

+/* Read Windows signal info. See nat/windows-nat.h. */
+
+bool
+windows_thread_info::xfer_siginfo (gdb_byte *readbuf,
+ ULONGEST offset, ULONGEST len,
+ ULONGEST *xfered_len)
+{
+ if (last_event.dwDebugEventCode != EXCEPTION_DEBUG_EVENT)
+ return false;
+
+ if (readbuf == nullptr)
+ return false;
+
+ EXCEPTION_RECORD &er = last_event.u.Exception.ExceptionRecord;
+
+ char *buf = (char *) &er;
+ size_t bufsize = sizeof (er);
+
+#ifdef __x86_64__
+ EXCEPTION_RECORD32 er32;
+ if (proc->wow64_process)
+ {
+ buf = (char *) &er32;
+ bufsize = sizeof (er32);
+
+ er32.ExceptionCode = er.ExceptionCode;
+ er32.ExceptionFlags = er.ExceptionFlags;
+ er32.ExceptionRecord
+ = (uintptr_t) er.ExceptionRecord;
+ er32.ExceptionAddress
+ = (uintptr_t) er.ExceptionAddress;
+ er32.NumberParameters = er.NumberParameters;
+ for (int i = 0; i < EXCEPTION_MAXIMUM_PARAMETERS; i++)
+ er32.ExceptionInformation[i] = er.ExceptionInformation[i];
+ }
+#endif
+
+ if (offset > bufsize)
+ return false;
+
+ if (offset + len > bufsize)
+ len = bufsize - offset;
+
+ memcpy (readbuf, buf + offset, len);
+ *xfered_len = len;
+
+ return true;
+}
+
/* Try to determine the executable filename.

EXE_NAME_RET is a pointer to a buffer whose size is EXE_NAME_MAX_LEN.
diff --git a/gdb/nat/windows-nat.h b/gdb/nat/windows-nat.h
index cba8098fb39..d0978f899fd 100644
--- a/gdb/nat/windows-nat.h
+++ b/gdb/nat/windows-nat.h
@@ -76,6 +76,15 @@ struct windows_thread_info
the next call. */
const char *thread_name ();

+ /* Read LEN bytes of the thread's $_siginfo into READBUF, starting
+ at OFFSET. Store the number of actually-read bytes in
+ XFERED_LEN. Returns true on success, false on failure. Passing
+ READBUF as NULL indicates that the caller is trying to write to
+ $_siginfo, which is a failure case. */
+ bool xfer_siginfo (gdb_byte *readbuf,
+ ULONGEST offset, ULONGEST len,
+ ULONGEST *xfered_len);
+
/* The process this thread belongs to. */
windows_process_info *const proc;

diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index 1ced313d7b1..bd3bc3701a6 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -3006,44 +3006,10 @@ windows_xfer_siginfo (gdb_byte *readbuf, ULONGEST offset, ULONGEST len,
{
windows_thread_info *th = windows_process.find_thread (inferior_ptid);

- if (th->last_event.dwDebugEventCode != EXCEPTION_DEBUG_EVENT)
- return TARGET_XFER_E_IO;
-
- EXCEPTION_RECORD &er = th->last_event.u.Exception.ExceptionRecord;
-
- char *buf = (char *) &er;
- size_t bufsize = sizeof (er);
-
-#ifdef __x86_64__
- EXCEPTION_RECORD32 er32;
- if (windows_process.wow64_process)
- {
- buf = (char *) &er32;
- bufsize = sizeof (er32);
-
- er32.ExceptionCode = er.ExceptionCode;
- er32.ExceptionFlags = er.ExceptionFlags;
- er32.ExceptionRecord = (uintptr_t) er.ExceptionRecord;
- er32.ExceptionAddress = (uintptr_t) er.ExceptionAddress;
- er32.NumberParameters = er.NumberParameters;
- for (int i = 0; i < EXCEPTION_MAXIMUM_PARAMETERS; i++)
- er32.ExceptionInformation[i] = er.ExceptionInformation[i];
- }
-#endif
-
- if (readbuf == nullptr)
- return TARGET_XFER_E_IO;
-
- if (offset > bufsize)
+ if (th->xfer_siginfo (readbuf, offset, len, xfered_len))
+ return TARGET_XFER_OK;
+ else
return TARGET_XFER_E_IO;
-
- if (offset + len > bufsize)
- len = bufsize - offset;
-
- memcpy (readbuf, buf + offset, len);
- *xfered_len = len;
-
- return TARGET_XFER_OK;
}

enum target_xfer_status
diff --git a/gdbserver/win32-low.cc b/gdbserver/win32-low.cc
index 4e2d95bd059..834af706786 100644
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -1285,45 +1285,11 @@ win32_process_target::qxfer_siginfo (const char *annex,
{
windows_thread_info *th = windows_process.find_thread (current_thread->id);

- if (th->last_event.dwDebugEventCode != EXCEPTION_DEBUG_EVENT)
- return -1;
-
- if (readbuf == nullptr)
- return -1;
-
- EXCEPTION_RECORD &er = th->last_event.u.Exception.ExceptionRecord;
-
- char *buf = (char *) &er;
- size_t bufsize = sizeof (er);
-
-#ifdef __x86_64__
- EXCEPTION_RECORD32 er32;
- if (windows_process.wow64_process)
- {
- buf = (char *) &er32;
- bufsize = sizeof (er32);
-
- er32.ExceptionCode = er.ExceptionCode;
- er32.ExceptionFlags = er.ExceptionFlags;
- er32.ExceptionRecord
- = (uintptr_t) er.ExceptionRecord;
- er32.ExceptionAddress
- = (uintptr_t) er.ExceptionAddress;
- er32.NumberParameters = er.NumberParameters;
- for (int i = 0; i < EXCEPTION_MAXIMUM_PARAMETERS; i++)
- er32.ExceptionInformation[i] = er.ExceptionInformation[i];
- }
-#endif
-
- if (offset > bufsize)
+ ULONGEST xfered_len;
+ if (th->xfer_siginfo (readbuf, offset, len, &xfered_len))
+ return xfered_len;
+ else
return -1;
-
- if (offset + len > bufsize)
- len = bufsize - offset;
-
- memcpy (readbuf, buf + offset, len);
-
- return len;
}

bool
--
2.49.0