[PATCH 5/6] gdb/amd-dbgapi: defer TARGET_OBJECT_AUXV xfers to the beneath target

[Simon Marchi <simon.marchi@efficios.com>]

From: Shahab Vahedi <shahab.vahedi@amd.com>

Reading the auxiliary vector of the inferior fails when a GPU wave is
the selected thread.  The read goes through
amd_dbgapi_target::xfer_partial, which only handles TARGET_OBJECT_MEMORY
for GPU threads, and returns TARGET_XFER_E_IO for everything else.

Most users of the auxiliary vector, including "info auxv", use the copy
cached in the inferior, which is normally populated early, while a host
thread is selected.  But if the cache is cleared while a wave is
selected, for instance by the "file" command, the next read fails, and
the failure is cached too.

A victim of that bug is the "gcore" command.  linux_make_corefile_notes
reads the auxiliary vector directly from the target (bypassing the
cache) to write the NT_AUXV note, so the note is always missing when a
GPU wave is selected.  As a consequence, when loading such a core file,
GDB can't find the shared libraries of a position independent
executable, and can't find the full program name (AT_EXECFN), so it
falls back to the possibly truncated name from the NT_PRPSINFO note.

Fix this by making amd_dbgapi_target::xfer_partial always let the target
beneath handle TARGET_OBJECT_AUXV.

Add the gdb.rocm/auxv-wave-selected.exp test, which reproduces the
"file" scenario above (perhaps we should have a maintenance command to
flush the auxv cache though).  The gcore scenario can't be tested yet,
because generating a core file while a GPU wave is selected fails for
another reason, fixed in the following patch.

The amd-dbgapi-target.c part of this change comes from the downstream
ROCgdb port, commit 47716f7de58 ("gdb/amd-dbgapi: defer
TARGET_OBJECT_AUXV xfers to the beneath target").

Co-Authored-By: Simon Marchi <simon.marchi@efficios.com>
Change-Id: I177eba5780706e4065e1b17f370a17dbea016d8d
---
 gdb/amd-dbgapi-target.c                       |  9 ++-
 gdb/testsuite/gdb.rocm/auxv-wave-selected.cpp | 42 ++++++++++++
 gdb/testsuite/gdb.rocm/auxv-wave-selected.exp | 65 +++++++++++++++++++
 3 files changed, 114 insertions(+), 2 deletions(-)
 create mode 100644 gdb/testsuite/gdb.rocm/auxv-wave-selected.cpp
 create mode 100644 gdb/testsuite/gdb.rocm/auxv-wave-selected.exp

diff --git a/gdb/amd-dbgapi-target.c b/gdb/amd-dbgapi-target.c
index 099deceaabad..1c6edb5a7fa3 100644
--- a/gdb/amd-dbgapi-target.c
+++ b/gdb/amd-dbgapi-target.c
@@ -752,9 +752,14 @@ amd_dbgapi_target::xfer_partial (enum target_object object, const char *annex,
      the parent, and inferior_ptid has the child's PTID.  We can use
      the parent's process_stratum_target (the one below us) to do the
      memory operation, but dbgapi knows nothing about the child and
-     would try to update the parent's memory.  */
+     would try to update the parent's memory.
+
+     The auxiliary vector is a property of the host process, so let the
+     target beneath handle it, even if the current thread is a GPU
+     thread.  */
   if ((!ptid_is_gpu (inferior_ptid) && object != TARGET_OBJECT_MEMORY)
-      || inferior_ptid.pid () != current_inferior ()->pid)
+      || inferior_ptid.pid () != current_inferior ()->pid
+      || object == TARGET_OBJECT_AUXV)
     return beneath ()->xfer_partial (object, annex, readbuf, writebuf,
 				     offset, requested_len, xfered_len);
 
diff --git a/gdb/testsuite/gdb.rocm/auxv-wave-selected.cpp b/gdb/testsuite/gdb.rocm/auxv-wave-selected.cpp
new file mode 100644
index 000000000000..0f8ca14fe90f
--- /dev/null
+++ b/gdb/testsuite/gdb.rocm/auxv-wave-selected.cpp
@@ -0,0 +1,42 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2026 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "hip/hip_runtime.h"
+#include <cassert>
+
+__global__ void
+kernel (int *out)
+{
+  *out = 1;
+}
+
+int
+main ()
+{
+  int *result_ptr, result;
+
+  hipError_t error = hipMalloc (&result_ptr, sizeof (int));
+  assert (error == hipSuccess);
+
+  kernel<<<dim3 (1), dim3 (1), 0, 0>>> (result_ptr);
+
+  error = hipMemcpyDtoH (&result, result_ptr, sizeof (int));
+  assert (error == hipSuccess);
+  assert (result == 1);
+
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.rocm/auxv-wave-selected.exp b/gdb/testsuite/gdb.rocm/auxv-wave-selected.exp
new file mode 100644
index 000000000000..637c5f2561b6
--- /dev/null
+++ b/gdb/testsuite/gdb.rocm/auxv-wave-selected.exp
@@ -0,0 +1,65 @@
+# Copyright 2026 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test that GDB can read the auxiliary vector of the inferior while a GPU
+# wave is selected.
+
+load_lib rocm.exp
+
+standard_testfile .cpp
+
+require allow_hip_tests
+
+# Build a position-independent executable.  To find the shared libraries
+# loaded by a PIE, GDB needs the auxiliary vector to find where the
+# executable is loaded.
+if {[build_executable "failed to prepare" $testfile $srcfile {debug hip pie}]} {
+    return
+}
+
+clean_restart $testfile
+
+with_rocm_gpu_lock {
+    if {![runto_main]} {
+	return
+    }
+
+    gdb_breakpoint "kernel" -allow-pending
+
+    gdb_test "continue" \
+	"Thread $::decimal hit Breakpoint ${::decimal}(?:\\.${::decimal})?, kernel .*"
+
+    gdb_test "thread" "Current thread is $::decimal \\(AMDGPU Wave .*" \
+	"wave is selected"
+
+    delete_breakpoints
+
+    # GDB caches the auxiliary vector, and the cache is normally populated
+    # early, while a host thread is selected.  Use the "file" command while a
+    # wave is selected, which clears the cache, so that the auxiliary vector is
+    # read again while the wave is selected.
+    gdb_test "with confirm off -- file $::binfile" \
+	"Reading symbols from [string_to_regexp $::binfile]\\.\\.\\..*" \
+	"reload executable"
+
+    gdb_test "info auxv" \
+	"AT_ENTRY +Entry point of program +$::hex\r\n.*AT_NULL +End of vector +0x0" \
+	"info auxv with wave selected"
+
+    # Check that GDB still finds the shared libraries loaded by the
+    # program.
+    gdb_test "info sharedlibrary" "/libamdhip64\\.so.*" \
+	"shared libraries after reload"
+}
-- 
2.56.0