Merge patch series "fix reading ESP during coredump"

Nam Cao <namcao@linutronix.de> says:

In /proc/PID/stat, there is the kstkesp field which is the stack pointer of
a thread. While the thread is active, this field reads zero. But during a
coredump, it should have a valid value.

However, at the moment, kstkesp is zero even during coredump.

The first commit fixes this problem, and the second commit adds a selftest
to detect if this problem appears again in the future.

* patches from https://lore.kernel.org/r/cover.1735805772.git.namcao@linutronix.de:
  selftests: coredump: Add stackdump test
  fs/proc: do_task_stat: Fix ESP not readable during coredump

Link: https://lore.kernel.org/r/cover.1735805772.git.namcao@linutronix.de
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/tools/testing/selftests/coredump/stackdump b/tools/testing/selftests/coredump/stackdump
new file mode 100755
index 000000000000..96714ce42d12
--- /dev/null
+++ b/tools/testing/selftests/coredump/stackdump
@@ -0,0 +1,14 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+CRASH_PROGRAM_ID=$1
+STACKDUMP_FILE=$2
+
+TMP=$(mktemp)
+
+for t in /proc/$CRASH_PROGRAM_ID/task/*; do
+	tid=$(basename $t)
+	cat /proc/$tid/stat | awk '{print $29}' >> $TMP
+done
+
+mv $TMP $STACKDUMP_FILE