The patch titled
Subject: fs/proc: expose RSEQ configuration
has been added to the -mm tree. Its filename is
fs-proc-expose-rseq-configuration.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/fs-proc-expose-rseq-configuration.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/fs-proc-expose-rseq-configuration.patch
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------------------------------------------------------
From: Piotr Figiel <figiel@xxxxxxxxxx>
Subject: fs/proc: expose RSEQ configuration
For userspace checkpoint and restore (C/R) some way of getting process
state containing RSEQ configuration is needed.
There are two ways this information is going to be used:
- to re-enable RSEQ for threads which had it enabled before C/R
- to detect if a thread was in a critical section during C/R
Since C/R preserves TLS memory and addresses RSEQ ABI will be restored
using the address registered before C/R.
Detection whether the thread is in a critical section during C/R is needed
to enforce behavior of RSEQ abort during C/R. Attaching with ptrace()
before registers are dumped itself doesn't cause RSEQ abort. Restoring
the instruction pointer within the critical section is problematic because
rseq_cs may get cleared before the control is passed to the migrated
application code leading to RSEQ invariants not being preserved.
Link: https://lkml.kernel.org/r/20210113174127.2500051-1-figiel@xxxxxxxxxx
Signed-off-by: Piotr Figiel <figiel@xxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Alexey Gladkov <gladkov.alexey@xxxxxxxxx>
Cc: Christian Brauner <christian.brauner@xxxxxxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Bernd Edlinger <bernd.edlinger@xxxxxxxxxx>
Cc: Andrei Vagin <avagin@xxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Peter Oskolkov <posk@xxxxxxxxxx>
Cc: Chris Kennelly <ckennelly@xxxxxxxxxx>
Cc: Paul Turner <pjt@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
--- a/fs/proc/base.c~fs-proc-expose-rseq-configuration
+++ a/fs/proc/base.c
@@ -659,6 +659,20 @@ static int proc_pid_syscall(struct seq_f
return 0;
}
+
+#ifdef CONFIG_RSEQ
+static int proc_pid_rseq(struct seq_file *m, struct pid_namespace *ns,
+ struct pid *pid, struct task_struct *task)
+{
+ int res = lock_trace(task);
+
+ if (res)
+ return res;
+ seq_printf(m, "0x%llx 0x%x\n", (uint64_t)task->rseq, task->rseq_sig);
+ unlock_trace(task);
+ return 0;
+}
+#endif /* CONFIG_RSEQ */
#endif /* CONFIG_HAVE_ARCH_TRACEHOOK */
/************************************************************************/
@@ -3179,6 +3193,9 @@ static const struct pid_entry tgid_base_
REG("comm", S_IRUGO|S_IWUSR, proc_pid_set_comm_operations),
#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
ONE("syscall", S_IRUSR, proc_pid_syscall),
+#ifdef CONFIG_RSEQ
+ ONE("rseq", S_IRUSR, proc_pid_rseq),
+#endif
#endif
REG("cmdline", S_IRUGO, proc_pid_cmdline_ops),
ONE("stat", S_IRUGO, proc_tgid_stat),
@@ -3519,6 +3536,9 @@ static const struct pid_entry tid_base_s
&proc_pid_set_comm_operations, {}),
#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
ONE("syscall", S_IRUSR, proc_pid_syscall),
+#ifdef CONFIG_RSEQ
+ ONE("rseq", S_IRUSR, proc_pid_rseq),
+#endif
#endif
REG("cmdline", S_IRUGO, proc_pid_cmdline_ops),
ONE("stat", S_IRUGO, proc_tid_stat),
_
Patches currently in -mm which might be from figiel@xxxxxxxxxx are
fs-proc-expose-rseq-configuration.patch
