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. Signed-off-by: Piotr Figiel <figiel@xxxxxxxxxx> --- v2: - fixed string formatting for 32-bit architectures v1: - https://lkml.kernel.org/r/20210113174127.2500051-1-figiel@xxxxxxxxxx --- fs/proc/base.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/fs/proc/base.c b/fs/proc/base.c index b3422cda2a91..7cc36a224b8b 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -662,6 +662,21 @@ static int proc_pid_syscall(struct seq_file *m, struct pid_namespace *ns, 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, "%tx %08x\n", (ptrdiff_t)((uintptr_t)task->rseq), + task->rseq_sig); + unlock_trace(task); + return 0; +} +#endif /* CONFIG_RSEQ */ #endif /* CONFIG_HAVE_ARCH_TRACEHOOK */ /************************************************************************/ @@ -3182,6 +3197,9 @@ static const struct pid_entry tgid_base_stuff[] = { 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), @@ -3522,6 +3540,9 @@ static const struct pid_entry tid_base_stuff[] = { &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), -- 2.30.0.284.gd98b1dd5eaa7-goog
