For the API, add a new flag to sys_rseq 'flags' argument called
RSEQ_FLAG_QUERY_CS_FLAGS.
When this flag is passed it returns a bit mask of all the supported
rseq cs flags in the user provided rseq struct's 'flags' member.
Signed-off-by: Prakash Sangappa <prakash.sangappa@oracle.com>
---
include/uapi/linux/rseq.h | 1 +
kernel/rseq.c | 15 +++++++++++++++
2 files changed, 16 insertions(+)
diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h
index 015534f064af..44baea9dd10a 100644
--- a/include/uapi/linux/rseq.h
+++ b/include/uapi/linux/rseq.h
@@ -20,6 +20,7 @@ enum rseq_cpu_id_state {
enum rseq_flags {
RSEQ_FLAG_UNREGISTER = (1 << 0),
+ RSEQ_FLAG_QUERY_CS_FLAGS = (1 << 1),
};
enum rseq_cs_flags_bit {
diff --git a/kernel/rseq.c b/kernel/rseq.c
index 6ca3ca959b66..7f4daeba6d0d 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -550,6 +550,21 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
return 0;
}
+ /*
+ * Return supported rseq_cs flags.
+ */
+ if (flags & RSEQ_FLAG_QUERY_CS_FLAGS) {
+ u32 rseq_csflags = RSEQ_CS_FLAG_DELAY_RESCHED |
+ RSEQ_CS_FLAG_RESCHEDULED;
+ if (!IS_ENABLED(CONFIG_RSEQ_RESCHED_DELAY))
+ return -EINVAL;
+ if (!rseq)
+ return -EINVAL;
+ if (copy_to_user(&rseq->flags, &rseq_csflags, sizeof(u32)))
+ return -EFAULT;
+ return 0;
+ }
+
if (unlikely(flags))
return -EINVAL;
--
2.43.5