pstore/pmsg: drop bounce buffer

Removing a bounce buffer copy operation in the pmsg driver path is
always better. We also gain in overall performance by not requesting
a vmalloc on every write as this can cause precious RT tasks, such
as user facing media operation, to stall while memory is being
reclaimed. Added a write_buf_user to the pstore functions, a backup
platform write_buf_user that uses the small buffer that is part of
the instance, and implemented a ramoops write_buf_user that only
supports PSTORE_TYPE_PMSG.

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 76dd604a0f2c..14984d902a99 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -623,6 +623,40 @@ static int pstore_write_compat(enum pstore_type_id type,
 			     size, psi);
 }
 
+static int pstore_write_buf_user_compat(enum pstore_type_id type,
+			       enum kmsg_dump_reason reason,
+			       u64 *id, unsigned int part,
+			       const char __user *buf,
+			       bool compressed, size_t size,
+			       struct pstore_info *psi)
+{
+	unsigned long flags = 0;
+	size_t i, bufsize = size;
+	long ret = 0;
+
+	if (unlikely(!access_ok(VERIFY_READ, buf, size)))
+		return -EFAULT;
+	if (bufsize > psinfo->bufsize)
+		bufsize = psinfo->bufsize;
+	spin_lock_irqsave(&psinfo->buf_lock, flags);
+	for (i = 0; i < size; ) {
+		size_t c = min(size - i, bufsize);
+
+		ret = __copy_from_user(psinfo->buf, buf + i, c);
+		if (unlikely(ret != 0)) {
+			ret = -EFAULT;
+			break;
+		}
+		ret = psi->write_buf(type, reason, id, part, psinfo->buf,
+				     compressed, c, psi);
+		if (unlikely(ret < 0))
+			break;
+		i += c;
+	}
+	spin_unlock_irqrestore(&psinfo->buf_lock, flags);
+	return unlikely(ret < 0) ? ret : size;
+}
+
 /*
  * platform specific persistent storage driver registers with
  * us here. If pstore is already mounted, call the platform
@@ -645,6 +679,8 @@ int pstore_register(struct pstore_info *psi)
 
 	if (!psi->write)
 		psi->write = pstore_write_compat;
+	if (!psi->write_buf_user)
+		psi->write_buf_user = pstore_write_buf_user_compat;
 	psinfo = psi;
 	mutex_init(&psinfo->read_mutex);
 	spin_unlock(&pstore_lock);