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    Subject[PATCH 6/8] block: sed-opal: split generation of bytestring header and content
    Date
    Split the header generation from the (normal) memcpy part if a
    bytestring is copied into the command buffer. This allows in-place
    generation of the bytestring content. For example, copy_from_user may be
    used without an intermediate buffer.

    Signed-off-by: Jonas Rabenstein <jonas.rabenstein@studium.uni-erlangen.de>
    ---
    block/sed-opal.c | 23 +++++++++++++++--------
    1 file changed, 15 insertions(+), 8 deletions(-)

    diff --git a/block/sed-opal.c b/block/sed-opal.c
    index f7925e6f607c..f169e621279a 100644
    --- a/block/sed-opal.c
    +++ b/block/sed-opal.c
    @@ -584,14 +584,11 @@ static void add_token_u64(int *err, struct opal_dev *cmd, u64 number)
    }
    }

    -static void add_token_bytestring(int *err, struct opal_dev *cmd,
    - const u8 *bytestring, size_t len)
    +static u8 *add_bytestring_header(int *err, struct opal_dev *cmd, size_t len)
    {
    size_t header_len = 1;
    bool is_short_atom = true;
    -
    - if (*err)
    - return;
    + char *start;

    if (len & ~SHORT_ATOM_LEN_MASK) {
    header_len = 2;
    @@ -600,17 +597,27 @@ static void add_token_bytestring(int *err, struct opal_dev *cmd,

    if (!can_add(err, cmd, header_len + len)) {
    pr_debug("Error adding bytestring: end of buffer.\n");
    - return;
    + return NULL;
    }

    if (is_short_atom)
    add_short_atom_header(cmd, true, false, len);
    else
    add_medium_atom_header(cmd, true, false, len);
    -
    - memcpy(&cmd->cmd[cmd->pos], bytestring, len);
    + start = &cmd->cmd[cmd->pos];
    cmd->pos += len;
    + return start;
    +}

    +static void add_token_bytestring(int *err, struct opal_dev *cmd,
    + const u8 *bytestring, size_t len)
    +{
    + u8 *start;
    +
    + start = add_bytestring_header(err, cmd, len);
    + if (!start)
    + return;
    + memcpy(start, bytestring, len);
    }

    static int build_locking_range(u8 *buffer, size_t length, u8 lr)
    --
    2.16.1
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