Re: [PATCH v2 6/6] soc/fsl/qe: qe.c: fold qe_get_num_of_snums into qe_snums_init

[Christophe Leroy]

Le 01/05/2019 à 11:29, Rasmus Villemoes a écrit :

The comment "No QE ever has fewer than 28 SNUMs" is false; e.g. the
MPC8309 has 14. The code path returning -EINVAL is also a recipe for
instant disaster, since the caller (qe_snums_init) uncritically
assigns the return value to the unsigned qe_num_of_snum, and would
thus proceed to attempt to copy 4GB from snum_init_46[] to the snum[]
array.

So fold the handling of the legacy fsl,qe-num-snums into
qe_snums_init, and make sure we do not end up using the snum_init_46
array in cases other than the two where we know it makes sense.

Signed-off-by: Rasmus Villemoes <rasmus.villem...@prevas.dk>

Reviewed-by: Christophe Leroy <christophe.le...@c-s.fr>

---
  drivers/soc/fsl/qe/qe.c | 46 ++++++++++++++---------------------------
  1 file changed, 16 insertions(+), 30 deletions(-)

diff --git a/drivers/soc/fsl/qe/qe.c b/drivers/soc/fsl/qe/qe.c
index 325d689cbf5c..276d7d78ebfc 100644
--- a/drivers/soc/fsl/qe/qe.c
+++ b/drivers/soc/fsl/qe/qe.c
@@ -308,24 +308,33 @@ static void qe_snums_init(void)
        int i;

bitmap_zero(snum_state, QE_NUM_OF_SNUM);

+       qe_num_of_snum = 28; /* The default number of snum for threads is 28 */
        qe = qe_get_device_node();
        if (qe) {
                i = of_property_read_variable_u8_array(qe, "fsl,qe-snums",
                                                       snums, 1, 
QE_NUM_OF_SNUM);
-               of_node_put(qe);
                if (i > 0) {
+                       of_node_put(qe);
                        qe_num_of_snum = i;
                        return;
                }
+               /*
+                * Fall back to legacy binding of using the value of
+                * fsl,qe-num-snums to choose one of the static arrays
+                * above.
+                */
+               of_property_read_u32(qe, "fsl,qe-num-snums", &qe_num_of_snum);
+               of_node_put(qe);
        }

- qe_num_of_snum = qe_get_num_of_snums();

-
-       if (qe_num_of_snum == 76)
+       if (qe_num_of_snum == 76) {
                snum_init = snum_init_76;
-       else
+       } else if (qe_num_of_snum == 28 || qe_num_of_snum == 46) {
                snum_init = snum_init_46;
-
+       } else {
+               pr_err("QE: unsupported value of fsl,qe-num-snums: %u\n", 
qe_num_of_snum);
+               return;
+       }
        memcpy(snums, snum_init, qe_num_of_snum);
  }

@@ -641,30 +650,7 @@ EXPORT_SYMBOL(qe_get_num_of_risc); unsigned int qe_get_num_of_snums(void)

  {
-       struct device_node *qe;
-       int size;
-       unsigned int num_of_snums;
-       const u32 *prop;
-
-       num_of_snums = 28; /* The default number of snum for threads is 28 */
-       qe = qe_get_device_node();
-       if (!qe)
-               return num_of_snums;
-
-       prop = of_get_property(qe, "fsl,qe-num-snums", &size);
-       if (prop && size == sizeof(*prop)) {
-               num_of_snums = *prop;
-               if ((num_of_snums < 28) || (num_of_snums > QE_NUM_OF_SNUM)) {
-                       /* No QE ever has fewer than 28 SNUMs */
-                       pr_err("QE: number of snum is invalid\n");
-                       of_node_put(qe);
-                       return -EINVAL;
-               }
-       }
-
-       of_node_put(qe);
-
-       return num_of_snums;
+       return qe_num_of_snum;
  }
  EXPORT_SYMBOL(qe_get_num_of_snums);