[v3,8/9] imx7-ccm: add digprog mmio write method

Commit Message

Prasad Pandit June 30, 2020, 12:27 p.m. UTC

From: Prasad J Pandit <[e-mail]>

Add digprog mmio write method to avoid assert failure during
initialisation.

Reviewed-by: Li Qiang <[e-mail]>
Signed-off-by: Prasad J Pandit <[e-mail]>
---
 hw/misc/imx7_ccm.c | 7 +++++++
 1 file changed, 7 insertions(+)

Update v3: Add Reviewed-by: ...
  -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg09452.html

Comments

Peter Maydell July 16, 2020, 4:21 p.m. UTC | #1

On Tue, 30 Jun 2020 at 13:31, P J P <[e-mail]> wrote:
>
> From: Prasad J Pandit <[e-mail]>
>
> Add digprog mmio write method to avoid assert failure during
> initialisation.
>
> Reviewed-by: Li Qiang <[e-mail]>
> Signed-off-by: Prasad J Pandit <[e-mail]>
> ---
>  hw/misc/imx7_ccm.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> Update v3: Add Reviewed-by: ...
>   -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg09452.html
>
> diff --git a/hw/misc/imx7_ccm.c b/hw/misc/imx7_ccm.c
> index 02fc1ae8d0..5ac5ecf74c 100644
> --- a/hw/misc/imx7_ccm.c
> +++ b/hw/misc/imx7_ccm.c
> @@ -131,8 +131,15 @@ static const struct MemoryRegionOps imx7_set_clr_tog_ops = {
>      },
>  };
>
> +static void imx7_digprog_write(void *opaque, hwaddr addr,
> +                                        uint64_t data, unsigned size)
> +{
> +    qemu_log_mask(LOG_UNIMP, "%s not implemented\n", __func__);
> +}

This covers a single register (DIGPROG) which is read-only
(it returns a silicon revision number). So this is not a
LOG_UNIMP, but a LOG_GUEST_ERROR:

     qemu_log_mask(LOG_GUEST_ERROR, "Guest write to read-only
ANALOG_DIGPROG register\n");

thanks
-- PMM

Prasad Pandit July 16, 2020, 4:55 p.m. UTC | #2

+-- On Thu, 16 Jul 2020, Peter Maydell wrote --+
| > +static void imx7_digprog_write(void *opaque, hwaddr addr,
| > +                                        uint64_t data, unsigned size)
| > +{
| > +    qemu_log_mask(LOG_UNIMP, "%s not implemented\n", __func__);
| > +}
| 
| This covers a single register (DIGPROG) which is read-only (it returns a 
| silicon revision number). So this is not a LOG_UNIMP, but a LOG_GUEST_ERROR:
| 
|      qemu_log_mask(LOG_GUEST_ERROR, "Guest write to read-only
| ANALOG_DIGPROG register\n");

Should this be g_assert_not_reached() in that case?

Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
8685 545E B54C 486B C6EB 271E E285 8B5A F050 DE8D

Peter Maydell July 16, 2020, 4:56 p.m. UTC | #3

On Thu, 16 Jul 2020 at 17:55, P J P <[e-mail]> wrote:
>
> +-- On Thu, 16 Jul 2020, Peter Maydell wrote --+
> | > +static void imx7_digprog_write(void *opaque, hwaddr addr,
> | > +                                        uint64_t data, unsigned size)
> | > +{
> | > +    qemu_log_mask(LOG_UNIMP, "%s not implemented\n", __func__);
> | > +}
> |
> | This covers a single register (DIGPROG) which is read-only (it returns a
> | silicon revision number). So this is not a LOG_UNIMP, but a LOG_GUEST_ERROR:
> |
> |      qemu_log_mask(LOG_GUEST_ERROR, "Guest write to read-only
> | ANALOG_DIGPROG register\n");
>
> Should this be g_assert_not_reached() in that case?

No, because a malicious guest can write to the register
(and cause the function to be called), it is merely that
it is a bug in guest code for it to do that.

-- PMM

Patch

diff --git a/hw/misc/imx7_ccm.c b/hw/misc/imx7_ccm.c
index 02fc1ae8d0..5ac5ecf74c 100644
--- a/hw/misc/imx7_ccm.c
+++ b/hw/misc/imx7_ccm.c
@@ -131,8 +131,15 @@  static const struct MemoryRegionOps imx7_set_clr_tog_ops = {
     },
 };
 
+static void imx7_digprog_write(void *opaque, hwaddr addr,
+                                        uint64_t data, unsigned size)
+{
+    qemu_log_mask(LOG_UNIMP, "%s not implemented\n", __func__);
+}
+
 static const struct MemoryRegionOps imx7_digprog_ops = {
     .read = imx7_set_clr_tog_read,
+    .write = imx7_digprog_write,
     .endianness = DEVICE_NATIVE_ENDIAN,
     .impl = {
         .min_access_size = 4,