2021-03-24 15:07:44

by Changbin Du

Subject: [PATCH] of/fdt: Check dtb pointer first in unflatten_device_tree

The setup_arch() would invoke unflatten_device_tree() even no
valid fdt found. So we'd better check it first and return early.

Signed-off-by: Changbin Du <[email protected]>
---
drivers/of/fdt.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index dcc1dd96911a..05d439d63bc5 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -1225,6 +1225,11 @@ bool __init early_init_dt_scan(void *params)
*/
void __init unflatten_device_tree(void)
{
+ if (!initial_boot_params) {
+ pr_warn("No valid device tree found, continuing without\n");
+ return;
+ }
+
__unflatten_device_tree(initial_boot_params, NULL, &of_root,
early_init_dt_alloc_memory_arch, false);

--
2.30.2

2021-03-25 03:17:56

by Rob Herring

Subject: Re: [PATCH] of/fdt: Check dtb pointer first in unflatten_device_tree

On Wed, Mar 24, 2021 at 9:04 AM Changbin Du <[email protected]> wrote:
>
> The setup_arch() would invoke unflatten_device_tree() even no
> valid fdt found. So we'd better check it first and return early.
>
> Signed-off-by: Changbin Du <[email protected]>
> ---
> drivers/of/fdt.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index dcc1dd96911a..05d439d63bc5 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -1225,6 +1225,11 @@ bool __init early_init_dt_scan(void *params)
> */
> void __init unflatten_device_tree(void)
> {
> + if (!initial_boot_params) {
> + pr_warn("No valid device tree found, continuing without\n");

How are you going to see this message if you have no DT?

> + return;

And the arch is supposed to just continue on oblivious that it has no DT?

> + }
> +
> __unflatten_device_tree(initial_boot_params, NULL, &of_root,
> early_init_dt_alloc_memory_arch, false);

Soon as you get here with a NULL initial_boot_params, you'll get a
backtrace and halt.

>
> --
> 2.30.2
>

2021-03-25 16:03:38

by Changbin Du

Subject: Re: [PATCH] of/fdt: Check dtb pointer first in unflatten_device_tree

On Wed, Mar 24, 2021 at 10:52:30AM -0600, Rob Herring wrote:
> On Wed, Mar 24, 2021 at 9:04 AM Changbin Du <[email protected]> wrote:
> >
> > The setup_arch() would invoke unflatten_device_tree() even no
> > valid fdt found. So we'd better check it first and return early.
> >
> > Signed-off-by: Changbin Du <[email protected]>
> > ---
> > drivers/of/fdt.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> > index dcc1dd96911a..05d439d63bc5 100644
> > --- a/drivers/of/fdt.c
> > +++ b/drivers/of/fdt.c
> > @@ -1225,6 +1225,11 @@ bool __init early_init_dt_scan(void *params)
> > */
> > void __init unflatten_device_tree(void)
> > {
> > + if (!initial_boot_params) {
> > + pr_warn("No valid device tree found, continuing without\n");
>
> How are you going to see this message if you have no DT?
>
This aligns to what unflatten_and_copy_device_tree() does.

> > + return;
>
> And the arch is supposed to just continue on oblivious that it has no DT?
>
As checking the arch code(arm, riscv), I suppose so.

> > + }
> > +
> > __unflatten_device_tree(initial_boot_params, NULL, &of_root,
> > early_init_dt_alloc_memory_arch, false);
>
> Soon as you get here with a NULL initial_boot_params, you'll get a
> backtrace and halt.
>
No, we have returned before.

> >
> > --
> > 2.30.2
> >

--
Cheers,
Changbin Du

2021-03-25 16:30:32

by Rob Herring

Subject: Re: [PATCH] of/fdt: Check dtb pointer first in unflatten_device_tree

On Thu, Mar 25, 2021 at 10:00 AM Changbin Du <[email protected]> wrote:
>
> On Wed, Mar 24, 2021 at 10:52:30AM -0600, Rob Herring wrote:
> > On Wed, Mar 24, 2021 at 9:04 AM Changbin Du <[email protected]> wrote:
> > >
> > > The setup_arch() would invoke unflatten_device_tree() even no
> > > valid fdt found. So we'd better check it first and return early.
> > >
> > > Signed-off-by: Changbin Du <[email protected]>
> > > ---
> > > drivers/of/fdt.c | 5 +++++
> > > 1 file changed, 5 insertions(+)
> > >
> > > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> > > index dcc1dd96911a..05d439d63bc5 100644
> > > --- a/drivers/of/fdt.c
> > > +++ b/drivers/of/fdt.c
> > > @@ -1225,6 +1225,11 @@ bool __init early_init_dt_scan(void *params)
> > > */
> > > void __init unflatten_device_tree(void)
> > > {
> > > + if (!initial_boot_params) {
> > > + pr_warn("No valid device tree found, continuing without\n");
> >
> > How are you going to see this message if you have no DT?
> >
> This aligns to what unflatten_and_copy_device_tree() does.

Humm, then we should have a single check that covers both cases. Or we
should remove that one.

>
> > > + return;
> >
> > And the arch is supposed to just continue on oblivious that it has no DT?
> >
> As checking the arch code(arm, riscv), I suppose so.
>
> > > + }
> > > +
> > > __unflatten_device_tree(initial_boot_params, NULL, &of_root,
> > > early_init_dt_alloc_memory_arch, false);
> >
> > Soon as you get here with a NULL initial_boot_params, you'll get a
> > backtrace and halt.
> >
> No, we have returned before.

I mean without your addition we'll get here with a NULL.

Rob