[U-Boot] fdt: Fix alignment issue when reading 64-bits properties
diff mbox series

Message ID 20191021124912.25569-1-jjhiblot@ti.com
State Superseded
Delegated to: Simon Glass
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Series
  • [U-Boot] fdt: Fix alignment issue when reading 64-bits properties
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Commit Message

Jean-Jacques Hiblot Oct. 21, 2019, 12:49 p.m. UTC
The FDT specification [0] gives a requirement of aligning properties on
32-bits. Make sure that the compiler is aware of this constraint when
accessing 64-bits properties.

[0]: https://github.com/devicetree-org/devicetree-specification/blob/master/source/flattened-format.rst

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
---
 common/fdt_support.c  | 2 +-
 drivers/core/ofnode.c | 2 +-
 lib/fdtdec.c          | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

Comments

Simon Glass Oct. 21, 2019, 11:46 p.m. UTC | #1
Hi Jean-Jacques,

On Mon, 21 Oct 2019 at 06:50, Jean-Jacques Hiblot <jjhiblot@ti.com> wrote:
>
> The FDT specification [0] gives a requirement of aligning properties on
> 32-bits. Make sure that the compiler is aware of this constraint when
> accessing 64-bits properties.
>
> [0]: https://github.com/devicetree-org/devicetree-specification/blob/master/source/flattened-format.rst
>
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
> ---
>  common/fdt_support.c  | 2 +-
>  drivers/core/ofnode.c | 2 +-
>  lib/fdtdec.c          | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/common/fdt_support.c b/common/fdt_support.c
> index baf7924ff6..d14cf7f61a 100644
> --- a/common/fdt_support.c
> +++ b/common/fdt_support.c
> @@ -1566,7 +1566,7 @@ static int fdt_read_prop(const fdt32_t *prop, int prop_len, int cell_off,
>                          uint64_t *val, int cells)
>  {
>         const fdt32_t *prop32 = &prop[cell_off];
> -       const fdt64_t *prop64 = (const fdt64_t *)&prop[cell_off];
> +       const fdt64_t *prop64 __aligned(4) = (const fdt64_t *)&prop[cell_off];

Excuse my ignorance, but what does this actually mean? That the
pointer points to something that is aligned?

Regards,
Simon
Jean-Jacques Hiblot Oct. 22, 2019, 7:56 a.m. UTC | #2
Hi Simon,

On 22/10/2019 01:46, Simon Glass wrote:
> Hi Jean-Jacques,
>
> On Mon, 21 Oct 2019 at 06:50, Jean-Jacques Hiblot <jjhiblot@ti.com> wrote:
>> The FDT specification [0] gives a requirement of aligning properties on
>> 32-bits. Make sure that the compiler is aware of this constraint when
>> accessing 64-bits properties.
>>
>> [0]: https://github.com/devicetree-org/devicetree-specification/blob/master/source/flattened-format.rst
>>
>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
>> ---
>>   common/fdt_support.c  | 2 +-
>>   drivers/core/ofnode.c | 2 +-
>>   lib/fdtdec.c          | 2 +-
>>   3 files changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/common/fdt_support.c b/common/fdt_support.c
>> index baf7924ff6..d14cf7f61a 100644
>> --- a/common/fdt_support.c
>> +++ b/common/fdt_support.c
>> @@ -1566,7 +1566,7 @@ static int fdt_read_prop(const fdt32_t *prop, int prop_len, int cell_off,
>>                           uint64_t *val, int cells)
>>   {
>>          const fdt32_t *prop32 = &prop[cell_off];
>> -       const fdt64_t *prop64 = (const fdt64_t *)&prop[cell_off];
>> +       const fdt64_t *prop64 __aligned(4) = (const fdt64_t *)&prop[cell_off];
> Excuse my ignorance, but what does this actually mean? That the
> pointer points to something that is aligned?

Well it should have made the compiler assume that the address is aligned 
on 32-bits not 64-bits. But I see now that it doesn't. As I didn't see 
the issue anymore iI thought it worked, but it just was my DTB not 
exposing the issue anymore.

Anyway I'll send a v2 with the effective changes.

Thanks.

JJ

> Regards,
> Simon
>

Patch
diff mbox series

diff --git a/common/fdt_support.c b/common/fdt_support.c
index baf7924ff6..d14cf7f61a 100644
--- a/common/fdt_support.c
+++ b/common/fdt_support.c
@@ -1566,7 +1566,7 @@  static int fdt_read_prop(const fdt32_t *prop, int prop_len, int cell_off,
 			 uint64_t *val, int cells)
 {
 	const fdt32_t *prop32 = &prop[cell_off];
-	const fdt64_t *prop64 = (const fdt64_t *)&prop[cell_off];
+	const fdt64_t *prop64 __aligned(4) = (const fdt64_t *)&prop[cell_off];
 
 	if ((cell_off + cells) > prop_len)
 		return -FDT_ERR_NOSPACE;
diff --git a/drivers/core/ofnode.c b/drivers/core/ofnode.c
index 297f0a0c7c..6bd4235029 100644
--- a/drivers/core/ofnode.c
+++ b/drivers/core/ofnode.c
@@ -57,7 +57,7 @@  int ofnode_read_s32_default(ofnode node, const char *propname, s32 def)
 
 int ofnode_read_u64(ofnode node, const char *propname, u64 *outp)
 {
-	const fdt64_t *cell;
+	const fdt64_t *cell __aligned(4);
 	int len;
 
 	assert(ofnode_valid(node));
diff --git a/lib/fdtdec.c b/lib/fdtdec.c
index 17736ce665..77a54b6433 100644
--- a/lib/fdtdec.c
+++ b/lib/fdtdec.c
@@ -242,7 +242,7 @@  int fdtdec_get_pci_bar32(struct udevice *dev, struct fdt_pci_addr *addr,
 uint64_t fdtdec_get_uint64(const void *blob, int node, const char *prop_name,
 			   uint64_t default_val)
 {
-	const uint64_t *cell64;
+	const uint64_t *cell64 __aligned(4);
 	int length;
 
 	cell64 = fdt_getprop(blob, node, prop_name, &length);