Re: [PATCH 1/1] arm: mmu: catch NULL pointer dereferences
On Mon, Sep 02, 2013 at 12:24:06PM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote: > On 11:05 Mon 02 Sep , Sascha Hauer wrote: > > On Sat, Aug 31, 2013 at 05:54:22PM +0200, Jean-Christophe PLAGNIOL-VILLARD > > wrote: > > > For high vectors if memory start at 0x0. We have to > > > live without being able to catch NULL pointer dereferences. > > > > > Why not add the check to vectors_init() instead of passing this as > > argument? > > > > I must say I'm not entirely happy with this approach. Being able to > > catch NULL pointer derefs is really a good thing. When exactly does the > > faulting zero SDRAM page become a problem for you? obviously something > > like > > > > cp /somehing /dev/ram0 > > > > does not work. Some care must probably be taken when setting up the > > kernel parameters. Are these the problems or is there something else? > yes it's get issue with uImage that get data load there :( > > as I can not control the load addr from uImage :( > > and on ux5x0 and arm board I have ddr starting at 0x0 Maybe we should add some hook which dynamically enables/disables the zero page. The bootm code could then disable it. Anyway, for now we can also apply the current patch, but please move the is_start_zero test to vectors_init(). Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0| Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917- | ___ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox
Re: [PATCH 1/1] arm: mmu: catch NULL pointer dereferences
On 11:05 Mon 02 Sep , Sascha Hauer wrote:
> On Sat, Aug 31, 2013 at 05:54:22PM +0200, Jean-Christophe PLAGNIOL-VILLARD
> wrote:
> > For high vectors if memory start at 0x0. We have to
> > live without being able to catch NULL pointer dereferences.
> >
> > Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD
> > ---
> > arch/arm/cpu/mmu.c | 27 +--
> > 1 file changed, 21 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/arm/cpu/mmu.c b/arch/arm/cpu/mmu.c
> > index e3ea3b6..2e69b16 100644
> > --- a/arch/arm/cpu/mmu.c
> > +++ b/arch/arm/cpu/mmu.c
> > @@ -218,9 +218,9 @@ static int arm_mmu_remap_sdram(struct memory_bank *bank)
> > /*
> > * Map vectors and zero page
> > */
> > -static void vectors_init(void)
> > +static void vectors_init(bool zero_valid_addr)
> > {
> > - u32 *exc, *zero = NULL;
> > + u32 *exc;
> > void *vectors;
> > u32 cr;
> >
> > @@ -235,10 +235,19 @@ static void vectors_init(void)
> > * page table for the high vectors and zero page
> > */
> > exc = arm_create_pte(0xfff0);
> > - zero = arm_create_pte(0x0);
> >
> > - /* Set the zero page to faulting */
> > - zero[0] = 0;
> > + /*
> > +* Memory start at 0x0. We have to
> > +* live without being able to catch NULL pointer dereferences
> > +*/
> > + if (!zero_valid_addr) {
> > + u32 *zero = NULL;
> > +
> > + zero = arm_create_pte(0x0);
> > +
> > + /* Set the zero page to faulting */
> > + zero[0] = 0;
> > + }
> > } else {
> > /*
> > * Otherwise map the vectors to the zero page. We have to
> > @@ -267,6 +276,7 @@ static int mmu_init(void)
> > {
> > struct memory_bank *bank;
> > int i;
> > + bool is_start_zero = 0;
> >
> > arm_set_cache_functions();
> >
> > @@ -303,7 +313,12 @@ static int mmu_init(void)
> > create_sections(0, 0, PAGE_SIZE, PMD_SECT_AP_WRITE | PMD_SECT_AP_READ |
> > PMD_TYPE_SECT);
> >
> > - vectors_init();
> > + for_each_memory_bank(bank) {
> > + if (bank->start == 0x0)
> > + is_start_zero = 1;
> > + }
> > +
> > + vectors_init(is_start_zero);
>
> Why not add the check to vectors_init() instead of passing this as
> argument?
>
> I must say I'm not entirely happy with this approach. Being able to
> catch NULL pointer derefs is really a good thing. When exactly does the
> faulting zero SDRAM page become a problem for you? obviously something
> like
>
> cp /somehing /dev/ram0
>
> does not work. Some care must probably be taken when setting up the
> kernel parameters. Are these the problems or is there something else?
yes it's get issue with uImage that get data load there :(
as I can not control the load addr from uImage :(
and on ux5x0 and arm board I have ddr starting at 0x0
Best Regards,
J.
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Re: [PATCH 1/1] arm: mmu: catch NULL pointer dereferences
On Sat, Aug 31, 2013 at 05:54:22PM +0200, Jean-Christophe PLAGNIOL-VILLARD
wrote:
> For high vectors if memory start at 0x0. We have to
> live without being able to catch NULL pointer dereferences.
>
> Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD
> ---
> arch/arm/cpu/mmu.c | 27 +--
> 1 file changed, 21 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm/cpu/mmu.c b/arch/arm/cpu/mmu.c
> index e3ea3b6..2e69b16 100644
> --- a/arch/arm/cpu/mmu.c
> +++ b/arch/arm/cpu/mmu.c
> @@ -218,9 +218,9 @@ static int arm_mmu_remap_sdram(struct memory_bank *bank)
> /*
> * Map vectors and zero page
> */
> -static void vectors_init(void)
> +static void vectors_init(bool zero_valid_addr)
> {
> - u32 *exc, *zero = NULL;
> + u32 *exc;
> void *vectors;
> u32 cr;
>
> @@ -235,10 +235,19 @@ static void vectors_init(void)
>* page table for the high vectors and zero page
>*/
> exc = arm_create_pte(0xfff0);
> - zero = arm_create_pte(0x0);
>
> - /* Set the zero page to faulting */
> - zero[0] = 0;
> + /*
> + * Memory start at 0x0. We have to
> + * live without being able to catch NULL pointer dereferences
> + */
> + if (!zero_valid_addr) {
> + u32 *zero = NULL;
> +
> + zero = arm_create_pte(0x0);
> +
> + /* Set the zero page to faulting */
> + zero[0] = 0;
> + }
> } else {
> /*
>* Otherwise map the vectors to the zero page. We have to
> @@ -267,6 +276,7 @@ static int mmu_init(void)
> {
> struct memory_bank *bank;
> int i;
> + bool is_start_zero = 0;
>
> arm_set_cache_functions();
>
> @@ -303,7 +313,12 @@ static int mmu_init(void)
> create_sections(0, 0, PAGE_SIZE, PMD_SECT_AP_WRITE | PMD_SECT_AP_READ |
> PMD_TYPE_SECT);
>
> - vectors_init();
> + for_each_memory_bank(bank) {
> + if (bank->start == 0x0)
> + is_start_zero = 1;
> + }
> +
> + vectors_init(is_start_zero);
Why not add the check to vectors_init() instead of passing this as
argument?
I must say I'm not entirely happy with this approach. Being able to
catch NULL pointer derefs is really a good thing. When exactly does the
faulting zero SDRAM page become a problem for you? obviously something
like
cp /somehing /dev/ram0
does not work. Some care must probably be taken when setting up the
kernel parameters. Are these the problems or is there something else?
Sascha
--
Pengutronix e.K. | |
Industrial Linux Solutions | http://www.pengutronix.de/ |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0|
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917- |
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[PATCH 1/1] arm: mmu: catch NULL pointer dereferences
For high vectors if memory start at 0x0. We have to
live without being able to catch NULL pointer dereferences.
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD
---
arch/arm/cpu/mmu.c | 27 +--
1 file changed, 21 insertions(+), 6 deletions(-)
diff --git a/arch/arm/cpu/mmu.c b/arch/arm/cpu/mmu.c
index e3ea3b6..2e69b16 100644
--- a/arch/arm/cpu/mmu.c
+++ b/arch/arm/cpu/mmu.c
@@ -218,9 +218,9 @@ static int arm_mmu_remap_sdram(struct memory_bank *bank)
/*
* Map vectors and zero page
*/
-static void vectors_init(void)
+static void vectors_init(bool zero_valid_addr)
{
- u32 *exc, *zero = NULL;
+ u32 *exc;
void *vectors;
u32 cr;
@@ -235,10 +235,19 @@ static void vectors_init(void)
* page table for the high vectors and zero page
*/
exc = arm_create_pte(0xfff0);
- zero = arm_create_pte(0x0);
- /* Set the zero page to faulting */
- zero[0] = 0;
+ /*
+* Memory start at 0x0. We have to
+* live without being able to catch NULL pointer dereferences
+*/
+ if (!zero_valid_addr) {
+ u32 *zero = NULL;
+
+ zero = arm_create_pte(0x0);
+
+ /* Set the zero page to faulting */
+ zero[0] = 0;
+ }
} else {
/*
* Otherwise map the vectors to the zero page. We have to
@@ -267,6 +276,7 @@ static int mmu_init(void)
{
struct memory_bank *bank;
int i;
+ bool is_start_zero = 0;
arm_set_cache_functions();
@@ -303,7 +313,12 @@ static int mmu_init(void)
create_sections(0, 0, PAGE_SIZE, PMD_SECT_AP_WRITE | PMD_SECT_AP_READ |
PMD_TYPE_SECT);
- vectors_init();
+ for_each_memory_bank(bank) {
+ if (bank->start == 0x0)
+ is_start_zero = 1;
+ }
+
+ vectors_init(is_start_zero);
/*
* First remap sdram cached using sections.
--
1.8.4.rc1
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