* [PATCH] powerpc/mm: tell if a bad page fault on data is read or write.
@ 2019-08-21 15:21 Christophe Leroy
2019-08-26 5:35 ` Santosh Sivaraj
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Christophe Leroy @ 2019-08-21 15:21 UTC (permalink / raw)
To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman
Cc: linux-kernel, linuxppc-dev
DSISR has a bit to tell if the fault is due to a read or a write.
Display it.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
arch/powerpc/mm/fault.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 8432c281de92..b5047f9b5dec 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -645,6 +645,7 @@ NOKPROBE_SYMBOL(do_page_fault);
void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
{
const struct exception_table_entry *entry;
+ int is_write = page_fault_is_write(regs->dsisr);
/* Are we prepared to handle this fault? */
if ((entry = search_exception_tables(regs->nip)) != NULL) {
@@ -658,9 +659,10 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
case 0x300:
case 0x380:
case 0xe00:
- pr_alert("BUG: %s at 0x%08lx\n",
+ pr_alert("BUG: %s on %s at 0x%08lx\n",
regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
- "Unable to handle kernel data access", regs->dar);
+ "Unable to handle kernel data access",
+ is_write ? "write" : "read", regs->dar);
break;
case 0x400:
case 0x480:
--
2.13.3
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] powerpc/mm: tell if a bad page fault on data is read or write.
2019-08-21 15:21 [PATCH] powerpc/mm: tell if a bad page fault on data is read or write Christophe Leroy
@ 2019-08-26 5:35 ` Santosh Sivaraj
2019-08-29 12:14 ` Michael Ellerman
2019-11-25 10:46 ` Michael Ellerman
2 siblings, 0 replies; 6+ messages in thread
From: Santosh Sivaraj @ 2019-08-26 5:35 UTC (permalink / raw)
To: Christophe Leroy, Benjamin Herrenschmidt, Paul Mackerras,
Michael Ellerman
Cc: linuxppc-dev, linux-kernel
Christophe Leroy <christophe.leroy@c-s.fr> writes:
> DSISR has a bit to tell if the fault is due to a read or a write.
>
> Display it.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Santosh Sivaraj <santosh@fossix.org>
> ---
> arch/powerpc/mm/fault.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index 8432c281de92..b5047f9b5dec 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -645,6 +645,7 @@ NOKPROBE_SYMBOL(do_page_fault);
> void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
> {
> const struct exception_table_entry *entry;
> + int is_write = page_fault_is_write(regs->dsisr);
>
> /* Are we prepared to handle this fault? */
> if ((entry = search_exception_tables(regs->nip)) != NULL) {
> @@ -658,9 +659,10 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
> case 0x300:
> case 0x380:
> case 0xe00:
> - pr_alert("BUG: %s at 0x%08lx\n",
> + pr_alert("BUG: %s on %s at 0x%08lx\n",
> regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
> - "Unable to handle kernel data access", regs->dar);
> + "Unable to handle kernel data access",
> + is_write ? "write" : "read", regs->dar);
> break;
> case 0x400:
> case 0x480:
> --
> 2.13.3
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] powerpc/mm: tell if a bad page fault on data is read or write.
2019-08-21 15:21 [PATCH] powerpc/mm: tell if a bad page fault on data is read or write Christophe Leroy
2019-08-26 5:35 ` Santosh Sivaraj
@ 2019-08-29 12:14 ` Michael Ellerman
2019-08-29 12:59 ` Christophe Leroy
2019-08-30 7:41 ` Christophe Leroy
2019-11-25 10:46 ` Michael Ellerman
2 siblings, 2 replies; 6+ messages in thread
From: Michael Ellerman @ 2019-08-29 12:14 UTC (permalink / raw)
To: Christophe Leroy, Benjamin Herrenschmidt, Paul Mackerras
Cc: linux-kernel, linuxppc-dev
Christophe Leroy <christophe.leroy@c-s.fr> writes:
> DSISR has a bit to tell if the fault is due to a read or a write.
Except some CPUs don't have a DSISR?
Which is why we have page_fault_is_write() that's used in
__do_page_fault().
Or is that old cruft?
I see eg. in head_40x.S we pass r5=0 for error code, and we don't set
regs->dsisr anywhere AFAICS. So it might just contain some junk.
cheers
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index 8432c281de92..b5047f9b5dec 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -645,6 +645,7 @@ NOKPROBE_SYMBOL(do_page_fault);
> void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
> {
> const struct exception_table_entry *entry;
> + int is_write = page_fault_is_write(regs->dsisr);
>
> /* Are we prepared to handle this fault? */
> if ((entry = search_exception_tables(regs->nip)) != NULL) {
> @@ -658,9 +659,10 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
> case 0x300:
> case 0x380:
> case 0xe00:
> - pr_alert("BUG: %s at 0x%08lx\n",
> + pr_alert("BUG: %s on %s at 0x%08lx\n",
> regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
> - "Unable to handle kernel data access", regs->dar);
> + "Unable to handle kernel data access",
> + is_write ? "write" : "read", regs->dar);
> break;
> case 0x400:
> case 0x480:
> --
> 2.13.3
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] powerpc/mm: tell if a bad page fault on data is read or write.
2019-08-29 12:14 ` Michael Ellerman
@ 2019-08-29 12:59 ` Christophe Leroy
2019-08-30 7:41 ` Christophe Leroy
1 sibling, 0 replies; 6+ messages in thread
From: Christophe Leroy @ 2019-08-29 12:59 UTC (permalink / raw)
To: Michael Ellerman, Benjamin Herrenschmidt, Paul Mackerras
Cc: linux-kernel, linuxppc-dev
Le 29/08/2019 à 14:14, Michael Ellerman a écrit :
> Christophe Leroy <christophe.leroy@c-s.fr> writes:
>> DSISR has a bit to tell if the fault is due to a read or a write.
>
> Except some CPUs don't have a DSISR?
>
> Which is why we have page_fault_is_write() that's used in
> __do_page_fault().
>
> Or is that old cruft?
>
> I see eg. in head_40x.S we pass r5=0 for error code, and we don't set
> regs->dsisr anywhere AFAICS. So it might just contain some junk.
But then we have a problem with show_regs() as well, havent't we ?
if (trap == 0x200 || trap == 0x300 || trap == 0x600)
#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
pr_cont("DEAR: "REG" ESR: "REG" ", regs->dar, regs->dsisr);
#else
pr_cont("DAR: "REG" DSISR: %08lx ", regs->dar, regs->dsisr);
#endif
I need to look closer.
Christophe
>
> cheers
>
>> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
>> index 8432c281de92..b5047f9b5dec 100644
>> --- a/arch/powerpc/mm/fault.c
>> +++ b/arch/powerpc/mm/fault.c
>> @@ -645,6 +645,7 @@ NOKPROBE_SYMBOL(do_page_fault);
>> void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
>> {
>> const struct exception_table_entry *entry;
>> + int is_write = page_fault_is_write(regs->dsisr);
>>
>> /* Are we prepared to handle this fault? */
>> if ((entry = search_exception_tables(regs->nip)) != NULL) {
>> @@ -658,9 +659,10 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
>> case 0x300:
>> case 0x380:
>> case 0xe00:
>> - pr_alert("BUG: %s at 0x%08lx\n",
>> + pr_alert("BUG: %s on %s at 0x%08lx\n",
>> regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
>> - "Unable to handle kernel data access", regs->dar);
>> + "Unable to handle kernel data access",
>> + is_write ? "write" : "read", regs->dar);
>
>> break;
>> case 0x400:
>> case 0x480:
>> --
>> 2.13.3
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] powerpc/mm: tell if a bad page fault on data is read or write.
2019-08-29 12:14 ` Michael Ellerman
2019-08-29 12:59 ` Christophe Leroy
@ 2019-08-30 7:41 ` Christophe Leroy
1 sibling, 0 replies; 6+ messages in thread
From: Christophe Leroy @ 2019-08-30 7:41 UTC (permalink / raw)
To: Michael Ellerman, Benjamin Herrenschmidt, Paul Mackerras
Cc: linux-kernel, linuxppc-dev
Le 29/08/2019 à 14:14, Michael Ellerman a écrit :
> Christophe Leroy <christophe.leroy@c-s.fr> writes:
>> DSISR has a bit to tell if the fault is due to a read or a write.
>
> Except some CPUs don't have a DSISR?
>
> Which is why we have page_fault_is_write() that's used in
> __do_page_fault().
And that's why I'm also using page_fault_is_write() in my patch.
>
> Or is that old cruft?
>
> I see eg. in head_40x.S we pass r5=0 for error code, and we don't set
> regs->dsisr anywhere AFAICS. So it might just contain some junk.
We pass r5=0 in ISI but r5=SPRN_ESR in DSI.
And r5 is also saved into _ESR(r11)
And in asm-offset.c, we have:
STACK_PT_REGS_OFFSET(_ESR, dsisr);
So regs->dsisr has the expected content.
Christophe
>
> cheers
>
>> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
>> index 8432c281de92..b5047f9b5dec 100644
>> --- a/arch/powerpc/mm/fault.c
>> +++ b/arch/powerpc/mm/fault.c
>> @@ -645,6 +645,7 @@ NOKPROBE_SYMBOL(do_page_fault);
>> void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
>> {
>> const struct exception_table_entry *entry;
>> + int is_write = page_fault_is_write(regs->dsisr);
>>
>> /* Are we prepared to handle this fault? */
>> if ((entry = search_exception_tables(regs->nip)) != NULL) {
>> @@ -658,9 +659,10 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
>> case 0x300:
>> case 0x380:
>> case 0xe00:
>> - pr_alert("BUG: %s at 0x%08lx\n",
>> + pr_alert("BUG: %s on %s at 0x%08lx\n",
>> regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
>> - "Unable to handle kernel data access", regs->dar);
>> + "Unable to handle kernel data access",
>> + is_write ? "write" : "read", regs->dar);
>
>> break;
>> case 0x400:
>> case 0x480:
>> --
>> 2.13.3
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] powerpc/mm: tell if a bad page fault on data is read or write.
2019-08-21 15:21 [PATCH] powerpc/mm: tell if a bad page fault on data is read or write Christophe Leroy
2019-08-26 5:35 ` Santosh Sivaraj
2019-08-29 12:14 ` Michael Ellerman
@ 2019-11-25 10:46 ` Michael Ellerman
2 siblings, 0 replies; 6+ messages in thread
From: Michael Ellerman @ 2019-11-25 10:46 UTC (permalink / raw)
To: Christophe Leroy, Benjamin Herrenschmidt, Paul Mackerras
Cc: linuxppc-dev, linux-kernel
On Wed, 2019-08-21 at 15:21:55 UTC, Christophe Leroy wrote:
> DSISR has a bit to tell if the fault is due to a read or a write.
>
> Display it.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/46ddcb3950a28c0df4815e8dbb8d4b91d5d9f22d
cheers
^ permalink raw reply [flat|nested] 6+ messages in thread
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2019-08-21 15:21 [PATCH] powerpc/mm: tell if a bad page fault on data is read or write Christophe Leroy
2019-08-26 5:35 ` Santosh Sivaraj
2019-08-29 12:14 ` Michael Ellerman
2019-08-29 12:59 ` Christophe Leroy
2019-08-30 7:41 ` Christophe Leroy
2019-11-25 10:46 ` Michael Ellerman
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