* [PATCH 1/2] powerpc: Use seq_buf to avoid pr_cont() in __die()
@ 2019-01-08 12:04 Michael Ellerman
2019-01-08 12:05 ` [PATCH 2/2] powerpc: Show PAGE_SIZE in __die() output Michael Ellerman
2019-01-08 12:18 ` [PATCH 1/2] powerpc: Use seq_buf to avoid pr_cont() in __die() Christophe Leroy
0 siblings, 2 replies; 7+ messages in thread
From: Michael Ellerman @ 2019-01-08 12:04 UTC (permalink / raw)
To: linuxppc-dev
Using pr_cont() risks having our output interleaved with other output
from other CPUs. Instead use a seq_buf to construct the line and then
print it as a whole.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
arch/powerpc/kernel/traps.c | 23 ++++++++++++++++-------
1 file changed, 16 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 64936b60d521..431a86d3f772 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -38,6 +38,7 @@
#include <linux/kdebug.h>
#include <linux/ratelimit.h>
#include <linux/context_tracking.h>
+#include <linux/seq_buf.h>
#include <linux/smp.h>
#include <linux/console.h>
#include <linux/kmsg_dump.h>
@@ -255,26 +256,34 @@ NOKPROBE_SYMBOL(oops_end);
static int __die(const char *str, struct pt_regs *regs, long err)
{
+ char buf[128]; /* enough for all flags and a long platform name */
+ struct seq_buf s;
+
+ seq_buf_init(&s, buf, sizeof(buf));
+
printk("Oops: %s, sig: %ld [#%d]\n", str, err, ++die_counter);
if (IS_ENABLED(CONFIG_CPU_LITTLE_ENDIAN))
- printk("LE ");
+ seq_buf_puts(&s, "LE ");
else
- printk("BE ");
+ seq_buf_puts(&s, "BE ");
if (IS_ENABLED(CONFIG_PREEMPT))
- pr_cont("PREEMPT ");
+ seq_buf_puts(&s, "PREEMPT ");
if (IS_ENABLED(CONFIG_SMP))
- pr_cont("SMP NR_CPUS=%d ", NR_CPUS);
+ seq_buf_printf(&s, "SMP NR_CPUS=%d ", NR_CPUS);
if (debug_pagealloc_enabled())
- pr_cont("DEBUG_PAGEALLOC ");
+ seq_buf_puts(&s, "DEBUG_PAGEALLOC ");
if (IS_ENABLED(CONFIG_NUMA))
- pr_cont("NUMA ");
+ seq_buf_puts(&s, "NUMA ");
+
+ if (ppc_md.name)
+ seq_buf_puts(&s, ppc_md.name);
- pr_cont("%s\n", ppc_md.name ? ppc_md.name : "");
+ printk("%s\n", buf);
if (notify_die(DIE_OOPS, str, regs, err, 255, SIGSEGV) == NOTIFY_STOP)
return 1;
--
2.20.1
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH 2/2] powerpc: Show PAGE_SIZE in __die() output
2019-01-08 12:04 [PATCH 1/2] powerpc: Use seq_buf to avoid pr_cont() in __die() Michael Ellerman
@ 2019-01-08 12:05 ` Michael Ellerman
2019-01-08 12:21 ` Christophe Leroy
2019-01-08 12:18 ` [PATCH 1/2] powerpc: Use seq_buf to avoid pr_cont() in __die() Christophe Leroy
1 sibling, 1 reply; 7+ messages in thread
From: Michael Ellerman @ 2019-01-08 12:05 UTC (permalink / raw)
To: linuxppc-dev
The page size the kernel is built with is useful info when debugging a
crash, so add it to the output in __die().
Result looks like eg:
kernel BUG at drivers/misc/lkdtm/bugs.c:63!
Oops: Exception in kernel mode, sig: 5 [#1]
LE PAGE_SIZE=64K SMP NR_CPUS=2048 NUMA pSeries
Modules linked in: vmx_crypto kvm binfmt_misc ip_tables
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
arch/powerpc/kernel/traps.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 431a86d3f772..fc972e4eee5f 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -268,6 +268,18 @@ static int __die(const char *str, struct pt_regs *regs, long err)
else
seq_buf_puts(&s, "BE ");
+ seq_buf_puts(&s, "PAGE_SIZE=");
+ if (IS_ENABLED(CONFIG_PPC_4K_PAGES))
+ seq_buf_puts(&s, "4K ");
+ else if (IS_ENABLED(CONFIG_PPC_16K_PAGES))
+ seq_buf_puts(&s, "16K ");
+ else if (IS_ENABLED(CONFIG_PPC_64K_PAGES))
+ seq_buf_puts(&s, "64K ");
+ else if (IS_ENABLED(CONFIG_PPC_256K_PAGES))
+ seq_buf_puts(&s, "256K ");
+ else
+ BUILD_BUG_ON(1);
+
if (IS_ENABLED(CONFIG_PREEMPT))
seq_buf_puts(&s, "PREEMPT ");
--
2.20.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 2/2] powerpc: Show PAGE_SIZE in __die() output
2019-01-08 12:05 ` [PATCH 2/2] powerpc: Show PAGE_SIZE in __die() output Michael Ellerman
@ 2019-01-08 12:21 ` Christophe Leroy
2019-01-09 7:47 ` Christophe Leroy
0 siblings, 1 reply; 7+ messages in thread
From: Christophe Leroy @ 2019-01-08 12:21 UTC (permalink / raw)
To: Michael Ellerman, linuxppc-dev
Le 08/01/2019 à 13:05, Michael Ellerman a écrit :
> The page size the kernel is built with is useful info when debugging a
> crash, so add it to the output in __die().
>
> Result looks like eg:
>
> kernel BUG at drivers/misc/lkdtm/bugs.c:63!
> Oops: Exception in kernel mode, sig: 5 [#1]
> LE PAGE_SIZE=64K SMP NR_CPUS=2048 NUMA pSeries
> Modules linked in: vmx_crypto kvm binfmt_misc ip_tables
>
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> ---
> arch/powerpc/kernel/traps.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index 431a86d3f772..fc972e4eee5f 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -268,6 +268,18 @@ static int __die(const char *str, struct pt_regs *regs, long err)
> else
> seq_buf_puts(&s, "BE ");
>
> + seq_buf_puts(&s, "PAGE_SIZE=");
> + if (IS_ENABLED(CONFIG_PPC_4K_PAGES))
> + seq_buf_puts(&s, "4K ");
> + else if (IS_ENABLED(CONFIG_PPC_16K_PAGES))
> + seq_buf_puts(&s, "16K ");
> + else if (IS_ENABLED(CONFIG_PPC_64K_PAGES))
> + seq_buf_puts(&s, "64K ");
> + else if (IS_ENABLED(CONFIG_PPC_256K_PAGES))
> + seq_buf_puts(&s, "256K ");
Can't we build all the above at once using PAGE_SHIFT ?
Something like (untested):
"%dK ", 1 << (PAGE_SHIFT - 10)
Christophe
> + else
> + BUILD_BUG_ON(1);
> +
> if (IS_ENABLED(CONFIG_PREEMPT))
> seq_buf_puts(&s, "PREEMPT ");
>
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 2/2] powerpc: Show PAGE_SIZE in __die() output
2019-01-08 12:21 ` Christophe Leroy
@ 2019-01-09 7:47 ` Christophe Leroy
2019-01-10 1:02 ` Michael Ellerman
0 siblings, 1 reply; 7+ messages in thread
From: Christophe Leroy @ 2019-01-09 7:47 UTC (permalink / raw)
To: Michael Ellerman, linuxppc-dev
Le 08/01/2019 à 13:21, Christophe Leroy a écrit :
>
>
> Le 08/01/2019 à 13:05, Michael Ellerman a écrit :
>> The page size the kernel is built with is useful info when debugging a
>> crash, so add it to the output in __die().
>>
>> Result looks like eg:
>>
>> kernel BUG at drivers/misc/lkdtm/bugs.c:63!
>> Oops: Exception in kernel mode, sig: 5 [#1]
>> LE PAGE_SIZE=64K SMP NR_CPUS=2048 NUMA pSeries
>> Modules linked in: vmx_crypto kvm binfmt_misc ip_tables
>>
>> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
>> ---
>> arch/powerpc/kernel/traps.c | 12 ++++++++++++
>> 1 file changed, 12 insertions(+)
>>
>> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
>> index 431a86d3f772..fc972e4eee5f 100644
>> --- a/arch/powerpc/kernel/traps.c
>> +++ b/arch/powerpc/kernel/traps.c
>> @@ -268,6 +268,18 @@ static int __die(const char *str, struct pt_regs
>> *regs, long err)
>> else
>> seq_buf_puts(&s, "BE ");
>> + seq_buf_puts(&s, "PAGE_SIZE=");
>> + if (IS_ENABLED(CONFIG_PPC_4K_PAGES))
>> + seq_buf_puts(&s, "4K ");
>> + else if (IS_ENABLED(CONFIG_PPC_16K_PAGES))
>> + seq_buf_puts(&s, "16K ");
>> + else if (IS_ENABLED(CONFIG_PPC_64K_PAGES))
>> + seq_buf_puts(&s, "64K ");
>> + else if (IS_ENABLED(CONFIG_PPC_256K_PAGES))
>> + seq_buf_puts(&s, "256K ");
>
> Can't we build all the above at once using PAGE_SHIFT ?
>
> Something like (untested):
>
> "%dK ", 1 << (PAGE_SHIFT - 10)
Or even simplier:
"%dK ", PAGE_SIZE / 1024
Christophe
>
> Christophe
>
>> + else
>> + BUILD_BUG_ON(1);
>> +
>> if (IS_ENABLED(CONFIG_PREEMPT))
>> seq_buf_puts(&s, "PREEMPT ");
>>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 2/2] powerpc: Show PAGE_SIZE in __die() output
2019-01-09 7:47 ` Christophe Leroy
@ 2019-01-10 1:02 ` Michael Ellerman
0 siblings, 0 replies; 7+ messages in thread
From: Michael Ellerman @ 2019-01-10 1:02 UTC (permalink / raw)
To: Christophe Leroy, linuxppc-dev
Christophe Leroy <christophe.leroy@c-s.fr> writes:
> Le 08/01/2019 à 13:21, Christophe Leroy a écrit :
>> Le 08/01/2019 à 13:05, Michael Ellerman a écrit :
>>> The page size the kernel is built with is useful info when debugging a
>>> crash, so add it to the output in __die().
>>>
>>> Result looks like eg:
>>>
>>> kernel BUG at drivers/misc/lkdtm/bugs.c:63!
>>> Oops: Exception in kernel mode, sig: 5 [#1]
>>> LE PAGE_SIZE=64K SMP NR_CPUS=2048 NUMA pSeries
>>> Modules linked in: vmx_crypto kvm binfmt_misc ip_tables
>>>
>>> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
>>> ---
>>> arch/powerpc/kernel/traps.c | 12 ++++++++++++
>>> 1 file changed, 12 insertions(+)
>>>
>>> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
>>> index 431a86d3f772..fc972e4eee5f 100644
>>> --- a/arch/powerpc/kernel/traps.c
>>> +++ b/arch/powerpc/kernel/traps.c
>>> @@ -268,6 +268,18 @@ static int __die(const char *str, struct pt_regs
>>> *regs, long err)
>>> else
>>> seq_buf_puts(&s, "BE ");
>>> + seq_buf_puts(&s, "PAGE_SIZE=");
>>> + if (IS_ENABLED(CONFIG_PPC_4K_PAGES))
>>> + seq_buf_puts(&s, "4K ");
>>> + else if (IS_ENABLED(CONFIG_PPC_16K_PAGES))
>>> + seq_buf_puts(&s, "16K ");
>>> + else if (IS_ENABLED(CONFIG_PPC_64K_PAGES))
>>> + seq_buf_puts(&s, "64K ");
>>> + else if (IS_ENABLED(CONFIG_PPC_256K_PAGES))
>>> + seq_buf_puts(&s, "256K ");
>>
>> Can't we build all the above at once using PAGE_SHIFT ?
>>
>> Something like (untested):
>>
>> "%dK ", 1 << (PAGE_SHIFT - 10)
>
> Or even simplier:
>
> "%dK ", PAGE_SIZE / 1024
Yep, good point.
Clearly I have forgotten how to program over the break (if I ever knew).
cheers
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 1/2] powerpc: Use seq_buf to avoid pr_cont() in __die()
2019-01-08 12:04 [PATCH 1/2] powerpc: Use seq_buf to avoid pr_cont() in __die() Michael Ellerman
2019-01-08 12:05 ` [PATCH 2/2] powerpc: Show PAGE_SIZE in __die() output Michael Ellerman
@ 2019-01-08 12:18 ` Christophe Leroy
2019-01-10 10:54 ` Michael Ellerman
1 sibling, 1 reply; 7+ messages in thread
From: Christophe Leroy @ 2019-01-08 12:18 UTC (permalink / raw)
To: Michael Ellerman, linuxppc-dev
Le 08/01/2019 à 13:04, Michael Ellerman a écrit :
> Using pr_cont() risks having our output interleaved with other output
> from other CPUs. Instead use a seq_buf to construct the line and then
> print it as a whole.
Why not simply doing a single printk() or similar on the same model as
X86 for instance ?
(https://elixir.bootlin.com/linux/v5.0-rc1/source/arch/x86/kernel/dumpstack.c#L368)
Christophe
>
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> ---
> arch/powerpc/kernel/traps.c | 23 ++++++++++++++++-------
> 1 file changed, 16 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index 64936b60d521..431a86d3f772 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -38,6 +38,7 @@
> #include <linux/kdebug.h>
> #include <linux/ratelimit.h>
> #include <linux/context_tracking.h>
> +#include <linux/seq_buf.h>
> #include <linux/smp.h>
> #include <linux/console.h>
> #include <linux/kmsg_dump.h>
> @@ -255,26 +256,34 @@ NOKPROBE_SYMBOL(oops_end);
>
> static int __die(const char *str, struct pt_regs *regs, long err)
> {
> + char buf[128]; /* enough for all flags and a long platform name */
> + struct seq_buf s;
> +
> + seq_buf_init(&s, buf, sizeof(buf));
> +
> printk("Oops: %s, sig: %ld [#%d]\n", str, err, ++die_counter);
>
> if (IS_ENABLED(CONFIG_CPU_LITTLE_ENDIAN))
> - printk("LE ");
> + seq_buf_puts(&s, "LE ");
> else
> - printk("BE ");
> + seq_buf_puts(&s, "BE ");
>
> if (IS_ENABLED(CONFIG_PREEMPT))
> - pr_cont("PREEMPT ");
> + seq_buf_puts(&s, "PREEMPT ");
>
> if (IS_ENABLED(CONFIG_SMP))
> - pr_cont("SMP NR_CPUS=%d ", NR_CPUS);
> + seq_buf_printf(&s, "SMP NR_CPUS=%d ", NR_CPUS);
>
> if (debug_pagealloc_enabled())
> - pr_cont("DEBUG_PAGEALLOC ");
> + seq_buf_puts(&s, "DEBUG_PAGEALLOC ");
>
> if (IS_ENABLED(CONFIG_NUMA))
> - pr_cont("NUMA ");
> + seq_buf_puts(&s, "NUMA ");
> +
> + if (ppc_md.name)
> + seq_buf_puts(&s, ppc_md.name);
>
> - pr_cont("%s\n", ppc_md.name ? ppc_md.name : "");
> + printk("%s\n", buf);
>
> if (notify_die(DIE_OOPS, str, regs, err, 255, SIGSEGV) == NOTIFY_STOP)
> return 1;
>
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH 1/2] powerpc: Use seq_buf to avoid pr_cont() in __die()
2019-01-08 12:18 ` [PATCH 1/2] powerpc: Use seq_buf to avoid pr_cont() in __die() Christophe Leroy
@ 2019-01-10 10:54 ` Michael Ellerman
0 siblings, 0 replies; 7+ messages in thread
From: Michael Ellerman @ 2019-01-10 10:54 UTC (permalink / raw)
To: Christophe Leroy, linuxppc-dev
Christophe Leroy <christophe.leroy@c-s.fr> writes:
> Le 08/01/2019 à 13:04, Michael Ellerman a écrit :
>> Using pr_cont() risks having our output interleaved with other output
>> from other CPUs. Instead use a seq_buf to construct the line and then
>> print it as a whole.
>
> Why not simply doing a single printk() or similar on the same model as
> X86 for instance ?
> (https://elixir.bootlin.com/linux/v5.0-rc1/source/arch/x86/kernel/dumpstack.c#L368)
Yeah we could do it that way, though it can become a bit of a mess.
In this case I guess it's not *too* bad:
printk("%s PAGE_SIZE=%luK%s%s%s%s%s %s\n",
IS_ENABLED(CONFIG_CPU_LITTLE_ENDIAN) ? "LE" : "BE",
PAGE_SIZE / 1024,
IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT" : "",
IS_ENABLED(CONFIG_SMP) ? " SMP" : "",
IS_ENABLED(CONFIG_SMP) ? (" NR_CPUS=" __stringify(NR_CPUS)) : "",
debug_pagealloc_enabled() ? " DEBUG_PAGEALLOC" : "",
IS_ENABLED(CONFIG_NUMA) ? " NUMA" : "",
ppc_md.name ? ppc_md.name : "");
And the generated code is obviously a lot smaller.
So yeah I'll go with that. Thanks for the review.
cheers
^ permalink raw reply [flat|nested] 7+ messages in thread
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2019-01-08 12:04 [PATCH 1/2] powerpc: Use seq_buf to avoid pr_cont() in __die() Michael Ellerman
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2019-01-08 12:21 ` Christophe Leroy
2019-01-09 7:47 ` Christophe Leroy
2019-01-10 1:02 ` Michael Ellerman
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2019-01-10 10:54 ` Michael Ellerman
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