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* [PATCH] powerpc: Allow relative pointers in bug table entries
@ 2020-11-27  3:02 Jordan Niethe
  2020-11-28 19:00 ` Christophe Leroy
  0 siblings, 1 reply; 6+ messages in thread
From: Jordan Niethe @ 2020-11-27  3:02 UTC (permalink / raw)
  To: linuxppc-dev; +Cc: Jordan Niethe

This enables GENERIC_BUG_RELATIVE_POINTERS on Power so that 32-bit
offsets are stored in the bug entries rather than 64-bit pointers.

Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
---
 arch/powerpc/Kconfig           |  4 ++++
 arch/powerpc/include/asm/bug.h | 37 ++++++++++++++++++++++++++++++++--
 arch/powerpc/xmon/xmon.c       | 17 ++++++++++++++--
 3 files changed, 54 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index e9f13fe08492..294108e0e5c6 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -311,6 +311,10 @@ config GENERIC_BUG
 	default y
 	depends on BUG
 
+config GENERIC_BUG_RELATIVE_POINTERS
+	def_bool y
+	depends on GENERIC_BUG
+
 config SYS_SUPPORTS_APM_EMULATION
 	default y if PMAC_APM_EMU
 	bool
diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
index 338f36cd9934..d03d834042a1 100644
--- a/arch/powerpc/include/asm/bug.h
+++ b/arch/powerpc/include/asm/bug.h
@@ -12,7 +12,11 @@
 #ifdef CONFIG_DEBUG_BUGVERBOSE
 .macro EMIT_BUG_ENTRY addr,file,line,flags
 	 .section __bug_table,"aw"
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
 5001:	 PPC_LONG \addr, 5002f
+#else
+5001:	 .4byte \addr - 5001b, 5002f - 5001b
+#endif /* CONFIG_GENERIC_BUG_RELATIVE_POINTERS */
 	 .short \line, \flags
 	 .org 5001b+BUG_ENTRY_SIZE
 	 .previous
@@ -23,7 +27,11 @@
 #else
 .macro EMIT_BUG_ENTRY addr,file,line,flags
 	 .section __bug_table,"aw"
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
 5001:	 PPC_LONG \addr
+#else
+5001:	 .4byte \addr - 5001b
+#endif /* CONFIG_GENERIC_BUG_RELATIVE_POINTERS */
 	 .short \flags
 	 .org 5001b+BUG_ENTRY_SIZE
 	 .previous
@@ -34,20 +42,45 @@
 /* _EMIT_BUG_ENTRY expects args %0,%1,%2,%3 to be FILE, LINE, flags and
    sizeof(struct bug_entry), respectively */
 #ifdef CONFIG_DEBUG_BUGVERBOSE
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
 #define _EMIT_BUG_ENTRY				\
 	".section __bug_table,\"aw\"\n"		\
 	"2:\t" PPC_LONG "1b, %0\n"		\
 	"\t.short %1, %2\n"			\
 	".org 2b+%3\n"				\
 	".previous\n"
-#else
+
+#else /* relative pointers */
+
+#define _EMIT_BUG_ENTRY				\
+	".section __bug_table,\"aw\"\n"		\
+	"2:\t.4byte 1b - 2b, %0 - 2b\n"		\
+	"\t.short %1, %2\n"			\
+	".org 2b+%3\n"				\
+	".previous\n"
+#endif /* relative pointers */
+
+#else /* verbose */
+
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
 #define _EMIT_BUG_ENTRY				\
 	".section __bug_table,\"aw\"\n"		\
 	"2:\t" PPC_LONG "1b\n"			\
 	"\t.short %2\n"				\
 	".org 2b+%3\n"				\
 	".previous\n"
-#endif
+
+#else /* relative pointers */
+
+#define _EMIT_BUG_ENTRY				\
+	".section __bug_table,\"aw\"\n"		\
+	"2:\t.4byte 1b - 2b\n"		\
+	"\t.short %2\n"				\
+	".org 2b+%3\n"				\
+	".previous\n"
+
+#endif /* relative pointers */
+#endif /* verbose */
 
 #define BUG_ENTRY(insn, flags, ...)			\
 	__asm__ __volatile__(				\
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 55c43a6c9111..5f7cf7e95767 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -1731,6 +1731,9 @@ static void print_bug_trap(struct pt_regs *regs)
 #ifdef CONFIG_BUG
 	const struct bug_entry *bug;
 	unsigned long addr;
+#ifdef CONFIG_DEBUG_BUGVERBOSE
+	char *file;
+#endif
 
 	if (regs->msr & MSR_PR)
 		return;		/* not in kernel */
@@ -1744,10 +1747,20 @@ static void print_bug_trap(struct pt_regs *regs)
 		return;
 
 #ifdef CONFIG_DEBUG_BUGVERBOSE
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
+	file = bug->file;
+#else /* relative pointers */
+	file = (char *)bug + bug->file_disp;
+#endif /* relative pointers */
 	printf("kernel BUG at %s:%u!\n",
-	       bug->file, bug->line);
+	       file, bug->line);
 #else
-	printf("kernel BUG at %px!\n", (void *)bug->bug_addr);
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
+	addr = bug->addr;
+#else /* relative pointers */
+	addr = (unsigned long)bug + bug->bug_addr_disp;
+#endif /* relative pointers */
+	printf("kernel BUG at %px!\n", (void *)addr);
 #endif
 #endif /* CONFIG_BUG */
 }
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* Re: [PATCH] powerpc: Allow relative pointers in bug table entries
  2020-11-27  3:02 [PATCH] powerpc: Allow relative pointers in bug table entries Jordan Niethe
@ 2020-11-28 19:00 ` Christophe Leroy
  2020-11-30  0:59   ` Jordan Niethe
  2020-11-30  1:42   ` Michael Ellerman
  0 siblings, 2 replies; 6+ messages in thread
From: Christophe Leroy @ 2020-11-28 19:00 UTC (permalink / raw)
  To: Jordan Niethe, linuxppc-dev



Le 27/11/2020 à 04:02, Jordan Niethe a écrit :
> This enables GENERIC_BUG_RELATIVE_POINTERS on Power so that 32-bit
> offsets are stored in the bug entries rather than 64-bit pointers.
> 
> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> ---
>   arch/powerpc/Kconfig           |  4 ++++
>   arch/powerpc/include/asm/bug.h | 37 ++++++++++++++++++++++++++++++++--
>   arch/powerpc/xmon/xmon.c       | 17 ++++++++++++++--
>   3 files changed, 54 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index e9f13fe08492..294108e0e5c6 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -311,6 +311,10 @@ config GENERIC_BUG
>   	default y
>   	depends on BUG
>   
> +config GENERIC_BUG_RELATIVE_POINTERS
> +	def_bool y
> +	depends on GENERIC_BUG
> +
>   config SYS_SUPPORTS_APM_EMULATION
>   	default y if PMAC_APM_EMU
>   	bool
> diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
> index 338f36cd9934..d03d834042a1 100644
> --- a/arch/powerpc/include/asm/bug.h
> +++ b/arch/powerpc/include/asm/bug.h
> @@ -12,7 +12,11 @@
>   #ifdef CONFIG_DEBUG_BUGVERBOSE
>   .macro EMIT_BUG_ENTRY addr,file,line,flags
>   	 .section __bug_table,"aw"
> +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS

As far as I understand, as soon as CONFIG_BUG is selected, GENERIC_BUG is automatically selected so 
GENERIC_BUG_RELATIVE_POINTERS is selected as well. Therefore this #ifndef is never possible.

>   5001:	 PPC_LONG \addr, 5002f
> +#else
> +5001:	 .4byte \addr - 5001b, 5002f - 5001b
> +#endif /* CONFIG_GENERIC_BUG_RELATIVE_POINTERS */
>   	 .short \line, \flags
>   	 .org 5001b+BUG_ENTRY_SIZE
>   	 .previous
> @@ -23,7 +27,11 @@
>   #else
>   .macro EMIT_BUG_ENTRY addr,file,line,flags
>   	 .section __bug_table,"aw"
> +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS

Same

>   5001:	 PPC_LONG \addr
> +#else
> +5001:	 .4byte \addr - 5001b
> +#endif /* CONFIG_GENERIC_BUG_RELATIVE_POINTERS */
>   	 .short \flags
>   	 .org 5001b+BUG_ENTRY_SIZE
>   	 .previous
> @@ -34,20 +42,45 @@
>   /* _EMIT_BUG_ENTRY expects args %0,%1,%2,%3 to be FILE, LINE, flags and
>      sizeof(struct bug_entry), respectively */
>   #ifdef CONFIG_DEBUG_BUGVERBOSE
> +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS

Same

>   #define _EMIT_BUG_ENTRY				\
>   	".section __bug_table,\"aw\"\n"		\
>   	"2:\t" PPC_LONG "1b, %0\n"		\
>   	"\t.short %1, %2\n"			\
>   	".org 2b+%3\n"				\
>   	".previous\n"
> -#else
> +
> +#else /* relative pointers */
> +
> +#define _EMIT_BUG_ENTRY				\
> +	".section __bug_table,\"aw\"\n"		\
> +	"2:\t.4byte 1b - 2b, %0 - 2b\n"		\
> +	"\t.short %1, %2\n"			\
> +	".org 2b+%3\n"				\
> +	".previous\n"
> +#endif /* relative pointers */
> +
> +#else /* verbose */
> +
> +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS

Same

>   #define _EMIT_BUG_ENTRY				\
>   	".section __bug_table,\"aw\"\n"		\
>   	"2:\t" PPC_LONG "1b\n"			\
>   	"\t.short %2\n"				\
>   	".org 2b+%3\n"				\
>   	".previous\n"
> -#endif
> +
> +#else /* relative pointers */
> +
> +#define _EMIT_BUG_ENTRY				\
> +	".section __bug_table,\"aw\"\n"		\
> +	"2:\t.4byte 1b - 2b\n"		\
> +	"\t.short %2\n"				\
> +	".org 2b+%3\n"				\
> +	".previous\n"
> +
> +#endif /* relative pointers */
> +#endif /* verbose */
>   
>   #define BUG_ENTRY(insn, flags, ...)			\
>   	__asm__ __volatile__(				\
> diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
> index 55c43a6c9111..5f7cf7e95767 100644
> --- a/arch/powerpc/xmon/xmon.c
> +++ b/arch/powerpc/xmon/xmon.c
> @@ -1731,6 +1731,9 @@ static void print_bug_trap(struct pt_regs *regs)
>   #ifdef CONFIG_BUG
>   	const struct bug_entry *bug;
>   	unsigned long addr;
> +#ifdef CONFIG_DEBUG_BUGVERBOSE
> +	char *file;
> +#endif
>   
>   	if (regs->msr & MSR_PR)
>   		return;		/* not in kernel */
> @@ -1744,10 +1747,20 @@ static void print_bug_trap(struct pt_regs *regs)
>   		return;
>   
>   #ifdef CONFIG_DEBUG_BUGVERBOSE
> +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS

Same

> +	file = bug->file;
> +#else /* relative pointers */
> +	file = (char *)bug + bug->file_disp;
> +#endif /* relative pointers */
>   	printf("kernel BUG at %s:%u!\n",
> -	       bug->file, bug->line);
> +	       file, bug->line);
>   #else
> -	printf("kernel BUG at %px!\n", (void *)bug->bug_addr);
> +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS

Same

> +	addr = bug->addr;
> +#else /* relative pointers */
> +	addr = (unsigned long)bug + bug->bug_addr_disp;
> +#endif /* relative pointers */
> +	printf("kernel BUG at %px!\n", (void *)addr);
>   #endif
>   #endif /* CONFIG_BUG */
>   }
> 

Christophe

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] powerpc: Allow relative pointers in bug table entries
  2020-11-28 19:00 ` Christophe Leroy
@ 2020-11-30  0:59   ` Jordan Niethe
  2020-11-30  1:42   ` Michael Ellerman
  1 sibling, 0 replies; 6+ messages in thread
From: Jordan Niethe @ 2020-11-30  0:59 UTC (permalink / raw)
  To: Christophe Leroy; +Cc: linuxppc-dev

On Sun, Nov 29, 2020 at 6:00 AM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
>
>
> Le 27/11/2020 à 04:02, Jordan Niethe a écrit :
> > This enables GENERIC_BUG_RELATIVE_POINTERS on Power so that 32-bit
> > offsets are stored in the bug entries rather than 64-bit pointers.
> >
> > Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> > ---
> >   arch/powerpc/Kconfig           |  4 ++++
> >   arch/powerpc/include/asm/bug.h | 37 ++++++++++++++++++++++++++++++++--
> >   arch/powerpc/xmon/xmon.c       | 17 ++++++++++++++--
> >   3 files changed, 54 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > index e9f13fe08492..294108e0e5c6 100644
> > --- a/arch/powerpc/Kconfig
> > +++ b/arch/powerpc/Kconfig
> > @@ -311,6 +311,10 @@ config GENERIC_BUG
> >       default y
> >       depends on BUG
> >
> > +config GENERIC_BUG_RELATIVE_POINTERS
> > +     def_bool y
> > +     depends on GENERIC_BUG
> > +
> >   config SYS_SUPPORTS_APM_EMULATION
> >       default y if PMAC_APM_EMU
> >       bool
> > diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
> > index 338f36cd9934..d03d834042a1 100644
> > --- a/arch/powerpc/include/asm/bug.h
> > +++ b/arch/powerpc/include/asm/bug.h
> > @@ -12,7 +12,11 @@
> >   #ifdef CONFIG_DEBUG_BUGVERBOSE
> >   .macro EMIT_BUG_ENTRY addr,file,line,flags
> >        .section __bug_table,"aw"
> > +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
>
> As far as I understand, as soon as CONFIG_BUG is selected, GENERIC_BUG is automatically selected so
> GENERIC_BUG_RELATIVE_POINTERS is selected as well. Therefore this #ifndef is never possible.
Thanks, you are right. I'll fix that up.
>
> >   5001:        PPC_LONG \addr, 5002f
> > +#else
> > +5001:         .4byte \addr - 5001b, 5002f - 5001b
> > +#endif /* CONFIG_GENERIC_BUG_RELATIVE_POINTERS */
> >        .short \line, \flags
> >        .org 5001b+BUG_ENTRY_SIZE
> >        .previous
> > @@ -23,7 +27,11 @@
> >   #else
> >   .macro EMIT_BUG_ENTRY addr,file,line,flags
> >        .section __bug_table,"aw"
> > +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
>
> Same
>
> >   5001:        PPC_LONG \addr
> > +#else
> > +5001:         .4byte \addr - 5001b
> > +#endif /* CONFIG_GENERIC_BUG_RELATIVE_POINTERS */
> >        .short \flags
> >        .org 5001b+BUG_ENTRY_SIZE
> >        .previous
> > @@ -34,20 +42,45 @@
> >   /* _EMIT_BUG_ENTRY expects args %0,%1,%2,%3 to be FILE, LINE, flags and
> >      sizeof(struct bug_entry), respectively */
> >   #ifdef CONFIG_DEBUG_BUGVERBOSE
> > +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
>
> Same
>
> >   #define _EMIT_BUG_ENTRY                             \
> >       ".section __bug_table,\"aw\"\n"         \
> >       "2:\t" PPC_LONG "1b, %0\n"              \
> >       "\t.short %1, %2\n"                     \
> >       ".org 2b+%3\n"                          \
> >       ".previous\n"
> > -#else
> > +
> > +#else /* relative pointers */
> > +
> > +#define _EMIT_BUG_ENTRY                              \
> > +     ".section __bug_table,\"aw\"\n"         \
> > +     "2:\t.4byte 1b - 2b, %0 - 2b\n"         \
> > +     "\t.short %1, %2\n"                     \
> > +     ".org 2b+%3\n"                          \
> > +     ".previous\n"
> > +#endif /* relative pointers */
> > +
> > +#else /* verbose */
> > +
> > +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
>
> Same
>
> >   #define _EMIT_BUG_ENTRY                             \
> >       ".section __bug_table,\"aw\"\n"         \
> >       "2:\t" PPC_LONG "1b\n"                  \
> >       "\t.short %2\n"                         \
> >       ".org 2b+%3\n"                          \
> >       ".previous\n"
> > -#endif
> > +
> > +#else /* relative pointers */
> > +
> > +#define _EMIT_BUG_ENTRY                              \
> > +     ".section __bug_table,\"aw\"\n"         \
> > +     "2:\t.4byte 1b - 2b\n"          \
> > +     "\t.short %2\n"                         \
> > +     ".org 2b+%3\n"                          \
> > +     ".previous\n"
> > +
> > +#endif /* relative pointers */
> > +#endif /* verbose */
> >
> >   #define BUG_ENTRY(insn, flags, ...)                 \
> >       __asm__ __volatile__(                           \
> > diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
> > index 55c43a6c9111..5f7cf7e95767 100644
> > --- a/arch/powerpc/xmon/xmon.c
> > +++ b/arch/powerpc/xmon/xmon.c
> > @@ -1731,6 +1731,9 @@ static void print_bug_trap(struct pt_regs *regs)
> >   #ifdef CONFIG_BUG
> >       const struct bug_entry *bug;
> >       unsigned long addr;
> > +#ifdef CONFIG_DEBUG_BUGVERBOSE
> > +     char *file;
> > +#endif
> >
> >       if (regs->msr & MSR_PR)
> >               return;         /* not in kernel */
> > @@ -1744,10 +1747,20 @@ static void print_bug_trap(struct pt_regs *regs)
> >               return;
> >
> >   #ifdef CONFIG_DEBUG_BUGVERBOSE
> > +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
>
> Same
>
> > +     file = bug->file;
> > +#else /* relative pointers */
> > +     file = (char *)bug + bug->file_disp;
> > +#endif /* relative pointers */
> >       printf("kernel BUG at %s:%u!\n",
> > -            bug->file, bug->line);
> > +            file, bug->line);
> >   #else
> > -     printf("kernel BUG at %px!\n", (void *)bug->bug_addr);
> > +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
>
> Same
>
> > +     addr = bug->addr;
> > +#else /* relative pointers */
> > +     addr = (unsigned long)bug + bug->bug_addr_disp;
> > +#endif /* relative pointers */
> > +     printf("kernel BUG at %px!\n", (void *)addr);
> >   #endif
> >   #endif /* CONFIG_BUG */
> >   }
> >
>
> Christophe

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] powerpc: Allow relative pointers in bug table entries
  2020-11-28 19:00 ` Christophe Leroy
  2020-11-30  0:59   ` Jordan Niethe
@ 2020-11-30  1:42   ` Michael Ellerman
  2020-11-30  1:50     ` Jordan Niethe
  1 sibling, 1 reply; 6+ messages in thread
From: Michael Ellerman @ 2020-11-30  1:42 UTC (permalink / raw)
  To: Christophe Leroy, Jordan Niethe, linuxppc-dev

Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> Le 27/11/2020 à 04:02, Jordan Niethe a écrit :
>> This enables GENERIC_BUG_RELATIVE_POINTERS on Power so that 32-bit
>> offsets are stored in the bug entries rather than 64-bit pointers.
>> 
>> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
>> ---
>>   arch/powerpc/Kconfig           |  4 ++++
>>   arch/powerpc/include/asm/bug.h | 37 ++++++++++++++++++++++++++++++++--
>>   arch/powerpc/xmon/xmon.c       | 17 ++++++++++++++--
>>   3 files changed, 54 insertions(+), 4 deletions(-)
>> 
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index e9f13fe08492..294108e0e5c6 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -311,6 +311,10 @@ config GENERIC_BUG
>>   	default y
>>   	depends on BUG
>>   
>> +config GENERIC_BUG_RELATIVE_POINTERS
>> +	def_bool y
>> +	depends on GENERIC_BUG
>> +
>>   config SYS_SUPPORTS_APM_EMULATION
>>   	default y if PMAC_APM_EMU
>>   	bool
>> diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
>> index 338f36cd9934..d03d834042a1 100644
>> --- a/arch/powerpc/include/asm/bug.h
>> +++ b/arch/powerpc/include/asm/bug.h
>> @@ -12,7 +12,11 @@
>>   #ifdef CONFIG_DEBUG_BUGVERBOSE
>>   .macro EMIT_BUG_ENTRY addr,file,line,flags
>>   	 .section __bug_table,"aw"
>> +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
>
> As far as I understand, as soon as CONFIG_BUG is selected, GENERIC_BUG is automatically selected so 
> GENERIC_BUG_RELATIVE_POINTERS is selected as well. Therefore this #ifndef is never possible.

Yeah.

There is one place in the generic code that has an ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
but that's because it has to support arches that don't select it.

In the arch code we know that it's enabled, so there should be no need
for any ifdefs.

cheers

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] powerpc: Allow relative pointers in bug table entries
  2020-11-30  1:42   ` Michael Ellerman
@ 2020-11-30  1:50     ` Jordan Niethe
  2020-11-30  6:27       ` Christophe Leroy
  0 siblings, 1 reply; 6+ messages in thread
From: Jordan Niethe @ 2020-11-30  1:50 UTC (permalink / raw)
  To: Michael Ellerman; +Cc: linuxppc-dev

On Mon, Nov 30, 2020 at 12:42 PM Michael Ellerman <mpe@ellerman.id.au> wrote:
>
> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> > Le 27/11/2020 à 04:02, Jordan Niethe a écrit :
> >> This enables GENERIC_BUG_RELATIVE_POINTERS on Power so that 32-bit
> >> offsets are stored in the bug entries rather than 64-bit pointers.
> >>
> >> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> >> ---
> >>   arch/powerpc/Kconfig           |  4 ++++
> >>   arch/powerpc/include/asm/bug.h | 37 ++++++++++++++++++++++++++++++++--
> >>   arch/powerpc/xmon/xmon.c       | 17 ++++++++++++++--
> >>   3 files changed, 54 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> >> index e9f13fe08492..294108e0e5c6 100644
> >> --- a/arch/powerpc/Kconfig
> >> +++ b/arch/powerpc/Kconfig
> >> @@ -311,6 +311,10 @@ config GENERIC_BUG
> >>      default y
> >>      depends on BUG
> >>
> >> +config GENERIC_BUG_RELATIVE_POINTERS
> >> +    def_bool y
> >> +    depends on GENERIC_BUG
> >> +
> >>   config SYS_SUPPORTS_APM_EMULATION
> >>      default y if PMAC_APM_EMU
> >>      bool
> >> diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
> >> index 338f36cd9934..d03d834042a1 100644
> >> --- a/arch/powerpc/include/asm/bug.h
> >> +++ b/arch/powerpc/include/asm/bug.h
> >> @@ -12,7 +12,11 @@
> >>   #ifdef CONFIG_DEBUG_BUGVERBOSE
> >>   .macro EMIT_BUG_ENTRY addr,file,line,flags
> >>       .section __bug_table,"aw"
> >> +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
> >
> > As far as I understand, as soon as CONFIG_BUG is selected, GENERIC_BUG is automatically selected so
> > GENERIC_BUG_RELATIVE_POINTERS is selected as well. Therefore this #ifndef is never possible.
>
> Yeah.
>
> There is one place in the generic code that has an ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
> but that's because it has to support arches that don't select it.
>
> In the arch code we know that it's enabled, so there should be no need
> for any ifdefs.
For 32bit, pointers are 4 bytes anyway so it would be pointless to
store a displacement, so won't we need some ifdefs for that?
>
> cheers

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] powerpc: Allow relative pointers in bug table entries
  2020-11-30  1:50     ` Jordan Niethe
@ 2020-11-30  6:27       ` Christophe Leroy
  0 siblings, 0 replies; 6+ messages in thread
From: Christophe Leroy @ 2020-11-30  6:27 UTC (permalink / raw)
  To: Jordan Niethe, Michael Ellerman; +Cc: linuxppc-dev



Le 30/11/2020 à 02:50, Jordan Niethe a écrit :
> On Mon, Nov 30, 2020 at 12:42 PM Michael Ellerman <mpe@ellerman.id.au> wrote:
>>
>> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
>>> Le 27/11/2020 à 04:02, Jordan Niethe a écrit :
>>>> This enables GENERIC_BUG_RELATIVE_POINTERS on Power so that 32-bit
>>>> offsets are stored in the bug entries rather than 64-bit pointers.
>>>>
>>>> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
>>>> ---
>>>>    arch/powerpc/Kconfig           |  4 ++++
>>>>    arch/powerpc/include/asm/bug.h | 37 ++++++++++++++++++++++++++++++++--
>>>>    arch/powerpc/xmon/xmon.c       | 17 ++++++++++++++--
>>>>    3 files changed, 54 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>>>> index e9f13fe08492..294108e0e5c6 100644
>>>> --- a/arch/powerpc/Kconfig
>>>> +++ b/arch/powerpc/Kconfig
>>>> @@ -311,6 +311,10 @@ config GENERIC_BUG
>>>>       default y
>>>>       depends on BUG
>>>>
>>>> +config GENERIC_BUG_RELATIVE_POINTERS
>>>> +    def_bool y
>>>> +    depends on GENERIC_BUG
>>>> +
>>>>    config SYS_SUPPORTS_APM_EMULATION
>>>>       default y if PMAC_APM_EMU
>>>>       bool
>>>> diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
>>>> index 338f36cd9934..d03d834042a1 100644
>>>> --- a/arch/powerpc/include/asm/bug.h
>>>> +++ b/arch/powerpc/include/asm/bug.h
>>>> @@ -12,7 +12,11 @@
>>>>    #ifdef CONFIG_DEBUG_BUGVERBOSE
>>>>    .macro EMIT_BUG_ENTRY addr,file,line,flags
>>>>        .section __bug_table,"aw"
>>>> +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
>>>
>>> As far as I understand, as soon as CONFIG_BUG is selected, GENERIC_BUG is automatically selected so
>>> GENERIC_BUG_RELATIVE_POINTERS is selected as well. Therefore this #ifndef is never possible.
>>
>> Yeah.
>>
>> There is one place in the generic code that has an ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
>> but that's because it has to support arches that don't select it.
>>
>> In the arch code we know that it's enabled, so there should be no need
>> for any ifdefs.
> For 32bit, pointers are 4 bytes anyway so it would be pointless to
> store a displacement, so won't we need some ifdefs for that?

I'd say it the other way round:

For 32bit, pointers are 4 bytes anyway so it would be pointless to
make it different from 64bit.

We are definitely not on a performance critical path when dealing with bug entries, so I think it is 
better to keep a common code for PPC32 and PPC64.

Christophe

^ permalink raw reply	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2020-11-30  6:29 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-11-27  3:02 [PATCH] powerpc: Allow relative pointers in bug table entries Jordan Niethe
2020-11-28 19:00 ` Christophe Leroy
2020-11-30  0:59   ` Jordan Niethe
2020-11-30  1:42   ` Michael Ellerman
2020-11-30  1:50     ` Jordan Niethe
2020-11-30  6:27       ` Christophe Leroy

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