[PATCH v2] powerpc: Allow relative pointers in bug table entries

[Christophe Leroy]

Le 01/12/2020 à 01:52, 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.
> While this doesn't save space for 32-bit machines, use it anyway so
> there is only one code path.
> 
> Signed-off-by: Jordan Niethe <jniethe5 at gmail.com>

Reviewed-by: Christophe Leroy <christophe.leroy at csgroup.eu>
Tested-by: Christophe Leroy <christophe.leroy at csgroup.eu> # on PPC32

> ---
> v2: Remove non-relative pointers code
> ---
>   arch/powerpc/Kconfig           | 4 ++++
>   arch/powerpc/include/asm/bug.h | 8 ++++----
>   arch/powerpc/xmon/xmon.c       | 4 ++--
>   3 files changed, 10 insertions(+), 6 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..ba0500872cce 100644
> --- a/arch/powerpc/include/asm/bug.h
> +++ b/arch/powerpc/include/asm/bug.h
> @@ -12,7 +12,7 @@
>   #ifdef CONFIG_DEBUG_BUGVERBOSE
>   .macro EMIT_BUG_ENTRY addr,file,line,flags
>   	 .section __bug_table,"aw"
> -5001:	 PPC_LONG \addr, 5002f
> +5001:	 .4byte \addr - 5001b, 5002f - 5001b
>   	 .short \line, \flags
>   	 .org 5001b+BUG_ENTRY_SIZE
>   	 .previous
> @@ -23,7 +23,7 @@
>   #else
>   .macro EMIT_BUG_ENTRY addr,file,line,flags
>   	 .section __bug_table,"aw"
> -5001:	 PPC_LONG \addr
> +5001:	 .4byte \addr - 5001b
>   	 .short \flags
>   	 .org 5001b+BUG_ENTRY_SIZE
>   	 .previous
> @@ -36,14 +36,14 @@
>   #ifdef CONFIG_DEBUG_BUGVERBOSE
>   #define _EMIT_BUG_ENTRY				\
>   	".section __bug_table,\"aw\"\n"		\
> -	"2:\t" PPC_LONG "1b, %0\n"		\
> +	"2:\t.4byte 1b - 2b, %0 - 2b\n"		\
>   	"\t.short %1, %2\n"			\
>   	".org 2b+%3\n"				\
>   	".previous\n"
>   #else
>   #define _EMIT_BUG_ENTRY				\
>   	".section __bug_table,\"aw\"\n"		\
> -	"2:\t" PPC_LONG "1b\n"			\
> +	"2:\t.4byte 1b - 2b\n"			\
>   	"\t.short %2\n"				\
>   	".org 2b+%3\n"				\
>   	".previous\n"
> diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
> index 55c43a6c9111..9704c81aff7d 100644
> --- a/arch/powerpc/xmon/xmon.c
> +++ b/arch/powerpc/xmon/xmon.c
> @@ -1745,9 +1745,9 @@ static void print_bug_trap(struct pt_regs *regs)
>   
>   #ifdef CONFIG_DEBUG_BUGVERBOSE
>   	printf("kernel BUG at %s:%u!\n",
> -	       bug->file, bug->line);
> +	       (char *)bug + bug->file_disp, bug->line);
>   #else
> -	printf("kernel BUG at %px!\n", (void *)bug->bug_addr);
> +	printf("kernel BUG at %px!\n", (void *)bug + bug->bug_addr_disp);
>   #endif
>   #endif /* CONFIG_BUG */
>   }
>