Re: [PATCH] dump_stack: convert generic dump_stack into a weak symbol
From: Petr Mladek
Date: Mon Mar 05 2018 - 09:48:55 EST
On Mon 2018-03-05 14:37:42, Sergey Senozhatsky wrote:
> We want to move dump_stack related functions out of printk C
> code and consolidate them in lib/dump_stack file. The reason why
> dump_stack_print_info()/etc ended up in printk.c was a "generic"
> (dummy) lib dump_stack() function, which archs can override.
> For example, blackfin and nds32, define their own EXPORT_SYMBOL
> dump_stack() functions.
>
> In case of blackfin that arch-specific dump_stack() symbol invokes
> a global dump_stack_print_info() function. So we can't easily move
> dump_stack_print_info() to lib/dump_stack, because this way we will
> link with lib/dump_stack.o file, which will bring in a generic
> dump_stack() symbol with it, causing a multiple definitions error:
> - one dump_stack() from arch/blackfin/dumpstack
> - the other one from lib/dump_stack
>
> Convert generic dump_stack() into a weak symbol. So we will be
> able link with lib/dump_stack and at the same time archs will
> be able to override dump_stack(). It also opens up a way for us
> to move dump_stack_set_arch_desc(), dump_stack_print_info() and
> show_regs_print_info() to lib/dump_stack.
>
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
> ---
> arch/blackfin/kernel/dumpstack.c | 1 -
> arch/nds32/kernel/traps.c | 2 --
> lib/dump_stack.c | 4 ++--
> 3 files changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/arch/blackfin/kernel/dumpstack.c b/arch/blackfin/kernel/dumpstack.c
> index 3c992c1f8ef2..61af017130cd 100644
> --- a/arch/blackfin/kernel/dumpstack.c
> +++ b/arch/blackfin/kernel/dumpstack.c
> @@ -174,4 +174,3 @@ void dump_stack(void)
> show_stack(current, &stack);
> trace_buffer_restore(tflags);
> }
> -EXPORT_SYMBOL(dump_stack);
I was afraid that blackfin modules would not longer be able
to use arch-specific dump_stack symbol. But it seems that only
the symbol name is important. Alos the list of symbols look
promissing:
before:
$> objdump -x vmlinux | less | grep dump_stack
00248530 l O __ksymtab 00000008 ___ksymtab_dump_stack
002500d4 l O __ksymtab_strings 0000000c ___kstrtab_dump_stack
00272bb6 l O .bss 00000080 _dump_stack_arch_desc_str
000051a8 g F .text 00000042 _dump_stack
002ab05c g F .init.text 0000002a _dump_stack_set_arch_desc
0003051c g F .text 000000a4 _dump_stack_print_info
after:
$> objdump -x vmlinux.patched | less | grep dump_stack
00000000 l df *ABS* 00000000 lib/dump_stack.c
0027c3e8 l O .bss 00000080 _dump_stack_arch_desc_str
00248580 l O __ksymtab 00000008 ___ksymtab_dump_stack
002653d4 l O __ksymtab_strings 0000000c ___kstrtab_dump_stack
000051a8 g F .text 00000042 _dump_stack
002b69dc g F .init.text 0000002a _dump_stack_set_arch_desc
001c2a90 g F .text 000000a4 _dump_stack_print_info
I hope that I did not miss anything. I could not try this at
runtime. I could just cross-compile.
Anyway, from my side:
Reviewed-by: Petr Mladek <pmladek@xxxxxxxx>
I'll wait a bit and push it into printk.git for-4.17.
Greentime Hu, you tested this on nds32. Could I use your Tested-by,
please?
Best Regards,
Petr