Re: [PATCH] handle renamed init_level4_pgt -> init_top_pgt

[Baoquan He <bhe@redhat.com>]

On 01/02/18 at 04:57pm, Dave Young wrote:
> The root cause is this commit makes mem_section as a pointer instead of
> the static array.
> 
> VMCOREINFO_SYMBOL() expand it as &mem_section, this is not correct in
> the test case any more.
> 
> This hack code works for me:
> 
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index b3663896278e..f5fe6068ae39 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -376,6 +376,8 @@ phys_addr_t __weak paddr_vmcoreinfo_note(void)
>  {
>  	return __pa(vmcoreinfo_note);
>  }
> +#define VMCOREINFO_SYMBOL_HACK(name) \
> +	vmcoreinfo_append_str("SYMBOL(%s)=%lx\n", #name, (unsigned long)name)

Oh, you made a new one. We may use vmcoreinfo_append_str directly since
there's an existing one in crash_save_vmcoreinfo():

vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds());

The thing is that VMCOREINFO_SYMBOL will reference symbol. While
checking all exported symbol, all of them are array names. So here
the value of &array_name is equal to the address of the first element of
array. Now the first exception appeared, mem_section, which could be not
an array name, but a pointer pointing at the allocated memory.

For this issue, we either change as Dave mentioned two options, or can
we adjust VMCOREINFO_SYMBOL(name)?

>  
>  static int __init crash_save_vmcoreinfo_init(void)
>  {
> @@ -410,10 +412,11 @@ static int __init crash_save_vmcoreinfo_init(void)
>  	VMCOREINFO_SYMBOL(contig_page_data);
>  #endif
>  #ifdef CONFIG_SPARSEMEM
> -	VMCOREINFO_SYMBOL(mem_section);
> +	VMCOREINFO_SYMBOL_HACK(mem_section);
>  	VMCOREINFO_LENGTH(mem_section, NR_SECTION_ROOTS);
>  	VMCOREINFO_STRUCT_SIZE(mem_section);
>  	VMCOREINFO_OFFSET(mem_section, section_mem_map);
> +
>  #endif
>  	VMCOREINFO_STRUCT_SIZE(page);
>  	VMCOREINFO_STRUCT_SIZE(pglist_data);
> 
> 
> But probably we need this instead, but I can not test it because I do
> not know how to fix makedumpfile to use a _NUMBER instead of a SYMBOL.
> Thus bring up the issue, seeking for thoughts and discussion.
> 
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index b3663896278e..dfa2238e2c28 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -410,10 +410,17 @@ static int __init crash_save_vmcoreinfo_init(void)
> 	VMCOREINFO_SYMBOL(contig_page_data);
>  #endif
>  #ifdef CONFIG_SPARSEMEM
> +#ifdef CONFIG_SPARSEMEM_EXTREME
> +	VMCOREINFO_NUMBER(mem_section);
> +#else
> 	VMCOREINFO_SYMBOL(mem_section);
> +#endif
> 	VMCOREINFO_LENGTH(mem_section, NR_SECTION_ROOTS);
> 	VMCOREINFO_STRUCT_SIZE(mem_section);
> 	VMCOREINFO_OFFSET(mem_section, section_mem_map);
> 
> [snip]
> 
> Thanks
> Dave

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