linux-kernel - Re: [PATCH] MIPS: Use common way to parse elfcorehdr

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Date:   Thu, 4 Feb 2021 11:57:44 +0800
From:   Jinyang He <hejinyang@...ngson.cn>
To:     Randy Dunlap <rdunlap@...radead.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MIPS: Use common way to parse elfcorehdr

On 02/04/2021 11:28 AM, Randy Dunlap wrote:

> On 2/3/21 7:07 PM, Jinyang He wrote:
>> "elfcorehdr" can be parsed at kernel/crash_dump.c
>>
>> Signed-off-by: Jinyang He <hejinyang@...ngson.cn>
> Hm, looks like that would require CONFIG_CRASH_DUMP?
Hi,

I don't think so. We expect to generate a /proc/vmcore when we reserved
memory for elfcorehdr. So put it under CONFIG_PROC_VMCORE. If only rely
on CONFIG_CRASH_DUMP and CONFIG_PROC_VMCORE is not enabled, we will
reserve these memory while cannot use these later. And the reason why
kernel/crash_dump.c being under CONFIG_CRASH_DUMP is that it provide
is_kdump_kernel() for others.

Thanks,
Jinyang

>
>> ---
>>   arch/mips/kernel/setup.c | 49 +++++++++++++++++++++---------------------------
>>   1 file changed, 21 insertions(+), 28 deletions(-)
>>
>> diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
>> index 7e1f8e2..4d2f915 100644
>> --- a/arch/mips/kernel/setup.c
>> +++ b/arch/mips/kernel/setup.c
>> @@ -29,6 +29,7 @@
>>   #include <linux/of_fdt.h>
>>   #include <linux/of_reserved_mem.h>
>>   #include <linux/dmi.h>
>> +#include <linux/crash_dump.h>
>>   
>>   #include <asm/addrspace.h>
>>   #include <asm/bootinfo.h>
>> @@ -404,34 +405,32 @@ static int __init early_parse_memmap(char *p)
>>   }
>>   early_param("memmap", early_parse_memmap);
>>   
>> -#ifdef CONFIG_PROC_VMCORE
>> -static unsigned long setup_elfcorehdr, setup_elfcorehdr_size;
>> -static int __init early_parse_elfcorehdr(char *p)
>> +static void __init mips_reserve_vmcore(void)
>>   {
>> +#ifdef CONFIG_PROC_VMCORE
>>   	phys_addr_t start, end;
>>   	u64 i;
>>   
>> -	setup_elfcorehdr = memparse(p, &p);
>> -
>> -	for_each_mem_range(i, &start, &end) {
>> -		if (setup_elfcorehdr >= start && setup_elfcorehdr < end) {
>> -			/*
>> -			 * Reserve from the elf core header to the end of
>> -			 * the memory segment, that should all be kdump
>> -			 * reserved memory.
>> -			 */
>> -			setup_elfcorehdr_size = end - setup_elfcorehdr;
>> -			break;
>> +	if (!elfcorehdr_size) {
>> +		for_each_mem_range(i, &start, &end) {
>> +			if (elfcorehdr_addr >= start && elfcorehdr_addr < end) {
>> +				/*
>> +				 * Reserve from the elf core header to the end of
>> +				 * the memory segment, that should all be kdump
>> +				 * reserved memory.
>> +				 */
>> +				elfcorehdr_size = end - elfcorehdr_addr;
>> +				break;
>> +			}
>>   		}
>>   	}
>> -	/*
>> -	 * If we don't find it in the memory map, then we shouldn't
>> -	 * have to worry about it, as the new kernel won't use it.
>> -	 */
>> -	return 0;
>> -}
>> -early_param("elfcorehdr", early_parse_elfcorehdr);
>> +
>> +	pr_info("Reserving %ldKB of memory at %ldKB for kdump\n",
>> +		(unsigned long)elfcorehdr_size >> 10, (unsigned long)elfcorehdr_addr >> 10);
>> +
>> +	memblock_reserve(elfcorehdr_addr, elfcorehdr_size);
>>   #endif
>> +}
>>   
>>   #ifdef CONFIG_KEXEC
>>   
>> @@ -653,13 +652,7 @@ static void __init arch_mem_init(char **cmdline_p)
>>   	 */
>>   	memblock_set_current_limit(PFN_PHYS(max_low_pfn));
>>   
>> -#ifdef CONFIG_PROC_VMCORE
>> -	if (setup_elfcorehdr && setup_elfcorehdr_size) {
>> -		printk(KERN_INFO "kdump reserved memory at %lx-%lx\n",
>> -		       setup_elfcorehdr, setup_elfcorehdr_size);
>> -		memblock_reserve(setup_elfcorehdr, setup_elfcorehdr_size);
>> -	}
>> -#endif
>> +	mips_reserve_vmcore();
>>   
>>   	mips_parse_crashkernel();
>>   #ifdef CONFIG_KEXEC
>>
>