where/how 2nd kernel's elfcorehdr_addr comes from

[lizhijian at fujitsu.com]

Hi folks,

I'm trying to add pmem's metadata(located at pmem device) to 
/proc/vmcore. To accomplish this, I think

something i need to know is where the contents of /proc/vmcore come 
from, and then append

something into it.

I have read 
https://opensource.com/article/17/6/kdump-usage-and-internals, and knew 
/proc/vmcore is a elf file.

It mentioned that "Creates /proc/vmcore as per elfcorehdr information 
received", but i don't get how it

elfcorehdr(maybe elfcorehdr_addr) be assigned in 2nd kernel.

I tried to grep it in the kernel source, but still no answer.  So i deep 
hope you guys can give me some hints or answer.

and thank you in advance :)

[root at iaas-rpma linux]# git grep elfcorehdr_addr | grep -v -w -e ia64 -e 
loongarch -e mips -e powerpc  -e riscv

arch/s390/kernel/setup.c:       elfcorehdr_addr = ELFCORE_ADDR_MAX;

drivers/of/fdt.c:       if (memblock_is_region_reserved(elfcorehdr_addr, 
elfcorehdr_size)) {

drivers/of/fdt.c:       memblock_reserve(elfcorehdr_addr, elfcorehdr_size);

drivers/of/fdt.c:               elfcorehdr_size >> 10, elfcorehdr_addr);

drivers/of/fdt.c:       elfcorehdr_addr = 
dt_mem_next_cell(dt_root_addr_cells, &prop);

drivers/of/fdt.c:                elfcorehdr_addr, elfcorehdr_size);

fs/proc/vmcore.c:       addr = elfcorehdr_addr;

fs/proc/vmcore.c:       addr = elfcorehdr_addr;

fs/proc/vmcore.c:       addr = elfcorehdr_addr;

fs/proc/vmcore.c:       addr = elfcorehdr_addr;

fs/proc/vmcore.c:       addr = elfcorehdr_addr;

fs/proc/vmcore.c:       rc = elfcorehdr_alloc(&elfcorehdr_addr, 
&elfcorehdr_size);

fs/proc/vmcore.c:       elfcorehdr_free(elfcorehdr_addr);

fs/proc/vmcore.c:       elfcorehdr_addr = ELFCORE_ADDR_ERR;

include/linux/crash_dump.h:extern unsigned long long elfcorehdr_addr;

include/linux/crash_dump.h:     return elfcorehdr_addr != ELFCORE_ADDR_MAX;

include/linux/crash_dump.h:     return is_kdump_kernel() && 
elfcorehdr_addr != ELFCORE_ADDR_ERR ? 1 : 0;

include/linux/crash_dump.h:             elfcorehdr_addr = ELFCORE_ADDR_ERR;

kernel/crash_dump.c: * Note: elfcorehdr_addr is not just limited to 
vmcore. It is also used by

kernel/crash_dump.c:unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;

kernel/crash_dump.c:EXPORT_SYMBOL_GPL(elfcorehdr_addr);

kernel/crash_dump.c:    elfcorehdr_addr = memparse(arg, &end);

kernel/crash_dump.c:            elfcorehdr_size = elfcorehdr_addr;

kernel/crash_dump.c:            elfcorehdr_addr = memparse(end + 1, &end);

Thanks

Zhijian