[PATCH] arm64/crashdump-arm64: Fix makedumpfile error caused by fail to get _text address

[Chen Wandun]

On 9/22/25 12:38 PM, Pingfan Liu wrote:
> Hi Chen,
>
> On Fri, Sep 19, 2025 at 3:35 PM Chen Wandun <chenwandun1 at gmail.com> wrote:
>> I encountered the following error while makedumpfile without enableing
>> kernel CONFIG_PROC_KCORE and CONFIG_KALLSYMS_ALL, this error only exists
>> before commit 29fe506 (kexec: make -a the default), this commit change
>> from kexec_load to kexec_file_load.
>>
>> read_from_vmcore: Can't seek the dump memory(/proc/vmcore). (offset: ffff800084f4c000) Invalid argument
>> readpage_elf: Can't read the dump memory(/proc/vmcore).
>> readmem: type_addr: 1, addr:41f29800, size:8
>> vaddr_to_paddr_arm64: Can't read pgd
>> readmem: Can't convert a virtual address(ffff800082edf8a0) to physical address.
>> readmem: type_addr: 0, addr:ffff800082edf8a0, size:390
>> check_release: Can't get the address of system_utsname.
>>
>> Although several error messages appear when loading second kernel using kexec without
>> kernel CONFIG_PROC_KCORE and CONFIG_KALLSYMS_ALL, but kexec return 0.
>>
>> Can't open (/proc/kcore).
>> Can't get the symbol of _text to calculate page_offset.
>> Can't get the symbol of _text to calculate page_offset.
>>
>> If kexec unable to get the _text address, it will result in elf_info.kern_paddr_start
>> to be a large value, and also phdr->p_filesz/phdr->p_offset to be a large value, such as:
>>
>> readelf -l /proc/vmcore
>> Program Headers:
>>    Type           Offset             VirtAddr           PhysAddr
>>                   FileSiz            MemSiz              Flags  Align
>>    NOTE           0x0000000000001000 0x0000000000000000 0x0000000000000000
>>                   0x0000000000001a44 0x0000000000001a44         0x4
>>    LOAD           0x0000000000003000 0xffffffffffffffff 0x00007fffc0200000
>>                   0xffff800083020000 0xffff800083020000  RWE    0x0
>>    LOAD           0xffff800083023000 0x0000000000000000 0x0000000040000000
>>                   0x00000001e6e00000 0x00000001e6e00000  RWE    0x0
>>    LOAD           0xffff800269e23000 0x00000001f6e00000 0x0000000236e00000
>>                   0x0000000009200000 0x0000000009200000  RWE    0x0
>>
>> This patch avoiding makedumpfile failure by ending the kexec process and explicitly
>> notifying error.
>>
> I'm afraid I cannot agree with your proposed fix. The makedumpfile
> works on /proc/vmcore. In my opinion, if there isn't enough
> information for makedumpfile to work properly, you should try to fix
> and supplement it in the first kernel.
Yes, you're right, and that's also how this patch is done;

Without this patch:
If kexec can't get the address of _text, kexec will finish “normally” 
with returning 0,
but will fail when makedumpfile. This is not what we expected.

With this patch:
kexec will abort if can't get the address ot _text and explicitly 
notifying error, and
first kernel should provide correct info based on error message.

Thanks,
Wandun

>
> Thanks,
>
> Pingfan
>
>> Reported-by: Zhao Meijing <zhaomeijing at lixiang.com>
>> Signed-off-by: Chen Wandun <chenwandun at lixiang.com>
>> ---
>>   kexec/arch/arm64/crashdump-arm64.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/kexec/arch/arm64/crashdump-arm64.c b/kexec/arch/arm64/crashdump-arm64.c
>> index 73cb611..8629610 100644
>> --- a/kexec/arch/arm64/crashdump-arm64.c
>> +++ b/kexec/arch/arm64/crashdump-arm64.c
>> @@ -94,9 +94,11 @@ static int iomem_range_callback(void *UNUSED(data), int UNUSED(nr),
>>                   * For compatibility, deduce by comparing the gap "__init_begin - _stext"
>>                   * and the res size of "Kernel code" in /proc/iomem
>>                   */
>> -               if (kva_text_end - kva_stext == length)
>> +               if (kva_text_end - kva_stext == length) {
>> +                       if (!kva_text)
>> +                               die("Cannot get kernel _text symbol address\n");
>>                          elf_info.kern_paddr_start = base - (kva_stext - kva_text);
>> -               else
>> +               } else
>>                          elf_info.kern_paddr_start = base;
>>          }
>>          else if (strncmp(str, KERNEL_DATA, strlen(KERNEL_DATA)) == 0)
>> --
>> 2.25.1
>>