On Mon, Jul 24, 2023 at 3:48 PM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab@xxxxxxx> wrote:
On 2023/07/24 16:33, lijiang wrote:
> On Mon, Jul 24, 2023 at 3:07 PM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab@xxxxxxx>
> wrote:
>
>> On 2023/07/24 15:51, lijiang wrote:
>>> How about reading out the linux_banner string to a buffer with readmem()?
>>
>> No, this is a version check for the namelist (vmlinux).
>>
>>
> Ah, you are right, Kazu.
>
>>> If the vmlinux does not have only the ".rodata" symbol, is it possible
>>>> to use "__start_rodata" symbol or something? i.e. is there no symbol
>>>> that has the same address as .rodata section?
>>>>
>>>>
>>> I tried the "__start_rodata" symbol, but it does not work.
>>
>> How did you try? There is no "__start_rodata" symbol?
>>
>> I mean something like this:
>>
>> --- a/kernel.c
>> +++ b/kernel.c
>> @@ -11893,8 +11893,13 @@ int get_linux_banner_from_vmlinux(char *buf,
>> size_t size)
>> {
>> struct bfd_section *sect;
>> long offset;
>> + ulong start_rodata;
>>
>> - if (!kernel_symbol_exists(".rodata"))
>> + if (kernel_symbol_exists(".rodata"))
>> + start_rodata = symbol_value(".rodata");
>> + else if (kernel_symbol_exists("__start_rodata"))
>> + start_rodata = symbol_value("__start_rodata");
>> + else
>> return FALSE;
>>
>> sect = bfd_get_section_by_name(st->bfd, ".rodata");
>>
>
> The ".rodata" is a section, I mistakenly replaced the ".rodata" with the
> symbol "__start_rodata" in a debug patch, so it does not work. :-)
>
> diff --git a/kernel.c b/kernel.c
> index 546eed9..3c50fa4 100644
> --- a/kernel.c
> +++ b/kernel.c
> @@ -11894,7 +11894,7 @@ int get_linux_banner_from_vmlinux(char *buf, size_t
> size)
> struct bfd_section *sect;
> long offset;
>
> - if (!kernel_symbol_exists(".rodata"))
> + if (!kernel_symbol_exists("__start_rodata"))
> return FALSE;
>
> sect = bfd_get_section_by_name(st->bfd, ".rodata");
> @@ -11907,7 +11907,7 @@ int get_linux_banner_from_vmlinux(char *buf, size_t
> size)
> * value in vmlinux file, but relative offset to linux_banner
> * object in .rodata section is idential.
> */
> - offset = symbol_value("linux_banner") - symbol_value(".rodata");
> + offset = symbol_value("linux_banner") -
> symbol_value("__start_rodata");
>
> if (!bfd_get_section_contents(st->bfd,
> sect,
> @@ -11916,5 +11916,6 @@ int get_linux_banner_from_vmlinux(char *buf, size_t
> size)
> size))
> return FALSE;
>
> + error(INFO, "%s\n", buf);
> return TRUE;
>
> For now, the get_linux_banner_from_vmlinux() works again with the debug
> patch.
Good, thanks for the test. I will send a patch for this.
Good idea.
Thanks
Lianbo
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