On Mon, Jul 24, 2023 at 3:48 PM HAGIO KAZUHITO(萩尾 一仁) <k-hagio...@nec.com>
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...@nec.com>
> > 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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