Re: [Crash-utility] [PATCH] Fix warning about kernel version inconsistency during crash startup

On Mon, Jul 24, 2023 at 3:07 PM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab(a)nec.com&gt; 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.