On 19/11/25 09:41, Tao Liu wrote:
Sorry I forgot to cc Aditya. Adding Aditya in the thread.
On Wed, Nov 19, 2025 at 5:09 PM Tao Liu <[email protected]> wrote:
This patch will cause a regression on some x86_64 vmcores.
$ crash -s vmcore vmlinux.gz
WARNING: vmcoreinfo is empty, will read from symbols
crash: cannot malloc vmcoreinfo buffer
crash: /var/tmp/vmlinux.gz_fWV3kA and vmcore do not match!
The root cause is, in main.c, is_kdump() calls is_netdump(), which will
set pc->read_vmcoreinfo as vmcoreinfo_read_from_memory(), rather than
original vmcoreinfo_read_string().
Later in machdep_init(PRE_SYMTAB), vmcoreinfo_read_from_memory() doesn't
get "relocate" string, so fails for set kaslr flag, then fails for
linux_banner detection:
Thread 1 "crash" hit Breakpoint 2, verify_version ():
1096 if (!IS_KVADDR(linux_banner))
(gdb) p/x linux_banner
$4 = 0xffffffff81e00100
crash> sym linux_banner
ffffffff9aa00100 (R) linux_banner
As we can see with the patch applied, linux_banner got a wrong address.
So this patch currently is unsafe, and should be reverted before the fix.
Signed-off-by: Tao Liu <[email protected]>
---
Since it is too close to the new release date of crash utility, I don't
have enough time for full root cause analysis and re-testing. So currently
the best option is to revert it for now, and fix it in the next release then
re-apply.
Hello Tao,
Can you share the vmcore and vmlinux somewhere ?
Is this with some special configuration, like something related kaslr
you mentioned ?
Thanks for the initial analysis, I will try to debug this.
Interestingly I did not hit this issue in my testing, but yes revert
makes sense since it has broken crash-utility.
Thanks,
- Aditya G
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