[Crash-utility] Re: [PATCH] Revert "vmcoreinfo: read vmcoreinfo using 'vmcoreinfo_data' when unavailable in elf note"

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 <ltao(a)redhat.com&gt; 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 <ltao(a)redhat.com&gt; >> --- >> >> 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