On 2020-11-19, HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab@xxxxxxx> wrote:
> From: John Ogness <john.ogness@xxxxxxxxxxxxx>
>
> Linux 5.10 introduces a new lockless ringbuffer. The new ringbuffer
> is structured completely different to the previous iterations.
> Add support for retrieving the ringbuffer from debug information
> and/or using vmcoreinfo. The new ringbuffer is detected based on
> the availability of the "prb" symbol.
>
> Signed-off-by: John Ogness <john.ogness@xxxxxxxxxxxxx>
> Signed-off-by: Kazuhito Hagio <k-hagio-ab@xxxxxxx>
> ---
> I've updated John's RFC makedumpfile patch to match 5.10-rc4 kernel.
> Changes from the RFC patch:
> - followed the following kernel commit
> cfe2790b163a ("printk: move printk_info into separate array")
> - divided members of struct printk_log in offset_table into each structure
> for readability
> - added some error handlings
> - also dump head record that was missed
I confirm that these changes are correct. Thanks for updating this,
adding the needed error handling, and catching that the head record was
missed!
I tested this by:
1. Boot kernel with: crashkernel=512M
2. Setup and trigger crash:
kexec -p /boot/bzImage --initrd=/boot/rescue-initrd --append="console=ttyS0,115200"
echo c > /proc/sysrq-trigger
3. From rescue environment, copy crashed vmcore to external machine:
cp /proc/vmcore /remote/nfs/mount/
4. From external machine, extract kernel log using vmcoreinfo:
makedumpfile -g ./vmcoreinfo -x ./vmlinux
makedumpfile --dump-dmesg -i ./vmcoreinfo ./vmcore dmesg1.txt
5. From external machine, extract kernel log using debug symbols:
makedumpfile --dump-dmesg -x ./vmlinux ./vmcore dmesg2.txt
6. Compare and inspect the kernel logs:
diff dmesg1.txt dmesg2.txt
cat dmesg1.txt
John Ogness
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