Re: [PATCH] kexec: Update vmcoreinfo after crash happened

Baoquan He
2017-03-16T12:27:39Z

Hi Xunlei,

Did you really see this ever happened? Because the vmcore size estimate
feature, namely --mem-usage option of makedumpfile, depends on the
vmcoreinfo in 1st kernel, your change will break it.

If not, it could be not good to change that.

Baoquan

On 03/16/17 at 08:16pm, Xunlei Pang wrote:
> Currently vmcoreinfo data is updated at boot time subsys_initcall(),
> it has the risk of being modified by some wrong code during system
> is running.
>
> As a result, vmcore dumped will contain the wrong vmcoreinfo. Later on,
> when using "crash" utility to parse this vmcore, we probably will get
> "Segmentation fault".
>
> Based on the fact that the value of each vmcoreinfo stays invariable
> once kernel boots up, we safely move all the vmcoreinfo operations into
> crash_save_vmcoreinfo() which is called after crash happened. In this
> way, vmcoreinfo data correctness is always guaranteed.
>
> Signed-off-by: Xunlei Pang <xlpang@redhat.com>
> ---
> kernel/kexec_core.c | 14 +++-----------
> 1 file changed, 3 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index bfe62d5..1bfdd96 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -1367,12 +1367,6 @@ static void update_vmcoreinfo_note(void)
> final_note(buf);
> }
>
> -void crash_save_vmcoreinfo(void)
> -{
> - vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds());
> - update_vmcoreinfo_note();
> -}
> -
> void vmcoreinfo_append_str(const char *fmt, ...)
> {
> va_list args;
> @@ -1402,7 +1396,7 @@ phys_addr_t __weak paddr_vmcoreinfo_note(void)
> return __pa_symbol((unsigned long)(char *)&vmcoreinfo_note);
> }
>
> -static int __init crash_save_vmcoreinfo_init(void)
> +void crash_save_vmcoreinfo(void)
> {
> VMCOREINFO_OSRELEASE(init_uts_ns.name.release);
> VMCOREINFO_PAGESIZE(PAGE_SIZE);
> @@ -1474,13 +1468,11 @@ static int __init crash_save_vmcoreinfo_init(void)
> #endif
>
> arch_crash_save_vmcoreinfo();
> - update_vmcoreinfo_note();
> + vmcoreinfo_append_str("CRASHTIME=%ld\n", get_seconds());
>
> - return 0;
> + update_vmcoreinfo_note();
> }
>
> -subsys_initcall(crash_save_vmcoreinfo_init);
> -
> /*
> * Move into place and start executing a preloaded standalone
> * executable. If nothing was preloaded return an error.
> --
> 1.8.3.1
>