Re: [PATCH] kexec: Export memory sections virtual addresses to vmcoreinfo

Baoquan He
2016-11-01T05:33:58Z

On 11/01/16 at 01:10pm, Dave Young wrote:
> On 10/06/16 at 04:46pm, Baoquan He wrote:
> > KASLR memory randomization can randomize the base of the physical memory
> > mapping (PAGE_OFFSET), vmalloc (VMALLOC_START) and vmemmap
> > (VMEMMAP_START). These need be exported to VMCOREINFO so that user space
> > utility, mainly makedumpfile can use them to identify the base of each
> > memory section. Here using VMCOREINFO_NUMBER we can reuse the existing
> > struct number_table in makedumpfile to import data easily.
> >
> > Since they are related to x86_64 only, put them into
> > arch_crash_save_vmcoreinfo. And move the exportion of KERNEL_IMAGE_SIZE
> > together since it's also for x86_64 only.
> >
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > ---
> > arch/x86/kernel/machine_kexec_64.c | 4 ++++
> > kernel/kexec_core.c | 3 ---
> > 2 files changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> > index 5a294e4..e150dd7 100644
> > --- a/arch/x86/kernel/machine_kexec_64.c
> > +++ b/arch/x86/kernel/machine_kexec_64.c
> > @@ -337,6 +337,10 @@ void arch_crash_save_vmcoreinfo(void)
> > #endif
> > vmcoreinfo_append_str("KERNELOFFSET=%lx\n",
> > kaslr_offset());
> > + VMCOREINFO_NUMBER(KERNEL_IMAGE_SIZE);
> > + VMCOREINFO_NUMBER(PAGE_OFFSET);
> > + VMCOREINFO_NUMBER(VMALLOC_START);
> > + VMCOREINFO_NUMBER(VMEMMAP_START);
>
> Pratyush has posted makedumpfile patches below to avoid the VMCOREINFO:
> http://lists.infradead.org/pipermail/kexec/2016-October/017540.html
>
> But we have this in mainline which also introduced the VMCOREINFO
> numbers, can you send a patch to revert them?

OK, will do.

However for find_vmemmap_x86_64() in makedumpfile, vmemmap_start is
still needed. I checked code, seems no better way to avoid. I am not
sure how many people are really using "-e" option to exclude unused
vmemmap pages.

Maybe just leave it as is, and fix it when people complain?

> commit 0549a3c02efb350776bc869685a361045efd3a29
> Author: Thomas Garnier <thgarnie@google.com>
> Date: Tue Oct 11 13:55:08 2016 -0700
>
> kdump, vmcoreinfo: report memory sections virtual addresses
> [snip]]
>
> > }
> >
> > /* arch-dependent functionality related to kexec file-based syscall */
> > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> > index 5616755..8ad3a29e 100644
> > --- a/kernel/kexec_core.c
> > +++ b/kernel/kexec_core.c
> > @@ -1467,9 +1467,6 @@ static int __init crash_save_vmcoreinfo_init(void)
> > #endif
> > VMCOREINFO_NUMBER(PG_head_mask);
> > VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE);
> > -#ifdef CONFIG_X86
> > - VMCOREINFO_NUMBER(KERNEL_IMAGE_SIZE);
> > -#endif
>
> Moving KERNEL_IMAGE_SIZE to x86 should be a standalone patch.
> I remember Dave Anderson said he use it in crash utility, cced him.
>
> > #ifdef CONFIG_HUGETLB_PAGE
> > VMCOREINFO_NUMBER(HUGETLB_PAGE_DTOR);
> > #endif
> > --
> > 2.5.5
> >
> >
> > _______________________________________________
> > kexec mailing list
> > kexec@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
>
> Thanks
> Dave