Messages in this thread | | | Date | Tue, 4 Oct 2011 10:30:12 -0400 | From | Vivek Goyal <> | Subject | Re: [Patch 1/4][kernel][slimdump] Add new elf-note of type NT_NOCOREDUMP to capture slimdump |
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On Mon, Oct 03, 2011 at 01:02:03PM +0530, K.Prasad wrote: > There are certain types of crashes induced by faulty hardware in which > capturing crashing kernel's memory (through kdump) makes no sense (or sometimes > dangerous). > > A case in point, is unrecoverable memory errors (resulting in fatal machine > check exceptions) in which reading from the faulty memory location from the > kexec'ed kernel will cause double fault and system reset (leaving no > information for the user). > > This patch introduces a framework called 'slimdump' enabled through a new > elf-note NT_NOCOREDUMP. Any error whose cause cannot be attributed to a > software error and cannot be detected by analysing the kernel memory may > decide to add this elf-note to the vmcore and indicate the futility of > such an exercise. Tools such as 'kexec', 'makedumpfile' and 'crash' are > also modified in tandem to recognise this new elf-note and capture > 'slimdump'. > > The physical address and size of the NT_NOCOREDUMP are made available to the > user-space through a "/sys/kernel/nt_nocoredump" sysfs file (just like other > kexec related files).
Even if kernel has to signal to user space the reason for crash, why not add this info to existing vmcoreinfo note. Something like another filed. PANIC_MCE=1.
Secondly, the note name NT_NOCOREDUMP itself sounds binding. Kernel can export the reason of panic and then it is up to user space what do they want to do with it.
So to me,
> > Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com> > --- > arch/x86/kernel/cpu/mcheck/mce.c | 28 ++++++++++++++++++++++++++++ > include/linux/elf.h | 18 ++++++++++++++++++ > include/linux/kexec.h | 1 + > kernel/kexec.c | 11 +++++++++++ > kernel/ksysfs.c | 10 ++++++++++ > 5 files changed, 68 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c > index 08363b0..483b2fc 100644 > --- a/arch/x86/kernel/cpu/mcheck/mce.c > +++ b/arch/x86/kernel/cpu/mcheck/mce.c > @@ -238,6 +238,34 @@ static atomic_t mce_paniced; > static int fake_panic; > static atomic_t mce_fake_paniced; > > +void arch_add_nocoredump_note(u32 *buf) > +{ > + struct elf_note note; > + const char note_name[] = "PANIC_MCE"; > + const char desc_msg[] = "Crash induced due to a fatal machine " > + "check error"; > +
Again, note_name and desc_msg seem to be only two exports. Frankly desc string seems pretty obivious and we should be able to ignore it. So just exporting PANIC_MCE=true or something like that in case of MCE.
Thanks Vivek
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