Re: [Crash-utility] [Patch 1/4][kernel][slimdump] Add new elf-note of type NT_NOCOREDUMP to capture slimdump

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).

Signed-off-by: K.Prasad <prasad(a)linux.vnet.ibm.com&gt; --- 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"; +