crash, the second/fadump boots and access the fadump header prepared by
first kernel and do the following in a platform-specific function
[rtas|opal]_fadump_process:
At present, the first kernel is responsible for preparing the fadump
header and storing it in the fadump reserved area. The fadump header
includes the start address of the elfcorehd, crashing CPU details, and
other relevant information. In the event of a crash in the first kernel,
the second/fadump boots and accesses the fadump header prepared by the
first kernel. It then performs the following steps in a
platform-specific function [rtas|opal]_fadump_process:
1. Sanity check for fadump header
2. Update CPU notes in elfcorehdr
3. Set the global variable elfcorehdr_addr to the address of the
fadump header's elfcorehdr. For vmcore module to process it later
on.
Along with the above, update the setup_fadump()/fadump.c to create
elfcorehdr in second/fadump kernel.
Section below outlines the information required to create the elfcorehdr
and the changes made to make it available to the fadump kernel if it's
not already.
To create elfcorehdr, the following crashed kernel information is
required: CPU notes, vmcoreinfo, and memory ranges.
At present, the CPU notes are already prepared in the fadump kernel, so
no changes are needed in that regard. The fadump kernel has access to
all crashed kernel memory regions, including boot memory regions that
are relocated by firmware to fadump reserved areas, so no changes for
that either. However, it is necessary to add new members to the fadump
header, i.e., the 'fadump_crash_info_header' structure, in order to pass
the crashed kernel's vmcoreinfo address and its size to fadump kernel.
In addition to the vmcoreinfo address and size, there are a few other
attributes also added to the fadump_crash_info_header structure.
1. version:
It stores the fadump header version, which is currently set to 1.
This provides flexibility to update the fadump crash info header in
the future without changing the magic number. For each change in the
fadump header, the version will be increased. This will help the
updated kernel determine how to handle kernel dumps from older
kernels. The magic number remains relevant for checking fadump
header
corruption.
2. elfcorehdr_size:
since elfcorehdr is now prepared in the fadump/second kernel and
it is not part of the reserved area, this attribute is needed to
track the memory allocated for elfcorehdr to do the deallocation
properly.
3. pt_regs_sz/cpu_mask_sz:
Store size of pt_regs and cpu_mask strucutre in first kernel. These
attributes are used avoid processing the dump if the sizes of
pt_regs
and cpu_mask are not the same across the crashed and fadump kernel.
Note: if either first/crashed kernel or second/fadump kernel do not have
the changes introduced here then kernel fail to collect the dump and
prints relevant error message on the console.
Signed-off-by: Sourabh Jain <sourabhj...@linux.ibm.com>
Cc: Aditya Gupta <adit...@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.ku...@kernel.org>
Cc: Hari Bathini <hbath...@linux.ibm.com>
Cc: Mahesh Salgaonkar <mah...@linux.ibm.com>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Naveen N Rao <nav...@kernel.org>
---
arch/powerpc/include/asm/fadump-internal.h | 31 +-
arch/powerpc/kernel/fadump.c | 355 +++++++++++--------
arch/powerpc/platforms/powernv/opal-fadump.c | 18 +-
arch/powerpc/platforms/pseries/rtas-fadump.c | 23 +-
4 files changed, 242 insertions(+), 185 deletions(-)
diff --git a/arch/powerpc/include/asm/fadump-internal.h
b/arch/powerpc/include/asm/fadump-internal.h
index 27f9e11eda28..a632e9708610 100644
--- a/arch/powerpc/include/asm/fadump-internal.h
+++ b/arch/powerpc/include/asm/fadump-internal.h
@@ -42,13 +42,40 @@ static inline u64 fadump_str_to_u64(const char *str)
#define FADUMP_CPU_UNKNOWN (~((u32)0))
-#define FADUMP_CRASH_INFO_MAGIC fadump_str_to_u64("FADMPINF")
+/*
+ * The introduction of new fields in the fadump crash info header has
+ * led to a change in the magic key from `FADMPINF` to `FADMPSIG` for
+ * identifying a kernel crash from an old kernel.
+ *
+ * To prevent the need for further changes to the magic number in the
+ * event of future modifications to the fadump crash info header, a
+ * version field has been introduced to track the fadump crash info
+ * header version.
+ *
+ * Consider a few points before adding new members to the fadump
crash info
+ * header structure:
+ *
+ * - Append new members; avoid adding them in between.
+ * - Non-primitive members should have a size member as well.
+ * - For every change in the fadump header, increment the
+ * fadump header version. This helps the updated kernel decide
how to
+ * handle kernel dumps from older kernels.
+ */
+#define FADUMP_CRASH_INFO_MAGIC_OLD fadump_str_to_u64("FADMPINF")
+#define FADUMP_CRASH_INFO_MAGIC fadump_str_to_u64("FADMPSIG")
+#define FADUMP_HEADER_VERSION 1
/* fadump crash info structure */
struct fadump_crash_info_header {
u64 magic_number;
- u64 elfcorehdr_addr;
+ u32 version;
u32 crashing_cpu;
