Sourabh Jain <sourabhj...@linux.ibm.com> writes: ....
> diff --git a/arch/powerpc/include/asm/fadump-internal.h > b/arch/powerpc/include/asm/fadump-internal.h > index 27f9e11eda28..7be3d8894520 100644 > --- a/arch/powerpc/include/asm/fadump-internal.h > +++ b/arch/powerpc/include/asm/fadump-internal.h > @@ -42,7 +42,25 @@ 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`. > + * This alteration ensures backward compatibility, enabling the kernel > + * with the updated fadump crash info to handle kernel dumps from older > + * kernels. > + * > + * To prevent the need for further changes to the magic number in the > + * event of future modifications to the fadump header, a version field > + * has been introduced to track the fadump crash info header version. > + * > + * Historically, there was no connection between the magic number and > + * the fadump crash info header version. However, moving forward, the > + * `FADMPINF` magic number in header will be treated as version 0, while > + * the `FADMPSIG` magic number in header will include a version field to > + * determine its version. > + */ > +#define FADUMP_CRASH_INFO_MAGIC fadump_str_to_u64("FADMPSIG") > +#define FADUMP_VERSION 1 > Can we keep the old magic details as #define FADUMP_CRASH_INFO_MAGIC_OLD fadump_str_to_u64("FADMPINF") #define FADUMP_CRASH_INFO_MAGIC fadump_str_to_u64("FADMPSIG") Also considering the struct need not be backward compatible, can we just do struct fadump_crash_info_header { u64 magic_number; u32 crashing_cpu; u64 elfcorehdr_addr; u64 elfcorehdr_size; u64 vmcoreinfo_raddr; u64 vmcoreinfo_size; struct pt_regs regs; struct cpumask cpu_mask; }; static inline bool fadump_compatible(struct fadump_crash_info_header *fdh) { return (fdh->magic_number == FADUMP_CRASH_INFO_MAGIC) } and fail fadump if we find it not compatible? -aneesh