Re: [PATCH v5 1/3] powerpc: make fadump resilient with memory add/remove events
From: Aneesh Kumar K.V <hidden>
Date: 2023-11-15 04:46:01
Sourabh Jain [off-list ref] writes: ....
quoted hunk ↗ jump to hunk
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