/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Persistent Storage - pstore.h
 *
 * Copyright (C) 2010 Intel Corporation <tony.luck@intel.com>
 *
 * This code is the generic layer to export data records from platform
 * level persistent storage via a file system.
 */
#ifndef _LINUX_PSTORE_H
#define _LINUX_PSTORE_H

#include <linux/compiler.h>
#include <linux/errno.h>
#include <linux/kmsg_dump.h>
#include <linux/mutex.h>
#include <linux/semaphore.h>
#include <linux/time.h>
#include <linux/types.h>

struct module;

/*
 * pstore record types (see fs/pstore/platform.c for pstore_type_names[])
 * These values may be written to storage (see EFI vars backend), so
 * they are kind of an ABI. Be careful changing the mappings.
 */
enum pstore_type_id {
        /* Frontend storage types */
        PSTORE_TYPE_DMESG       = 0,
        PSTORE_TYPE_MCE         = 1,
        PSTORE_TYPE_CONSOLE     = 2,
        PSTORE_TYPE_FTRACE      = 3,

        /* PPC64-specific partition types */
        PSTORE_TYPE_PPC_RTAS    = 4,
        PSTORE_TYPE_PPC_OF      = 5,
        PSTORE_TYPE_PPC_COMMON  = 6,
        PSTORE_TYPE_PMSG        = 7,
        PSTORE_TYPE_PPC_OPAL    = 8,

        /* End of the list */
        PSTORE_TYPE_MAX
};

const char *pstore_type_to_name(enum pstore_type_id type);
enum pstore_type_id pstore_name_to_type(const char *name);

struct pstore_info;
/**
 * struct pstore_record - details of a pstore record entry
 * @psi:        pstore backend driver information
 * @type:       pstore record type
 * @id:         per-type unique identifier for record
 * @time:       timestamp of the record
 * @buf:        pointer to record contents
 * @size:       size of @buf
 * @ecc_notice_size:
 *              ECC information for @buf
 *
 * Valid for PSTORE_TYPE_DMESG @type:
 *
 * @count:      Oops count since boot
 * @reason:     kdump reason for notification
 * @part:       position in a multipart record
 * @compressed: whether the buffer is compressed
 *
 */
struct pstore_record {
        struct pstore_info      *psi;
        enum pstore_type_id     type;
        u64                     id;
        struct timespec64       time;
        char                    *buf;
        ssize_t                 size;
        ssize_t                 ecc_notice_size;

        int                     count;
        enum kmsg_dump_reason   reason;
        unsigned int            part;
        bool                    compressed;
};

/**
 * struct pstore_info - backend pstore driver structure
 *
 * @owner:      module which is responsible for this backend driver
 * @name:       name of the backend driver
 *
 * @buf_lock:   semaphore to serialize access to @buf
 * @buf:        preallocated crash dump buffer
 * @bufsize:    size of @buf available for crash dump bytes (must match
 *              smallest number of bytes available for writing to a
 *              backend entry, since compressed bytes don't take kindly
 *              to being truncated)
 *
 * @read_mutex: serializes @open, @read, @close, and @erase callbacks
 * @flags:      bitfield of frontends the backend can accept writes for
 * @max_reason: Used when PSTORE_FLAGS_DMESG is set. Contains the
 *              kmsg_dump_reason enum value. KMSG_DUMP_UNDEF means
 *              "use existing kmsg_dump() filtering, based on the
 *              printk.always_kmsg_dump boot param" (which is either
 *              KMSG_DUMP_OOPS when false, or KMSG_DUMP_MAX when
 *              true); see printk.always_kmsg_dump for more details.
 * @data:       backend-private pointer passed back during callbacks
 *
 * Callbacks:
 *
 * @open:
 *      Notify backend that pstore is starting a full read of backend
 *      records. Followed by one or more @read calls, and a final @close.
 *
 *      @psi:   in: pointer to the struct pstore_info for the backend
 *
 *      Returns 0 on success, and non-zero on error.
 *
 * @close:
 *      Notify backend that pstore has finished a full read of backend
 *      records. Always preceded by an @open call and one or more @read
 *      calls.
 *
 *      @psi:   in: pointer to the struct pstore_info for the backend
 *
 *      Returns 0 on success, and non-zero on error. (Though pstore will
 *      ignore the error.)
 *
 * @read:
 *      Read next available backend record. Called after a successful
 *      @open.
 *
 *      @record:
 *              pointer to record to populate. @buf should be allocated
 *              by the backend and filled. At least @type and @id should
 *              be populated, since these are used when creating pstorefs
 *              file names.
 *
 *      Returns record size on success, zero when no more records are
 *      available, or negative on error.
 *
 * @write:
 *      A newly generated record needs to be written to backend storage.
 *
 *      @record:
 *              pointer to record metadata. When @type is PSTORE_TYPE_DMESG,
 *              @buf will be pointing to the preallocated @psi.buf, since
 *              memory allocation may be broken during an Oops. Regardless,
 *              @buf must be proccesed or copied before returning. The
 *              backend is also expected to write @id with something that
 *              can help identify this record to a future @erase callback.
 *              The @time field will be prepopulated with the current time,
 *              when available. The @size field will have the size of data
 *              in @buf.
 *
 *      Returns 0 on success, and non-zero on error.
 *
 * @write_user:
 *      Perform a frontend write to a backend record, using a specified
 *      buffer that is coming directly from userspace, instead of the
 *      @record @buf.
 *
 *      @record:        pointer to record metadata.
 *      @buf:           pointer to userspace contents to write to backend
 *
 *      Returns 0 on success, and non-zero on error.
 *
 * @erase:
 *      Delete a record from backend storage.  Different backends
 *      identify records differently, so entire original record is
 *      passed back to assist in identification of what the backend
 *      should remove from storage.
 *
 *      @record:        pointer to record metadata.
 *
 *      Returns 0 on success, and non-zero on error.
 *
 */
struct pstore_info {
        struct module   *owner;
        const char      *name;

        struct semaphore buf_lock;
        char            *buf;
        size_t          bufsize;

        struct mutex    read_mutex;

        int             flags;
        int             max_reason;
        void            *data;

        int             (*open)(struct pstore_info *psi);
        int             (*close)(struct pstore_info *psi);
        ssize_t         (*read)(struct pstore_record *record);
        int             (*write)(struct pstore_record *record);
        int             (*write_user)(struct pstore_record *record,
                                      const char __user *buf);
        int             (*erase)(struct pstore_record *record);
};

/* Supported frontends */
#define PSTORE_FLAGS_DMESG      BIT(0)
#define PSTORE_FLAGS_CONSOLE    BIT(1)
#define PSTORE_FLAGS_FTRACE     BIT(2)
#define PSTORE_FLAGS_PMSG       BIT(3)

extern int pstore_register(struct pstore_info *);
extern void pstore_unregister(struct pstore_info *);

struct pstore_ftrace_record {
        unsigned long ip;
        unsigned long parent_ip;
        u64 ts;
};

/*
 * ftrace related stuff: Both backends and frontends need these so expose
 * them here.
 */

#if NR_CPUS <= 2 && defined(CONFIG_ARM_THUMB)
#define PSTORE_CPU_IN_IP 0x1
#elif NR_CPUS <= 4 && defined(CONFIG_ARM)
#define PSTORE_CPU_IN_IP 0x3
#endif

#define TS_CPU_SHIFT 8
#define TS_CPU_MASK (BIT(TS_CPU_SHIFT) - 1)

/*
 * If CPU number can be stored in IP, store it there, otherwise store it in
 * the time stamp. This means more timestamp resolution is available when
 * the CPU can be stored in the IP.
 */
#ifdef PSTORE_CPU_IN_IP
static inline void
pstore_ftrace_encode_cpu(struct pstore_ftrace_record *rec, unsigned int cpu)
{
        rec->ip |= cpu;
}

static inline unsigned int
pstore_ftrace_decode_cpu(struct pstore_ftrace_record *rec)
{
        return rec->ip & PSTORE_CPU_IN_IP;
}

static inline u64
pstore_ftrace_read_timestamp(struct pstore_ftrace_record *rec)
{
        return rec->ts;
}

static inline void
pstore_ftrace_write_timestamp(struct pstore_ftrace_record *rec, u64 val)
{
        rec->ts = val;
}
#else
static inline void
pstore_ftrace_encode_cpu(struct pstore_ftrace_record *rec, unsigned int cpu)
{
        rec->ts &= ~(TS_CPU_MASK);
        rec->ts |= cpu;
}

static inline unsigned int
pstore_ftrace_decode_cpu(struct pstore_ftrace_record *rec)
{
        return rec->ts & TS_CPU_MASK;
}

static inline u64
pstore_ftrace_read_timestamp(struct pstore_ftrace_record *rec)
{
        return rec->ts >> TS_CPU_SHIFT;
}

static inline void
pstore_ftrace_write_timestamp(struct pstore_ftrace_record *rec, u64 val)
{
        rec->ts = (rec->ts & TS_CPU_MASK) | (val << TS_CPU_SHIFT);
}
#endif

#endif /*_LINUX_PSTORE_H*/