On Thu, Feb 25, 2021 at 09:24:35PM +0100, John Ogness wrote:
> Rather than storing the iterator information in the registered
> kmsg_dumper structure, create a separate iterator structure. The
> kmsg_dump_iter structure can reside on the stack of the caller, thus
> allowing lockless use of the kmsg_dump functions.
> 
> This change also means that the kmsg_dumper dump() callback no
> longer needs to pass in the kmsg_dumper as an argument. If
> kmsg_dumpers want to access the kernel logs, they can use the new
> iterator.
> 
> Update the kmsg_dumper callback prototype. Update code that accesses
> the kernel logs using the kmsg_dumper structure to use the new
> kmsg_dump_iter structure. For kmsg_dumpers, this also means adding a
> call to kmsg_dump_rewind() to initialize the iterator.
> 
> All this is in preparation for removal of @logbuf_lock.
> 
> Signed-off-by: John Ogness <john.ogn...@linutronix.de>
> ---
>  arch/powerpc/kernel/nvram_64.c             | 14 +++---
>  arch/powerpc/platforms/powernv/opal-kmsg.c |  3 +-
>  arch/powerpc/xmon/xmon.c                   |  6 +--
>  arch/um/kernel/kmsg_dump.c                 |  8 +--
>  drivers/hv/vmbus_drv.c                     |  7 +--
>  drivers/mtd/mtdoops.c                      |  8 +--
>  fs/pstore/platform.c                       |  8 +--

Reviewed-by: Kees Cook <keesc...@chromium.org> # pstore

-Kees

>  include/linux/kmsg_dump.h                  | 38 ++++++++-------
>  kernel/debug/kdb/kdb_main.c                | 10 ++--
>  kernel/printk/printk.c                     | 57 ++++++++++------------
>  10 files changed, 81 insertions(+), 78 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/nvram_64.c b/arch/powerpc/kernel/nvram_64.c
> index 532f22637783..5a64b24a91c2 100644
> --- a/arch/powerpc/kernel/nvram_64.c
> +++ b/arch/powerpc/kernel/nvram_64.c
> @@ -72,8 +72,7 @@ static const char *nvram_os_partitions[] = {
>       NULL
>  };
>  
> -static void oops_to_nvram(struct kmsg_dumper *dumper,
> -                       enum kmsg_dump_reason reason);
> +static void oops_to_nvram(enum kmsg_dump_reason reason);
>  
>  static struct kmsg_dumper nvram_kmsg_dumper = {
>       .dump = oops_to_nvram
> @@ -642,11 +641,11 @@ void __init nvram_init_oops_partition(int 
> rtas_partition_exists)
>   * that we think will compress sufficiently to fit in the lnx,oops-log
>   * partition.  If that's too much, go back and capture uncompressed text.
>   */
> -static void oops_to_nvram(struct kmsg_dumper *dumper,
> -                       enum kmsg_dump_reason reason)
> +static void oops_to_nvram(enum kmsg_dump_reason reason)
>  {
>       struct oops_log_info *oops_hdr = (struct oops_log_info *)oops_buf;
>       static unsigned int oops_count = 0;
> +     static struct kmsg_dump_iter iter;
>       static bool panicking = false;
>       static DEFINE_SPINLOCK(lock);
>       unsigned long flags;
> @@ -681,13 +680,14 @@ static void oops_to_nvram(struct kmsg_dumper *dumper,
>               return;
>  
>       if (big_oops_buf) {
> -             kmsg_dump_get_buffer(dumper, false,
> +             kmsg_dump_rewind(&iter);
> +             kmsg_dump_get_buffer(&iter, false,
>                                    big_oops_buf, big_oops_buf_sz, &text_len);
>               rc = zip_oops(text_len);
>       }
>       if (rc != 0) {
> -             kmsg_dump_rewind(dumper);
> -             kmsg_dump_get_buffer(dumper, false,
> +             kmsg_dump_rewind(&iter);
> +             kmsg_dump_get_buffer(&iter, false,
>                                    oops_data, oops_data_sz, &text_len);
>               err_type = ERR_TYPE_KERNEL_PANIC;
>               oops_hdr->version = cpu_to_be16(OOPS_HDR_VERSION);
> diff --git a/arch/powerpc/platforms/powernv/opal-kmsg.c 
> b/arch/powerpc/platforms/powernv/opal-kmsg.c
> index 6c3bc4b4da98..a7bd6ac681f4 100644
> --- a/arch/powerpc/platforms/powernv/opal-kmsg.c
> +++ b/arch/powerpc/platforms/powernv/opal-kmsg.c
> @@ -19,8 +19,7 @@
>   * may not be completely printed.  This function does not actually dump the
>   * message, it just ensures that OPAL completely flushes the console buffer.
>   */
> -static void kmsg_dump_opal_console_flush(struct kmsg_dumper *dumper,
> -                                  enum kmsg_dump_reason reason)
> +static void kmsg_dump_opal_console_flush(enum kmsg_dump_reason reason)
>  {
>       /*
>        * Outside of a panic context the pollers will continue to run,
> diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
> index 80ed3e1becf9..5978b90a885f 100644
> --- a/arch/powerpc/xmon/xmon.c
> +++ b/arch/powerpc/xmon/xmon.c
> @@ -3001,7 +3001,7 @@ print_address(unsigned long addr)
>  static void
>  dump_log_buf(void)
>  {
> -     struct kmsg_dumper dumper;
> +     struct kmsg_dump_iter iter;
>       unsigned char buf[128];
>       size_t len;
>  
> @@ -3013,9 +3013,9 @@ dump_log_buf(void)
>       catch_memory_errors = 1;
>       sync();
>  
> -     kmsg_dump_rewind_nolock(&dumper);
> +     kmsg_dump_rewind_nolock(&iter);
>       xmon_start_pagination();
> -     while (kmsg_dump_get_line_nolock(&dumper, false, buf, sizeof(buf), 
> &len)) {
> +     while (kmsg_dump_get_line_nolock(&iter, false, buf, sizeof(buf), &len)) 
> {
>               buf[len] = '\0';
>               printf("%s", buf);
>       }
> diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c
> index 4869e2cc787c..9fbc5e5b1023 100644
> --- a/arch/um/kernel/kmsg_dump.c
> +++ b/arch/um/kernel/kmsg_dump.c
> @@ -7,9 +7,9 @@
>  #include <shared/kern.h>
>  #include <os.h>
>  
> -static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
> -                             enum kmsg_dump_reason reason)
> +static void kmsg_dumper_stdout(enum kmsg_dump_reason reason)
>  {
> +     static struct kmsg_dump_iter iter;
>       static DEFINE_SPINLOCK(lock);
>       static char line[1024];
>       struct console *con;
> @@ -34,8 +34,10 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
>       if (!spin_trylock(&lock))
>               return;
>  
> +     kmsg_dump_rewind(&iter);
> +
>       printf("kmsg_dump:\n");
> -     while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) {
> +     while (kmsg_dump_get_line(&iter, true, line, sizeof(line), &len)) {
>               line[len] = '\0';
>               printf("%s", line);
>       }
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 10dce9f91216..1b858f280e22 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -1388,9 +1388,9 @@ static void vmbus_isr(void)
>   * Callback from kmsg_dump. Grab as much as possible from the end of the kmsg
>   * buffer and call into Hyper-V to transfer the data.
>   */
> -static void hv_kmsg_dump(struct kmsg_dumper *dumper,
> -                      enum kmsg_dump_reason reason)
> +static void hv_kmsg_dump(enum kmsg_dump_reason reason)
>  {
> +     struct kmsg_dump_iter iter;
>       size_t bytes_written;
>       phys_addr_t panic_pa;
>  
> @@ -1404,7 +1404,8 @@ static void hv_kmsg_dump(struct kmsg_dumper *dumper,
>        * Write dump contents to the page. No need to synchronize; panic should
>        * be single-threaded.
>        */
> -     kmsg_dump_get_buffer(dumper, false, hv_panic_page, HV_HYP_PAGE_SIZE,
> +     kmsg_dump_rewind(&iter);
> +     kmsg_dump_get_buffer(&iter, false, hv_panic_page, HV_HYP_PAGE_SIZE,
>                            &bytes_written);
>       if (bytes_written)
>               hyperv_report_panic_msg(panic_pa, bytes_written);
> diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
> index 8bbfba40a554..d179b726a1c9 100644
> --- a/drivers/mtd/mtdoops.c
> +++ b/drivers/mtd/mtdoops.c
> @@ -272,19 +272,21 @@ static void find_next_position(struct mtdoops_context 
> *cxt)
>       mtdoops_inc_counter(cxt);
>  }
>  
> -static void mtdoops_do_dump(struct kmsg_dumper *dumper,
> -                         enum kmsg_dump_reason reason)
> +static void mtdoops_do_dump(enum kmsg_dump_reason reason)
>  {
>       struct mtdoops_context *cxt = container_of(dumper,
>                       struct mtdoops_context, dump);
> +     struct kmsg_dump_iter iter;
>  
>       /* Only dump oopses if dump_oops is set */
>       if (reason == KMSG_DUMP_OOPS && !dump_oops)
>               return;
>  
> +     kmsg_dump_rewind(&iter);
> +
>       if (test_and_set_bit(0, &cxt->oops_buf_busy))
>               return;
> -     kmsg_dump_get_buffer(dumper, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE,
> +     kmsg_dump_get_buffer(&iter, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE,
>                            record_size - MTDOOPS_HEADER_SIZE, NULL);
>       clear_bit(0, &cxt->oops_buf_busy);
>  
> diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
> index d963ae7902f9..edfc9504e024 100644
> --- a/fs/pstore/platform.c
> +++ b/fs/pstore/platform.c
> @@ -382,9 +382,9 @@ void pstore_record_init(struct pstore_record *record,
>   * callback from kmsg_dump. Save as much as we can (up to kmsg_bytes) from 
> the
>   * end of the buffer.
>   */
> -static void pstore_dump(struct kmsg_dumper *dumper,
> -                     enum kmsg_dump_reason reason)
> +static void pstore_dump(enum kmsg_dump_reason reason)
>  {
> +     struct kmsg_dump_iter iter;
>       unsigned long   total = 0;
>       const char      *why;
>       unsigned int    part = 1;
> @@ -405,6 +405,8 @@ static void pstore_dump(struct kmsg_dumper *dumper,
>               }
>       }
>  
> +     kmsg_dump_rewind(&iter);
> +
>       oopscount++;
>       while (total < kmsg_bytes) {
>               char *dst;
> @@ -435,7 +437,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
>               dst_size -= header_size;
>  
>               /* Write dump contents. */
> -             if (!kmsg_dump_get_buffer(dumper, true, dst + header_size,
> +             if (!kmsg_dump_get_buffer(&iter, true, dst + header_size,
>                                         dst_size, &dump_size))
>                       break;
>  
> diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
> index 84eaa2090efa..5d3bf20f9f0a 100644
> --- a/include/linux/kmsg_dump.h
> +++ b/include/linux/kmsg_dump.h
> @@ -29,6 +29,16 @@ enum kmsg_dump_reason {
>       KMSG_DUMP_MAX
>  };
>  
> +/**
> + * struct kmsg_dump_iter - iterator for retrieving kernel messages
> + * @cur_seq: Points to the oldest message to dump
> + * @next_seq:        Points after the newest message to dump
> + */
> +struct kmsg_dump_iter {
> +     u64     cur_seq;
> +     u64     next_seq;
> +};
> +
>  /**
>   * struct kmsg_dumper - kernel crash message dumper structure
>   * @list:    Entry in the dumper list (private)
> @@ -36,35 +46,29 @@ enum kmsg_dump_reason {
>   *           through the record iterator
>   * @max_reason:      filter for highest reason number that should be dumped
>   * @registered:      Flag that specifies if this is already registered
> - * @cur_seq: Points to the oldest message to dump
> - * @next_seq:        Points after the newest message to dump
>   */
>  struct kmsg_dumper {
>       struct list_head list;
> -     void (*dump)(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason);
> +     void (*dump)(enum kmsg_dump_reason reason);
>       enum kmsg_dump_reason max_reason;
>       bool registered;
> -
> -     /* private state of the kmsg iterator */
> -     u64 cur_seq;
> -     u64 next_seq;
>  };
>  
>  #ifdef CONFIG_PRINTK
>  void kmsg_dump(enum kmsg_dump_reason reason);
>  
> -bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
> +bool kmsg_dump_get_line_nolock(struct kmsg_dump_iter *iter, bool syslog,
>                              char *line, size_t size, size_t *len);
>  
> -bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
> +bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
>                       char *line, size_t size, size_t *len);
>  
> -bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
> +bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
>                         char *buf, size_t size, size_t *len_out);
>  
> -void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper);
> +void kmsg_dump_rewind_nolock(struct kmsg_dump_iter *iter);
>  
> -void kmsg_dump_rewind(struct kmsg_dumper *dumper);
> +void kmsg_dump_rewind(struct kmsg_dump_iter *iter);
>  
>  int kmsg_dump_register(struct kmsg_dumper *dumper);
>  
> @@ -76,30 +80,30 @@ static inline void kmsg_dump(enum kmsg_dump_reason reason)
>  {
>  }
>  
> -static inline bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper,
> +static inline bool kmsg_dump_get_line_nolock(struct kmsg_dump_iter *iter,
>                                            bool syslog, const char *line,
>                                            size_t size, size_t *len)
>  {
>       return false;
>  }
>  
> -static inline bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool 
> syslog,
> +static inline bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool 
> syslog,
>                               const char *line, size_t size, size_t *len)
>  {
>       return false;
>  }
>  
> -static inline bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool 
> syslog,
> +static inline bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool 
> syslog,
>                                       char *buf, size_t size, size_t *len)
>  {
>       return false;
>  }
>  
> -static inline void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
> +static inline void kmsg_dump_rewind_nolock(struct kmsg_dump_iter *iter)
>  {
>  }
>  
> -static inline void kmsg_dump_rewind(struct kmsg_dumper *dumper)
> +static inline void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
>  {
>  }
>  
> diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
> index 315169d5e119..8544d7a55a57 100644
> --- a/kernel/debug/kdb/kdb_main.c
> +++ b/kernel/debug/kdb/kdb_main.c
> @@ -2101,7 +2101,7 @@ static int kdb_dmesg(int argc, const char **argv)
>       int adjust = 0;
>       int n = 0;
>       int skip = 0;
> -     struct kmsg_dumper dumper;
> +     struct kmsg_dump_iter iter;
>       size_t len;
>       char buf[201];
>  
> @@ -2126,8 +2126,8 @@ static int kdb_dmesg(int argc, const char **argv)
>               kdb_set(2, setargs);
>       }
>  
> -     kmsg_dump_rewind_nolock(&dumper);
> -     while (kmsg_dump_get_line_nolock(&dumper, 1, NULL, 0, NULL))
> +     kmsg_dump_rewind_nolock(&iter);
> +     while (kmsg_dump_get_line_nolock(&iter, 1, NULL, 0, NULL))
>               n++;
>  
>       if (lines < 0) {
> @@ -2159,8 +2159,8 @@ static int kdb_dmesg(int argc, const char **argv)
>       if (skip >= n || skip < 0)
>               return 0;
>  
> -     kmsg_dump_rewind_nolock(&dumper);
> -     while (kmsg_dump_get_line_nolock(&dumper, 1, buf, sizeof(buf), &len)) {
> +     kmsg_dump_rewind_nolock(&iter);
> +     while (kmsg_dump_get_line_nolock(&iter, 1, buf, sizeof(buf), &len)) {
>               if (skip) {
>                       skip--;
>                       continue;
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 45cb3e9c62c5..e58ccc368348 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -3390,7 +3390,6 @@ EXPORT_SYMBOL_GPL(kmsg_dump_reason_str);
>  void kmsg_dump(enum kmsg_dump_reason reason)
>  {
>       struct kmsg_dumper *dumper;
> -     unsigned long flags;
>  
>       rcu_read_lock();
>       list_for_each_entry_rcu(dumper, &dump_list, list) {
> @@ -3407,21 +3406,15 @@ void kmsg_dump(enum kmsg_dump_reason reason)
>               if (reason > max_reason)
>                       continue;
>  
> -             /* initialize iterator with data about the stored records */
> -             logbuf_lock_irqsave(flags);
> -             dumper->cur_seq = latched_seq_read_nolock(&clear_seq);
> -             dumper->next_seq = prb_next_seq(prb);
> -             logbuf_unlock_irqrestore(flags);
> -
>               /* invoke dumper which will iterate over records */
> -             dumper->dump(dumper, reason);
> +             dumper->dump(reason);
>       }
>       rcu_read_unlock();
>  }
>  
>  /**
>   * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
> - * @dumper: registered kmsg dumper
> + * @iter: kmsg dump iterator
>   * @syslog: include the "<4>" prefixes
>   * @line: buffer to copy the line to
>   * @size: maximum size of the buffer
> @@ -3438,7 +3431,7 @@ void kmsg_dump(enum kmsg_dump_reason reason)
>   *
>   * The function is similar to kmsg_dump_get_line(), but grabs no locks.
>   */
> -bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
> +bool kmsg_dump_get_line_nolock(struct kmsg_dump_iter *iter, bool syslog,
>                              char *line, size_t size, size_t *len)
>  {
>       struct printk_info info;
> @@ -3451,11 +3444,11 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper 
> *dumper, bool syslog,
>  
>       /* Read text or count text lines? */
>       if (line) {
> -             if (!prb_read_valid(prb, dumper->cur_seq, &r))
> +             if (!prb_read_valid(prb, iter->cur_seq, &r))
>                       goto out;
>               l = record_print_text(&r, syslog, printk_time);
>       } else {
> -             if (!prb_read_valid_info(prb, dumper->cur_seq,
> +             if (!prb_read_valid_info(prb, iter->cur_seq,
>                                        &info, &line_count)) {
>                       goto out;
>               }
> @@ -3464,7 +3457,7 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper 
> *dumper, bool syslog,
>  
>       }
>  
> -     dumper->cur_seq = r.info->seq + 1;
> +     iter->cur_seq = r.info->seq + 1;
>       ret = true;
>  out:
>       if (len)
> @@ -3474,7 +3467,7 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper 
> *dumper, bool syslog,
>  
>  /**
>   * kmsg_dump_get_line - retrieve one kmsg log line
> - * @dumper: registered kmsg dumper
> + * @iter: kmsg dump iterator
>   * @syslog: include the "<4>" prefixes
>   * @line: buffer to copy the line to
>   * @size: maximum size of the buffer
> @@ -3489,14 +3482,14 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper 
> *dumper, bool syslog,
>   * A return value of FALSE indicates that there are no more records to
>   * read.
>   */
> -bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
> +bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
>                       char *line, size_t size, size_t *len)
>  {
>       unsigned long flags;
>       bool ret;
>  
>       logbuf_lock_irqsave(flags);
> -     ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
> +     ret = kmsg_dump_get_line_nolock(iter, syslog, line, size, len);
>       logbuf_unlock_irqrestore(flags);
>  
>       return ret;
> @@ -3505,7 +3498,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
>  
>  /**
>   * kmsg_dump_get_buffer - copy kmsg log lines
> - * @dumper: registered kmsg dumper
> + * @iter: kmsg dump iterator
>   * @syslog: include the "<4>" prefixes
>   * @buf: buffer to copy the line to
>   * @size: maximum size of the buffer
> @@ -3522,7 +3515,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
>   * A return value of FALSE indicates that there are no more records to
>   * read.
>   */
> -bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
> +bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
>                         char *buf, size_t size, size_t *len_out)
>  {
>       struct printk_info info;
> @@ -3538,15 +3531,15 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, 
> bool syslog,
>               goto out;
>  
>       logbuf_lock_irqsave(flags);
> -     if (prb_read_valid_info(prb, dumper->cur_seq, &info, NULL)) {
> -             if (info.seq != dumper->cur_seq) {
> +     if (prb_read_valid_info(prb, iter->cur_seq, &info, NULL)) {
> +             if (info.seq != iter->cur_seq) {
>                       /* messages are gone, move to first available one */
> -                     dumper->cur_seq = info.seq;
> +                     iter->cur_seq = info.seq;
>               }
>       }
>  
>       /* last entry */
> -     if (dumper->cur_seq >= dumper->next_seq) {
> +     if (iter->cur_seq >= iter->next_seq) {
>               logbuf_unlock_irqrestore(flags);
>               goto out;
>       }
> @@ -3557,7 +3550,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, 
> bool syslog,
>        * because this function (by way of record_print_text()) will
>        * not write more than size-1 bytes of text into @buf.
>        */
> -     seq = find_first_fitting_seq(dumper->cur_seq, dumper->next_seq,
> +     seq = find_first_fitting_seq(iter->cur_seq, iter->next_seq,
>                                    size - 1, syslog, time);
>  
>       /*
> @@ -3570,7 +3563,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, 
> bool syslog,
>  
>       len = 0;
>       prb_for_each_record(seq, prb, seq, &r) {
> -             if (r.info->seq >= dumper->next_seq)
> +             if (r.info->seq >= iter->next_seq)
>                       break;
>  
>               len += record_print_text(&r, syslog, time);
> @@ -3579,7 +3572,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, 
> bool syslog,
>               prb_rec_init_rd(&r, &info, buf + len, size - len);
>       }
>  
> -     dumper->next_seq = next_seq;
> +     iter->next_seq = next_seq;
>       ret = true;
>       logbuf_unlock_irqrestore(flags);
>  out:
> @@ -3591,7 +3584,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
>  
>  /**
>   * kmsg_dump_rewind_nolock - reset the iterator (unlocked version)
> - * @dumper: registered kmsg dumper
> + * @iter: kmsg dump iterator
>   *
>   * Reset the dumper's iterator so that kmsg_dump_get_line() and
>   * kmsg_dump_get_buffer() can be called again and used multiple
> @@ -3599,26 +3592,26 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
>   *
>   * The function is similar to kmsg_dump_rewind(), but grabs no locks.
>   */
> -void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
> +void kmsg_dump_rewind_nolock(struct kmsg_dump_iter *iter)
>  {
> -     dumper->cur_seq = latched_seq_read_nolock(&clear_seq);
> -     dumper->next_seq = prb_next_seq(prb);
> +     iter->cur_seq = latched_seq_read_nolock(&clear_seq);
> +     iter->next_seq = prb_next_seq(prb);
>  }
>  
>  /**
>   * kmsg_dump_rewind - reset the iterator
> - * @dumper: registered kmsg dumper
> + * @iter: kmsg dump iterator
>   *
>   * Reset the dumper's iterator so that kmsg_dump_get_line() and
>   * kmsg_dump_get_buffer() can be called again and used multiple
>   * times within the same dumper.dump() callback.
>   */
> -void kmsg_dump_rewind(struct kmsg_dumper *dumper)
> +void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
>  {
>       unsigned long flags;
>  
>       logbuf_lock_irqsave(flags);
> -     kmsg_dump_rewind_nolock(dumper);
> +     kmsg_dump_rewind_nolock(iter);
>       logbuf_unlock_irqrestore(flags);
>  }
>  EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
> -- 
> 2.20.1
> 

-- 
Kees Cook


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