From 4260e0e5510158d704898603331e5365ebe957de Mon Sep 17 00:00:00 2001 From: John Ogness Date: Wed, 3 Mar 2021 11:15:19 +0100 Subject: printk: consolidate kmsg_dump_get_buffer/syslog_print_all code The logic for finding records to fit into a buffer is the same for kmsg_dump_get_buffer() and syslog_print_all(). Introduce a helper function find_first_fitting_seq() to handle this logic. Signed-off-by: John Ogness Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20210303101528.29901-7-john.ogness@linutronix.de --- kernel/printk/printk.c | 87 +++++++++++++++++++++++++++++--------------------- 1 file changed, 50 insertions(+), 37 deletions(-) (limited to 'kernel/printk') diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index ed678d84dc51..9a5f9ccc46ea 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1421,6 +1421,50 @@ static size_t get_record_print_text_size(struct printk_info *info, return ((prefix_len * line_count) + info->text_len + 1); } +/* + * Beginning with @start_seq, find the first record where it and all following + * records up to (but not including) @max_seq fit into @size. + * + * @max_seq is simply an upper bound and does not need to exist. If the caller + * does not require an upper bound, -1 can be used for @max_seq. + */ +static u64 find_first_fitting_seq(u64 start_seq, u64 max_seq, size_t size, + bool syslog, bool time) +{ + struct printk_info info; + unsigned int line_count; + size_t len = 0; + u64 seq; + + /* Determine the size of the records up to @max_seq. */ + prb_for_each_info(start_seq, prb, seq, &info, &line_count) { + if (info.seq >= max_seq) + break; + len += get_record_print_text_size(&info, line_count, syslog, time); + } + + /* + * Adjust the upper bound for the next loop to avoid subtracting + * lengths that were never added. + */ + if (seq < max_seq) + max_seq = seq; + + /* + * Move first record forward until length fits into the buffer. Ignore + * newest messages that were not counted in the above cycle. Messages + * might appear and get lost in the meantime. This is a best effort + * that prevents an infinite loop that could occur with a retry. + */ + prb_for_each_info(start_seq, prb, seq, &info, &line_count) { + if (len <= size || info.seq >= max_seq) + break; + len -= get_record_print_text_size(&info, line_count, syslog, time); + } + + return seq; +} + static int syslog_print(char __user *buf, int size) { struct printk_info info; @@ -1492,9 +1536,7 @@ static int syslog_print(char __user *buf, int size) static int syslog_print_all(char __user *buf, int size, bool clear) { struct printk_info info; - unsigned int line_count; struct printk_record r; - u64 max_seq; char *text; int len = 0; u64 seq; @@ -1510,21 +1552,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) * Find first record that fits, including all following records, * into the user-provided buffer for this dump. */ - prb_for_each_info(clear_seq, prb, seq, &info, &line_count) - len += get_record_print_text_size(&info, line_count, true, time); - - /* - * Set an upper bound for the next loop to avoid subtracting lengths - * that were never added. - */ - max_seq = seq; - - /* move first record forward until length fits into the buffer */ - prb_for_each_info(clear_seq, prb, seq, &info, &line_count) { - if (len <= size || info.seq >= max_seq) - break; - len -= get_record_print_text_size(&info, line_count, true, time); - } + seq = find_first_fitting_seq(clear_seq, -1, size, true, time); prb_rec_init_rd(&r, &info, text, LOG_LINE_MAX + PREFIX_MAX); @@ -3427,7 +3455,6 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, char *buf, size_t size, size_t *len_out) { struct printk_info info; - unsigned int line_count; struct printk_record r; unsigned long flags; u64 seq; @@ -3455,26 +3482,12 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, /* * Find first record that fits, including all following records, - * into the user-provided buffer for this dump. + * into the user-provided buffer for this dump. Pass in size-1 + * because this function (by way of record_print_text()) will + * not write more than size-1 bytes of text into @buf. */ - - prb_for_each_info(dumper->cur_seq, prb, seq, &info, &line_count) { - if (info.seq >= dumper->next_seq) - break; - len += get_record_print_text_size(&info, line_count, syslog, time); - } - - /* - * Move first record forward until length fits into the buffer. Ignore - * newest messages that were not counted in the above cycle. Messages - * might appear and get lost in the meantime. This is the best effort - * that prevents an infinite loop. - */ - prb_for_each_info(dumper->cur_seq, prb, seq, &info, &line_count) { - if (len < size || info.seq >= dumper->next_seq) - break; - len -= get_record_print_text_size(&info, line_count, syslog, time); - } + seq = find_first_fitting_seq(dumper->cur_seq, dumper->next_seq, + size - 1, syslog, time); /* * Next kmsg_dump_get_buffer() invocation will dump block of -- cgit v1.2.3