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-rw-r--r--features/rt/printk-consolidate-kmsg_dump_get_buffer-syslog_print.patch146
1 files changed, 146 insertions, 0 deletions
diff --git a/features/rt/printk-consolidate-kmsg_dump_get_buffer-syslog_print.patch b/features/rt/printk-consolidate-kmsg_dump_get_buffer-syslog_print.patch
new file mode 100644
index 00000000..97ae80c8
--- /dev/null
+++ b/features/rt/printk-consolidate-kmsg_dump_get_buffer-syslog_print.patch
@@ -0,0 +1,146 @@
+From b29f148df0ca450ed3a53ed20ca0bdb921c54c9a Mon Sep 17 00:00:00 2001
+From: John Ogness <john.ogness@linutronix.de>
+Date: Wed, 13 Jan 2021 11:29:53 +0106
+Subject: [PATCH 010/191] 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 <john.ogness@linutronix.de>
+---
+ kernel/printk/printk.c | 87 ++++++++++++++++++++++++------------------
+ 1 file changed, 50 insertions(+), 37 deletions(-)
+
+diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
+index 3f17ff13fd51..ff16a29aa620 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
+--
+2.19.1
+