[PATCH 5.10 037/236] s390/debug: keep debug data on resize

Greg Kroah-Hartman
2021-09-13T13:37:57Z

From: Peter Oberparleiter <oberpar@linux.ibm.com>

[ Upstream commit 1204777867e8486a88dbb4793fe256b31ea05eeb ]

Any previously recorded s390dbf debug data is reset when a debug area
is resized using the 'pages' sysfs attribute. This can make
live-debugging unnecessarily complex.

Fix this by copying existing debug data to the newly allocated debug
area when resizing.

Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/s390/kernel/debug.c | 74 ++++++++++++++++++++++++++++------------
1 file changed, 53 insertions(+), 21 deletions(-)

diff --git a/arch/s390/kernel/debug.c b/arch/s390/kernel/debug.c
index b6619ae9a3e0..e392d3e42b1d 100644
--- a/arch/s390/kernel/debug.c
+++ b/arch/s390/kernel/debug.c
@@ -24,6 +24,7 @@
#include <linux/export.h>
#include <linux/init.h>
#include <linux/fs.h>
+#include <linux/minmax.h>
#include <linux/debugfs.h>

#include <asm/debug.h>
@@ -92,6 +93,8 @@ static int debug_hex_ascii_format_fn(debug_info_t *id, struct debug_view *view,
char *out_buf, const char *in_buf);
static int debug_sprintf_format_fn(debug_info_t *id, struct debug_view *view,
char *out_buf, debug_sprintf_entry_t *curr_event);
+static void debug_areas_swap(debug_info_t *a, debug_info_t *b);
+static void debug_events_append(debug_info_t *dest, debug_info_t *src);

/* globals */

@@ -726,35 +729,28 @@ EXPORT_SYMBOL(debug_unregister);
*/
static int debug_set_size(debug_info_t *id, int nr_areas, int pages_per_area)
{
- debug_entry_t ***new_areas;
+ debug_info_t *new_id;
unsigned long flags;
- int rc = 0;

if (!id || (nr_areas <= 0) || (pages_per_area < 0))
return -EINVAL;
- if (pages_per_area > 0) {
- new_areas = debug_areas_alloc(pages_per_area, nr_areas);
- if (!new_areas) {
- pr_info("Allocating memory for %i pages failed\n",
- pages_per_area);
- rc = -ENOMEM;
- goto out;
- }
- } else {
- new_areas = NULL;
+
+ new_id = debug_info_alloc("", pages_per_area, nr_areas, id->buf_size,
+ id->level, ALL_AREAS);
+ if (!new_id) {
+ pr_info("Allocating memory for %i pages failed\n",
+ pages_per_area);
+ return -ENOMEM;
}
+
spin_lock_irqsave(&id->lock, flags);
- debug_areas_free(id);
- id->areas = new_areas;
- id->nr_areas = nr_areas;
- id->pages_per_area = pages_per_area;
- id->active_area = 0;
- memset(id->active_entries, 0, sizeof(int)*id->nr_areas);
- memset(id->active_pages, 0, sizeof(int)*id->nr_areas);
+ debug_events_append(new_id, id);
+ debug_areas_swap(new_id, id);
+ debug_info_free(new_id);
spin_unlock_irqrestore(&id->lock, flags);
pr_info("%s: set new size (%i pages)\n", id->name, pages_per_area);
-out:
- return rc;
+
+ return 0;
}

/**
@@ -821,6 +817,42 @@ static inline debug_entry_t *get_active_entry(debug_info_t *id)
id->active_entries[id->active_area]);
}

+/* Swap debug areas of a and b. */
+static void debug_areas_swap(debug_info_t *a, debug_info_t *b)
+{
+ swap(a->nr_areas, b->nr_areas);
+ swap(a->pages_per_area, b->pages_per_area);
+ swap(a->areas, b->areas);
+ swap(a->active_area, b->active_area);
+ swap(a->active_pages, b->active_pages);
+ swap(a->active_entries, b->active_entries);
+}
+
+/* Append all debug events in active area from source to destination log. */
+static void debug_events_append(debug_info_t *dest, debug_info_t *src)
+{
+ debug_entry_t *from, *to, *last;
+
+ if (!src->areas || !dest->areas)
+ return;
+
+ /* Loop over all entries in src, starting with oldest. */
+ from = get_active_entry(src);
+ last = from;
+ do {
+ if (from->clock != 0LL) {
+ to = get_active_entry(dest);
+ memset(to, 0, dest->entry_size);
+ memcpy(to, from, min(src->entry_size,
+ dest->entry_size));
+ proceed_active_entry(dest);
+ }
+
+ proceed_active_entry(src);
+ from = get_active_entry(src);
+ } while (from != last);
+}
+
/*
* debug_finish_entry:
* - set timestamp, caller address, cpu number etc.
--
2.30.2