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s390/debug: keep debug data on resize

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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>
This commit is contained in:
Peter Oberparleiter 2021-08-13 15:05:02 +02:00 committed by Heiko Carstens
parent 2879048c7e
commit 1204777867
1 changed files with 53 additions and 21 deletions
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74
arch/s390/kernel/debug.c
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@ -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.