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ftrace: Fix possible warning on checking all pages used in ftrace_process_locs() 

As comments in ftrace_process_locs(), there may be NULL pointers in
mcount_loc section:
 > Some architecture linkers will pad between
 > the different mcount_loc sections of different
 > object files to satisfy alignments.
 > Skip any NULL pointers.

After commit 20e5227e9f ("ftrace: allow NULL pointers in mcount_loc"),
NULL pointers will be accounted when allocating ftrace pages but skipped
before adding into ftrace pages, this may result in some pages not being
used. Then after commit 706c81f87f ("ftrace: Remove extra helper
functions"), warning may occur at:
  WARN_ON(pg->next);

To fix it, only warn for case that no pointers skipped but pages not used
up, then free those unused pages after releasing ftrace_lock.

Link: https://lore.kernel.org/linux-trace-kernel/20230712060452.3175675-1-zhengyejian1@huawei.com

Cc: stable@vger.kernel.org
Fixes: 706c81f87f ("ftrace: Remove extra helper functions")
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Zheng Yejian 2023-07-12 14:04:52 +08:00 committed by Steven Rostedt (Google)
parent 7e42907f3a
commit 26efd79c46
1 changed files with 31 additions and 14 deletions
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45
kernel/trace/ftrace.c
View File

@ -3305,6 +3305,22 @@ static int ftrace_allocate_records(struct ftrace_page *pg, int count)
return cnt;
}
static void ftrace_free_pages(struct ftrace_page *pages)
{
struct ftrace_page *pg = pages;
while (pg) {
if (pg->records) {
free_pages((unsigned long)pg->records, pg->order);
ftrace_number_of_pages -= 1 << pg->order;
}
pages = pg->next;
kfree(pg);
pg = pages;
ftrace_number_of_groups--;
}
}
static struct ftrace_page *
ftrace_allocate_pages(unsigned long num_to_init)
{
@ -3343,17 +3359,7 @@ ftrace_allocate_pages(unsigned long num_to_init)
return start_pg;
free_pages:
pg = start_pg;
while (pg) {
if (pg->records) {
free_pages((unsigned long)pg->records, pg->order);
ftrace_number_of_pages -= 1 << pg->order;
}
start_pg = pg->next;
kfree(pg);
pg = start_pg;
ftrace_number_of_groups--;
}
ftrace_free_pages(start_pg);
pr_info("ftrace: FAILED to allocate memory for functions\n");
return NULL;
}
@ -6471,9 +6477,11 @@ static int ftrace_process_locs(struct module *mod,
unsigned long *start,
unsigned long *end)
{
struct ftrace_page *pg_unuse = NULL;
struct ftrace_page *start_pg;
struct ftrace_page *pg;
struct dyn_ftrace *rec;
unsigned long skipped = 0;
unsigned long count;
unsigned long *p;
unsigned long addr;
@ -6536,8 +6544,10 @@ static int ftrace_process_locs(struct module *mod,
* object files to satisfy alignments.
* Skip any NULL pointers.
*/
if (!addr)
if (!addr) {
skipped++;
continue;
}
end_offset = (pg->index+1) * sizeof(pg->records[0]);
if (end_offset > PAGE_SIZE << pg->order) {
@ -6551,8 +6561,10 @@ static int ftrace_process_locs(struct module *mod,
rec->ip = addr;
}
/* We should have used all pages */
WARN_ON(pg->next);
if (pg->next) {
pg_unuse = pg->next;
pg->next = NULL;
}
/* Assign the last page to ftrace_pages */
ftrace_pages = pg;
@ -6574,6 +6586,11 @@ static int ftrace_process_locs(struct module *mod,
out:
mutex_unlock(&ftrace_lock);
/* We should have used all pages unless we skipped some */
if (pg_unuse) {
WARN_ON(!skipped);
ftrace_free_pages(pg_unuse);
}
return ret;
}