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Commit 680e1455 authored by Zheng Yejian's avatar Zheng Yejian Committed by Greg Kroah-Hartman
Browse files

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

[ Upstream commit 26efd79c4624294e553aeaa3439c646729bad084 ]

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 20e5227e ("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 706c81f8 ("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: 706c81f8 ("ftrace: Remove extra helper functions")
Suggested-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarZheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 05ff1d35

kernel/trace/ftrace.c

+31 −14
Original line number Diff line number Diff line
@@ -3037,6 +3037,22 @@ 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)

{
@@ -3075,17 +3091,7 @@ 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;

}
@@ -5627,9 +5633,11 @@ 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;
@@ -5683,8 +5691,10 @@ 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) {
@@ -5698,8 +5708,10 @@ 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;
@@ -5721,6 +5733,11 @@ 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;

}