Commit e92606fa authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Peter Zijlstra
Browse files

livepatch: Convert stack entries array to percpu 



The entries array in klp_check_stack() is static local because it's too
big to be reasonably allocated on the stack.  Serialized access is
enforced by the klp_mutex.

In preparation for calling klp_check_stack() without the mutex (from
cond_resched), convert it to a percpu variable.

Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230313233346.kayh4t2lpicjkpsv@treble
parent 41abdba9

kernel/livepatch/transition.c

+7 −2
Original line number Diff line number Diff line
@@ -14,6 +14,8 @@ 
#include "transition.h"



#define MAX_STACK_ENTRIES  100

DEFINE_PER_CPU(unsigned long[MAX_STACK_ENTRIES], klp_stack_entries);



#define STACK_ERR_BUF_SIZE 128



#define SIGNALS_TIMEOUT 15
@@ -240,12 +242,15 @@ static int klp_check_stack_func(struct klp_func *func, unsigned long *entries, 
 */

static int klp_check_stack(struct task_struct *task, const char **oldname)

{

	static unsigned long entries[MAX_STACK_ENTRIES];

	unsigned long *entries = this_cpu_ptr(klp_stack_entries);

	struct klp_object *obj;

	struct klp_func *func;

	int ret, nr_entries;



	ret = stack_trace_save_tsk_reliable(task, entries, ARRAY_SIZE(entries));

	/* Protect 'klp_stack_entries' */

	lockdep_assert_preemption_disabled();



	ret = stack_trace_save_tsk_reliable(task, entries, MAX_STACK_ENTRIES);

	if (ret < 0)

		return -EINVAL;

	nr_entries = ret;