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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: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230313233346.kayh4t2lpicjkpsv@treble
This commit is contained in:
Josh Poimboeuf 2023-03-13 16:33:46 -07:00 committed by Peter Zijlstra
parent 41abdba937
commit e92606fa17
1 changed files with 7 additions and 2 deletions
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9
kernel/livepatch/transition.c
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@ -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;