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sched,livepatch: Use task_call_func()

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Instead of frobbing around with scheduler internals, use the shiny new
task_call_func() interface.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929152428.709906138@infradead.org
This commit is contained in:
Peter Zijlstra 2021-09-21 21:54:32 +02:00
parent 9b3c4ab304
commit 00619f7c65
1 changed files with 44 additions and 46 deletions
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90
kernel/livepatch/transition.c
View File

@ -13,7 +13,6 @@
#include "core.h"
#include "patch.h"
#include "transition.h"
#include "../sched/sched.h"
#define MAX_STACK_ENTRIES 100
#define STACK_ERR_BUF_SIZE 128
@ -240,7 +239,7 @@ static int klp_check_stack_func(struct klp_func *func, unsigned long *entries,
* Determine whether it's safe to transition the task to the target patch state
* by looking for any to-be-patched or to-be-unpatched functions on its stack.
*/
static int klp_check_stack(struct task_struct *task, char *err_buf)
static int klp_check_stack(struct task_struct *task, const char **oldname)
{
static unsigned long entries[MAX_STACK_ENTRIES];
struct klp_object *obj;
@ -248,12 +247,8 @@ static int klp_check_stack(struct task_struct *task, char *err_buf)
int ret, nr_entries;
ret = stack_trace_save_tsk_reliable(task, entries, ARRAY_SIZE(entries));
if (ret < 0) {
snprintf(err_buf, STACK_ERR_BUF_SIZE,
"%s: %s:%d has an unreliable stack\n",
__func__, task->comm, task->pid);
return ret;
}
if (ret < 0)
return -EINVAL;
nr_entries = ret;
klp_for_each_object(klp_transition_patch, obj) {
@ -262,11 +257,8 @@ static int klp_check_stack(struct task_struct *task, char *err_buf)
klp_for_each_func(obj, func) {
ret = klp_check_stack_func(func, entries, nr_entries);
if (ret) {
snprintf(err_buf, STACK_ERR_BUF_SIZE,
"%s: %s:%d is sleeping on function %s\n",
__func__, task->comm, task->pid,
func->old_name);
return ret;
*oldname = func->old_name;
return -EADDRINUSE;
}
}
}
@ -274,6 +266,22 @@ static int klp_check_stack(struct task_struct *task, char *err_buf)
return 0;
}
static int klp_check_and_switch_task(struct task_struct *task, void *arg)
{
int ret;
if (task_curr(task) && task != current)
return -EBUSY;
ret = klp_check_stack(task, arg);
if (ret)
return ret;
clear_tsk_thread_flag(task, TIF_PATCH_PENDING);
task->patch_state = klp_target_state;
return 0;
}
/*
* Try to safely switch a task to the target patch state. If it's currently
* running, or it's sleeping on a to-be-patched or to-be-unpatched function, or
@ -281,13 +289,8 @@ static int klp_check_stack(struct task_struct *task, char *err_buf)
*/
static bool klp_try_switch_task(struct task_struct *task)
{
static char err_buf[STACK_ERR_BUF_SIZE];
struct rq *rq;
struct rq_flags flags;
const char *old_name;
int ret;
bool success = false;
err_buf[0] = '\0';
/* check if this task has already switched over */
if (task->patch_state == klp_target_state)
@ -305,36 +308,31 @@ static bool klp_try_switch_task(struct task_struct *task)
* functions. If all goes well, switch the task to the target patch
* state.
*/
rq = task_rq_lock(task, &flags);
ret = task_call_func(task, klp_check_and_switch_task, &old_name);
switch (ret) {
case 0: /* success */
break;
if (task_running(rq, task) && task != current) {
snprintf(err_buf, STACK_ERR_BUF_SIZE,
"%s: %s:%d is running\n", __func__, task->comm,
task->pid);
goto done;
case -EBUSY: /* klp_check_and_switch_task() */
pr_debug("%s: %s:%d is running\n",
__func__, task->comm, task->pid);
break;
case -EINVAL: /* klp_check_and_switch_task() */
pr_debug("%s: %s:%d has an unreliable stack\n",
__func__, task->comm, task->pid);
break;
case -EADDRINUSE: /* klp_check_and_switch_task() */
pr_debug("%s: %s:%d is sleeping on function %s\n",
__func__, task->comm, task->pid, old_name);
break;
default:
pr_debug("%s: Unknown error code (%d) when trying to switch %s:%d\n",
__func__, ret, task->comm, task->pid);
break;
}
ret = klp_check_stack(task, err_buf);
if (ret)
goto done;
success = true;
clear_tsk_thread_flag(task, TIF_PATCH_PENDING);
task->patch_state = klp_target_state;
done:
task_rq_unlock(rq, task, &flags);
/*
* Due to console deadlock issues, pr_debug() can't be used while
* holding the task rq lock. Instead we have to use a temporary buffer
* and print the debug message after releasing the lock.
*/
if (err_buf[0] != '\0')
pr_debug("%s", err_buf);
return success;
return !ret;
}
/*