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Date: Wed, 25 Jun 2014 13:07:05 +0200
From: Jiri Slaby <jslaby@...e.cz>
To: linux-kernel@...r.kernel.org
Cc: tj@...nel.org, rostedt@...dmis.org, mingo@...hat.com,
akpm@...ux-foundation.org, andi@...stfloor.org,
paulmck@...ux.vnet.ibm.com, pavel@....cz, jirislaby@...il.com,
Vojtech Pavlik <vojtech@...e.cz>, Michael Matz <matz@...e.de>,
Jiri Kosina <jkosina@...e.cz>, Jiri Slaby <jslaby@...e.cz>,
Frederic Weisbecker <fweisbec@...il.com>,
Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH -repost 11/21] kgr: handle irqs
Introduce a per-cpu flag to check whether we should use the old or new
function in the slow stub. The new function starts being used on a
processor only after a scheduled function sets the flag via
schedule_on_each_cpu. Presumably this happens in the process context,
no irq is running. And protect the flag setting by disabling
interrupts so that we 1) have a barrier and 2) no interrupt triggers
while setting the flag (but the set should be atomic anyway as it is
bool).
js: fix fail paths
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
---
include/linux/kgraft.h | 6 +++--
kernel/kgraft.c | 59 ++++++++++++++++++++++++++++++++---------
samples/kgraft/kgraft_patcher.c | 2 +-
3 files changed, 51 insertions(+), 16 deletions(-)
diff --git a/include/linux/kgraft.h b/include/linux/kgraft.h
index e87623fe74ad..93bb1c50e079 100644
--- a/include/linux/kgraft.h
+++ b/include/linux/kgraft.h
@@ -18,6 +18,7 @@
#define LINUX_KGR_H
#include <linux/bitops.h>
+#include <linux/compiler.h>
#include <linux/ftrace.h>
#include <linux/sched.h>
@@ -28,7 +29,7 @@
#define KGR_TIMEOUT 30
struct kgr_patch {
- char reserved;
+ bool __percpu *irq_use_new;
const struct kgr_patch_fun {
const char *name;
const char *new_name;
@@ -47,6 +48,7 @@ struct kgr_patch {
struct kgr_loc_caches {
unsigned long old;
unsigned long new;
+ bool __percpu *irq_use_new;
};
#define KGR_PATCHED_FUNCTION(_name, _new_function) \
@@ -67,7 +69,7 @@ struct kgr_loc_caches {
#define KGR_PATCH(name) &__kgr_patch_ ## name
#define KGR_PATCH_END NULL
-extern int kgr_start_patching(const struct kgr_patch *);
+extern int kgr_start_patching(struct kgr_patch *);
static inline void kgr_mark_task_in_progress(struct task_struct *p)
{
diff --git a/kernel/kgraft.c b/kernel/kgraft.c
index d21eaad8d48d..fd0ded7ce725 100644
--- a/kernel/kgraft.c
+++ b/kernel/kgraft.c
@@ -15,9 +15,11 @@
*/
#include <linux/ftrace.h>
+#include <linux/hardirq.h> /* for in_interrupt() */
#include <linux/kallsyms.h>
#include <linux/kgraft.h>
#include <linux/module.h>
+#include <linux/percpu.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/sort.h>
@@ -25,7 +27,8 @@
#include <linux/types.h>
#include <linux/workqueue.h>
-static int kgr_patch_code(const struct kgr_patch_fun *patch_fun, bool final);
+static int kgr_patch_code(const struct kgr_patch *patch,
+ const struct kgr_patch_fun *patch_fun, bool final);
static void kgr_work_fn(struct work_struct *work);
static struct workqueue_struct *kgr_wq;
@@ -52,8 +55,10 @@ static void kgr_stub_slow(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct pt_regs *regs)
{
struct kgr_loc_caches *c = ops->private;
+ bool irq = !!in_interrupt();
- if (kgr_task_in_progress(current)) {
+ if ((!irq && kgr_task_in_progress(current)) ||
+ (irq && !*this_cpu_ptr(c->irq_use_new))) {
pr_info("kgr: slow stub: calling old code at %lx\n",
c->old);
kgr_set_regs_ip(regs, c->old + MCOUNT_INSN_SIZE);
@@ -86,7 +91,7 @@ static void kgr_finalize(void)
const struct kgr_patch_fun *const *patch_fun;
for (patch_fun = kgr_patch->patches; *patch_fun; patch_fun++) {
- int ret = kgr_patch_code(*patch_fun, true);
+ int ret = kgr_patch_code(kgr_patch, *patch_fun, true);
/*
* In case any of the symbol resolutions in the set
* has failed, patch all the previously replaced fentry
@@ -96,6 +101,7 @@ static void kgr_finalize(void)
pr_err("kgr: finalize for %s failed, trying to continue\n",
(*patch_fun)->name);
}
+ free_percpu(kgr_patch->irq_use_new);
}
static void kgr_work_fn(struct work_struct *work)
@@ -167,6 +173,20 @@ static unsigned long kgr_get_fentry_loc(const char *f_name)
return fentry_loc;
}
+static void kgr_handle_irq_cpu(struct work_struct *work)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ *this_cpu_ptr(kgr_patch->irq_use_new) = true;
+ local_irq_restore(flags);
+}
+
+static void kgr_handle_irqs(void)
+{
+ schedule_on_each_cpu(kgr_handle_irq_cpu);
+}
+
static int kgr_init_ftrace_ops(const struct kgr_patch_fun *patch_fun)
{
struct kgr_loc_caches *caches;
@@ -220,7 +240,8 @@ free_caches:
return ret;
}
-static int kgr_patch_code(const struct kgr_patch_fun *patch_fun, bool final)
+static int kgr_patch_code(const struct kgr_patch *patch,
+ const struct kgr_patch_fun *patch_fun, bool final)
{
struct ftrace_ops *new_ops;
struct kgr_loc_caches *caches;
@@ -241,6 +262,7 @@ static int kgr_patch_code(const struct kgr_patch_fun *patch_fun, bool final)
/* Flip the switch */
caches = new_ops->private;
+ caches->irq_use_new = patch->irq_use_new;
fentry_loc = caches->old;
err = ftrace_set_filter_ip(new_ops, fentry_loc, 0, 0);
if (err) {
@@ -280,28 +302,33 @@ static int kgr_patch_code(const struct kgr_patch_fun *patch_fun, bool final)
* kgr_start_patching -- the entry for a kgraft patch
* @patch: patch to be applied
*
- * Start patching of code that is not running in IRQ context.
+ * Start patching of code.
*/
-int kgr_start_patching(const struct kgr_patch *patch)
+int kgr_start_patching(struct kgr_patch *patch)
{
const struct kgr_patch_fun *const *patch_fun;
+ int ret;
if (!kgr_initialized) {
pr_err("kgr: can't patch, not initialized\n");
return -EINVAL;
}
+ patch->irq_use_new = alloc_percpu(bool);
+ if (!patch->irq_use_new) {
+ pr_err("kgr: can't patch, cannot allocate percpu data\n");
+ return -ENOMEM;
+ }
+
mutex_lock(&kgr_in_progress_lock);
if (kgr_in_progress) {
pr_err("kgr: can't patch, another patching not yet finalized\n");
- mutex_unlock(&kgr_in_progress_lock);
- return -EAGAIN;
+ ret = -EAGAIN;
+ goto unlock_free;
}
for (patch_fun = patch->patches; *patch_fun; patch_fun++) {
- int ret;
-
- ret = kgr_patch_code(*patch_fun, false);
+ ret = kgr_patch_code(patch, *patch_fun, false);
/*
* In case any of the symbol resolutions in the set
* has failed, patch all the previously replaced fentry
@@ -311,14 +338,14 @@ int kgr_start_patching(const struct kgr_patch *patch)
for (patch_fun--; patch_fun >= patch->patches;
patch_fun--)
unregister_ftrace_function((*patch_fun)->ftrace_ops_slow);
- mutex_unlock(&kgr_in_progress_lock);
- return ret;
+ goto unlock_free;
}
}
kgr_in_progress = true;
kgr_patch = patch;
mutex_unlock(&kgr_in_progress_lock);
+ kgr_handle_irqs();
kgr_handle_processes();
/*
@@ -327,6 +354,12 @@ int kgr_start_patching(const struct kgr_patch *patch)
queue_delayed_work(kgr_wq, &kgr_work, 5 * HZ);
return 0;
+unlock_free:
+ mutex_unlock(&kgr_in_progress_lock);
+
+ free_percpu(patch->irq_use_new);
+
+ return ret;
}
EXPORT_SYMBOL_GPL(kgr_start_patching);
diff --git a/samples/kgraft/kgraft_patcher.c b/samples/kgraft/kgraft_patcher.c
index abb0c05bf739..7cb94f728128 100644
--- a/samples/kgraft/kgraft_patcher.c
+++ b/samples/kgraft/kgraft_patcher.c
@@ -63,7 +63,7 @@ static bool new_capable(int cap)
}
KGR_PATCHED_FUNCTION(capable, new_capable);
-static const struct kgr_patch patch = {
+static struct kgr_patch patch = {
.patches = {
KGR_PATCH(SyS_iopl),
KGR_PATCH(capable),
--
2.0.0
--
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