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Date: Wed, 30 Apr 2014 16:30:44 +0200
From: Jiri Slaby <jslaby@...e.cz>
To: linux-kernel@...r.kernel.org
Cc: jirislaby@...il.com, Vojtech Pavlik <vojtech@...e.cz>,
Michael Matz <matz@...e.de>, Jiri Kosina <jkosina@...e.cz>,
Jiri Slaby <jslaby@...e.cz>,
Steven Rostedt <rostedt@...dmis.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>
Subject: [RFC 11/16] 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 functoins is being used on a
processor 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 disable 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).
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>
---
arch/x86/include/asm/kgr.h | 4 +++-
include/linux/kgr.h | 5 +++--
kernel/kgr.c | 38 ++++++++++++++++++++++++++++++++------
samples/kgr/kgr_patcher.c | 2 +-
4 files changed, 39 insertions(+), 10 deletions(-)
diff --git a/arch/x86/include/asm/kgr.h b/arch/x86/include/asm/kgr.h
index 49daa46243fc..f36661681b33 100644
--- a/arch/x86/include/asm/kgr.h
+++ b/arch/x86/include/asm/kgr.h
@@ -12,8 +12,10 @@ static void _new_function ##_stub_slow (unsigned long ip, unsigned long parent_i
struct ftrace_ops *ops, struct pt_regs *regs) \
{ \
struct kgr_loc_caches *c = ops->private; \
+ bool irq = !!in_interrupt(); \
\
- if (task_thread_info(current)->kgr_in_progress) { \
+ if ((!irq && task_thread_info(current)->kgr_in_progress) || \
+ (irq && !*this_cpu_ptr(c->irq_use_new))) { \
pr_info("kgr: slow stub: calling old code at %lx\n", \
c->old); \
regs->ip = c->old + MCOUNT_INSN_SIZE; \
diff --git a/include/linux/kgr.h b/include/linux/kgr.h
index d72add7f3d5d..ebc6f5bc1ec1 100644
--- a/include/linux/kgr.h
+++ b/include/linux/kgr.h
@@ -19,7 +19,7 @@
#endif
struct kgr_patch {
- char reserved;
+ bool __percpu *irq_use_new;
const struct kgr_patch_fun {
const char *name;
const char *new_name;
@@ -37,6 +37,7 @@ struct kgr_patch {
struct kgr_loc_caches {
unsigned long old;
unsigned long new;
+ bool __percpu *irq_use_new;
};
#define KGR_PATCHED_FUNCTION(patch, _name, _new_function) \
@@ -65,7 +66,7 @@ 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 *);
#endif /* CONFIG_KGR */
#endif /* LINUX_KGR_H */
diff --git a/kernel/kgr.c b/kernel/kgr.c
index ea63e857a78a..ff5afaf6f0e7 100644
--- a/kernel/kgr.c
+++ b/kernel/kgr.c
@@ -18,6 +18,7 @@
#include <linux/kallsyms.h>
#include <linux/kgr.h>
#include <linux/module.h>
+#include <linux/percpu.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/sort.h>
@@ -25,7 +26,8 @@
#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;
@@ -57,7 +59,7 @@ 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
@@ -67,6 +69,7 @@ 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)
@@ -139,6 +142,20 @@ 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;
@@ -184,7 +201,8 @@ static int kgr_init_ftrace_ops(const struct kgr_patch_fun *patch_fun)
return 0;
}
-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;
@@ -205,6 +223,7 @@ 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) {
@@ -243,9 +262,9 @@ 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;
@@ -254,6 +273,12 @@ int kgr_start_patching(const struct kgr_patch *patch)
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");
@@ -264,7 +289,7 @@ int kgr_start_patching(const struct kgr_patch *patch)
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
@@ -281,6 +306,7 @@ int kgr_start_patching(const struct kgr_patch *patch)
kgr_patch = patch;
mutex_unlock(&kgr_in_progress_lock);
+ kgr_handle_irqs();
kgr_handle_processes();
/*
diff --git a/samples/kgr/kgr_patcher.c b/samples/kgr/kgr_patcher.c
index 828543e36f3f..b1465cff8d5b 100644
--- a/samples/kgr/kgr_patcher.c
+++ b/samples/kgr/kgr_patcher.c
@@ -68,7 +68,7 @@ static bool new_capable(int cap)
}
KGR_PATCHED_FUNCTION(patch, capable, new_capable);
-static const struct kgr_patch patch = {
+static struct kgr_patch patch = {
.patches = {
KGR_PATCH(SyS_iopl),
KGR_PATCH(capable),
--
1.9.2
--
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