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Date: Mon, 26 Dec 2016 23:50:23 +0900
From: Masami Hiramatsu <mhiramat@...nel.org>
To: Ingo Molnar <mingo@...hat.com>,
Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
linux-kernel@...r.kernel.org,
Peter Zijlstra <peterz@...radead.org>,
Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
Thomas Gleixner <tglx@...utronix.de>,
"H . Peter Anvin" <hpa@...or.com>,
Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH tip/master] kprobes: extable: Identify kprobes' insn-slots as kernel text area
Make __kernel_text_address()/kernel_text_address() returns
true if the given address is on a kprobe's instruction slot,
which is generated by kprobes as a trampoline code.
This can help stacktraces to determine the address is on a
text area or not.
To implement this without any sleep in is_kprobe_*_slot(),
this also modify insn_cache page list as a rcu list. It may
increase processing deley (not processing time) for garbage
slot collection, because it requires to wait an additional
rcu grance period when freeing a page from the list.
However, since it is not a hot path, we may not take care of it.
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
Hi Josh, could check this patch fixes your issue? It will
enable unwinder code to validate return address by using
__kernel_text_address() again.
---
include/linux/kprobes.h | 14 +++++++++
kernel/extable.c | 9 +++++-
kernel/kprobes.c | 70 ++++++++++++++++++++++++++++++++++++-----------
3 files changed, 74 insertions(+), 19 deletions(-)
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 8f68490..400c5c1 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -281,6 +281,9 @@ struct kprobe_insn_cache {
extern kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c);
extern void __free_insn_slot(struct kprobe_insn_cache *c,
kprobe_opcode_t *slot, int dirty);
+/* sleep-less address checking routine */
+extern bool __is_insn_slot_addr(struct kprobe_insn_cache *c,
+ unsigned long addr);
#define DEFINE_INSN_CACHE_OPS(__name) \
extern struct kprobe_insn_cache kprobe_##__name##_slots; \
@@ -294,6 +297,11 @@ static inline void free_##__name##_slot(kprobe_opcode_t *slot, int dirty)\
{ \
__free_insn_slot(&kprobe_##__name##_slots, slot, dirty); \
} \
+ \
+static inline bool is_kprobe_##__name##_slot(unsigned long addr) \
+{ \
+ return __is_insn_slot_addr(&kprobe_##__name##_slots, addr); \
+}
DEFINE_INSN_CACHE_OPS(insn);
@@ -330,7 +338,11 @@ extern int proc_kprobes_optimization_handler(struct ctl_table *table,
int write, void __user *buffer,
size_t *length, loff_t *ppos);
#endif
-
+#else /* CONFIG_OPTPROBES */
+static inline bool is_kprobe_optinsn_slot(unsigned long addr)
+{
+ return false;
+}
#endif /* CONFIG_OPTPROBES */
#ifdef CONFIG_KPROBES_ON_FTRACE
extern void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
diff --git a/kernel/extable.c b/kernel/extable.c
index e820cce..81c9633 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -20,6 +20,7 @@
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/init.h>
+#include <linux/kprobes.h>
#include <asm/sections.h>
#include <asm/uaccess.h>
@@ -104,6 +105,8 @@ int __kernel_text_address(unsigned long addr)
return 1;
if (is_ftrace_trampoline(addr))
return 1;
+ if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
+ return 1;
/*
* There might be init symbols in saved stacktraces.
* Give those symbols a chance to be printed in
@@ -123,7 +126,11 @@ int kernel_text_address(unsigned long addr)
return 1;
if (is_module_text_address(addr))
return 1;
- return is_ftrace_trampoline(addr);
+ if (is_ftrace_trampoline(addr))
+ return 1;
+ if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr))
+ return 1;
+ return 0;
}
/*
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index d630954..1bd1c17 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -149,9 +149,11 @@ kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c)
struct kprobe_insn_page *kip;
kprobe_opcode_t *slot = NULL;
+ /* Since the slot array is not protected by rcu, we need a mutex */
mutex_lock(&c->mutex);
retry:
- list_for_each_entry(kip, &c->pages, list) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(kip, &c->pages, list) {
if (kip->nused < slots_per_page(c)) {
int i;
for (i = 0; i < slots_per_page(c); i++) {
@@ -167,6 +169,7 @@ kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c)
WARN_ON(1);
}
}
+ rcu_read_unlock();
/* If there are any garbage slots, collect it and try again. */
if (c->nr_garbage && collect_garbage_slots(c) == 0)
@@ -193,13 +196,15 @@ kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c)
kip->nused = 1;
kip->ngarbage = 0;
kip->cache = c;
- list_add(&kip->list, &c->pages);
+ list_add_rcu(&kip->list, &c->pages);
slot = kip->insns;
out:
mutex_unlock(&c->mutex);
return slot;
}
+
+
/* Return 1 if all garbages are collected, otherwise 0. */
static int collect_one_slot(struct kprobe_insn_page *kip, int idx)
{
@@ -213,7 +218,8 @@ static int collect_one_slot(struct kprobe_insn_page *kip, int idx)
* next time somebody inserts a probe.
*/
if (!list_is_singular(&kip->list)) {
- list_del(&kip->list);
+ list_del_rcu(&kip->list);
+ synchronize_rcu();
kip->cache->free(kip->insns);
kfree(kip);
}
@@ -248,29 +254,59 @@ void __free_insn_slot(struct kprobe_insn_cache *c,
kprobe_opcode_t *slot, int dirty)
{
struct kprobe_insn_page *kip;
+ long idx;
mutex_lock(&c->mutex);
- list_for_each_entry(kip, &c->pages, list) {
- long idx = ((long)slot - (long)kip->insns) /
- (c->insn_size * sizeof(kprobe_opcode_t));
- if (idx >= 0 && idx < slots_per_page(c)) {
- WARN_ON(kip->slot_used[idx] != SLOT_USED);
- if (dirty) {
- kip->slot_used[idx] = SLOT_DIRTY;
- kip->ngarbage++;
- if (++c->nr_garbage > slots_per_page(c))
- collect_garbage_slots(c);
- } else
- collect_one_slot(kip, idx);
+ rcu_read_lock();
+ list_for_each_entry_rcu(kip, &c->pages, list) {
+ idx = ((long)slot - (long)kip->insns) /
+ (c->insn_size * sizeof(kprobe_opcode_t));
+ if (idx >= 0 && idx < slots_per_page(c))
goto out;
- }
}
- /* Could not free this slot. */
+ /* Could not find this slot. */
WARN_ON(1);
+ kip = NULL;
out:
+ rcu_read_unlock();
+ /* Mark and sweep: this may sleep */
+ if (kip) {
+ /* Check double free */
+ WARN_ON(kip->slot_used[idx] != SLOT_USED);
+ if (dirty) {
+ kip->slot_used[idx] = SLOT_DIRTY;
+ kip->ngarbage++;
+ if (++c->nr_garbage > slots_per_page(c))
+ collect_garbage_slots(c);
+ } else
+ collect_one_slot(kip, idx);
+ }
mutex_unlock(&c->mutex);
}
+/*
+ * Check given address is on the page of kprobe instruction slots.
+ * This will be used for checking whether the address on a stack
+ * is on a text area or not.
+ */
+bool __is_insn_slot_addr(struct kprobe_insn_cache *c, unsigned long addr)
+{
+ struct kprobe_insn_page *kip;
+ bool ret = false;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(kip, &c->pages, list) {
+ if (addr >= (unsigned long)kip->insns &&
+ addr < (unsigned long)kip->insns + PAGE_SIZE) {
+ ret = true;
+ break;
+ }
+ }
+ rcu_read_unlock();
+
+ return ret;
+}
+
#ifdef CONFIG_OPTPROBES
/* For optimized_kprobe buffer */
struct kprobe_insn_cache kprobe_optinsn_slots = {
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