[PATCH -tip v2 2/6] kprobes: Fix coding style issues

From: Masami Hiramatsu
Date: Sun Jul 11 2021 - 03:34:26 EST

Fix coding style issues reported by checkpatch.pl and update
comments to quote variable names and add "()" to function
name.
One TODO comment in __disarm_kprobe() is removed because
it has been done by following commit.

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
include/linux/kprobes.h | 40 +++++---
kernel/kprobes.c | 238 ++++++++++++++++++++++++-----------------------
2 files changed, 146 insertions(+), 132 deletions(-)

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index e4f3bfe08757..28c04f1f2b73 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -3,7 +3,6 @@
#define _LINUX_KPROBES_H
/*
* Kernel Probes (KProbes)
- * include/linux/kprobes.h
*
* Copyright (C) IBM Corporation, 2002, 2004
*
@@ -39,7 +38,7 @@
#define KPROBE_REENTER 0x00000004
#define KPROBE_HIT_SSDONE 0x00000008

-#else /* CONFIG_KPROBES */
+#else /* !CONFIG_KPROBES */
#include <asm-generic/kprobes.h>
typedef int kprobe_opcode_t;
struct arch_specific_insn {
@@ -228,7 +227,7 @@ static nokprobe_inline struct kretprobe *get_kretprobe(struct kretprobe_instance
return READ_ONCE(ri->rph->rp);
}

-#else /* CONFIG_KRETPROBES */
+#else /* !CONFIG_KRETPROBES */
static inline void arch_prepare_kretprobe(struct kretprobe *rp,
struct pt_regs *regs)
{
@@ -239,11 +238,15 @@ static inline int arch_trampoline_kprobe(struct kprobe *p)
}
#endif /* CONFIG_KRETPROBES */

+/* Markers of '_kprobe_blacklist' section */
+extern unsigned long __start_kprobe_blacklist[];
+extern unsigned long __stop_kprobe_blacklist[];
+
extern struct kretprobe_blackpoint kretprobe_blacklist[];

#ifdef CONFIG_KPROBES_SANITY_TEST
extern int init_test_probes(void);
-#else
+#else /* !CONFIG_KPROBES_SANITY_TEST */
static inline int init_test_probes(void)
{
return 0;
@@ -303,7 +306,7 @@ static inline bool is_kprobe_##__name##_slot(unsigned long addr) \
#define KPROBE_OPTINSN_PAGE_SYM "kprobe_optinsn_page"
int kprobe_cache_get_kallsym(struct kprobe_insn_cache *c, unsigned int *symnum,
unsigned long *value, char *type, char *sym);
-#else /* __ARCH_WANT_KPROBES_INSN_SLOT */
+#else /* !__ARCH_WANT_KPROBES_INSN_SLOT */
#define DEFINE_INSN_CACHE_OPS(__name) \
static inline bool is_kprobe_##__name##_slot(unsigned long addr) \
{ \
@@ -345,16 +348,17 @@ extern int sysctl_kprobes_optimization;
extern int proc_kprobes_optimization_handler(struct ctl_table *table,
int write, void *buffer,
size_t *length, loff_t *ppos);
-#endif
+#endif /* CONFIG_SYSCTL */
extern void wait_for_kprobe_optimizer(void);
-#else
+#else /* !CONFIG_OPTPROBES */
static inline void wait_for_kprobe_optimizer(void) { }
#endif /* CONFIG_OPTPROBES */
+
#ifdef CONFIG_KPROBES_ON_FTRACE
extern void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct ftrace_regs *fregs);
extern int arch_prepare_kprobe_ftrace(struct kprobe *p);
-#endif
+#endif /* CONFIG_KPROBES_ON_FTRACE */

int arch_check_ftrace_location(struct kprobe *p);

@@ -364,7 +368,7 @@ struct kprobe *get_kprobe(void *addr);
/* kprobe_running() will just return the current_kprobe on this CPU */
static inline struct kprobe *kprobe_running(void)
{
- return (__this_cpu_read(current_kprobe));
+ return __this_cpu_read(current_kprobe);
}

static inline void reset_current_kprobe(void)
@@ -428,11 +432,11 @@ static inline struct kprobe *kprobe_running(void)
}
static inline int register_kprobe(struct kprobe *p)
{
- return -ENOSYS;
+ return -EOPNOTSUPP;
}
static inline int register_kprobes(struct kprobe **kps, int num)
{
- return -ENOSYS;
+ return -EOPNOTSUPP;
}
static inline void unregister_kprobe(struct kprobe *p)
{
@@ -442,11 +446,11 @@ static inline void unregister_kprobes(struct kprobe **kps, int num)
}
static inline int register_kretprobe(struct kretprobe *rp)
{
- return -ENOSYS;
+ return -EOPNOTSUPP;
}
static inline int register_kretprobes(struct kretprobe **rps, int num)
{
- return -ENOSYS;
+ return -EOPNOTSUPP;
}
static inline void unregister_kretprobe(struct kretprobe *rp)
{
@@ -462,11 +466,11 @@ static inline void kprobe_free_init_mem(void)
}
static inline int disable_kprobe(struct kprobe *kp)
{
- return -ENOSYS;
+ return -EOPNOTSUPP;
}
static inline int enable_kprobe(struct kprobe *kp)
{
- return -ENOSYS;
+ return -EOPNOTSUPP;
}

static inline bool within_kprobe_blacklist(unsigned long addr)
@@ -479,6 +483,7 @@ static inline int kprobe_get_kallsym(unsigned int symnum, unsigned long *value,
return -ERANGE;
}
#endif /* CONFIG_KPROBES */
+
static inline int disable_kretprobe(struct kretprobe *rp)
{
return disable_kprobe(&rp->kp);
@@ -493,13 +498,14 @@ static inline bool is_kprobe_insn_slot(unsigned long addr)
{
return false;
}
-#endif
+#endif /* !CONFIG_KPROBES */
+
#ifndef CONFIG_OPTPROBES
static inline bool is_kprobe_optinsn_slot(unsigned long addr)
{
return false;
}
-#endif
+#endif /* !CONFIG_OPTPROBES */

/* Returns true if kprobes handled the fault */
static nokprobe_inline bool kprobe_page_fault(struct pt_regs *regs,
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 63532991ccb4..e5e1400072c8 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1,7 +1,6 @@
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Kernel Probes (KProbes)
- * kernel/kprobes.c
*
* Copyright (C) IBM Corporation, 2002, 2004
*
@@ -52,18 +51,18 @@

static int kprobes_initialized;
/* kprobe_table can be accessed by
- * - Normal hlist traversal and RCU add/del under kprobe_mutex is held.
+ * - Normal hlist traversal and RCU add/del under 'kprobe_mutex' is held.
* Or
* - RCU hlist traversal under disabling preempt (breakpoint handlers)
*/
static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];

-/* NOTE: change this value only with kprobe_mutex held */
+/* NOTE: change this value only with 'kprobe_mutex' held */
static bool kprobes_all_disarmed;

-/* This protects kprobe_table and optimizing_list */
+/* This protects 'kprobe_table' and 'optimizing_list' */
static DEFINE_MUTEX(kprobe_mutex);
-static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
+static DEFINE_PER_CPU(struct kprobe *, kprobe_instance);

kprobe_opcode_t * __weak kprobe_lookup_name(const char *name,
unsigned int __unused)
@@ -71,12 +70,15 @@ kprobe_opcode_t * __weak kprobe_lookup_name(const char *name,
return ((kprobe_opcode_t *)(kallsyms_lookup_name(name)));
}

-/* Blacklist -- list of struct kprobe_blacklist_entry */
+/*
+ * Blacklist -- list of 'struct kprobe_blacklist_entry' to store info where
+ * kprobes can not probe.
+ */
static LIST_HEAD(kprobe_blacklist);

#ifdef __ARCH_WANT_KPROBES_INSN_SLOT
/*
- * kprobe->ainsn.insn points to the copy of the instruction to be
+ * 'kprobe::ainsn.insn' points to the copy of the instruction to be
* single-stepped. x86_64, POWER4 and above have no-exec support and
* stepping on the instruction on a vmalloced/kmalloced/data page
* is a recipe for disaster
@@ -107,6 +109,12 @@ enum kprobe_slot_state {

void __weak *alloc_insn_page(void)
{
+ /*
+ * Use module_alloc() so this page is within +/- 2GB of where the
+ * kernel image and loaded module images reside. This is required
+ * for most of the architectures.
+ * (e.g. x86-64 needs this to handle the %rip-relative fixups.)
+ */
return module_alloc(PAGE_SIZE);
}

@@ -142,6 +150,7 @@ kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c)
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++) {
if (kip->slot_used[i] == SLOT_CLEAN) {
kip->slot_used[i] = SLOT_USED;
@@ -167,11 +176,6 @@ kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c)
if (!kip)
goto out;

- /*
- * Use module_alloc so this page is within +/- 2GB of where the
- * kernel image and loaded module images reside. This is required
- * so x86_64 can correctly handle the %rip-relative fixups.
- */
kip->insns = c->alloc();
if (!kip->insns) {
kfree(kip);
@@ -233,6 +237,7 @@ static int collect_garbage_slots(struct kprobe_insn_cache *c)

list_for_each_entry_safe(kip, next, &c->pages, list) {
int i;
+
if (kip->ngarbage == 0)
continue;
kip->ngarbage = 0; /* we will collect all garbages */
@@ -313,7 +318,7 @@ int kprobe_cache_get_kallsym(struct kprobe_insn_cache *c, unsigned int *symnum,
list_for_each_entry_rcu(kip, &c->pages, list) {
if ((*symnum)--)
continue;
- strlcpy(sym, c->sym, KSYM_NAME_LEN);
+ strscpy(sym, c->sym, KSYM_NAME_LEN);
*type = 't';
*value = (unsigned long)kip->insns;
ret = 0;
@@ -361,9 +366,9 @@ static inline void reset_kprobe_instance(void)

/*
* This routine is called either:
- * - under the kprobe_mutex - during kprobe_[un]register()
- * OR
- * - with preemption disabled - from arch/xxx/kernel/kprobes.c
+ * - under the 'kprobe_mutex' - during kprobe_[un]register().
+ * OR
+ * - with preemption disabled - from architecture specific code.
*/
struct kprobe *get_kprobe(void *addr)
{
@@ -383,22 +388,20 @@ NOKPROBE_SYMBOL(get_kprobe);

static int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs);

-/* Return true if the kprobe is an aggregator */
+/* Return true if 'p' is an aggregator */
static inline int kprobe_aggrprobe(struct kprobe *p)
{
return p->pre_handler == aggr_pre_handler;
}

-/* Return true(!0) if the kprobe is unused */
+/* Return true if 'p' is unused */
static inline int kprobe_unused(struct kprobe *p)
{
return kprobe_aggrprobe(p) && kprobe_disabled(p) &&
list_empty(&p->list);
}

-/*
- * Keep all fields in the kprobe consistent
- */
+/* Keep all fields in the kprobe consistent. */
static inline void copy_kprobe(struct kprobe *ap, struct kprobe *p)
{
memcpy(&p->opcode, &ap->opcode, sizeof(kprobe_opcode_t));
@@ -406,11 +409,11 @@ static inline void copy_kprobe(struct kprobe *ap, struct kprobe *p)
}

#ifdef CONFIG_OPTPROBES
-/* NOTE: change this value only with kprobe_mutex held */
+/* NOTE: This is protected by 'kprobe_mutex'. */
static bool kprobes_allow_optimization;

/*
- * Call all pre_handler on the list, but ignores its return value.
+ * Call all 'kprobe::pre_handler' on the list, but ignores its return value.
* This must be called from arch-dep optimized caller.
*/
void opt_pre_handler(struct kprobe *p, struct pt_regs *regs)
@@ -438,7 +441,7 @@ static void free_aggr_kprobe(struct kprobe *p)
kfree(op);
}

-/* Return true(!0) if the kprobe is ready for optimization. */
+/* Return true if the kprobe is ready for optimization. */
static inline int kprobe_optready(struct kprobe *p)
{
struct optimized_kprobe *op;
@@ -451,7 +454,7 @@ static inline int kprobe_optready(struct kprobe *p)
return 0;
}

-/* Return true(!0) if the kprobe is disarmed. Note: p must be on hash list */
+/* Return true if the kprobe is disarmed. Note: p must be on hash list */
static inline int kprobe_disarmed(struct kprobe *p)
{
struct optimized_kprobe *op;
@@ -465,7 +468,7 @@ static inline int kprobe_disarmed(struct kprobe *p)
return kprobe_disabled(p) && list_empty(&op->list);
}

-/* Return true(!0) if the probe is queued on (un)optimizing lists */
+/* Return true if the probe is queued on (un)optimizing lists */
static int kprobe_queued(struct kprobe *p)
{
struct optimized_kprobe *op;
@@ -480,7 +483,7 @@ static int kprobe_queued(struct kprobe *p)

/*
* Return an optimized kprobe whose optimizing code replaces
- * instructions including addr (exclude breakpoint).
+ * instructions including 'addr' (exclude breakpoint).
*/
static struct kprobe *get_optimized_kprobe(unsigned long addr)
{
@@ -501,7 +504,7 @@ static struct kprobe *get_optimized_kprobe(unsigned long addr)
return NULL;
}

-/* Optimization staging list, protected by kprobe_mutex */
+/* Optimization staging list, protected by 'kprobe_mutex' */
static LIST_HEAD(optimizing_list);
static LIST_HEAD(unoptimizing_list);
static LIST_HEAD(freeing_list);
@@ -512,20 +515,20 @@ static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);

/*
* Optimize (replace a breakpoint with a jump) kprobes listed on
- * optimizing_list.
+ * 'optimizing_list'.
*/
static void do_optimize_kprobes(void)
{
lockdep_assert_held(&text_mutex);
/*
- * The optimization/unoptimization refers online_cpus via
- * stop_machine() and cpu-hotplug modifies online_cpus.
- * And same time, text_mutex will be held in cpu-hotplug and here.
- * This combination can cause a deadlock (cpu-hotplug try to lock
- * text_mutex but stop_machine can not be done because online_cpus
- * has been changed)
- * To avoid this deadlock, caller must have locked cpu hotplug
- * for preventing cpu-hotplug outside of text_mutex locking.
+ * The optimization/unoptimization refers 'online_cpus' via
+ * stop_machine() and cpu-hotplug modifies the 'online_cpus'.
+ * And same time, 'text_mutex' will be held in cpu-hotplug and here.
+ * This combination can cause a deadlock (cpu-hotplug tries to lock
+ * 'text_mutex' but stop_machine() can not be done because
+ * the 'online_cpus' has been changed)
+ * To avoid this deadlock, caller must have locked cpu-hotplug
+ * for preventing cpu-hotplug outside of 'text_mutex' locking.
*/
lockdep_assert_cpus_held();

@@ -539,7 +542,7 @@ static void do_optimize_kprobes(void)

/*
* Unoptimize (replace a jump with a breakpoint and remove the breakpoint
- * if need) kprobes listed on unoptimizing_list.
+ * if need) kprobes listed on 'unoptimizing_list'.
*/
static void do_unoptimize_kprobes(void)
{
@@ -554,7 +557,7 @@ static void do_unoptimize_kprobes(void)
return;

arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);
- /* Loop free_list for disarming */
+ /* Loop on 'freeing_list' for disarming */
list_for_each_entry_safe(op, tmp, &freeing_list, list) {
/* Switching from detour code to origin */
op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
@@ -565,7 +568,7 @@ static void do_unoptimize_kprobes(void)
/*
* Remove unused probes from hash list. After waiting
* for synchronization, these probes are reclaimed.
- * (reclaiming is done by do_free_cleaned_kprobes.)
+ * (reclaiming is done by do_free_cleaned_kprobes().)
*/
hlist_del_rcu(&op->kp.hlist);
} else
@@ -573,7 +576,7 @@ static void do_unoptimize_kprobes(void)
}
}

-/* Reclaim all kprobes on the free_list */
+/* Reclaim all kprobes on the 'freeing_list' */
static void do_free_cleaned_kprobes(void)
{
struct optimized_kprobe *op, *tmp;
@@ -645,9 +648,9 @@ void wait_for_kprobe_optimizer(void)
while (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list)) {
mutex_unlock(&kprobe_mutex);

- /* this will also make optimizing_work execute immmediately */
+ /* This will also make 'optimizing_work' execute immmediately */
flush_delayed_work(&optimizing_work);
- /* @optimizing_work might not have been queued yet, relax */
+ /* 'optimizing_work' might not have been queued yet, relax */
cpu_relax();

mutex_lock(&kprobe_mutex);
@@ -678,7 +681,7 @@ static void optimize_kprobe(struct kprobe *p)
(kprobe_disabled(p) || kprobes_all_disarmed))
return;

- /* kprobes with post_handler can not be optimized */
+ /* kprobes with 'post_handler' can not be optimized */
if (p->post_handler)
return;

@@ -698,7 +701,10 @@ static void optimize_kprobe(struct kprobe *p)
}
op->kp.flags |= KPROBE_FLAG_OPTIMIZED;

- /* On unoptimizing/optimizing_list, op must have OPTIMIZED flag */
+ /*
+ * On the 'unoptimizing_list' and 'optimizing_list',
+ * 'op' must have OPTIMIZED flag
+ */
if (WARN_ON_ONCE(!list_empty(&op->list)))
return;

@@ -768,7 +774,7 @@ static int reuse_unused_kprobe(struct kprobe *ap)
WARN_ON_ONCE(list_empty(&op->list));
/* Enable the probe again */
ap->flags &= ~KPROBE_FLAG_DISABLED;
- /* Optimize it again (remove from op->list) */
+ /* Optimize it again. (remove from 'op->list') */
if (!kprobe_optready(ap))
return -EINVAL;

@@ -818,7 +824,7 @@ static void prepare_optimized_kprobe(struct kprobe *p)
__prepare_optimized_kprobe(op, p);
}

-/* Allocate new optimized_kprobe and try to prepare optimized instructions */
+/* Allocate new optimized_kprobe and try to prepare optimized instructions. */
static struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
{
struct optimized_kprobe *op;
@@ -837,19 +843,19 @@ static struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p);

/*
- * Prepare an optimized_kprobe and optimize it
- * NOTE: p must be a normal registered kprobe
+ * Prepare an optimized_kprobe and optimize it.
+ * NOTE: 'p' must be a normal registered kprobe.
*/
static void try_to_optimize_kprobe(struct kprobe *p)
{
struct kprobe *ap;
struct optimized_kprobe *op;

- /* Impossible to optimize ftrace-based kprobe */
+ /* Impossible to optimize ftrace-based kprobe. */
if (kprobe_ftrace(p))
return;

- /* For preparing optimization, jump_label_text_reserved() is called */
+ /* For preparing optimization, jump_label_text_reserved() is called. */
cpus_read_lock();
jump_label_lock();
mutex_lock(&text_mutex);
@@ -860,14 +866,14 @@ static void try_to_optimize_kprobe(struct kprobe *p)

op = container_of(ap, struct optimized_kprobe, kp);
if (!arch_prepared_optinsn(&op->optinsn)) {
- /* If failed to setup optimizing, fallback to kprobe */
+ /* If failed to setup optimizing, fallback to kprobe. */
arch_remove_optimized_kprobe(op);
kfree(op);
goto out;
}

init_aggr_kprobe(ap, p);
- optimize_kprobe(ap); /* This just kicks optimizer thread */
+ optimize_kprobe(ap); /* This just kicks optimizer thread. */

out:
mutex_unlock(&text_mutex);
@@ -882,7 +888,7 @@ static void optimize_all_kprobes(void)
unsigned int i;

mutex_lock(&kprobe_mutex);
- /* If optimization is already allowed, just return */
+ /* If optimization is already allowed, just return. */
if (kprobes_allow_optimization)
goto out;

@@ -908,7 +914,7 @@ static void unoptimize_all_kprobes(void)
unsigned int i;

mutex_lock(&kprobe_mutex);
- /* If optimization is already prohibited, just return */
+ /* If optimization is already prohibited, just return. */
if (!kprobes_allow_optimization) {
mutex_unlock(&kprobe_mutex);
return;
@@ -926,7 +932,7 @@ static void unoptimize_all_kprobes(void)
cpus_read_unlock();
mutex_unlock(&kprobe_mutex);

- /* Wait for unoptimizing completion */
+ /* Wait for unoptimizing completion. */
wait_for_kprobe_optimizer();
pr_info("kprobe jump-optimization is disabled. All kprobes are based on software breakpoint.\n");
}
@@ -953,12 +959,12 @@ int proc_kprobes_optimization_handler(struct ctl_table *table, int write,
}
#endif /* CONFIG_SYSCTL */

-/* Put a breakpoint for a probe. Must be called with text_mutex locked */
+/* Put a breakpoint for a probe. Must be called with 'text_mutex' locked. */
static void __arm_kprobe(struct kprobe *p)
{
struct kprobe *_p;

- /* Check collision with other optimized kprobes */
+ /* Find the overlapping optimized kprobes. */
_p = get_optimized_kprobe((unsigned long)p->addr);
if (unlikely(_p))
/* Fallback to unoptimized kprobe */
@@ -968,7 +974,7 @@ static void __arm_kprobe(struct kprobe *p)
optimize_kprobe(p); /* Try to optimize (add kprobe to a list) */
}

-/* Remove the breakpoint of a probe. Must be called with text_mutex locked */
+/* Remove the breakpoint of a probe. Must be called with 'text_mutex' locked. */
static void __disarm_kprobe(struct kprobe *p, bool reopt)
{
struct kprobe *_p;
@@ -978,12 +984,17 @@ static void __disarm_kprobe(struct kprobe *p, bool reopt)

if (!kprobe_queued(p)) {
arch_disarm_kprobe(p);
- /* If another kprobe was blocked, optimize it. */
+ /* If another kprobe was blocked, re-optimize it. */
_p = get_optimized_kprobe((unsigned long)p->addr);
if (unlikely(_p) && reopt)
optimize_kprobe(_p);
}
- /* TODO: reoptimize others after unoptimized this probe */
+ /*
+ * TODO: Since unoptimization and real disarming will be done by
+ * the worker thread, we can not check whether another probe are
+ * unoptimized because of this probe here. It should be re-optimized
+ * by the worker thread.
+ */
}

#else /* !CONFIG_OPTPROBES */
@@ -1036,7 +1047,7 @@ static struct ftrace_ops kprobe_ipmodify_ops __read_mostly = {
static int kprobe_ipmodify_enabled;
static int kprobe_ftrace_enabled;

-/* Must ensure p->addr is really on ftrace */
+/* Must ensure 'p->addr' is really on ftrace. */
static int prepare_kprobe(struct kprobe *p)
{
if (!kprobe_ftrace(p))
@@ -1045,7 +1056,7 @@ static int prepare_kprobe(struct kprobe *p)
return arch_prepare_kprobe_ftrace(p);
}

-/* Caller must lock kprobe_mutex */
+/* Caller must lock 'kprobe_mutex' */
static int __arm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
int *cnt)
{
@@ -1082,7 +1093,7 @@ static int arm_kprobe_ftrace(struct kprobe *p)
ipmodify ? &kprobe_ipmodify_enabled : &kprobe_ftrace_enabled);
}

-/* Caller must lock kprobe_mutex */
+/* Caller must lock 'kprobe_mutex'. */
static int __disarm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
int *cnt)
{
@@ -1127,7 +1138,7 @@ static inline int disarm_kprobe_ftrace(struct kprobe *p)
}
#endif

-/* Arm a kprobe with text_mutex */
+/* Arm a kprobe with 'text_mutex'. */
static int arm_kprobe(struct kprobe *kp)
{
if (unlikely(kprobe_ftrace(kp)))
@@ -1142,7 +1153,7 @@ static int arm_kprobe(struct kprobe *kp)
return 0;
}

-/* Disarm a kprobe with text_mutex */
+/* Disarm a kprobe with 'text_mutex'. */
static int disarm_kprobe(struct kprobe *kp, bool reopt)
{
if (unlikely(kprobe_ftrace(kp)))
@@ -1192,17 +1203,17 @@ static void aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
}
NOKPROBE_SYMBOL(aggr_post_handler);

-/* Walks the list and increments nmissed count for multiprobe case */
+/* Walks the list and increments 'nmissed' if 'p' has child probes. */
void kprobes_inc_nmissed_count(struct kprobe *p)
{
struct kprobe *kp;
+
if (!kprobe_aggrprobe(p)) {
p->nmissed++;
} else {
list_for_each_entry_rcu(kp, &p->list, list)
kp->nmissed++;
}
- return;
}
NOKPROBE_SYMBOL(kprobes_inc_nmissed_count);

@@ -1220,9 +1231,9 @@ static void recycle_rp_inst(struct kretprobe_instance *ri)
{
struct kretprobe *rp = get_kretprobe(ri);

- if (likely(rp)) {
+ if (likely(rp))
freelist_add(&ri->freelist, &rp->freelist);
- } else
+ else
call_rcu(&ri->rcu, free_rp_inst_rcu);
}
NOKPROBE_SYMBOL(recycle_rp_inst);
@@ -1248,8 +1259,8 @@ void kprobe_busy_end(void)
}

/*
- * This function is called from finish_task_switch when task tk becomes dead,
- * so that we can recycle any function-return probe instances associated
+ * This function is called from finish_task_switch() when task 'tk' becomes
+ * dead, so that we can recycle any kretprobe instances associated
* with this task. These left over instances represent probed functions
* that have been called but will never return.
*/
@@ -1297,7 +1308,7 @@ static inline void free_rp_inst(struct kretprobe *rp)
}
}

-/* Add the new probe to ap->list */
+/* Add the new probe to 'ap->list'. */
static int add_new_kprobe(struct kprobe *ap, struct kprobe *p)
{
if (p->post_handler)
@@ -1311,12 +1322,12 @@ static int add_new_kprobe(struct kprobe *ap, struct kprobe *p)
}

/*
- * Fill in the required fields of the "manager kprobe". Replace the
- * earlier kprobe in the hlist with the manager kprobe
+ * Fill in the required fields of the aggregator kprobe. Replace the
+ * earlier kprobe in the hlist with the aggregator kprobe.
*/
static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
{
- /* Copy p's insn slot to ap */
+ /* Copy the insn slot of 'p' to 'ap'. */
copy_kprobe(p, ap);
flush_insn_slot(ap);
ap->addr = p->addr;
@@ -1334,8 +1345,7 @@ static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
}

/*
- * This is the second or subsequent kprobe at the address - handle
- * the intricacies
+ * This registers the second or subsequent kprobe at the same address.
*/
static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
{
@@ -1349,7 +1359,7 @@ static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
mutex_lock(&text_mutex);

if (!kprobe_aggrprobe(orig_p)) {
- /* If orig_p is not an aggr_kprobe, create new aggr_kprobe. */
+ /* If 'orig_p' is not an 'aggr_kprobe', create new one. */
ap = alloc_aggr_kprobe(orig_p);
if (!ap) {
ret = -ENOMEM;
@@ -1374,8 +1384,8 @@ static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
if (ret)
/*
* Even if fail to allocate new slot, don't need to
- * free aggr_probe. It will be used next time, or
- * freed by unregister_kprobe.
+ * free the 'ap'. It will be used next time, or
+ * freed by unregister_kprobe().
*/
goto out;

@@ -1390,7 +1400,7 @@ static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
| KPROBE_FLAG_DISABLED;
}

- /* Copy ap's insn slot to p */
+ /* Copy the insn slot of 'p' to 'ap'. */
copy_kprobe(ap, p);
ret = add_new_kprobe(ap, p);

@@ -1416,7 +1426,7 @@ static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)

bool __weak arch_within_kprobe_blacklist(unsigned long addr)
{
- /* The __kprobes marked functions and entry code must not be probed */
+ /* The '__kprobes' functions and entry code must not be probed. */
return addr >= (unsigned long)__kprobes_text_start &&
addr < (unsigned long)__kprobes_text_end;
}
@@ -1428,8 +1438,8 @@ static bool __within_kprobe_blacklist(unsigned long addr)
if (arch_within_kprobe_blacklist(addr))
return true;
/*
- * If there exists a kprobe_blacklist, verify and
- * fail any probe registration in the prohibited area
+ * If 'kprobe_blacklist' is defined, check the address and
+ * reject any probe registration in the prohibited area.
*/
list_for_each_entry(ent, &kprobe_blacklist, list) {
if (addr >= ent->start_addr && addr < ent->end_addr)
@@ -1459,7 +1469,7 @@ bool within_kprobe_blacklist(unsigned long addr)
}

/*
- * If we have a symbol_name argument, look it up and add the offset field
+ * If 'symbol_name' is specified, look it up and add the 'offset'
* to it. This way, we can specify a relative address to a symbol.
* This returns encoded errors if it fails to look up symbol or invalid
* combination of parameters.
@@ -1489,7 +1499,10 @@ static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
return _kprobe_addr(p->addr, p->symbol_name, p->offset);
}

-/* Check passed kprobe is valid and return kprobe in kprobe_table. */
+/*
+ * Check the 'p' is valid and return the aggregator kprobe
+ * at the same address.
+ */
static struct kprobe *__get_valid_kprobe(struct kprobe *p)
{
struct kprobe *ap, *list_p;
@@ -1566,7 +1579,7 @@ static int check_kprobe_address_safe(struct kprobe *p,
goto out;
}

- /* Check if are we probing a module */
+ /* Check if 'p' is probing a module. */
*probed_mod = __module_text_address((unsigned long) p->addr);
if (*probed_mod) {
/*
@@ -1579,7 +1592,7 @@ static int check_kprobe_address_safe(struct kprobe *p,
}

/*
- * If the module freed .init.text, we couldn't insert
+ * If the module freed '.init.text', we couldn't insert
* kprobes in there.
*/
if (within_module_init((unsigned long)p->addr, *probed_mod) &&
@@ -1626,7 +1639,7 @@ int register_kprobe(struct kprobe *p)

old_p = get_kprobe(p->addr);
if (old_p) {
- /* Since this may unoptimize old_p, locking text_mutex. */
+ /* Since this may unoptimize 'old_p', locking 'text_mutex'. */
ret = register_aggr_kprobe(old_p, p);
goto out;
}
@@ -1665,7 +1678,7 @@ int register_kprobe(struct kprobe *p)
}
EXPORT_SYMBOL_GPL(register_kprobe);

-/* Check if all probes on the aggrprobe are disabled */
+/* Check if all probes on the 'ap' are disabled. */
static int aggr_kprobe_disabled(struct kprobe *ap)
{
struct kprobe *kp;
@@ -1675,15 +1688,15 @@ static int aggr_kprobe_disabled(struct kprobe *ap)
list_for_each_entry(kp, &ap->list, list)
if (!kprobe_disabled(kp))
/*
- * There is an active probe on the list.
- * We can't disable this ap.
+ * Since there is an active probe on the list,
+ * we can't disable this 'ap'.
*/
return 0;

return 1;
}

-/* Disable one kprobe: Make sure called under kprobe_mutex is locked */
+/* Disable one kprobe: Make sure called under 'kprobe_mutex' is locked. */
static struct kprobe *__disable_kprobe(struct kprobe *p)
{
struct kprobe *orig_p;
@@ -1702,7 +1715,7 @@ static struct kprobe *__disable_kprobe(struct kprobe *p)
/* Try to disarm and disable this/parent probe */
if (p == orig_p || aggr_kprobe_disabled(orig_p)) {
/*
- * If kprobes_all_disarmed is set, orig_p
+ * If 'kprobes_all_disarmed' is set, 'orig_p'
* should have already been disarmed, so
* skip unneed disarming process.
*/
@@ -1989,7 +2002,7 @@ int register_kretprobe(struct kretprobe *rp)
if (ret)
return ret;

- /* If only rp->kp.addr is specified, check reregistering kprobes */
+ /* If only 'rp->kp.addr' is specified, check reregistering kprobes */
if (rp->kp.addr && warn_kprobe_rereg(&rp->kp))
return -EINVAL;

@@ -2094,13 +2107,13 @@ EXPORT_SYMBOL_GPL(unregister_kretprobes);
#else /* CONFIG_KRETPROBES */
int register_kretprobe(struct kretprobe *rp)
{
- return -ENOSYS;
+ return -EOPNOTSUPP;
}
EXPORT_SYMBOL_GPL(register_kretprobe);

int register_kretprobes(struct kretprobe **rps, int num)
{
- return -ENOSYS;
+ return -EOPNOTSUPP;
}
EXPORT_SYMBOL_GPL(register_kretprobes);

@@ -2149,7 +2162,7 @@ static void kill_kprobe(struct kprobe *p)
/*
* The module is going away. We should disarm the kprobe which
* is using ftrace, because ftrace framework is still available at
- * MODULE_STATE_GOING notification.
+ * 'MODULE_STATE_GOING' notification.
*/
if (kprobe_ftrace(p) && !kprobe_disabled(p) && !kprobes_all_disarmed)
disarm_kprobe_ftrace(p);
@@ -2322,13 +2335,13 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
return ret;
}

- /* Symbols in __kprobes_text are blacklisted */
+ /* Symbols in '__kprobes_text' are blacklisted */
ret = kprobe_add_area_blacklist((unsigned long)__kprobes_text_start,
(unsigned long)__kprobes_text_end);
if (ret)
return ret;

- /* Symbols in noinstr section are blacklisted */
+ /* Symbols in 'noinstr' section are blacklisted */
ret = kprobe_add_area_blacklist((unsigned long)__noinstr_text_start,
(unsigned long)__noinstr_text_end);

@@ -2400,9 +2413,9 @@ static int kprobes_module_callback(struct notifier_block *nb,
return NOTIFY_DONE;

/*
- * When MODULE_STATE_GOING was notified, both of module .text and
- * .init.text sections would be freed. When MODULE_STATE_LIVE was
- * notified, only .init.text section would be freed. We need to
+ * When 'MODULE_STATE_GOING' was notified, both of module '.text' and
+ * '.init.text' sections would be freed. When 'MODULE_STATE_LIVE' was
+ * notified, only '.init.text' section would be freed. We need to
* disable kprobes which have been inserted in the sections.
*/
mutex_lock(&kprobe_mutex);
@@ -2419,9 +2432,9 @@ static int kprobes_module_callback(struct notifier_block *nb,
*
* Note, this will also move any optimized probes
* that are pending to be removed from their
- * corresponding lists to the freeing_list and
+ * corresponding lists to the 'freeing_list' and
* will not be touched by the delayed
- * kprobe_optimizer work handler.
+ * kprobe_optimizer() work handler.
*/
kill_kprobe(p);
}
@@ -2437,10 +2450,6 @@ static struct notifier_block kprobe_module_nb = {
.priority = 0
};

-/* Markers of _kprobe_blacklist section */
-extern unsigned long __start_kprobe_blacklist[];
-extern unsigned long __stop_kprobe_blacklist[];
-
void kprobe_free_init_mem(void)
{
void *start = (void *)(&__init_begin);
@@ -2451,7 +2460,7 @@ void kprobe_free_init_mem(void)

mutex_lock(&kprobe_mutex);

- /* Kill all kprobes on initmem */
+ /* Kill all kprobes on initmem because the target code has been freed. */
for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
head = &kprobe_table[i];
hlist_for_each_entry(p, head, hlist) {
@@ -2474,9 +2483,8 @@ static int __init init_kprobes(void)

err = populate_kprobe_blacklist(__start_kprobe_blacklist,
__stop_kprobe_blacklist);
- if (err) {
+ if (err)
pr_err("Failed to populate blacklist (error %d), kprobes not restricted, be careful using them!\n", err);
- }

if (kretprobe_blacklist_size) {
/* lookup the function address from its name */
@@ -2493,7 +2501,7 @@ static int __init init_kprobes(void)
kprobes_all_disarmed = false;

#if defined(CONFIG_OPTPROBES) && defined(__ARCH_WANT_KPROBES_INSN_SLOT)
- /* Init kprobe_optinsn_slots for allocation */
+ /* Init 'kprobe_optinsn_slots' for allocation */
kprobe_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
#endif

@@ -2627,7 +2635,7 @@ static int kprobe_blacklist_seq_show(struct seq_file *m, void *v)
list_entry(v, struct kprobe_blacklist_entry, list);

/*
- * If /proc/kallsyms is not showing kernel address, we won't
+ * If '/proc/kallsyms' is not showing kernel address, we won't
* show them here either.
*/
if (!kallsyms_show_value(m->file->f_cred))