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Date: Fri, 25 Mar 2022 23:23:04 +0900
From: Masami Hiramatsu <mhiramat@...nel.org>
To: Alexei Starovoitov <ast@...nel.org>,
Andrii Nakryiko <andrii.nakryiko@...il.com>, x86@...nel.org,
Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Dan Carpenter <dan.carpenter@...cle.com>,
kernel-janitors@...r.kernel.org,
Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Jiri Olsa <jolsa@...nel.org>, bpf@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next v2 1/4] kprobes: Use rethook for kretprobe if possible
Use rethook for kretprobe function return hooking if the arch sets
CONFIG_HAVE_RETHOOK=y. In this case, CONFIG_KRETPROBE_ON_RETHOOK is
set to 'y' automatically, and the kretprobe internal data fields
switches to use rethook. If not, it continues to use kretprobe
specific function return hooks.
Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
arch/Kconfig | 7 ++
include/linux/kprobes.h | 51 +++++++++++++++++-
kernel/kprobes.c | 124 ++++++++++++++++++++++++++++++++++++-------
kernel/trace/trace_kprobe.c | 4 +
4 files changed, 161 insertions(+), 25 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index e12a4268c01d..9570854c4683 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -164,7 +164,12 @@ config ARCH_USE_BUILTIN_BSWAP
config KRETPROBES
def_bool y
- depends on KPROBES && HAVE_KRETPROBES
+ depends on KPROBES && (HAVE_KRETPROBES || HAVE_RETHOOK)
+
+config KRETPROBE_ON_RETHOOK
+ def_bool y
+ depends on HAVE_RETHOOK
+ select RETHOOK
config USER_RETURN_NOTIFIER
bool
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 312ff997c743..157168769fc2 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -28,6 +28,7 @@
#include <linux/ftrace.h>
#include <linux/refcount.h>
#include <linux/freelist.h>
+#include <linux/rethook.h>
#include <asm/kprobes.h>
#ifdef CONFIG_KPROBES
@@ -149,13 +150,20 @@ struct kretprobe {
int maxactive;
int nmissed;
size_t data_size;
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+ struct rethook *rh;
+#else
struct freelist_head freelist;
struct kretprobe_holder *rph;
+#endif
};
#define KRETPROBE_MAX_DATA_SIZE 4096
struct kretprobe_instance {
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+ struct rethook_node node;
+#else
union {
struct freelist_node freelist;
struct rcu_head rcu;
@@ -164,6 +172,7 @@ struct kretprobe_instance {
struct kretprobe_holder *rph;
kprobe_opcode_t *ret_addr;
void *fp;
+#endif
char data[];
};
@@ -186,10 +195,24 @@ extern void kprobe_busy_begin(void);
extern void kprobe_busy_end(void);
#ifdef CONFIG_KRETPROBES
-extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
- struct pt_regs *regs);
+/* Check whether @p is used for implementing a trampoline. */
extern int arch_trampoline_kprobe(struct kprobe *p);
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+static nokprobe_inline struct kretprobe *get_kretprobe(struct kretprobe_instance *ri)
+{
+ RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(),
+ "Kretprobe is accessed from instance under preemptive context");
+
+ return (struct kretprobe *)READ_ONCE(ri->node.rethook->data);
+}
+static nokprobe_inline unsigned long get_kretprobe_retaddr(struct kretprobe_instance *ri)
+{
+ return ri->node.ret_addr;
+}
+#else
+extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
+ struct pt_regs *regs);
void arch_kretprobe_fixup_return(struct pt_regs *regs,
kprobe_opcode_t *correct_ret_addr);
@@ -232,6 +255,12 @@ static nokprobe_inline struct kretprobe *get_kretprobe(struct kretprobe_instance
return READ_ONCE(ri->rph->rp);
}
+static nokprobe_inline unsigned long get_kretprobe_retaddr(struct kretprobe_instance *ri)
+{
+ return (unsigned long)ri->ret_addr;
+}
+#endif /* CONFIG_KRETPROBE_ON_RETHOOK */
+
#else /* !CONFIG_KRETPROBES */
static inline void arch_prepare_kretprobe(struct kretprobe *rp,
struct pt_regs *regs)
@@ -395,7 +424,11 @@ void unregister_kretprobe(struct kretprobe *rp);
int register_kretprobes(struct kretprobe **rps, int num);
void unregister_kretprobes(struct kretprobe **rps, int num);
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+#define kprobe_flush_task(tk) do {} while (0)
+#else
void kprobe_flush_task(struct task_struct *tk);
+#endif
void kprobe_free_init_mem(void);
@@ -509,6 +542,19 @@ static inline bool is_kprobe_optinsn_slot(unsigned long addr)
#endif /* !CONFIG_OPTPROBES */
#ifdef CONFIG_KRETPROBES
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+static nokprobe_inline bool is_kretprobe_trampoline(unsigned long addr)
+{
+ return is_rethook_trampoline(addr);
+}
+
+static nokprobe_inline
+unsigned long kretprobe_find_ret_addr(struct task_struct *tsk, void *fp,
+ struct llist_node **cur)
+{
+ return rethook_find_ret_addr(tsk, (unsigned long)fp, cur);
+}
+#else
static nokprobe_inline bool is_kretprobe_trampoline(unsigned long addr)
{
return (void *)addr == kretprobe_trampoline_addr();
@@ -516,6 +562,7 @@ static nokprobe_inline bool is_kretprobe_trampoline(unsigned long addr)
unsigned long kretprobe_find_ret_addr(struct task_struct *tsk, void *fp,
struct llist_node **cur);
+#endif
#else
static nokprobe_inline bool is_kretprobe_trampoline(unsigned long addr)
{
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 185badc780b7..dbe57df2e199 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1237,6 +1237,27 @@ void kprobes_inc_nmissed_count(struct kprobe *p)
}
NOKPROBE_SYMBOL(kprobes_inc_nmissed_count);
+static struct kprobe kprobe_busy = {
+ .addr = (void *) get_kprobe,
+};
+
+void kprobe_busy_begin(void)
+{
+ struct kprobe_ctlblk *kcb;
+
+ preempt_disable();
+ __this_cpu_write(current_kprobe, &kprobe_busy);
+ kcb = get_kprobe_ctlblk();
+ kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+}
+
+void kprobe_busy_end(void)
+{
+ __this_cpu_write(current_kprobe, NULL);
+ preempt_enable();
+}
+
+#if !defined(CONFIG_KRETPROBE_ON_RETHOOK)
static void free_rp_inst_rcu(struct rcu_head *head)
{
struct kretprobe_instance *ri = container_of(head, struct kretprobe_instance, rcu);
@@ -1258,26 +1279,6 @@ static void recycle_rp_inst(struct kretprobe_instance *ri)
}
NOKPROBE_SYMBOL(recycle_rp_inst);
-static struct kprobe kprobe_busy = {
- .addr = (void *) get_kprobe,
-};
-
-void kprobe_busy_begin(void)
-{
- struct kprobe_ctlblk *kcb;
-
- preempt_disable();
- __this_cpu_write(current_kprobe, &kprobe_busy);
- kcb = get_kprobe_ctlblk();
- kcb->kprobe_status = KPROBE_HIT_ACTIVE;
-}
-
-void kprobe_busy_end(void)
-{
- __this_cpu_write(current_kprobe, NULL);
- preempt_enable();
-}
-
/*
* This function is called from delayed_put_task_struct() when a task is
* dead and cleaned up to recycle any kretprobe instances associated with
@@ -1327,6 +1328,7 @@ static inline void free_rp_inst(struct kretprobe *rp)
rp->rph = NULL;
}
}
+#endif /* !CONFIG_KRETPROBE_ON_RETHOOK */
/* Add the new probe to 'ap->list'. */
static int add_new_kprobe(struct kprobe *ap, struct kprobe *p)
@@ -1925,6 +1927,7 @@ static struct notifier_block kprobe_exceptions_nb = {
#ifdef CONFIG_KRETPROBES
+#if !defined(CONFIG_KRETPROBE_ON_RETHOOK)
/* This assumes the 'tsk' is the current task or the is not running. */
static kprobe_opcode_t *__kretprobe_find_ret_addr(struct task_struct *tsk,
struct llist_node **cur)
@@ -2087,6 +2090,57 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
return 0;
}
NOKPROBE_SYMBOL(pre_handler_kretprobe);
+#else /* CONFIG_KRETPROBE_ON_RETHOOK */
+/*
+ * This kprobe pre_handler is registered with every kretprobe. When probe
+ * hits it will set up the return probe.
+ */
+static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
+{
+ struct kretprobe *rp = container_of(p, struct kretprobe, kp);
+ struct kretprobe_instance *ri;
+ struct rethook_node *rhn;
+
+ rhn = rethook_try_get(rp->rh);
+ if (!rhn) {
+ rp->nmissed++;
+ return 0;
+ }
+
+ ri = container_of(rhn, struct kretprobe_instance, node);
+
+ if (rp->entry_handler && rp->entry_handler(ri, regs))
+ rethook_recycle(rhn);
+ else
+ rethook_hook(rhn, regs, kprobe_ftrace(p));
+
+ return 0;
+}
+NOKPROBE_SYMBOL(pre_handler_kretprobe);
+
+static void kretprobe_rethook_handler(struct rethook_node *rh, void *data,
+ struct pt_regs *regs)
+{
+ struct kretprobe *rp = (struct kretprobe *)data;
+ struct kretprobe_instance *ri;
+ struct kprobe_ctlblk *kcb;
+
+ /* The data must NOT be null. This means rethook data structure is broken. */
+ if (WARN_ON_ONCE(!data))
+ return;
+
+ __this_cpu_write(current_kprobe, &rp->kp);
+ kcb = get_kprobe_ctlblk();
+ kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+
+ ri = container_of(rh, struct kretprobe_instance, node);
+ rp->handler(ri, regs);
+
+ __this_cpu_write(current_kprobe, NULL);
+}
+NOKPROBE_SYMBOL(kretprobe_rethook_handler);
+
+#endif /* !CONFIG_KRETPROBE_ON_RETHOOK */
/**
* kprobe_on_func_entry() -- check whether given address is function entry
@@ -2155,6 +2209,29 @@ int register_kretprobe(struct kretprobe *rp)
rp->maxactive = num_possible_cpus();
#endif
}
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+ rp->rh = rethook_alloc((void *)rp, kretprobe_rethook_handler);
+ if (!rp->rh)
+ return -ENOMEM;
+
+ for (i = 0; i < rp->maxactive; i++) {
+ inst = kzalloc(sizeof(struct kretprobe_instance) +
+ rp->data_size, GFP_KERNEL);
+ if (inst == NULL) {
+ rethook_free(rp->rh);
+ rp->rh = NULL;
+ return -ENOMEM;
+ }
+ rethook_add_node(rp->rh, &inst->node);
+ }
+ rp->nmissed = 0;
+ /* Establish function entry probe point */
+ ret = register_kprobe(&rp->kp);
+ if (ret != 0) {
+ rethook_free(rp->rh);
+ rp->rh = NULL;
+ }
+#else /* !CONFIG_KRETPROBE_ON_RETHOOK */
rp->freelist.head = NULL;
rp->rph = kzalloc(sizeof(struct kretprobe_holder), GFP_KERNEL);
if (!rp->rph)
@@ -2179,6 +2256,7 @@ int register_kretprobe(struct kretprobe *rp)
ret = register_kprobe(&rp->kp);
if (ret != 0)
free_rp_inst(rp);
+#endif
return ret;
}
EXPORT_SYMBOL_GPL(register_kretprobe);
@@ -2217,7 +2295,11 @@ void unregister_kretprobes(struct kretprobe **rps, int num)
for (i = 0; i < num; i++) {
if (__unregister_kprobe_top(&rps[i]->kp) < 0)
rps[i]->kp.addr = NULL;
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+ rethook_free(rps[i]->rh);
+#else
rps[i]->rph->rp = NULL;
+#endif
}
mutex_unlock(&kprobe_mutex);
@@ -2225,7 +2307,9 @@ void unregister_kretprobes(struct kretprobe **rps, int num)
for (i = 0; i < num; i++) {
if (rps[i]->kp.addr) {
__unregister_kprobe_bottom(&rps[i]->kp);
+#ifndef CONFIG_KRETPROBE_ON_RETHOOK
free_rp_inst(rps[i]);
+#endif
}
}
}
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index b62fd785b599..47cebef78532 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1433,7 +1433,7 @@ __kretprobe_trace_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
fbuffer.regs = regs;
entry = fbuffer.entry = ring_buffer_event_data(fbuffer.event);
entry->func = (unsigned long)tk->rp.kp.addr;
- entry->ret_ip = (unsigned long)ri->ret_addr;
+ entry->ret_ip = get_kretprobe_retaddr(ri);
store_trace_args(&entry[1], &tk->tp, regs, sizeof(*entry), dsize);
trace_event_buffer_commit(&fbuffer);
@@ -1628,7 +1628,7 @@ kretprobe_perf_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
return;
entry->func = (unsigned long)tk->rp.kp.addr;
- entry->ret_ip = (unsigned long)ri->ret_addr;
+ entry->ret_ip = get_kretprobe_retaddr(ri);
store_trace_args(&entry[1], &tk->tp, regs, sizeof(*entry), dsize);
perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
head, NULL);
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