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Date: Tue, 27 Mar 2018 14:58:24 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Alexei Starovoitov <ast@...com>
Cc: <davem@...emloft.net>, <daniel@...earbox.net>,
<torvalds@...ux-foundation.org>, <peterz@...radead.org>,
<netdev@...r.kernel.org>, <kernel-team@...com>,
<linux-api@...r.kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v6 bpf-next 08/11] bpf: introduce BPF_RAW_TRACEPOINT
On Tue, 27 Mar 2018 13:11:43 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:
> On Tue, 27 Mar 2018 13:02:11 -0400
> Steven Rostedt <rostedt@...dmis.org> wrote:
>
> > Honestly, I think this is too much of a short cut and a hack. I know
> > you want to keep it "simple" and save space, but you really should do
> > it the same way ftrace and perf do it. That is, create a section and
> > have all tracepoints create a structure that holds a pointer to the
> > tracepoint and to the bpf probe function. Then you don't even need the
> > kernel_tracepoint_find_by_name(), you just iterate over your table and
> > you get the tracepoint and the bpf function associated to it.
>
> Also, if you do it the perf/ftrace way, you get support for module
> tracepoints pretty much for free. Which would include tracepoints in
> networking code that is loaded by a module.
This doesn't include module code (but that wouldn't be too hard to set
up), but I compiled and booted this. I didn't test if it works (I
didn't have the way to test bpf here). But this patch applies on top of
this patch (patch 8). You can remove patch 7 and fold this into this
patch. And then you can also make the __bpf_trace_* function static.
This would be much more robust and less error prone.
-- Steve
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 1ab0e520d6fc..4fab7392e237 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -178,6 +178,15 @@
#define TRACE_SYSCALLS()
#endif
+#ifdef CONFIG_BPF_EVENTS
+#define BPF_RAW_TP() . = ALIGN(8); \
+ VMLINUX_SYMBOL(__start__bpf_raw_tp) = .; \
+ KEEP(*(__bpf_raw_tp_map)) \
+ VMLINUX_SYMBOL(__stop__bpf_raw_tp) = .;
+#else
+#define BPF_RAW_TP()
+#endif
+
#ifdef CONFIG_SERIAL_EARLYCON
#define EARLYCON_TABLE() STRUCT_ALIGN(); \
VMLINUX_SYMBOL(__earlycon_table) = .; \
@@ -576,6 +585,7 @@
*(.init.rodata) \
FTRACE_EVENTS() \
TRACE_SYSCALLS() \
+ BPF_RAW_TP() \
KPROBE_BLACKLIST() \
ERROR_INJECT_WHITELIST() \
MEM_DISCARD(init.rodata) \
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 399ebe6f90cf..fb4778c0a248 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -470,8 +470,9 @@ unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx);
int perf_event_attach_bpf_prog(struct perf_event *event, struct bpf_prog *prog);
void perf_event_detach_bpf_prog(struct perf_event *event);
int perf_event_query_prog_array(struct perf_event *event, void __user *info);
-int bpf_probe_register(struct tracepoint *tp, struct bpf_prog *prog);
-int bpf_probe_unregister(struct tracepoint *tp, struct bpf_prog *prog);
+int bpf_probe_register(struct bpf_raw_event_map *btp, struct bpf_prog *prog);
+int bpf_probe_unregister(struct bpf_raw_event_map *btp, struct bpf_prog *prog);
+struct bpf_raw_event_map *bpf_find_raw_tracepoint(const char *name);
#else
static inline unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx)
{
@@ -491,14 +492,18 @@ perf_event_query_prog_array(struct perf_event *event, void __user *info)
{
return -EOPNOTSUPP;
}
-static inline int bpf_probe_register(struct tracepoint *tp, struct bpf_prog *p)
+static inline int bpf_probe_register(struct bpf_raw_event_map *btp, struct bpf_prog *p)
{
return -EOPNOTSUPP;
}
-static inline int bpf_probe_unregister(struct tracepoint *tp, struct bpf_prog *p)
+static inline int bpf_probe_unregister(struct bpf_raw_event_map *btp, struct bpf_prog *p)
{
return -EOPNOTSUPP;
}
+static inline struct bpf_raw_event_map *bpf_find_raw_tracepoint(const char *name)
+{
+ return NULL;
+}
#endif
enum {
diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
index 39a283c61c51..35db8dd48c4c 100644
--- a/include/linux/tracepoint-defs.h
+++ b/include/linux/tracepoint-defs.h
@@ -36,4 +36,9 @@ struct tracepoint {
u32 num_args;
};
+struct bpf_raw_event_map {
+ struct tracepoint *tp;
+ void *bpf_func;
+};
+
#endif
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index f100c63ff19e..6037a2f0108a 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1312,7 +1312,7 @@ static int bpf_obj_get(const union bpf_attr *attr)
}
struct bpf_raw_tracepoint {
- struct tracepoint *tp;
+ struct bpf_raw_event_map *btp;
struct bpf_prog *prog;
};
@@ -1321,7 +1321,7 @@ static int bpf_raw_tracepoint_release(struct inode *inode, struct file *filp)
struct bpf_raw_tracepoint *raw_tp = filp->private_data;
if (raw_tp->prog) {
- bpf_probe_unregister(raw_tp->tp, raw_tp->prog);
+ bpf_probe_unregister(raw_tp->btp, raw_tp->prog);
bpf_prog_put(raw_tp->prog);
}
kfree(raw_tp);
@@ -1339,7 +1339,7 @@ static const struct file_operations bpf_raw_tp_fops = {
static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
{
struct bpf_raw_tracepoint *raw_tp;
- struct tracepoint *tp;
+ struct bpf_raw_event_map *btp;
struct bpf_prog *prog;
char tp_name[128];
int tp_fd, err;
@@ -1349,14 +1349,14 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
return -EFAULT;
tp_name[sizeof(tp_name) - 1] = 0;
- tp = kernel_tracepoint_find_by_name(tp_name);
- if (!tp)
+ btp = bpf_find_raw_tracepoint(tp_name);
+ if (!btp)
return -ENOENT;
raw_tp = kmalloc(sizeof(*raw_tp), GFP_USER | __GFP_ZERO);
if (!raw_tp)
return -ENOMEM;
- raw_tp->tp = tp;
+ raw_tp->btp = btp;
prog = bpf_prog_get_type(attr->raw_tracepoint.prog_fd,
BPF_PROG_TYPE_RAW_TRACEPOINT);
@@ -1365,7 +1365,7 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
goto out_free_tp;
}
- err = bpf_probe_register(raw_tp->tp, prog);
+ err = bpf_probe_register(raw_tp->btp, prog);
if (err)
goto out_put_prog;
@@ -1373,7 +1373,7 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
tp_fd = anon_inode_getfd("bpf-raw-tracepoint", &bpf_raw_tp_fops, raw_tp,
O_CLOEXEC);
if (tp_fd < 0) {
- bpf_probe_unregister(raw_tp->tp, prog);
+ bpf_probe_unregister(raw_tp->btp, prog);
err = tp_fd;
goto out_put_prog;
}
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index eb58ef156d36..e578b173fe1d 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -965,6 +965,19 @@ int perf_event_query_prog_array(struct perf_event *event, void __user *info)
return ret;
}
+extern struct bpf_raw_event_map *__start__bpf_raw_tp[];
+extern struct bpf_raw_event_map *__stop__bpf_raw_tp[];
+
+struct bpf_raw_event_map *bpf_find_raw_tracepoint(const char *name)
+{
+ struct bpf_raw_event_map* const *btp = __start__bpf_raw_tp;
+
+ for (; btp < __stop__bpf_raw_tp; btp++)
+ if (!strcmp((*btp)->tp->name, name))
+ return *btp;
+ return NULL;
+}
+
static __always_inline
void __bpf_trace_run(struct bpf_prog *prog, u64 *args)
{
@@ -1020,10 +1033,9 @@ BPF_TRACE_DEFN_x(10);
BPF_TRACE_DEFN_x(11);
BPF_TRACE_DEFN_x(12);
-static int __bpf_probe_register(struct tracepoint *tp, struct bpf_prog *prog)
+static int __bpf_probe_register(struct bpf_raw_event_map *btp, struct bpf_prog *prog)
{
- unsigned long addr;
- char buf[128];
+ struct tracepoint *tp = btp->tp;
/*
* check that program doesn't access arguments beyond what's
@@ -1032,43 +1044,25 @@ static int __bpf_probe_register(struct tracepoint *tp, struct bpf_prog *prog)
if (prog->aux->max_ctx_offset > tp->num_args * sizeof(u64))
return -EINVAL;
- snprintf(buf, sizeof(buf), "__bpf_trace_%s", tp->name);
- addr = kallsyms_lookup_name(buf);
- if (!addr)
- return -ENOENT;
-
- return tracepoint_probe_register(tp, (void *)addr, prog);
+ return tracepoint_probe_register(tp, (void *)btp->bpf_func, prog);
}
-int bpf_probe_register(struct tracepoint *tp, struct bpf_prog *prog)
+int bpf_probe_register(struct bpf_raw_event_map *btp, struct bpf_prog *prog)
{
int err;
mutex_lock(&bpf_event_mutex);
- err = __bpf_probe_register(tp, prog);
+ err = __bpf_probe_register(btp, prog);
mutex_unlock(&bpf_event_mutex);
return err;
}
-static int __bpf_probe_unregister(struct tracepoint *tp, struct bpf_prog *prog)
-{
- unsigned long addr;
- char buf[128];
-
- snprintf(buf, sizeof(buf), "__bpf_trace_%s", tp->name);
- addr = kallsyms_lookup_name(buf);
- if (!addr)
- return -ENOENT;
-
- return tracepoint_probe_unregister(tp, (void *)addr, prog);
-}
-
-int bpf_probe_unregister(struct tracepoint *tp, struct bpf_prog *prog)
+int bpf_probe_unregister(struct bpf_raw_event_map *btp, struct bpf_prog *prog)
{
int err;
mutex_lock(&bpf_event_mutex);
- err = __bpf_probe_unregister(tp, prog);
+ err = tracepoint_probe_unregister(btp->tp, (void *)btp->bpf_func, prog);
mutex_unlock(&bpf_event_mutex);
return err;
}
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