This adds an opt-in interface for tracepoints to expose a writable context to
BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE programs that are attached, while
supporting read-only access from existing BPF_PROG_TYPE_RAW_TRACEPOINT
programs, as well as from non-BPF-based tracepoints.
The initial motivation is to support tracing that can be observed from the
remote end of an NBD socket, e.g. by adding flags to the struct nbd_request
header. Earlier attempts included adding an NBD-specific tracepoint fd, but in
code review, I was recommended to implement it more generically -- as a result,
this patchset is far simpler than my initial try.
Andrew Hall (1):
nbd: add tracepoints for send/receive timing
Matt Mullins (2):
bpf: add writable context for raw tracepoints
nbd: trace sending nbd requests
MAINTAINERS | 1 +
drivers/block/nbd.c | 13 +++
include/linux/bpf.h | 2 +
include/linux/bpf_types.h | 1 +
include/linux/tracepoint-defs.h | 1 +
include/trace/bpf_probe.h | 27 +++++-
include/trace/events/nbd.h | 148 ++++++++++++++++++++++++++++++++
include/uapi/linux/bpf.h | 1 +
kernel/bpf/syscall.c | 8 +-
kernel/bpf/verifier.c | 11 +++
kernel/trace/bpf_trace.c | 21 +++++
11 files changed, 230 insertions(+), 4 deletions(-)
create mode 100644 include/trace/events/nbd.h
--
2.17.1
This is an opt-in interface that allows a tracepoint to provide a safe
buffer that can be written from a BPF_PROG_TYPE_RAW_TRACEPOINT program.
The size of the buffer must be a compile-time constant, and is checked
before allowing a BPF program to attach to a tracepoint that uses this
feature.
The pointer to this buffer will be the first argument of tracepoints
that opt in; the buffer is readable by both BPF_PROG_TYPE_RAW_TRACEPOINT
and BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE programs that attach to such a
tracepoint, but the buffer to which it points may only be written by the
latter.
bpf_probe: assert that writable tracepoint size is correct
Signed-off-by: Matt Mullins <[email protected]>
---
include/linux/bpf.h | 2 ++
include/linux/bpf_types.h | 1 +
include/linux/tracepoint-defs.h | 1 +
include/trace/bpf_probe.h | 27 +++++++++++++++++++++++++--
include/uapi/linux/bpf.h | 1 +
kernel/bpf/syscall.c | 8 ++++++--
kernel/bpf/verifier.c | 11 +++++++++++
kernel/trace/bpf_trace.c | 21 +++++++++++++++++++++
8 files changed, 68 insertions(+), 4 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index a2132e09dc1c..d3c71fd67476 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -263,6 +263,7 @@ enum bpf_reg_type {
PTR_TO_SOCK_COMMON_OR_NULL, /* reg points to sock_common or NULL */
PTR_TO_TCP_SOCK, /* reg points to struct tcp_sock */
PTR_TO_TCP_SOCK_OR_NULL, /* reg points to struct tcp_sock or NULL */
+ PTR_TO_TP_BUFFER, /* reg points to a writable raw tp's buffer */
};
/* The information passed from prog-specific *_is_valid_access
@@ -352,6 +353,7 @@ struct bpf_prog_aux {
u32 used_map_cnt;
u32 max_ctx_offset;
u32 max_pkt_offset;
+ u32 max_tp_access;
u32 stack_depth;
u32 id;
u32 func_cnt; /* used by non-func prog as the number of func progs */
diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index 08bf2f1fe553..c766108608cb 100644
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h
@@ -25,6 +25,7 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_KPROBE, kprobe)
BPF_PROG_TYPE(BPF_PROG_TYPE_TRACEPOINT, tracepoint)
BPF_PROG_TYPE(BPF_PROG_TYPE_PERF_EVENT, perf_event)
BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT, raw_tracepoint)
+BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, raw_tracepoint_writable)
#endif
#ifdef CONFIG_CGROUP_BPF
BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_DEVICE, cg_dev)
diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
index 49ba9cde7e4b..b29950a19205 100644
--- a/include/linux/tracepoint-defs.h
+++ b/include/linux/tracepoint-defs.h
@@ -45,6 +45,7 @@ struct bpf_raw_event_map {
struct tracepoint *tp;
void *bpf_func;
u32 num_args;
+ u32 writable_size;
} __aligned(32);
#endif
diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h
index 505dae0bed80..d6e556c0a085 100644
--- a/include/trace/bpf_probe.h
+++ b/include/trace/bpf_probe.h
@@ -69,8 +69,7 @@ __bpf_trace_##call(void *__data, proto) \
* to make sure that if the tracepoint handling changes, the
* bpf probe will fail to compile unless it too is updated.
*/
-#undef DEFINE_EVENT
-#define DEFINE_EVENT(template, call, proto, args) \
+#define __DEFINE_EVENT(template, call, proto, args, size) \
static inline void bpf_test_probe_##call(void) \
{ \
check_trace_callback_type_##call(__bpf_trace_##template); \
@@ -81,12 +80,36 @@ __bpf_trace_tp_map_##call = { \
.tp = &__tracepoint_##call, \
.bpf_func = (void *)__bpf_trace_##template, \
.num_args = COUNT_ARGS(args), \
+ .writable_size = size, \
};
+#define FIRST(x, ...) x
+
+#undef DEFINE_EVENT_WRITABLE
+#define DEFINE_EVENT_WRITABLE(template, call, proto, args, size) \
+static inline void bpf_test_buffer_##call(void) \
+{ \
+ /* BUILD_BUG_ON() is ignored if the code is completely eliminated, but \
+ * BUILD_BUG_ON_ZERO() uses a different mechanism that is not \
+ * dead-code-eliminated. \
+ */ \
+ FIRST(proto); \
+ (void)BUILD_BUG_ON_ZERO(size != sizeof(*FIRST(args))); \
+} \
+__DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size)
+
+#undef DEFINE_EVENT
+#define DEFINE_EVENT(template, call, proto, args) \
+ __DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), 0)
#undef DEFINE_EVENT_PRINT
#define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
DEFINE_EVENT(template, name, PARAMS(proto), PARAMS(args))
#include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
+
+#undef DEFINE_EVENT_WRITABLE
+#undef __DEFINE_EVENT
+#undef FIRST
+
#endif /* CONFIG_BPF_EVENTS */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 3c38ac9a92a7..c5335d53ce82 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -166,6 +166,7 @@ enum bpf_prog_type {
BPF_PROG_TYPE_LIRC_MODE2,
BPF_PROG_TYPE_SK_REUSEPORT,
BPF_PROG_TYPE_FLOW_DISSECTOR,
+ BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
};
enum bpf_attach_type {
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 62f6bced3a3c..27e2f22879a4 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1720,12 +1720,16 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
}
raw_tp->btp = btp;
- prog = bpf_prog_get_type(attr->raw_tracepoint.prog_fd,
- BPF_PROG_TYPE_RAW_TRACEPOINT);
+ prog = bpf_prog_get(attr->raw_tracepoint.prog_fd);
if (IS_ERR(prog)) {
err = PTR_ERR(prog);
goto out_free_tp;
}
+ if (prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT &&
+ prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE) {
+ err = -EINVAL;
+ goto out_put_prog;
+ }
err = bpf_probe_register(raw_tp->btp, prog);
if (err)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ce166a002d16..b6b4a2ca9f0c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2100,6 +2100,17 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
err = check_sock_access(env, insn_idx, regno, off, size, t);
if (!err && value_regno >= 0)
mark_reg_unknown(env, regs, value_regno);
+ } else if (reg->type == PTR_TO_TP_BUFFER) {
+ if (off < 0) {
+ verbose(env,
+ "R%d invalid tracepoint buffer access: off=%d, size=%d",
+ value_regno, off, size);
+ return -EACCES;
+ }
+ if (off + size > env->prog->aux->max_tp_access)
+ env->prog->aux->max_tp_access = off + size;
+ if (t == BPF_READ && value_regno >= 0)
+ mark_reg_unknown(env, regs, value_regno);
} else {
verbose(env, "R%d invalid mem access '%s'\n", regno,
reg_type_str[reg->type]);
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index d64c00afceb5..a2dd79dc6871 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -909,6 +909,24 @@ const struct bpf_verifier_ops raw_tracepoint_verifier_ops = {
const struct bpf_prog_ops raw_tracepoint_prog_ops = {
};
+static bool raw_tp_writable_prog_is_valid_access(int off, int size,
+ enum bpf_access_type type,
+ const struct bpf_prog *prog,
+ struct bpf_insn_access_aux *info)
+{
+ if (off == 0 && size == sizeof(u64))
+ info->reg_type = PTR_TO_TP_BUFFER;
+ return raw_tp_prog_is_valid_access(off, size, type, prog, info);
+}
+
+const struct bpf_verifier_ops raw_tracepoint_writable_verifier_ops = {
+ .get_func_proto = raw_tp_prog_func_proto,
+ .is_valid_access = raw_tp_writable_prog_is_valid_access,
+};
+
+const struct bpf_prog_ops raw_tracepoint_writable_prog_ops = {
+};
+
static bool pe_prog_is_valid_access(int off, int size, enum bpf_access_type type,
const struct bpf_prog *prog,
struct bpf_insn_access_aux *info)
@@ -1198,6 +1216,9 @@ static int __bpf_probe_register(struct bpf_raw_event_map *btp, struct bpf_prog *
if (prog->aux->max_ctx_offset > btp->num_args * sizeof(u64))
return -EINVAL;
+ if (prog->aux->max_tp_access > btp->writable_size)
+ return -EINVAL;
+
return tracepoint_probe_register(tp, (void *)btp->bpf_func, prog);
}
--
2.17.1
From: Andrew Hall <[email protected]>
This adds four tracepoints to nbd, enabling separate tracing of payload
and header sending/receipt.
In the send path for headers that have already been sent, we also
explicitly initialize the handle so it can be referenced by the later
tracepoint.
Signed-off-by: Andrew Hall <[email protected]>
Signed-off-by: Matt Mullins <[email protected]>
---
drivers/block/nbd.c | 8 ++++
include/trace/events/nbd.h | 92 ++++++++++++++++++++++++++++++++++++++
2 files changed, 100 insertions(+)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 7393d04d255c..d3d914620f66 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -513,6 +513,10 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
if (sent) {
if (sent >= sizeof(request)) {
skip = sent - sizeof(request);
+
+ // initialize handle for tracing purposes
+ handle = nbd_cmd_handle(cmd);
+
goto send_pages;
}
iov_iter_advance(&from, sent);
@@ -536,6 +540,7 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
(unsigned long long)blk_rq_pos(req) << 9, blk_rq_bytes(req));
result = sock_xmit(nbd, index, 1, &from,
(type == NBD_CMD_WRITE) ? MSG_MORE : 0, &sent);
+ trace_nbd_header_sent(req, handle);
if (result <= 0) {
if (was_interrupted(result)) {
/* If we havne't sent anything we can just return BUSY,
@@ -608,6 +613,7 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
bio = next;
}
out:
+ trace_nbd_payload_sent(req, handle);
nsock->pending = NULL;
nsock->sent = 0;
return 0;
@@ -655,6 +661,7 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
tag, req);
return ERR_PTR(-ENOENT);
}
+ trace_nbd_header_received(req, handle);
cmd = blk_mq_rq_to_pdu(req);
mutex_lock(&cmd->lock);
@@ -708,6 +715,7 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
}
}
out:
+ trace_nbd_payload_received(req, handle);
mutex_unlock(&cmd->lock);
return ret ? ERR_PTR(ret) : cmd;
}
diff --git a/include/trace/events/nbd.h b/include/trace/events/nbd.h
index 5928255ed02e..eef476fef95a 100644
--- a/include/trace/events/nbd.h
+++ b/include/trace/events/nbd.h
@@ -7,6 +7,98 @@
#include <linux/tracepoint.h>
+TRACE_EVENT(nbd_header_sent,
+
+ TP_PROTO(struct request *req, u64 handle),
+
+ TP_ARGS(req, handle),
+
+ TP_STRUCT__entry(
+ __field(struct request *, req)
+ __field(u64, handle)
+ ),
+
+ TP_fast_assign(
+ __entry->req = req;
+ __entry->handle = handle;
+ ),
+
+ TP_printk(
+ "nbd header sent: request %p, handle 0x%016llx",
+ __entry->req,
+ __entry->handle
+ )
+);
+
+TRACE_EVENT(nbd_payload_sent,
+
+ TP_PROTO(struct request *req, u64 handle),
+
+ TP_ARGS(req, handle),
+
+ TP_STRUCT__entry(
+ __field(struct request *, req)
+ __field(u64, handle)
+ ),
+
+ TP_fast_assign(
+ __entry->req = req;
+ __entry->handle = handle;
+ ),
+
+ TP_printk(
+ "nbd payload sent: request %p, handle 0x%016llx",
+ __entry->req,
+ __entry->handle
+ )
+);
+
+TRACE_EVENT(nbd_header_received,
+
+ TP_PROTO(struct request *req, u64 handle),
+
+ TP_ARGS(req, handle),
+
+ TP_STRUCT__entry(
+ __field(struct request *, req)
+ __field(u64, handle)
+ ),
+
+ TP_fast_assign(
+ __entry->req = req;
+ __entry->handle = handle;
+ ),
+
+ TP_printk(
+ "nbd header received: request %p, handle 0x%016llx",
+ __entry->req,
+ __entry->handle
+ )
+);
+
+TRACE_EVENT(nbd_payload_received,
+
+ TP_PROTO(struct request *req, u64 handle),
+
+ TP_ARGS(req, handle),
+
+ TP_STRUCT__entry(
+ __field(struct request *, req)
+ __field(u64, handle)
+ ),
+
+ TP_fast_assign(
+ __entry->req = req;
+ __entry->handle = handle;
+ ),
+
+ TP_printk(
+ "nbd payload received: request %p, handle 0x%016llx",
+ __entry->req,
+ __entry->handle
+ )
+);
+
DECLARE_EVENT_CLASS(nbd_send_request,
TP_PROTO(struct nbd_request *nbd_request, int index,
--
2.17.1
On 03/29/2019 01:07 AM, Matt Mullins wrote:
> This is an opt-in interface that allows a tracepoint to provide a safe
> buffer that can be written from a BPF_PROG_TYPE_RAW_TRACEPOINT program.
> The size of the buffer must be a compile-time constant, and is checked
> before allowing a BPF program to attach to a tracepoint that uses this
> feature.
>
> The pointer to this buffer will be the first argument of tracepoints
> that opt in; the buffer is readable by both BPF_PROG_TYPE_RAW_TRACEPOINT
> and BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE programs that attach to such a
> tracepoint, but the buffer to which it points may only be written by the
> latter.
>
> bpf_probe: assert that writable tracepoint size is correct
Maybe also add a kselftest into bpf test suite to i) demo it and ii) make
sure it's continuously been tested by bots running the suite?
> Signed-off-by: Matt Mullins <[email protected]>
> ---
> include/linux/bpf.h | 2 ++
> include/linux/bpf_types.h | 1 +
> include/linux/tracepoint-defs.h | 1 +
> include/trace/bpf_probe.h | 27 +++++++++++++++++++++++++--
> include/uapi/linux/bpf.h | 1 +
> kernel/bpf/syscall.c | 8 ++++++--
> kernel/bpf/verifier.c | 11 +++++++++++
> kernel/trace/bpf_trace.c | 21 +++++++++++++++++++++
> 8 files changed, 68 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index a2132e09dc1c..d3c71fd67476 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -263,6 +263,7 @@ enum bpf_reg_type {
> PTR_TO_SOCK_COMMON_OR_NULL, /* reg points to sock_common or NULL */
> PTR_TO_TCP_SOCK, /* reg points to struct tcp_sock */
> PTR_TO_TCP_SOCK_OR_NULL, /* reg points to struct tcp_sock or NULL */
> + PTR_TO_TP_BUFFER, /* reg points to a writable raw tp's buffer */
> };
>
> /* The information passed from prog-specific *_is_valid_access
> @@ -352,6 +353,7 @@ struct bpf_prog_aux {
> u32 used_map_cnt;
> u32 max_ctx_offset;
> u32 max_pkt_offset;
> + u32 max_tp_access;
> u32 stack_depth;
> u32 id;
> u32 func_cnt; /* used by non-func prog as the number of func progs */
> diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
> index 08bf2f1fe553..c766108608cb 100644
> --- a/include/linux/bpf_types.h
> +++ b/include/linux/bpf_types.h
> @@ -25,6 +25,7 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_KPROBE, kprobe)
> BPF_PROG_TYPE(BPF_PROG_TYPE_TRACEPOINT, tracepoint)
> BPF_PROG_TYPE(BPF_PROG_TYPE_PERF_EVENT, perf_event)
> BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT, raw_tracepoint)
> +BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, raw_tracepoint_writable)
> #endif
> #ifdef CONFIG_CGROUP_BPF
> BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_DEVICE, cg_dev)
> diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
> index 49ba9cde7e4b..b29950a19205 100644
> --- a/include/linux/tracepoint-defs.h
> +++ b/include/linux/tracepoint-defs.h
> @@ -45,6 +45,7 @@ struct bpf_raw_event_map {
> struct tracepoint *tp;
> void *bpf_func;
> u32 num_args;
> + u32 writable_size;
> } __aligned(32);
>
> #endif
> diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h
> index 505dae0bed80..d6e556c0a085 100644
> --- a/include/trace/bpf_probe.h
> +++ b/include/trace/bpf_probe.h
> @@ -69,8 +69,7 @@ __bpf_trace_##call(void *__data, proto) \
> * to make sure that if the tracepoint handling changes, the
> * bpf probe will fail to compile unless it too is updated.
> */
> -#undef DEFINE_EVENT
> -#define DEFINE_EVENT(template, call, proto, args) \
> +#define __DEFINE_EVENT(template, call, proto, args, size) \
> static inline void bpf_test_probe_##call(void) \
> { \
> check_trace_callback_type_##call(__bpf_trace_##template); \
> @@ -81,12 +80,36 @@ __bpf_trace_tp_map_##call = { \
> .tp = &__tracepoint_##call, \
> .bpf_func = (void *)__bpf_trace_##template, \
> .num_args = COUNT_ARGS(args), \
> + .writable_size = size, \
> };
>
> +#define FIRST(x, ...) x
> +
> +#undef DEFINE_EVENT_WRITABLE
> +#define DEFINE_EVENT_WRITABLE(template, call, proto, args, size) \
> +static inline void bpf_test_buffer_##call(void) \
> +{ \
> + /* BUILD_BUG_ON() is ignored if the code is completely eliminated, but \
> + * BUILD_BUG_ON_ZERO() uses a different mechanism that is not \
> + * dead-code-eliminated. \
> + */ \
> + FIRST(proto); \
> + (void)BUILD_BUG_ON_ZERO(size != sizeof(*FIRST(args))); \
> +} \
> +__DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size)
> +
> +#undef DEFINE_EVENT
> +#define DEFINE_EVENT(template, call, proto, args) \
> + __DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), 0)
>
> #undef DEFINE_EVENT_PRINT
> #define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
> DEFINE_EVENT(template, name, PARAMS(proto), PARAMS(args))
>
> #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
> +
> +#undef DEFINE_EVENT_WRITABLE
> +#undef __DEFINE_EVENT
> +#undef FIRST
> +
> #endif /* CONFIG_BPF_EVENTS */
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 3c38ac9a92a7..c5335d53ce82 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -166,6 +166,7 @@ enum bpf_prog_type {
> BPF_PROG_TYPE_LIRC_MODE2,
> BPF_PROG_TYPE_SK_REUSEPORT,
> BPF_PROG_TYPE_FLOW_DISSECTOR,
> + BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
> };
>
> enum bpf_attach_type {
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 62f6bced3a3c..27e2f22879a4 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -1720,12 +1720,16 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
> }
> raw_tp->btp = btp;
>
> - prog = bpf_prog_get_type(attr->raw_tracepoint.prog_fd,
> - BPF_PROG_TYPE_RAW_TRACEPOINT);
> + prog = bpf_prog_get(attr->raw_tracepoint.prog_fd);
> if (IS_ERR(prog)) {
> err = PTR_ERR(prog);
> goto out_free_tp;
> }
> + if (prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT &&
> + prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE) {
I don't think we'd gain a lot by making this an extra prog type which can do the
same as BPF_PROG_TYPE_RAW_TRACEPOINT modulo optional writing. Why not integrating
this directly into BPF_PROG_TYPE_RAW_TRACEPOINT then? The actual opt-in comes from
the DEFINE_EVENT_WRITABLE(), not from the prog type.
> + err = -EINVAL;
> + goto out_put_prog;
> + }
>
> err = bpf_probe_register(raw_tp->btp, prog);
> if (err)
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index ce166a002d16..b6b4a2ca9f0c 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -2100,6 +2100,17 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
> err = check_sock_access(env, insn_idx, regno, off, size, t);
> if (!err && value_regno >= 0)
> mark_reg_unknown(env, regs, value_regno);
> + } else if (reg->type == PTR_TO_TP_BUFFER) {
> + if (off < 0) {
> + verbose(env,
> + "R%d invalid tracepoint buffer access: off=%d, size=%d",
> + value_regno, off, size);
> + return -EACCES;
> + }
> + if (off + size > env->prog->aux->max_tp_access)
> + env->prog->aux->max_tp_access = off + size;
> + if (t == BPF_READ && value_regno >= 0)
> + mark_reg_unknown(env, regs, value_regno);
This should also disallow variable access into the reg, I presume (see check_ctx_reg())?
Or is there a clear rationale for having it enabled?
> } else {
> verbose(env, "R%d invalid mem access '%s'\n", regno,
> reg_type_str[reg->type]);
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index d64c00afceb5..a2dd79dc6871 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -909,6 +909,24 @@ const struct bpf_verifier_ops raw_tracepoint_verifier_ops = {
> const struct bpf_prog_ops raw_tracepoint_prog_ops = {
> };
>
> +static bool raw_tp_writable_prog_is_valid_access(int off, int size,
> + enum bpf_access_type type,
> + const struct bpf_prog *prog,
> + struct bpf_insn_access_aux *info)
> +{
> + if (off == 0 && size == sizeof(u64))
> + info->reg_type = PTR_TO_TP_BUFFER;
> + return raw_tp_prog_is_valid_access(off, size, type, prog, info);
> +}
> +
> +const struct bpf_verifier_ops raw_tracepoint_writable_verifier_ops = {
> + .get_func_proto = raw_tp_prog_func_proto,
> + .is_valid_access = raw_tp_writable_prog_is_valid_access,
> +};
> +
> +const struct bpf_prog_ops raw_tracepoint_writable_prog_ops = {
> +};
> +
> static bool pe_prog_is_valid_access(int off, int size, enum bpf_access_type type,
> const struct bpf_prog *prog,
> struct bpf_insn_access_aux *info)
> @@ -1198,6 +1216,9 @@ static int __bpf_probe_register(struct bpf_raw_event_map *btp, struct bpf_prog *
> if (prog->aux->max_ctx_offset > btp->num_args * sizeof(u64))
> return -EINVAL;
>
> + if (prog->aux->max_tp_access > btp->writable_size)
> + return -EINVAL;
> +
> return tracepoint_probe_register(tp, (void *)btp->bpf_func, prog);
> }
>
>
On Mon, 2019-04-01 at 22:40 +0200, Daniel Borkmann wrote:
> On 03/29/2019 01:07 AM, Matt Mullins wrote:
> > This is an opt-in interface that allows a tracepoint to provide a safe
> > buffer that can be written from a BPF_PROG_TYPE_RAW_TRACEPOINT program.
> > The size of the buffer must be a compile-time constant, and is checked
> > before allowing a BPF program to attach to a tracepoint that uses this
> > feature.
> >
> > The pointer to this buffer will be the first argument of tracepoints
> > that opt in; the buffer is readable by both BPF_PROG_TYPE_RAW_TRACEPOINT
> > and BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE programs that attach to such a
> > tracepoint, but the buffer to which it points may only be written by the
> > latter.
> >
> > bpf_probe: assert that writable tracepoint size is correct
>
> Maybe also add a kselftest into bpf test suite to i) demo it and ii) make
> sure it's continuously been tested by bots running the suite?
Will do.
>
> > Signed-off-by: Matt Mullins <[email protected]>
> > ---
> > include/linux/bpf.h | 2 ++
> > include/linux/bpf_types.h | 1 +
> > include/linux/tracepoint-defs.h | 1 +
> > include/trace/bpf_probe.h | 27 +++++++++++++++++++++++++--
> > include/uapi/linux/bpf.h | 1 +
> > kernel/bpf/syscall.c | 8 ++++++--
> > kernel/bpf/verifier.c | 11 +++++++++++
> > kernel/trace/bpf_trace.c | 21 +++++++++++++++++++++
> > 8 files changed, 68 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index a2132e09dc1c..d3c71fd67476 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -263,6 +263,7 @@ enum bpf_reg_type {
> > PTR_TO_SOCK_COMMON_OR_NULL, /* reg points to sock_common or NULL */
> > PTR_TO_TCP_SOCK, /* reg points to struct tcp_sock */
> > PTR_TO_TCP_SOCK_OR_NULL, /* reg points to struct tcp_sock or NULL */
> > + PTR_TO_TP_BUFFER, /* reg points to a writable raw tp's buffer */
> > };
> >
> > /* The information passed from prog-specific *_is_valid_access
> > @@ -352,6 +353,7 @@ struct bpf_prog_aux {
> > u32 used_map_cnt;
> > u32 max_ctx_offset;
> > u32 max_pkt_offset;
> > + u32 max_tp_access;
> > u32 stack_depth;
> > u32 id;
> > u32 func_cnt; /* used by non-func prog as the number of func progs */
> > diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
> > index 08bf2f1fe553..c766108608cb 100644
> > --- a/include/linux/bpf_types.h
> > +++ b/include/linux/bpf_types.h
> > @@ -25,6 +25,7 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_KPROBE, kprobe)
> > BPF_PROG_TYPE(BPF_PROG_TYPE_TRACEPOINT, tracepoint)
> > BPF_PROG_TYPE(BPF_PROG_TYPE_PERF_EVENT, perf_event)
> > BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT, raw_tracepoint)
> > +BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, raw_tracepoint_writable)
> > #endif
> > #ifdef CONFIG_CGROUP_BPF
> > BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_DEVICE, cg_dev)
> > diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
> > index 49ba9cde7e4b..b29950a19205 100644
> > --- a/include/linux/tracepoint-defs.h
> > +++ b/include/linux/tracepoint-defs.h
> > @@ -45,6 +45,7 @@ struct bpf_raw_event_map {
> > struct tracepoint *tp;
> > void *bpf_func;
> > u32 num_args;
> > + u32 writable_size;
> > } __aligned(32);
> >
> > #endif
> > diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h
> > index 505dae0bed80..d6e556c0a085 100644
> > --- a/include/trace/bpf_probe.h
> > +++ b/include/trace/bpf_probe.h
> > @@ -69,8 +69,7 @@ __bpf_trace_##call(void *__data, proto) \
> > * to make sure that if the tracepoint handling changes, the
> > * bpf probe will fail to compile unless it too is updated.
> > */
> > -#undef DEFINE_EVENT
> > -#define DEFINE_EVENT(template, call, proto, args) \
> > +#define __DEFINE_EVENT(template, call, proto, args, size) \
> > static inline void bpf_test_probe_##call(void) \
> > { \
> > check_trace_callback_type_##call(__bpf_trace_##template); \
> > @@ -81,12 +80,36 @@ __bpf_trace_tp_map_##call = { \
> > .tp = &__tracepoint_##call, \
> > .bpf_func = (void *)__bpf_trace_##template, \
> > .num_args = COUNT_ARGS(args), \
> > + .writable_size = size, \
> > };
> >
> > +#define FIRST(x, ...) x
> > +
> > +#undef DEFINE_EVENT_WRITABLE
> > +#define DEFINE_EVENT_WRITABLE(template, call, proto, args, size) \
> > +static inline void bpf_test_buffer_##call(void) \
> > +{ \
> > + /* BUILD_BUG_ON() is ignored if the code is completely eliminated, but \
> > + * BUILD_BUG_ON_ZERO() uses a different mechanism that is not \
> > + * dead-code-eliminated. \
> > + */ \
> > + FIRST(proto); \
> > + (void)BUILD_BUG_ON_ZERO(size != sizeof(*FIRST(args))); \
> > +} \
> > +__DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size)
> > +
> > +#undef DEFINE_EVENT
> > +#define DEFINE_EVENT(template, call, proto, args) \
> > + __DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), 0)
> >
> > #undef DEFINE_EVENT_PRINT
> > #define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
> > DEFINE_EVENT(template, name, PARAMS(proto), PARAMS(args))
> >
> > #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
> > +
> > +#undef DEFINE_EVENT_WRITABLE
> > +#undef __DEFINE_EVENT
> > +#undef FIRST
> > +
> > #endif /* CONFIG_BPF_EVENTS */
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 3c38ac9a92a7..c5335d53ce82 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -166,6 +166,7 @@ enum bpf_prog_type {
> > BPF_PROG_TYPE_LIRC_MODE2,
> > BPF_PROG_TYPE_SK_REUSEPORT,
> > BPF_PROG_TYPE_FLOW_DISSECTOR,
> > + BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
> > };
> >
> > enum bpf_attach_type {
> > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > index 62f6bced3a3c..27e2f22879a4 100644
> > --- a/kernel/bpf/syscall.c
> > +++ b/kernel/bpf/syscall.c
> > @@ -1720,12 +1720,16 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
> > }
> > raw_tp->btp = btp;
> >
> > - prog = bpf_prog_get_type(attr->raw_tracepoint.prog_fd,
> > - BPF_PROG_TYPE_RAW_TRACEPOINT);
> > + prog = bpf_prog_get(attr->raw_tracepoint.prog_fd);
> > if (IS_ERR(prog)) {
> > err = PTR_ERR(prog);
> > goto out_free_tp;
> > }
> > + if (prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT &&
> > + prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE) {
>
> I don't think we'd gain a lot by making this an extra prog type which can do the
> same as BPF_PROG_TYPE_RAW_TRACEPOINT modulo optional writing. Why not integrating
> this directly into BPF_PROG_TYPE_RAW_TRACEPOINT then? The actual opt-in comes from
> the DEFINE_EVENT_WRITABLE(), not from the prog type.
I did that to separate the hook into
raw_tp_writable_prog_is_valid_access, which (compared to
raw_tp_prog_is_valid_access):
1) permits writes, and
2) encodes the assumption than the context begins with the pointer to
that writable buffer
I'm not sure those are appropriate for all users of
BPF_PROG_TYPE_RAW_TRACEPOINT, but I can't immediately point out any
harm in doing so -- some dereferences of ctx that have historically
returned a SCALAR_VALUE would end up tagged as a PTR_TO_TP_BUFFER, but
they still won't be able to access through that pointer unless they're
attached to the right tracepoint.
I'll try to unify the two and see what I get.
>
> > + err = -EINVAL;
> > + goto out_put_prog;
> > + }
> >
> > err = bpf_probe_register(raw_tp->btp, prog);
> > if (err)
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index ce166a002d16..b6b4a2ca9f0c 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -2100,6 +2100,17 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
> > err = check_sock_access(env, insn_idx, regno, off, size, t);
> > if (!err && value_regno >= 0)
> > mark_reg_unknown(env, regs, value_regno);
> > + } else if (reg->type == PTR_TO_TP_BUFFER) {
> > + if (off < 0) {
> > + verbose(env,
> > + "R%d invalid tracepoint buffer access: off=%d, size=%d",
> > + value_regno, off, size);
> > + return -EACCES;
> > + }
> > + if (off + size > env->prog->aux->max_tp_access)
> > + env->prog->aux->max_tp_access = off + size;
> > + if (t == BPF_READ && value_regno >= 0)
> > + mark_reg_unknown(env, regs, value_regno);
>
> This should also disallow variable access into the reg, I presume (see check_ctx_reg())?
> Or is there a clear rationale for having it enabled?
Nope, that was an oversight from an (incorrect) assumption that
arithmetic would be disallowed on a PTR_TO_TP_BUFFER. I'll fix this in
v2.
>
> > } else {
> > verbose(env, "R%d invalid mem access '%s'\n", regno,
> > reg_type_str[reg->type]);
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index d64c00afceb5..a2dd79dc6871 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -909,6 +909,24 @@ const struct bpf_verifier_ops raw_tracepoint_verifier_ops = {
> > const struct bpf_prog_ops raw_tracepoint_prog_ops = {
> > };
> >
> > +static bool raw_tp_writable_prog_is_valid_access(int off, int size,
> > + enum bpf_access_type type,
> > + const struct bpf_prog *prog,
> > + struct bpf_insn_access_aux *info)
> > +{
> > + if (off == 0 && size == sizeof(u64))
> > + info->reg_type = PTR_TO_TP_BUFFER;
> > + return raw_tp_prog_is_valid_access(off, size, type, prog, info);
> > +}
> > +
> > +const struct bpf_verifier_ops raw_tracepoint_writable_verifier_ops = {
> > + .get_func_proto = raw_tp_prog_func_proto,
> > + .is_valid_access = raw_tp_writable_prog_is_valid_access,
> > +};
> > +
> > +const struct bpf_prog_ops raw_tracepoint_writable_prog_ops = {
> > +};
> > +
> > static bool pe_prog_is_valid_access(int off, int size, enum bpf_access_type type,
> > const struct bpf_prog *prog,
> > struct bpf_insn_access_aux *info)
> > @@ -1198,6 +1216,9 @@ static int __bpf_probe_register(struct bpf_raw_event_map *btp, struct bpf_prog *
> > if (prog->aux->max_ctx_offset > btp->num_args * sizeof(u64))
> > return -EINVAL;
> >
> > + if (prog->aux->max_tp_access > btp->writable_size)
> > + return -EINVAL;
> > +
> > return tracepoint_probe_register(tp, (void *)btp->bpf_func, prog);
> > }
> >
> >
>
>
On Wed, Apr 03, 2019 at 06:39:12PM +0000, Matt Mullins wrote:
> On Mon, 2019-04-01 at 22:40 +0200, Daniel Borkmann wrote:
> > On 03/29/2019 01:07 AM, Matt Mullins wrote:
> > > This is an opt-in interface that allows a tracepoint to provide a safe
> > > buffer that can be written from a BPF_PROG_TYPE_RAW_TRACEPOINT program.
> > > The size of the buffer must be a compile-time constant, and is checked
> > > before allowing a BPF program to attach to a tracepoint that uses this
> > > feature.
> > >
> > > The pointer to this buffer will be the first argument of tracepoints
> > > that opt in; the buffer is readable by both BPF_PROG_TYPE_RAW_TRACEPOINT
> > > and BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE programs that attach to such a
> > > tracepoint, but the buffer to which it points may only be written by the
> > > latter.
> > >
> > > bpf_probe: assert that writable tracepoint size is correct
> >
> > Maybe also add a kselftest into bpf test suite to i) demo it and ii) make
> > sure it's continuously been tested by bots running the suite?
>
> Will do.
>
> >
> > > Signed-off-by: Matt Mullins <[email protected]>
> > > ---
> > > include/linux/bpf.h | 2 ++
> > > include/linux/bpf_types.h | 1 +
> > > include/linux/tracepoint-defs.h | 1 +
> > > include/trace/bpf_probe.h | 27 +++++++++++++++++++++++++--
> > > include/uapi/linux/bpf.h | 1 +
> > > kernel/bpf/syscall.c | 8 ++++++--
> > > kernel/bpf/verifier.c | 11 +++++++++++
> > > kernel/trace/bpf_trace.c | 21 +++++++++++++++++++++
> > > 8 files changed, 68 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > > index a2132e09dc1c..d3c71fd67476 100644
> > > --- a/include/linux/bpf.h
> > > +++ b/include/linux/bpf.h
> > > @@ -263,6 +263,7 @@ enum bpf_reg_type {
> > > PTR_TO_SOCK_COMMON_OR_NULL, /* reg points to sock_common or NULL */
> > > PTR_TO_TCP_SOCK, /* reg points to struct tcp_sock */
> > > PTR_TO_TCP_SOCK_OR_NULL, /* reg points to struct tcp_sock or NULL */
> > > + PTR_TO_TP_BUFFER, /* reg points to a writable raw tp's buffer */
> > > };
> > >
> > > /* The information passed from prog-specific *_is_valid_access
> > > @@ -352,6 +353,7 @@ struct bpf_prog_aux {
> > > u32 used_map_cnt;
> > > u32 max_ctx_offset;
> > > u32 max_pkt_offset;
> > > + u32 max_tp_access;
> > > u32 stack_depth;
> > > u32 id;
> > > u32 func_cnt; /* used by non-func prog as the number of func progs */
> > > diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
> > > index 08bf2f1fe553..c766108608cb 100644
> > > --- a/include/linux/bpf_types.h
> > > +++ b/include/linux/bpf_types.h
> > > @@ -25,6 +25,7 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_KPROBE, kprobe)
> > > BPF_PROG_TYPE(BPF_PROG_TYPE_TRACEPOINT, tracepoint)
> > > BPF_PROG_TYPE(BPF_PROG_TYPE_PERF_EVENT, perf_event)
> > > BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT, raw_tracepoint)
> > > +BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, raw_tracepoint_writable)
> > > #endif
> > > #ifdef CONFIG_CGROUP_BPF
> > > BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_DEVICE, cg_dev)
> > > diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
> > > index 49ba9cde7e4b..b29950a19205 100644
> > > --- a/include/linux/tracepoint-defs.h
> > > +++ b/include/linux/tracepoint-defs.h
> > > @@ -45,6 +45,7 @@ struct bpf_raw_event_map {
> > > struct tracepoint *tp;
> > > void *bpf_func;
> > > u32 num_args;
> > > + u32 writable_size;
> > > } __aligned(32);
> > >
> > > #endif
> > > diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h
> > > index 505dae0bed80..d6e556c0a085 100644
> > > --- a/include/trace/bpf_probe.h
> > > +++ b/include/trace/bpf_probe.h
> > > @@ -69,8 +69,7 @@ __bpf_trace_##call(void *__data, proto) \
> > > * to make sure that if the tracepoint handling changes, the
> > > * bpf probe will fail to compile unless it too is updated.
> > > */
> > > -#undef DEFINE_EVENT
> > > -#define DEFINE_EVENT(template, call, proto, args) \
> > > +#define __DEFINE_EVENT(template, call, proto, args, size) \
> > > static inline void bpf_test_probe_##call(void) \
> > > { \
> > > check_trace_callback_type_##call(__bpf_trace_##template); \
> > > @@ -81,12 +80,36 @@ __bpf_trace_tp_map_##call = { \
> > > .tp = &__tracepoint_##call, \
> > > .bpf_func = (void *)__bpf_trace_##template, \
> > > .num_args = COUNT_ARGS(args), \
> > > + .writable_size = size, \
> > > };
> > >
> > > +#define FIRST(x, ...) x
> > > +
> > > +#undef DEFINE_EVENT_WRITABLE
> > > +#define DEFINE_EVENT_WRITABLE(template, call, proto, args, size) \
> > > +static inline void bpf_test_buffer_##call(void) \
> > > +{ \
> > > + /* BUILD_BUG_ON() is ignored if the code is completely eliminated, but \
> > > + * BUILD_BUG_ON_ZERO() uses a different mechanism that is not \
> > > + * dead-code-eliminated. \
> > > + */ \
> > > + FIRST(proto); \
> > > + (void)BUILD_BUG_ON_ZERO(size != sizeof(*FIRST(args))); \
> > > +} \
> > > +__DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size)
> > > +
> > > +#undef DEFINE_EVENT
> > > +#define DEFINE_EVENT(template, call, proto, args) \
> > > + __DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), 0)
> > >
> > > #undef DEFINE_EVENT_PRINT
> > > #define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
> > > DEFINE_EVENT(template, name, PARAMS(proto), PARAMS(args))
> > >
> > > #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
> > > +
> > > +#undef DEFINE_EVENT_WRITABLE
> > > +#undef __DEFINE_EVENT
> > > +#undef FIRST
> > > +
> > > #endif /* CONFIG_BPF_EVENTS */
> > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > > index 3c38ac9a92a7..c5335d53ce82 100644
> > > --- a/include/uapi/linux/bpf.h
> > > +++ b/include/uapi/linux/bpf.h
> > > @@ -166,6 +166,7 @@ enum bpf_prog_type {
> > > BPF_PROG_TYPE_LIRC_MODE2,
> > > BPF_PROG_TYPE_SK_REUSEPORT,
> > > BPF_PROG_TYPE_FLOW_DISSECTOR,
> > > + BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
> > > };
> > >
> > > enum bpf_attach_type {
> > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > > index 62f6bced3a3c..27e2f22879a4 100644
> > > --- a/kernel/bpf/syscall.c
> > > +++ b/kernel/bpf/syscall.c
> > > @@ -1720,12 +1720,16 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
> > > }
> > > raw_tp->btp = btp;
> > >
> > > - prog = bpf_prog_get_type(attr->raw_tracepoint.prog_fd,
> > > - BPF_PROG_TYPE_RAW_TRACEPOINT);
> > > + prog = bpf_prog_get(attr->raw_tracepoint.prog_fd);
> > > if (IS_ERR(prog)) {
> > > err = PTR_ERR(prog);
> > > goto out_free_tp;
> > > }
> > > + if (prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT &&
> > > + prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE) {
> >
> > I don't think we'd gain a lot by making this an extra prog type which can do the
> > same as BPF_PROG_TYPE_RAW_TRACEPOINT modulo optional writing. Why not integrating
> > this directly into BPF_PROG_TYPE_RAW_TRACEPOINT then? The actual opt-in comes from
> > the DEFINE_EVENT_WRITABLE(), not from the prog type.
>
> I did that to separate the hook into
> raw_tp_writable_prog_is_valid_access, which (compared to
> raw_tp_prog_is_valid_access):
>
> 1) permits writes, and
> 2) encodes the assumption than the context begins with the pointer to
> that writable buffer
>
> I'm not sure those are appropriate for all users of
> BPF_PROG_TYPE_RAW_TRACEPOINT, but I can't immediately point out any
> harm in doing so -- some dereferences of ctx that have historically
> returned a SCALAR_VALUE would end up tagged as a PTR_TO_TP_BUFFER, but
> they still won't be able to access through that pointer unless they're
> attached to the right tracepoint.
>
> I'll try to unify the two and see what I get.
I think combining raw_tp prog type with raw_tp_writeable is possible,
but too cumbersome to use from user pov.
Since such raw_tp will be accepted at prog load time,
but only at the time of attach it will be rejected in __bpf_probe_register.
raw_tp_writable_prog_is_valid_access() doesn't know future attach point.
we cannot use bpf_attr.expected_attach_type here.
That's why it simply does:
+ if (off == 0 && size == sizeof(u64))
+ info->reg_type = PTR_TO_TP_BUFFER;
essentially hard coding first argument of writeable tp to be the buffer.
TP invocation is also new.
Like in patch 2:
trace_nbd_send_request(&request, nbd->index, blk_mq_rq_from_pdu(cmd));
Patches 1,2,3 actually look fine to me,
but I agree that selftests are necessary.
Matt, could you add new writeable tracepoint somewhere in bpf_test_run()
and corresponding selftest?
Thanks
On Thu, 2019-04-04 at 18:17 -0700, Alexei Starovoitov wrote:
> On Wed, Apr 03, 2019 at 06:39:12PM +0000, Matt Mullins wrote:
> > On Mon, 2019-04-01 at 22:40 +0200, Daniel Borkmann wrote:
> > > On 03/29/2019 01:07 AM, Matt Mullins wrote:
> > > > This is an opt-in interface that allows a tracepoint to provide a safe
> > > > buffer that can be written from a BPF_PROG_TYPE_RAW_TRACEPOINT program.
> > > > The size of the buffer must be a compile-time constant, and is checked
> > > > before allowing a BPF program to attach to a tracepoint that uses this
> > > > feature.
> > > >
> > > > The pointer to this buffer will be the first argument of tracepoints
> > > > that opt in; the buffer is readable by both BPF_PROG_TYPE_RAW_TRACEPOINT
> > > > and BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE programs that attach to such a
> > > > tracepoint, but the buffer to which it points may only be written by the
> > > > latter.
> > > >
> > > > bpf_probe: assert that writable tracepoint size is correct
> > >
> > > Maybe also add a kselftest into bpf test suite to i) demo it and ii) make
> > > sure it's continuously been tested by bots running the suite?
> >
> > Will do.
> >
> > >
> > > > Signed-off-by: Matt Mullins <[email protected]>
> > > > ---
> > > > include/linux/bpf.h | 2 ++
> > > > include/linux/bpf_types.h | 1 +
> > > > include/linux/tracepoint-defs.h | 1 +
> > > > include/trace/bpf_probe.h | 27 +++++++++++++++++++++++++--
> > > > include/uapi/linux/bpf.h | 1 +
> > > > kernel/bpf/syscall.c | 8 ++++++--
> > > > kernel/bpf/verifier.c | 11 +++++++++++
> > > > kernel/trace/bpf_trace.c | 21 +++++++++++++++++++++
> > > > 8 files changed, 68 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > > > index a2132e09dc1c..d3c71fd67476 100644
> > > > --- a/include/linux/bpf.h
> > > > +++ b/include/linux/bpf.h
> > > > @@ -263,6 +263,7 @@ enum bpf_reg_type {
> > > > PTR_TO_SOCK_COMMON_OR_NULL, /* reg points to sock_common or NULL */
> > > > PTR_TO_TCP_SOCK, /* reg points to struct tcp_sock */
> > > > PTR_TO_TCP_SOCK_OR_NULL, /* reg points to struct tcp_sock or NULL */
> > > > + PTR_TO_TP_BUFFER, /* reg points to a writable raw tp's buffer */
> > > > };
> > > >
> > > > /* The information passed from prog-specific *_is_valid_access
> > > > @@ -352,6 +353,7 @@ struct bpf_prog_aux {
> > > > u32 used_map_cnt;
> > > > u32 max_ctx_offset;
> > > > u32 max_pkt_offset;
> > > > + u32 max_tp_access;
> > > > u32 stack_depth;
> > > > u32 id;
> > > > u32 func_cnt; /* used by non-func prog as the number of func progs */
> > > > diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
> > > > index 08bf2f1fe553..c766108608cb 100644
> > > > --- a/include/linux/bpf_types.h
> > > > +++ b/include/linux/bpf_types.h
> > > > @@ -25,6 +25,7 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_KPROBE, kprobe)
> > > > BPF_PROG_TYPE(BPF_PROG_TYPE_TRACEPOINT, tracepoint)
> > > > BPF_PROG_TYPE(BPF_PROG_TYPE_PERF_EVENT, perf_event)
> > > > BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT, raw_tracepoint)
> > > > +BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, raw_tracepoint_writable)
> > > > #endif
> > > > #ifdef CONFIG_CGROUP_BPF
> > > > BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_DEVICE, cg_dev)
> > > > diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
> > > > index 49ba9cde7e4b..b29950a19205 100644
> > > > --- a/include/linux/tracepoint-defs.h
> > > > +++ b/include/linux/tracepoint-defs.h
> > > > @@ -45,6 +45,7 @@ struct bpf_raw_event_map {
> > > > struct tracepoint *tp;
> > > > void *bpf_func;
> > > > u32 num_args;
> > > > + u32 writable_size;
> > > > } __aligned(32);
> > > >
> > > > #endif
> > > > diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h
> > > > index 505dae0bed80..d6e556c0a085 100644
> > > > --- a/include/trace/bpf_probe.h
> > > > +++ b/include/trace/bpf_probe.h
> > > > @@ -69,8 +69,7 @@ __bpf_trace_##call(void *__data, proto) \
> > > > * to make sure that if the tracepoint handling changes, the
> > > > * bpf probe will fail to compile unless it too is updated.
> > > > */
> > > > -#undef DEFINE_EVENT
> > > > -#define DEFINE_EVENT(template, call, proto, args) \
> > > > +#define __DEFINE_EVENT(template, call, proto, args, size) \
> > > > static inline void bpf_test_probe_##call(void) \
> > > > { \
> > > > check_trace_callback_type_##call(__bpf_trace_##template); \
> > > > @@ -81,12 +80,36 @@ __bpf_trace_tp_map_##call = { \
> > > > .tp = &__tracepoint_##call, \
> > > > .bpf_func = (void *)__bpf_trace_##template, \
> > > > .num_args = COUNT_ARGS(args), \
> > > > + .writable_size = size, \
> > > > };
> > > >
> > > > +#define FIRST(x, ...) x
> > > > +
> > > > +#undef DEFINE_EVENT_WRITABLE
> > > > +#define DEFINE_EVENT_WRITABLE(template, call, proto, args, size) \
> > > > +static inline void bpf_test_buffer_##call(void) \
> > > > +{ \
> > > > + /* BUILD_BUG_ON() is ignored if the code is completely eliminated, but \
> > > > + * BUILD_BUG_ON_ZERO() uses a different mechanism that is not \
> > > > + * dead-code-eliminated. \
> > > > + */ \
> > > > + FIRST(proto); \
> > > > + (void)BUILD_BUG_ON_ZERO(size != sizeof(*FIRST(args))); \
> > > > +} \
> > > > +__DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size)
> > > > +
> > > > +#undef DEFINE_EVENT
> > > > +#define DEFINE_EVENT(template, call, proto, args) \
> > > > + __DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), 0)
> > > >
> > > > #undef DEFINE_EVENT_PRINT
> > > > #define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
> > > > DEFINE_EVENT(template, name, PARAMS(proto), PARAMS(args))
> > > >
> > > > #include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
> > > > +
> > > > +#undef DEFINE_EVENT_WRITABLE
> > > > +#undef __DEFINE_EVENT
> > > > +#undef FIRST
> > > > +
> > > > #endif /* CONFIG_BPF_EVENTS */
> > > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > > > index 3c38ac9a92a7..c5335d53ce82 100644
> > > > --- a/include/uapi/linux/bpf.h
> > > > +++ b/include/uapi/linux/bpf.h
> > > > @@ -166,6 +166,7 @@ enum bpf_prog_type {
> > > > BPF_PROG_TYPE_LIRC_MODE2,
> > > > BPF_PROG_TYPE_SK_REUSEPORT,
> > > > BPF_PROG_TYPE_FLOW_DISSECTOR,
> > > > + BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
> > > > };
> > > >
> > > > enum bpf_attach_type {
> > > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > > > index 62f6bced3a3c..27e2f22879a4 100644
> > > > --- a/kernel/bpf/syscall.c
> > > > +++ b/kernel/bpf/syscall.c
> > > > @@ -1720,12 +1720,16 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
> > > > }
> > > > raw_tp->btp = btp;
> > > >
> > > > - prog = bpf_prog_get_type(attr->raw_tracepoint.prog_fd,
> > > > - BPF_PROG_TYPE_RAW_TRACEPOINT);
> > > > + prog = bpf_prog_get(attr->raw_tracepoint.prog_fd);
> > > > if (IS_ERR(prog)) {
> > > > err = PTR_ERR(prog);
> > > > goto out_free_tp;
> > > > }
> > > > + if (prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT &&
> > > > + prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE) {
> > >
> > > I don't think we'd gain a lot by making this an extra prog type which can do the
> > > same as BPF_PROG_TYPE_RAW_TRACEPOINT modulo optional writing. Why not integrating
> > > this directly into BPF_PROG_TYPE_RAW_TRACEPOINT then? The actual opt-in comes from
> > > the DEFINE_EVENT_WRITABLE(), not from the prog type.
> >
> > I did that to separate the hook into
> > raw_tp_writable_prog_is_valid_access, which (compared to
> > raw_tp_prog_is_valid_access):
> >
> > 1) permits writes, and
> > 2) encodes the assumption than the context begins with the pointer to
> > that writable buffer
> >
> > I'm not sure those are appropriate for all users of
> > BPF_PROG_TYPE_RAW_TRACEPOINT, but I can't immediately point out any
> > harm in doing so -- some dereferences of ctx that have historically
> > returned a SCALAR_VALUE would end up tagged as a PTR_TO_TP_BUFFER, but
> > they still won't be able to access through that pointer unless they're
> > attached to the right tracepoint.
> >
> > I'll try to unify the two and see what I get.
>
> I think combining raw_tp prog type with raw_tp_writeable is possible,
> but too cumbersome to use from user pov.
> Since such raw_tp will be accepted at prog load time,
> but only at the time of attach it will be rejected in __bpf_probe_register.
>
> raw_tp_writable_prog_is_valid_access() doesn't know future attach point.
> we cannot use bpf_attr.expected_attach_type here.
We could use any load-time flag of sorts, but I overlooked
expected_attach_type since that should match the enum bpf_attach_type
values, and we don't use BPF_PROG_ATTACH for tracepoints.
> That's why it simply does:
> + if (off == 0 && size == sizeof(u64))
> + info->reg_type = PTR_TO_TP_BUFFER;
>
> essentially hard coding first argument of writeable tp to be the buffer.
It appears to be possible to xdo this to all
BPF_PROG_TYPE_RAW_TRACEPOINTs, but I think it's clearer to keep a
separate bpf_prog_type for programs that assume ctx[0] is the pointer
to the buffer.
>
> TP invocation is also new.
> Like in patch 2:
> trace_nbd_send_request(&request, nbd->index, blk_mq_rq_from_pdu(cmd));
>
> Patches 1,2,3 actually look fine to me,
> but I agree that selftests are necessary.
>
> Matt, could you add new writeable tracepoint somewhere in bpf_test_run()
> and corresponding selftest?
Yep, I've just got that working, will be included in v2 (along with
some other minor bugfixes).
>
> Thanks
>