* [PATCH bpf-next 1/5] bpf: block bpf_get_[stack|stackid] on perf_event with PEBS entries
2020-07-11 1:26 [PATCH bpf-next 0/5] bpf: fix stackmap on perf_events with PEBS Song Liu
@ 2020-07-11 1:26 ` Song Liu
2020-07-11 3:53 ` Andrii Nakryiko
2020-07-11 1:26 ` [PATCH bpf-next 2/5] bpf: add callchain to bpf_perf_event_data Song Liu
` (3 subsequent siblings)
4 siblings, 1 reply; 10+ messages in thread
From: Song Liu @ 2020-07-11 1:26 UTC (permalink / raw)
To: linux-kernel, bpf, netdev
Cc: ast, daniel, kernel-team, john.fastabend, kpsingh, brouer,
peterz, Song Liu
Calling get_perf_callchain() on perf_events from PEBS entries may cause
unwinder errors. To fix this issue, the callchain is fetched early. Such
perf_events are marked with __PERF_SAMPLE_CALLCHAIN_EARLY.
Similarly, calling bpf_get_[stack|stackid] on perf_events from PEBS may
also cause unwinder errors. To fix this, block bpf_get_[stack|stackid] on
these perf_events. Unfortunately, bpf verifier cannot tell whether the
program will be attached to perf_event with PEBS entries. Therefore,
block such programs during ioctl(PERF_EVENT_IOC_SET_BPF).
Signed-off-by: Song Liu <songliubraving@fb.com>
---
include/linux/filter.h | 3 ++-
kernel/bpf/verifier.c | 3 +++
kernel/events/core.c | 10 ++++++++++
3 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 2593777236037..fb34dc40f039b 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -534,7 +534,8 @@ struct bpf_prog {
is_func:1, /* program is a bpf function */
kprobe_override:1, /* Do we override a kprobe? */
has_callchain_buf:1, /* callchain buffer allocated? */
- enforce_expected_attach_type:1; /* Enforce expected_attach_type checking at attach time */
+ enforce_expected_attach_type:1, /* Enforce expected_attach_type checking at attach time */
+ call_get_perf_callchain:1; /* Do we call helpers that uses get_perf_callchain()? */
enum bpf_prog_type type; /* Type of BPF program */
enum bpf_attach_type expected_attach_type; /* For some prog types */
u32 len; /* Number of filter blocks */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index b608185e1ffd5..1e11b0f6fba31 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4884,6 +4884,9 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
env->prog->has_callchain_buf = true;
}
+ if (func_id == BPF_FUNC_get_stackid || func_id == BPF_FUNC_get_stack)
+ env->prog->call_get_perf_callchain = true;
+
if (changes_data)
clear_all_pkt_pointers(env);
return 0;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 856d98c36f562..f2f575a286bb4 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9544,6 +9544,16 @@ static int perf_event_set_bpf_handler(struct perf_event *event, u32 prog_fd)
if (IS_ERR(prog))
return PTR_ERR(prog);
+ if ((event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY) &&
+ prog->call_get_perf_callchain) {
+ /*
+ * The perf_event get_perf_callchain() early, the attached
+ * BPF program shouldn't call get_perf_callchain() again.
+ */
+ bpf_prog_put(prog);
+ return -EINVAL;
+ }
+
event->prog = prog;
event->orig_overflow_handler = READ_ONCE(event->overflow_handler);
WRITE_ONCE(event->overflow_handler, bpf_overflow_handler);
--
2.24.1
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH bpf-next 1/5] bpf: block bpf_get_[stack|stackid] on perf_event with PEBS entries
2020-07-11 1:26 ` [PATCH bpf-next 1/5] bpf: block bpf_get_[stack|stackid] on perf_event with PEBS entries Song Liu
@ 2020-07-11 3:53 ` Andrii Nakryiko
2020-07-11 6:28 ` Song Liu
0 siblings, 1 reply; 10+ messages in thread
From: Andrii Nakryiko @ 2020-07-11 3:53 UTC (permalink / raw)
To: Song Liu
Cc: open list, bpf, Networking, Alexei Starovoitov, Daniel Borkmann,
Kernel Team, john fastabend, KP Singh, Jesper Dangaard Brouer,
Peter Ziljstra
On Fri, Jul 10, 2020 at 6:30 PM Song Liu <songliubraving@fb.com> wrote:
>
> Calling get_perf_callchain() on perf_events from PEBS entries may cause
> unwinder errors. To fix this issue, the callchain is fetched early. Such
> perf_events are marked with __PERF_SAMPLE_CALLCHAIN_EARLY.
>
> Similarly, calling bpf_get_[stack|stackid] on perf_events from PEBS may
> also cause unwinder errors. To fix this, block bpf_get_[stack|stackid] on
> these perf_events. Unfortunately, bpf verifier cannot tell whether the
> program will be attached to perf_event with PEBS entries. Therefore,
> block such programs during ioctl(PERF_EVENT_IOC_SET_BPF).
>
> Signed-off-by: Song Liu <songliubraving@fb.com>
> ---
Perhaps it's a stupid question, but why bpf_get_stack/bpf_get_stackid
can't figure out automatically that they are called from
__PERF_SAMPLE_CALLCHAIN_EARLY perf event and use different callchain,
if necessary?
It is quite suboptimal from a user experience point of view to require
two different BPF helpers depending on PEBS or non-PEBS perf events.
[...]
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH bpf-next 1/5] bpf: block bpf_get_[stack|stackid] on perf_event with PEBS entries
2020-07-11 3:53 ` Andrii Nakryiko
@ 2020-07-11 6:28 ` Song Liu
2020-07-12 5:06 ` Andrii Nakryiko
0 siblings, 1 reply; 10+ messages in thread
From: Song Liu @ 2020-07-11 6:28 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: open list, bpf, Networking, Alexei Starovoitov, Daniel Borkmann,
Kernel Team, john fastabend, KP Singh, Jesper Dangaard Brouer,
Peter Ziljstra
> On Jul 10, 2020, at 8:53 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>
> On Fri, Jul 10, 2020 at 6:30 PM Song Liu <songliubraving@fb.com> wrote:
>>
>> Calling get_perf_callchain() on perf_events from PEBS entries may cause
>> unwinder errors. To fix this issue, the callchain is fetched early. Such
>> perf_events are marked with __PERF_SAMPLE_CALLCHAIN_EARLY.
>>
>> Similarly, calling bpf_get_[stack|stackid] on perf_events from PEBS may
>> also cause unwinder errors. To fix this, block bpf_get_[stack|stackid] on
>> these perf_events. Unfortunately, bpf verifier cannot tell whether the
>> program will be attached to perf_event with PEBS entries. Therefore,
>> block such programs during ioctl(PERF_EVENT_IOC_SET_BPF).
>>
>> Signed-off-by: Song Liu <songliubraving@fb.com>
>> ---
>
> Perhaps it's a stupid question, but why bpf_get_stack/bpf_get_stackid
> can't figure out automatically that they are called from
> __PERF_SAMPLE_CALLCHAIN_EARLY perf event and use different callchain,
> if necessary?
>
> It is quite suboptimal from a user experience point of view to require
> two different BPF helpers depending on PEBS or non-PEBS perf events.
I am not aware of an easy way to tell the difference in bpf_get_stack.
But I do agree that would be much better.
Thanks,
Song
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH bpf-next 1/5] bpf: block bpf_get_[stack|stackid] on perf_event with PEBS entries
2020-07-11 6:28 ` Song Liu
@ 2020-07-12 5:06 ` Andrii Nakryiko
2020-07-12 6:34 ` Song Liu
0 siblings, 1 reply; 10+ messages in thread
From: Andrii Nakryiko @ 2020-07-12 5:06 UTC (permalink / raw)
To: Song Liu
Cc: open list, bpf, Networking, Alexei Starovoitov, Daniel Borkmann,
Kernel Team, john fastabend, KP Singh, Jesper Dangaard Brouer,
Peter Ziljstra
On Fri, Jul 10, 2020 at 11:28 PM Song Liu <songliubraving@fb.com> wrote:
>
>
>
> > On Jul 10, 2020, at 8:53 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
> >
> > On Fri, Jul 10, 2020 at 6:30 PM Song Liu <songliubraving@fb.com> wrote:
> >>
> >> Calling get_perf_callchain() on perf_events from PEBS entries may cause
> >> unwinder errors. To fix this issue, the callchain is fetched early. Such
> >> perf_events are marked with __PERF_SAMPLE_CALLCHAIN_EARLY.
> >>
> >> Similarly, calling bpf_get_[stack|stackid] on perf_events from PEBS may
> >> also cause unwinder errors. To fix this, block bpf_get_[stack|stackid] on
> >> these perf_events. Unfortunately, bpf verifier cannot tell whether the
> >> program will be attached to perf_event with PEBS entries. Therefore,
> >> block such programs during ioctl(PERF_EVENT_IOC_SET_BPF).
> >>
> >> Signed-off-by: Song Liu <songliubraving@fb.com>
> >> ---
> >
> > Perhaps it's a stupid question, but why bpf_get_stack/bpf_get_stackid
> > can't figure out automatically that they are called from
> > __PERF_SAMPLE_CALLCHAIN_EARLY perf event and use different callchain,
> > if necessary?
> >
> > It is quite suboptimal from a user experience point of view to require
> > two different BPF helpers depending on PEBS or non-PEBS perf events.
>
> I am not aware of an easy way to tell the difference in bpf_get_stack.
> But I do agree that would be much better.
>
Hm... Looking a bit more how all this is tied together in the kernel,
I think it's actually quite easy. So, for perf_event BPF program type:
1. return a special prototype for bpf_get_stack/bpf_get_stackid, which
will have this extra bit of logic for callchain. All other program
types with access to bpf_get_stack/bpf_get_stackid should use the
current one, probably.
2. For that special program, just like for bpf_read_branch_records(),
we know that context is actually `struct bpf_perf_event_data_kern *`,
and it has pt_regs, perf_sample_data and perf_event itself.
3. With that, it seems like you'll have everything you need to
automatically choose a proper callchain.
All this absolutely transparently to the BPF program.
Am I missing something?
> Thanks,
> Song
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH bpf-next 1/5] bpf: block bpf_get_[stack|stackid] on perf_event with PEBS entries
2020-07-12 5:06 ` Andrii Nakryiko
@ 2020-07-12 6:34 ` Song Liu
0 siblings, 0 replies; 10+ messages in thread
From: Song Liu @ 2020-07-12 6:34 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: open list, bpf, Networking, Alexei Starovoitov, Daniel Borkmann,
Kernel Team, john fastabend, KP Singh, Jesper Dangaard Brouer,
Peter Ziljstra
> On Jul 11, 2020, at 10:06 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>
> On Fri, Jul 10, 2020 at 11:28 PM Song Liu <songliubraving@fb.com> wrote:
>>
>>
>>
>>> On Jul 10, 2020, at 8:53 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>>>
>>> On Fri, Jul 10, 2020 at 6:30 PM Song Liu <songliubraving@fb.com> wrote:
>>>>
>>>> Calling get_perf_callchain() on perf_events from PEBS entries may cause
>>>> unwinder errors. To fix this issue, the callchain is fetched early. Such
>>>> perf_events are marked with __PERF_SAMPLE_CALLCHAIN_EARLY.
>>>>
>>>> Similarly, calling bpf_get_[stack|stackid] on perf_events from PEBS may
>>>> also cause unwinder errors. To fix this, block bpf_get_[stack|stackid] on
>>>> these perf_events. Unfortunately, bpf verifier cannot tell whether the
>>>> program will be attached to perf_event with PEBS entries. Therefore,
>>>> block such programs during ioctl(PERF_EVENT_IOC_SET_BPF).
>>>>
>>>> Signed-off-by: Song Liu <songliubraving@fb.com>
>>>> ---
>>>
>>> Perhaps it's a stupid question, but why bpf_get_stack/bpf_get_stackid
>>> can't figure out automatically that they are called from
>>> __PERF_SAMPLE_CALLCHAIN_EARLY perf event and use different callchain,
>>> if necessary?
>>>
>>> It is quite suboptimal from a user experience point of view to require
>>> two different BPF helpers depending on PEBS or non-PEBS perf events.
>>
>> I am not aware of an easy way to tell the difference in bpf_get_stack.
>> But I do agree that would be much better.
>>
>
> Hm... Looking a bit more how all this is tied together in the kernel,
> I think it's actually quite easy. So, for perf_event BPF program type:
>
> 1. return a special prototype for bpf_get_stack/bpf_get_stackid, which
> will have this extra bit of logic for callchain. All other program
> types with access to bpf_get_stack/bpf_get_stackid should use the
> current one, probably.
> 2. For that special program, just like for bpf_read_branch_records(),
> we know that context is actually `struct bpf_perf_event_data_kern *`,
> and it has pt_regs, perf_sample_data and perf_event itself.
> 3. With that, it seems like you'll have everything you need to
> automatically choose a proper callchain.
>
> All this absolutely transparently to the BPF program.
>
> Am I missing something?
Good idea! A separate prototype should work here.
Thanks,
Song
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH bpf-next 2/5] bpf: add callchain to bpf_perf_event_data
2020-07-11 1:26 [PATCH bpf-next 0/5] bpf: fix stackmap on perf_events with PEBS Song Liu
2020-07-11 1:26 ` [PATCH bpf-next 1/5] bpf: block bpf_get_[stack|stackid] on perf_event with PEBS entries Song Liu
@ 2020-07-11 1:26 ` Song Liu
2020-07-11 1:26 ` [PATCH bpf-next 3/5] bpf: introduce bpf_get_callchain_stackid Song Liu
` (2 subsequent siblings)
4 siblings, 0 replies; 10+ messages in thread
From: Song Liu @ 2020-07-11 1:26 UTC (permalink / raw)
To: linux-kernel, bpf, netdev
Cc: ast, daniel, kernel-team, john.fastabend, kpsingh, brouer,
peterz, Song Liu
If the callchain is available, BPF program can use bpf_probe_read_kernel()
to fetch the callchain, or use it in a BPF helper.
Signed-off-by: Song Liu <songliubraving@fb.com>
---
include/linux/perf_event.h | 5 -----
include/linux/trace_events.h | 5 +++++
include/uapi/linux/bpf_perf_event.h | 7 ++++++
kernel/bpf/btf.c | 5 +++++
kernel/trace/bpf_trace.c | 27 +++++++++++++++++++++++
tools/include/uapi/linux/bpf_perf_event.h | 8 +++++++
6 files changed, 52 insertions(+), 5 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 00ab5efa38334..3a68c999f50d1 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -59,11 +59,6 @@ struct perf_guest_info_callbacks {
#include <linux/security.h>
#include <asm/local.h>
-struct perf_callchain_entry {
- __u64 nr;
- __u64 ip[]; /* /proc/sys/kernel/perf_event_max_stack */
-};
-
struct perf_callchain_entry_ctx {
struct perf_callchain_entry *entry;
u32 max_stack;
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 5c69433540494..8e1e88f40eef9 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -631,6 +631,7 @@ void bpf_put_raw_tracepoint(struct bpf_raw_event_map *btp);
int bpf_get_perf_event_info(const struct perf_event *event, u32 *prog_id,
u32 *fd_type, const char **buf,
u64 *probe_offset, u64 *probe_addr);
+int bpf_trace_init_btf_ids(struct btf *btf);
#else
static inline unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx)
{
@@ -672,6 +673,10 @@ static inline int bpf_get_perf_event_info(const struct perf_event *event,
{
return -EOPNOTSUPP;
}
+int bpf_trace_init_btf_ids(struct btf *btf)
+{
+ return -EOPNOTSUPP;
+}
#endif
enum {
diff --git a/include/uapi/linux/bpf_perf_event.h b/include/uapi/linux/bpf_perf_event.h
index eb1b9d21250c6..40f4df80ab4fa 100644
--- a/include/uapi/linux/bpf_perf_event.h
+++ b/include/uapi/linux/bpf_perf_event.h
@@ -9,11 +9,18 @@
#define _UAPI__LINUX_BPF_PERF_EVENT_H__
#include <asm/bpf_perf_event.h>
+#include <linux/bpf.h>
+
+struct perf_callchain_entry {
+ __u64 nr;
+ __u64 ip[]; /* /proc/sys/kernel/perf_event_max_stack */
+};
struct bpf_perf_event_data {
bpf_user_pt_regs_t regs;
__u64 sample_period;
__u64 addr;
+ __bpf_md_ptr(struct perf_callchain_entry *, callchain);
};
#endif /* _UAPI__LINUX_BPF_PERF_EVENT_H__ */
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 4c3007f428b16..cb122e14dba38 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -20,6 +20,7 @@
#include <linux/btf.h>
#include <linux/skmsg.h>
#include <linux/perf_event.h>
+#include <linux/trace_events.h>
#include <net/sock.h>
/* BTF (BPF Type Format) is the meta data format which describes
@@ -3673,6 +3674,10 @@ struct btf *btf_parse_vmlinux(void)
if (err < 0)
goto errout;
+ err = bpf_trace_init_btf_ids(btf);
+ if (err < 0)
+ goto errout;
+
bpf_struct_ops_init(btf, log);
init_btf_sock_ids(btf);
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index e0b7775039ab9..c014846c2723c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -6,6 +6,7 @@
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/bpf.h>
+#include <linux/btf.h>
#include <linux/bpf_perf_event.h>
#include <linux/filter.h>
#include <linux/uaccess.h>
@@ -31,6 +32,20 @@ struct bpf_trace_module {
static LIST_HEAD(bpf_trace_modules);
static DEFINE_MUTEX(bpf_module_mutex);
+static u32 perf_callchain_entry_btf_id;
+
+int bpf_trace_init_btf_ids(struct btf *btf)
+{
+ s32 type_id;
+
+ type_id = btf_find_by_name_kind(btf, "perf_callchain_entry",
+ BTF_KIND_STRUCT);
+ if (type_id < 0)
+ return -EINVAL;
+ perf_callchain_entry_btf_id = type_id;
+ return 0;
+}
+
static struct bpf_raw_event_map *bpf_get_raw_tracepoint_module(const char *name)
{
struct bpf_raw_event_map *btp, *ret = NULL;
@@ -1650,6 +1665,10 @@ static bool pe_prog_is_valid_access(int off, int size, enum bpf_access_type type
if (!bpf_ctx_narrow_access_ok(off, size, size_u64))
return false;
break;
+ case bpf_ctx_range(struct bpf_perf_event_data, callchain):
+ info->reg_type = PTR_TO_BTF_ID;
+ info->btf_id = perf_callchain_entry_btf_id;
+ break;
default:
if (size != sizeof(long))
return false;
@@ -1682,6 +1701,14 @@ static u32 pe_prog_convert_ctx_access(enum bpf_access_type type,
bpf_target_off(struct perf_sample_data, addr, 8,
target_size));
break;
+ case offsetof(struct bpf_perf_event_data, callchain):
+ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_perf_event_data_kern,
+ data), si->dst_reg, si->src_reg,
+ offsetof(struct bpf_perf_event_data_kern, data));
+ *insn++ = BPF_LDX_MEM(BPF_DW, si->dst_reg, si->dst_reg,
+ bpf_target_off(struct perf_sample_data, callchain,
+ 8, target_size));
+ break;
default:
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_perf_event_data_kern,
regs), si->dst_reg, si->src_reg,
diff --git a/tools/include/uapi/linux/bpf_perf_event.h b/tools/include/uapi/linux/bpf_perf_event.h
index 8f95303f9d807..40f4df80ab4fa 100644
--- a/tools/include/uapi/linux/bpf_perf_event.h
+++ b/tools/include/uapi/linux/bpf_perf_event.h
@@ -9,10 +9,18 @@
#define _UAPI__LINUX_BPF_PERF_EVENT_H__
#include <asm/bpf_perf_event.h>
+#include <linux/bpf.h>
+
+struct perf_callchain_entry {
+ __u64 nr;
+ __u64 ip[]; /* /proc/sys/kernel/perf_event_max_stack */
+};
struct bpf_perf_event_data {
bpf_user_pt_regs_t regs;
__u64 sample_period;
+ __u64 addr;
+ __bpf_md_ptr(struct perf_callchain_entry *, callchain);
};
#endif /* _UAPI__LINUX_BPF_PERF_EVENT_H__ */
--
2.24.1
^ permalink raw reply related [flat|nested] 10+ messages in thread* [PATCH bpf-next 3/5] bpf: introduce bpf_get_callchain_stackid
2020-07-11 1:26 [PATCH bpf-next 0/5] bpf: fix stackmap on perf_events with PEBS Song Liu
2020-07-11 1:26 ` [PATCH bpf-next 1/5] bpf: block bpf_get_[stack|stackid] on perf_event with PEBS entries Song Liu
2020-07-11 1:26 ` [PATCH bpf-next 2/5] bpf: add callchain to bpf_perf_event_data Song Liu
@ 2020-07-11 1:26 ` Song Liu
2020-07-11 1:26 ` [PATCH bpf-next 4/5] selftests/bpf: add get_stackid_cannot_attach Song Liu
2020-07-11 1:26 ` [PATCH bpf-next 5/5] selftests/bpf: add callchain_stackid Song Liu
4 siblings, 0 replies; 10+ messages in thread
From: Song Liu @ 2020-07-11 1:26 UTC (permalink / raw)
To: linux-kernel, bpf, netdev
Cc: ast, daniel, kernel-team, john.fastabend, kpsingh, brouer,
peterz, Song Liu
This helper is only used by BPF program attached to perf_event. If the
perf_event has PEBS entries, calling get_perf_callchain from BPF program
may cause unwinder errors. bpf_get_callchain_stackid serves as alternative
to bpf_get_stackid for these BPF programs.
Signed-off-by: Song Liu <songliubraving@fb.com>
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 43 +++++++++++++++++++++++
kernel/bpf/stackmap.c | 63 ++++++++++++++++++++++++++--------
kernel/bpf/verifier.c | 4 ++-
kernel/trace/bpf_trace.c | 2 ++
scripts/bpf_helpers_doc.py | 2 ++
tools/include/uapi/linux/bpf.h | 43 +++++++++++++++++++++++
7 files changed, 142 insertions(+), 16 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 0cd7f6884c5cd..45cf12acb0e26 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1628,6 +1628,7 @@ extern const struct bpf_func_proto bpf_get_current_comm_proto;
extern const struct bpf_func_proto bpf_get_stackid_proto;
extern const struct bpf_func_proto bpf_get_stack_proto;
extern const struct bpf_func_proto bpf_get_task_stack_proto;
+extern const struct bpf_func_proto bpf_get_callchain_stackid_proto;
extern const struct bpf_func_proto bpf_sock_map_update_proto;
extern const struct bpf_func_proto bpf_sock_hash_update_proto;
extern const struct bpf_func_proto bpf_get_current_cgroup_id_proto;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 548a749aebb3e..a808accfbd457 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3319,6 +3319,48 @@ union bpf_attr {
* A non-negative value equal to or less than *size* on success,
* or a negative error in case of failure.
*
+ * long bpf_get_callchain_stackid(struct perf_callchain_entry *callchain, struct bpf_map *map, u64 flags)
+ * Description
+ * Walk a user or a kernel stack and return its id. To achieve
+ * this, the helper needs *callchain*, which is a pointer to a
+ * valid perf_callchain_entry, and a pointer to a *map* of type
+ * **BPF_MAP_TYPE_STACK_TRACE**.
+ *
+ * The last argument, *flags*, holds the number of stack frames to
+ * skip (from 0 to 255), masked with
+ * **BPF_F_SKIP_FIELD_MASK**. The next bits can be used to set
+ * a combination of the following flags:
+ *
+ * **BPF_F_USER_STACK**
+ * Collect a user space stack instead of a kernel stack.
+ * **BPF_F_FAST_STACK_CMP**
+ * Compare stacks by hash only.
+ * **BPF_F_REUSE_STACKID**
+ * If two different stacks hash into the same *stackid*,
+ * discard the old one.
+ *
+ * The stack id retrieved is a 32 bit long integer handle which
+ * can be further combined with other data (including other stack
+ * ids) and used as a key into maps. This can be useful for
+ * generating a variety of graphs (such as flame graphs or off-cpu
+ * graphs).
+ *
+ * For walking a stack, this helper is an improvement over
+ * **bpf_probe_read**\ (), which can be used with unrolled loops
+ * but is not efficient and consumes a lot of eBPF instructions.
+ * Instead, **bpf_get_callchain_stackid**\ () can collect up to
+ * **PERF_MAX_STACK_DEPTH** both kernel and user frames. Note that
+ * this limit can be controlled with the **sysctl** program, and
+ * that it should be manually increased in order to profile long
+ * user stacks (such as stacks for Java programs). To do so, use:
+ *
+ * ::
+ *
+ * # sysctl kernel.perf_event_max_stack=<new value>
+ * Return
+ * The positive or null stack id on success, or a negative error
+ * in case of failure.
+ *
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3463,6 +3505,7 @@ union bpf_attr {
FN(skc_to_tcp_request_sock), \
FN(skc_to_udp6_sock), \
FN(get_task_stack), \
+ FN(get_callchain_stackid), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index a6c361ed7937b..28acc610f7f94 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -386,11 +386,10 @@ get_callchain_entry_for_task(struct task_struct *task, u32 init_nr)
#endif
}
-BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
- u64, flags)
+static long __bpf_get_stackid(struct bpf_map *map, struct perf_callchain_entry *trace,
+ u64 flags)
{
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
- struct perf_callchain_entry *trace;
struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
u32 max_depth = map->value_size / stack_map_data_size(map);
/* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
@@ -398,21 +397,9 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
u32 hash, id, trace_nr, trace_len;
bool user = flags & BPF_F_USER_STACK;
- bool kernel = !user;
u64 *ips;
bool hash_matches;
- if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
- BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
- return -EINVAL;
-
- trace = get_perf_callchain(regs, init_nr, kernel, user,
- sysctl_perf_event_max_stack, false, false);
-
- if (unlikely(!trace))
- /* couldn't fetch the stack trace */
- return -EFAULT;
-
/* get_perf_callchain() guarantees that trace->nr >= init_nr
* and trace-nr <= sysctl_perf_event_max_stack, so trace_nr <= max_depth
*/
@@ -477,6 +464,30 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
return id;
}
+BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
+ u64, flags)
+{
+ u32 max_depth = map->value_size / stack_map_data_size(map);
+ /* stack_map_alloc() checks that max_depth <= sysctl_perf_event_max_stack */
+ u32 init_nr = sysctl_perf_event_max_stack - max_depth;
+ bool user = flags & BPF_F_USER_STACK;
+ struct perf_callchain_entry *trace;
+ bool kernel = !user;
+
+ if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
+ BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
+ return -EINVAL;
+
+ trace = get_perf_callchain(regs, init_nr, kernel, user,
+ sysctl_perf_event_max_stack, false, false);
+
+ if (unlikely(!trace))
+ /* couldn't fetch the stack trace */
+ return -EFAULT;
+
+ return __bpf_get_stackid(map, trace, flags);
+}
+
const struct bpf_func_proto bpf_get_stackid_proto = {
.func = bpf_get_stackid,
.gpl_only = true,
@@ -486,6 +497,28 @@ const struct bpf_func_proto bpf_get_stackid_proto = {
.arg3_type = ARG_ANYTHING,
};
+BPF_CALL_3(bpf_get_callchain_stackid, struct perf_callchain_entry *, callchain,
+ struct bpf_map *, map, u64, flags)
+{
+ if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
+ BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
+ return -EINVAL;
+ if (!callchain)
+ return -EFAULT;
+ return __bpf_get_stackid(map, callchain, flags);
+}
+
+static int bpf_get_callchain_stackid_btf_ids[5];
+const struct bpf_func_proto bpf_get_callchain_stackid_proto = {
+ .func = bpf_get_callchain_stackid,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_BTF_ID,
+ .arg2_type = ARG_CONST_MAP_PTR,
+ .arg3_type = ARG_ANYTHING,
+ .btf_id = bpf_get_callchain_stackid_btf_ids,
+};
+
static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
void *buf, u32 size, u64 flags)
{
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1e11b0f6fba31..07be75550ca93 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4094,7 +4094,8 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
goto error;
break;
case BPF_MAP_TYPE_STACK_TRACE:
- if (func_id != BPF_FUNC_get_stackid)
+ if (func_id != BPF_FUNC_get_stackid &&
+ func_id != BPF_FUNC_get_callchain_stackid)
goto error;
break;
case BPF_MAP_TYPE_CGROUP_ARRAY:
@@ -4187,6 +4188,7 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
goto error;
break;
case BPF_FUNC_get_stackid:
+ case BPF_FUNC_get_callchain_stackid:
if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
goto error;
break;
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index c014846c2723c..7a504f734a025 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1396,6 +1396,8 @@ pe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_perf_prog_read_value_proto;
case BPF_FUNC_read_branch_records:
return &bpf_read_branch_records_proto;
+ case BPF_FUNC_get_callchain_stackid:
+ return &bpf_get_callchain_stackid_proto;
default:
return bpf_tracing_func_proto(func_id, prog);
}
diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py
index 6843376733df8..1b99e3618e492 100755
--- a/scripts/bpf_helpers_doc.py
+++ b/scripts/bpf_helpers_doc.py
@@ -427,6 +427,7 @@ class PrinterHelpers(Printer):
'struct tcp_request_sock',
'struct udp6_sock',
'struct task_struct',
+ 'struct perf_callchain_entry',
'struct __sk_buff',
'struct sk_msg_md',
@@ -470,6 +471,7 @@ class PrinterHelpers(Printer):
'struct tcp_request_sock',
'struct udp6_sock',
'struct task_struct',
+ 'struct perf_callchain_entry',
}
mapped_types = {
'u8': '__u8',
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 548a749aebb3e..a808accfbd457 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3319,6 +3319,48 @@ union bpf_attr {
* A non-negative value equal to or less than *size* on success,
* or a negative error in case of failure.
*
+ * long bpf_get_callchain_stackid(struct perf_callchain_entry *callchain, struct bpf_map *map, u64 flags)
+ * Description
+ * Walk a user or a kernel stack and return its id. To achieve
+ * this, the helper needs *callchain*, which is a pointer to a
+ * valid perf_callchain_entry, and a pointer to a *map* of type
+ * **BPF_MAP_TYPE_STACK_TRACE**.
+ *
+ * The last argument, *flags*, holds the number of stack frames to
+ * skip (from 0 to 255), masked with
+ * **BPF_F_SKIP_FIELD_MASK**. The next bits can be used to set
+ * a combination of the following flags:
+ *
+ * **BPF_F_USER_STACK**
+ * Collect a user space stack instead of a kernel stack.
+ * **BPF_F_FAST_STACK_CMP**
+ * Compare stacks by hash only.
+ * **BPF_F_REUSE_STACKID**
+ * If two different stacks hash into the same *stackid*,
+ * discard the old one.
+ *
+ * The stack id retrieved is a 32 bit long integer handle which
+ * can be further combined with other data (including other stack
+ * ids) and used as a key into maps. This can be useful for
+ * generating a variety of graphs (such as flame graphs or off-cpu
+ * graphs).
+ *
+ * For walking a stack, this helper is an improvement over
+ * **bpf_probe_read**\ (), which can be used with unrolled loops
+ * but is not efficient and consumes a lot of eBPF instructions.
+ * Instead, **bpf_get_callchain_stackid**\ () can collect up to
+ * **PERF_MAX_STACK_DEPTH** both kernel and user frames. Note that
+ * this limit can be controlled with the **sysctl** program, and
+ * that it should be manually increased in order to profile long
+ * user stacks (such as stacks for Java programs). To do so, use:
+ *
+ * ::
+ *
+ * # sysctl kernel.perf_event_max_stack=<new value>
+ * Return
+ * The positive or null stack id on success, or a negative error
+ * in case of failure.
+ *
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3463,6 +3505,7 @@ union bpf_attr {
FN(skc_to_tcp_request_sock), \
FN(skc_to_udp6_sock), \
FN(get_task_stack), \
+ FN(get_callchain_stackid), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.24.1
^ permalink raw reply related [flat|nested] 10+ messages in thread* [PATCH bpf-next 4/5] selftests/bpf: add get_stackid_cannot_attach
2020-07-11 1:26 [PATCH bpf-next 0/5] bpf: fix stackmap on perf_events with PEBS Song Liu
` (2 preceding siblings ...)
2020-07-11 1:26 ` [PATCH bpf-next 3/5] bpf: introduce bpf_get_callchain_stackid Song Liu
@ 2020-07-11 1:26 ` Song Liu
2020-07-11 1:26 ` [PATCH bpf-next 5/5] selftests/bpf: add callchain_stackid Song Liu
4 siblings, 0 replies; 10+ messages in thread
From: Song Liu @ 2020-07-11 1:26 UTC (permalink / raw)
To: linux-kernel, bpf, netdev
Cc: ast, daniel, kernel-team, john.fastabend, kpsingh, brouer,
peterz, Song Liu
This test confirms that BPF program that calls bpf_get_stackid() cannot
attach to perf_event with PEBS entry.
Signed-off-by: Song Liu <songliubraving@fb.com>
---
.../prog_tests/get_stackid_cannot_attach.c | 57 +++++++++++++++++++
1 file changed, 57 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/get_stackid_cannot_attach.c
diff --git a/tools/testing/selftests/bpf/prog_tests/get_stackid_cannot_attach.c b/tools/testing/selftests/bpf/prog_tests/get_stackid_cannot_attach.c
new file mode 100644
index 0000000000000..ae943c502b62b
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/get_stackid_cannot_attach.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Facebook
+#include <test_progs.h>
+#include "test_stacktrace_build_id.skel.h"
+
+void test_get_stackid_cannot_attach(void)
+{
+ struct perf_event_attr attr = {
+ /* .type = PERF_TYPE_SOFTWARE, */
+ .type = PERF_TYPE_HARDWARE,
+ .config = PERF_COUNT_HW_CPU_CYCLES,
+ .precise_ip = 2,
+ .sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_BRANCH_STACK |
+ PERF_SAMPLE_CALLCHAIN,
+ .branch_sample_type = PERF_SAMPLE_BRANCH_USER |
+ PERF_SAMPLE_BRANCH_NO_FLAGS |
+ PERF_SAMPLE_BRANCH_NO_CYCLES |
+ PERF_SAMPLE_BRANCH_CALL_STACK,
+ .sample_period = 5000,
+ .size = sizeof(struct perf_event_attr),
+ };
+ struct test_stacktrace_build_id *skel;
+ __u32 duration = 0;
+ int pmu_fd, err;
+
+ skel = test_stacktrace_build_id__open();
+ if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
+ return;
+
+ /* override program type */
+ bpf_program__set_perf_event(skel->progs.oncpu);
+
+ err = test_stacktrace_build_id__load(skel);
+ if (CHECK(err, "skel_load", "skeleton load failed: %d\n", err))
+ goto cleanup;
+
+ pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
+ 0 /* cpu 0 */, -1 /* group id */,
+ 0 /* flags */);
+ if (pmu_fd < 0 && errno == ENOENT) {
+ printf("%s:SKIP:no PERF_COUNT_HW_CPU_CYCLES\n", __func__);
+ test__skip();
+ goto cleanup;
+ }
+ if (CHECK(pmu_fd < 0, "perf_event_open", "err %d errno %d\n",
+ pmu_fd, errno))
+ goto cleanup;
+
+ skel->links.oncpu = bpf_program__attach_perf_event(skel->progs.oncpu,
+ pmu_fd);
+ CHECK(!IS_ERR(skel->links.oncpu), "attach_perf_event",
+ "should have failed\n");
+ close(pmu_fd);
+
+cleanup:
+ test_stacktrace_build_id__destroy(skel);
+}
--
2.24.1
^ permalink raw reply related [flat|nested] 10+ messages in thread* [PATCH bpf-next 5/5] selftests/bpf: add callchain_stackid
2020-07-11 1:26 [PATCH bpf-next 0/5] bpf: fix stackmap on perf_events with PEBS Song Liu
` (3 preceding siblings ...)
2020-07-11 1:26 ` [PATCH bpf-next 4/5] selftests/bpf: add get_stackid_cannot_attach Song Liu
@ 2020-07-11 1:26 ` Song Liu
4 siblings, 0 replies; 10+ messages in thread
From: Song Liu @ 2020-07-11 1:26 UTC (permalink / raw)
To: linux-kernel, bpf, netdev
Cc: ast, daniel, kernel-team, john.fastabend, kpsingh, brouer,
peterz, Song Liu
This tests new helper function bpf_get_callchain_stackid(), which is the
alternative to bpf_get_stackid() for perf_event with PEBS entry.
Signed-off-by: Song Liu <songliubraving@fb.com>
---
.../bpf/prog_tests/callchain_stackid.c | 61 +++++++++++++++++++
.../selftests/bpf/progs/callchain_stackid.c | 37 +++++++++++
2 files changed, 98 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/callchain_stackid.c
create mode 100644 tools/testing/selftests/bpf/progs/callchain_stackid.c
diff --git a/tools/testing/selftests/bpf/prog_tests/callchain_stackid.c b/tools/testing/selftests/bpf/prog_tests/callchain_stackid.c
new file mode 100644
index 0000000000000..ebe6251324a1a
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/callchain_stackid.c
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Facebook
+#include <test_progs.h>
+#include "callchain_stackid.skel.h"
+
+void test_callchain_stackid(void)
+{
+ struct perf_event_attr attr = {
+ /* .type = PERF_TYPE_SOFTWARE, */
+ .type = PERF_TYPE_HARDWARE,
+ .config = PERF_COUNT_HW_CPU_CYCLES,
+ .precise_ip = 2,
+ .sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_BRANCH_STACK |
+ PERF_SAMPLE_CALLCHAIN,
+ .branch_sample_type = PERF_SAMPLE_BRANCH_USER |
+ PERF_SAMPLE_BRANCH_NO_FLAGS |
+ PERF_SAMPLE_BRANCH_NO_CYCLES |
+ PERF_SAMPLE_BRANCH_CALL_STACK,
+ .sample_period = 5000,
+ .size = sizeof(struct perf_event_attr),
+ };
+ struct callchain_stackid *skel;
+ __u32 duration = 0;
+ int pmu_fd, err;
+
+ skel = callchain_stackid__open();
+
+ if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
+ return;
+
+ /* override program type */
+ bpf_program__set_perf_event(skel->progs.oncpu);
+
+ err = callchain_stackid__load(skel);
+ if (CHECK(err, "skel_load", "skeleton load failed: %d\n", err))
+ goto cleanup;
+
+ pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
+ 0 /* cpu 0 */, -1 /* group id */,
+ 0 /* flags */);
+ if (pmu_fd < 0) {
+ printf("%s:SKIP:cpu doesn't support the event\n", __func__);
+ test__skip();
+ goto cleanup;
+ }
+
+ skel->links.oncpu = bpf_program__attach_perf_event(skel->progs.oncpu,
+ pmu_fd);
+ if (CHECK(IS_ERR(skel->links.oncpu), "attach_perf_event",
+ "err %ld\n", PTR_ERR(skel->links.oncpu))) {
+ close(pmu_fd);
+ goto cleanup;
+ }
+ usleep(500000);
+
+ CHECK(skel->data->total_val == 1, "get_callchain_stack", "failed\n");
+ close(pmu_fd);
+
+cleanup:
+ callchain_stackid__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/callchain_stackid.c b/tools/testing/selftests/bpf/progs/callchain_stackid.c
new file mode 100644
index 0000000000000..aab2c736a0a45
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/callchain_stackid.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Facebook
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+#ifndef PERF_MAX_STACK_DEPTH
+#define PERF_MAX_STACK_DEPTH 127
+#endif
+
+#ifndef BPF_F_USER_STACK
+#define BPF_F_USER_STACK (1ULL << 8)
+#endif
+
+typedef __u64 stack_trace_t[PERF_MAX_STACK_DEPTH];
+struct {
+ __uint(type, BPF_MAP_TYPE_STACK_TRACE);
+ __uint(max_entries, 16384);
+ __uint(key_size, sizeof(__u32));
+ __uint(value_size, sizeof(stack_trace_t));
+} stackmap SEC(".maps");
+
+long total_val = 1;
+
+SEC("perf_event")
+int oncpu(struct bpf_perf_event_data *ctx)
+{
+ long val;
+
+ val = bpf_get_callchain_stackid(ctx->callchain, &stackmap, 0);
+
+ if (val > 0)
+ total_val += val;
+
+ return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";
--
2.24.1
^ permalink raw reply related [flat|nested] 10+ messages in thread