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Message-ID: <20200716225933.196342-2-songliubraving@fb.com>
Date: Thu, 16 Jul 2020 15:59:32 -0700
From: Song Liu <songliubraving@...com>
To: <linux-kernel@...r.kernel.org>, <bpf@...r.kernel.org>,
<netdev@...r.kernel.org>
CC: <ast@...nel.org>, <daniel@...earbox.net>, <kernel-team@...com>,
<john.fastabend@...il.com>, <kpsingh@...omium.org>,
<brouer@...hat.com>, <peterz@...radead.org>,
Song Liu <songliubraving@...com>
Subject: [PATCH v3 bpf-next 1/2] bpf: separate bpf_get_[stack|stackid] for perf events BPF
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, add separate version of these
two helpers, bpf_get_[stack|stackid]_pe. These two hepers use callchain in
bpf_perf_event_data_kern->data->callchain.
Signed-off-by: Song Liu <songliubraving@...com>
---
include/linux/bpf.h | 2 +
kernel/bpf/stackmap.c | 202 +++++++++++++++++++++++++++++++++++----
kernel/trace/bpf_trace.c | 4 +-
3 files changed, 188 insertions(+), 20 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 54ad426dbea1a..cf8804e302257 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1643,6 +1643,8 @@ 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_stackid_proto_pe;
+extern const struct bpf_func_proto bpf_get_stack_proto_pe;
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/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 48d8e739975fa..7a03d1c24b25f 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -4,6 +4,7 @@
#include <linux/bpf.h>
#include <linux/jhash.h>
#include <linux/filter.h>
+#include <linux/kernel.h>
#include <linux/stacktrace.h>
#include <linux/perf_event.h>
#include <linux/elf.h>
@@ -387,11 +388,10 @@ 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 */
@@ -399,21 +399,9 @@ 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
*/
@@ -478,6 +466,30 @@ 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,
@@ -487,7 +499,86 @@ const struct bpf_func_proto bpf_get_stackid_proto = {
.arg3_type = ARG_ANYTHING,
};
+static __u64 count_kernel_ip(struct perf_callchain_entry *trace)
+{
+ __u64 nr_kernel = 0;
+
+ while (nr_kernel < trace->nr) {
+ if (trace->ip[nr_kernel] == PERF_CONTEXT_USER)
+ break;
+ nr_kernel++;
+ }
+ return nr_kernel;
+}
+
+BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
+ struct bpf_map *, map, u64, flags)
+{
+ struct perf_event *event = ctx->event;
+ struct perf_callchain_entry *trace;
+ bool has_kernel, has_user;
+ bool kernel, user;
+
+ /* perf_sample_data doesn't have callchain, use bpf_get_stackid */
+ if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
+ return bpf_get_stackid((unsigned long)(ctx->regs),
+ (unsigned long) map, flags, 0, 0);
+
+ if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
+ BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
+ return -EINVAL;
+
+ user = flags & BPF_F_USER_STACK;
+ kernel = !user;
+
+ has_kernel = !event->attr.exclude_callchain_kernel;
+ has_user = !event->attr.exclude_callchain_user;
+
+ if ((kernel && !has_kernel) || (user && !has_user))
+ return -EINVAL;
+
+ trace = ctx->data->callchain;
+ if (unlikely(!trace))
+ return -EFAULT;
+
+ if (has_kernel && has_user) {
+ __u64 nr_kernel = count_kernel_ip(trace);
+ int ret;
+
+ if (kernel) {
+ __u64 nr = trace->nr;
+
+ trace->nr = nr_kernel;
+ ret = __bpf_get_stackid(map, trace, flags);
+
+ /* restore nr */
+ trace->nr = nr;
+ } else { /* user */
+ u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
+
+ skip += nr_kernel;
+ if (skip > BPF_F_SKIP_FIELD_MASK)
+ return -EFAULT;
+
+ flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
+ ret = __bpf_get_stackid(map, trace, flags);
+ }
+ return ret;
+ }
+ return __bpf_get_stackid(map, trace, flags);
+}
+
+const struct bpf_func_proto bpf_get_stackid_proto_pe = {
+ .func = bpf_get_stackid_pe,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+ .arg2_type = ARG_CONST_MAP_PTR,
+ .arg3_type = ARG_ANYTHING,
+};
+
static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
+ struct perf_callchain_entry *trace_in,
void *buf, u32 size, u64 flags)
{
u32 init_nr, trace_nr, copy_len, elem_size, num_elem;
@@ -520,7 +611,9 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
else
init_nr = sysctl_perf_event_max_stack - num_elem;
- if (kernel && task)
+ if (trace_in)
+ trace = trace_in;
+ else if (kernel && task)
trace = get_callchain_entry_for_task(task, init_nr);
else
trace = get_perf_callchain(regs, init_nr, kernel, user,
@@ -556,7 +649,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size,
u64, flags)
{
- return __bpf_get_stack(regs, NULL, buf, size, flags);
+ return __bpf_get_stack(regs, NULL, NULL, buf, size, flags);
}
const struct bpf_func_proto bpf_get_stack_proto = {
@@ -574,7 +667,7 @@ BPF_CALL_4(bpf_get_task_stack, struct task_struct *, task, void *, buf,
{
struct pt_regs *regs = task_pt_regs(task);
- return __bpf_get_stack(regs, task, buf, size, flags);
+ return __bpf_get_stack(regs, task, NULL, buf, size, flags);
}
BTF_ID_LIST(bpf_get_task_stack_btf_ids)
@@ -591,6 +684,79 @@ const struct bpf_func_proto bpf_get_task_stack_proto = {
.btf_id = bpf_get_task_stack_btf_ids,
};
+BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx,
+ void *, buf, u32, size, u64, flags)
+{
+ struct perf_event *event = ctx->event;
+ struct perf_callchain_entry *trace;
+ bool has_kernel, has_user;
+ bool kernel, user;
+ int err = -EINVAL;
+
+ if (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY))
+ return __bpf_get_stack(ctx->regs, NULL, NULL, buf, size, flags);
+
+ if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
+ BPF_F_USER_BUILD_ID)))
+ goto clear;
+
+ user = flags & BPF_F_USER_STACK;
+ kernel = !user;
+
+ has_kernel = !event->attr.exclude_callchain_kernel;
+ has_user = !event->attr.exclude_callchain_user;
+
+ if ((kernel && !has_kernel) || (user && !has_user))
+ goto clear;
+
+ err = -EFAULT;
+ trace = ctx->data->callchain;
+ if (unlikely(!trace))
+ goto clear;
+
+ if (has_kernel && has_user) {
+ __u64 nr_kernel = count_kernel_ip(trace);
+ int ret;
+
+ if (kernel) {
+ __u64 nr = trace->nr;
+
+ trace->nr = nr_kernel;
+ ret = __bpf_get_stack(ctx->regs, NULL, trace, buf,
+ size, flags);
+
+ /* restore nr */
+ trace->nr = nr;
+ } else { /* user */
+ u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
+
+ skip += nr_kernel;
+ if (skip > BPF_F_SKIP_FIELD_MASK)
+ goto clear;
+
+ flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
+ ret = __bpf_get_stack(ctx->regs, NULL, trace, buf,
+ size, flags);
+ }
+ return ret;
+ }
+ return __bpf_get_stack(ctx->regs, NULL, trace, buf, size, flags);
+clear:
+ memset(buf, 0, size);
+ return err;
+
+}
+
+const struct bpf_func_proto bpf_get_stack_proto_pe = {
+ .func = bpf_get_stack_pe,
+ .gpl_only = true,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+ .arg2_type = ARG_PTR_TO_UNINIT_MEM,
+ .arg3_type = ARG_CONST_SIZE_OR_ZERO,
+ .arg4_type = ARG_ANYTHING,
+};
+
/* Called from eBPF program */
static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
{
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 3cc0dcb60ca20..cb91ef902cc43 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1411,9 +1411,9 @@ pe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
case BPF_FUNC_perf_event_output:
return &bpf_perf_event_output_proto_tp;
case BPF_FUNC_get_stackid:
- return &bpf_get_stackid_proto_tp;
+ return &bpf_get_stackid_proto_pe;
case BPF_FUNC_get_stack:
- return &bpf_get_stack_proto_tp;
+ return &bpf_get_stack_proto_pe;
case BPF_FUNC_perf_prog_read_value:
return &bpf_perf_prog_read_value_proto;
case BPF_FUNC_read_branch_records:
--
2.24.1
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