* [RFC bpf-next 0/2] stackmap with build_id+offset
@ 2018-02-02 22:53 Song Liu
2018-02-02 22:53 ` [RFC bpf-next 1/2] bpf: extend stackmap to save binary_build_id+offset instead of address Song Liu
2018-02-02 22:53 ` [RFC bpf-next 2/2] bpf: add selftest for stackmap with BPF_F_STACK_BUILD_ID Song Liu
0 siblings, 2 replies; 3+ messages in thread
From: Song Liu @ 2018-02-02 22:53 UTC (permalink / raw)
To: netdev, ast, peterz, daniel; +Cc: kernel-team, hannes, Song Liu
This work follows up discussion at Plumbers'17 on improving addr->sym
resolution of user stack traces. The following links have more information
of the discussion:
http://www.linuxplumbersconf.org/2017/ocw/proposals/4764
https://lwn.net/Articles/734453/ Section "Stack traces and kprobes"
Currently, bpf stackmap store address for each entry in the call trace.
To map these addresses to user space files, it is necessary to maintain
the mapping from these virtual address to symbols in the binary. Usually,
the user space profiler (such as perf) has to scan /proc/pid/maps at the
beginning of profiling, and monitor mmap2() calls afterwards. Given the
cost of maintaining the address map, this solution is not practical for
system wide profiling that is always on.
This patch tries to address this with a variation to stackmap. Instead
of storing addresses, the variation stores ELF file build_id + offset.
After profiling, a user space tool will look up these functions with
build_id (to find the binary or shared library) and the offset.
I also updated bcc/cc library for the stackmap (no python/lua support yet).
You can find the work at:
https://github.com/liu-song-6/bcc/commits/bpf_get_stackid_v02
Thanks,
Song
Song Liu (2):
bpf: extend stackmap to save binary_build_id+offset instead of address
bpf: add selftest for stackmap with BPF_F_STACK_BUILD_ID
include/uapi/linux/bpf.h | 15 ++
kernel/bpf/stackmap.c | 261 +++++++++++++++++++--
tools/include/uapi/linux/bpf.h | 15 ++
tools/testing/selftests/bpf/Makefile | 12 +-
tools/testing/selftests/bpf/test_progs.c | 164 ++++++++++++-
.../selftests/bpf/test_stacktrace_build_id.c | 60 +++++
tools/testing/selftests/bpf/urandom_read.c | 22 ++
7 files changed, 525 insertions(+), 24 deletions(-)
create mode 100644 tools/testing/selftests/bpf/test_stacktrace_build_id.c
create mode 100644 tools/testing/selftests/bpf/urandom_read.c
^ permalink raw reply [flat|nested] 3+ messages in thread
* [RFC bpf-next 1/2] bpf: extend stackmap to save binary_build_id+offset instead of address
2018-02-02 22:53 [RFC bpf-next 0/2] stackmap with build_id+offset Song Liu
@ 2018-02-02 22:53 ` Song Liu
2018-02-02 22:53 ` [RFC bpf-next 2/2] bpf: add selftest for stackmap with BPF_F_STACK_BUILD_ID Song Liu
1 sibling, 0 replies; 3+ messages in thread
From: Song Liu @ 2018-02-02 22:53 UTC (permalink / raw)
To: netdev, ast, peterz, daniel; +Cc: kernel-team, hannes, Song Liu
Currently, bpf stackmap store address for each entry in the call trace.
To map these addresses to user space files, it is necessary to maintain
the mapping from these virtual address to symbols in the binary. Usually,
the user space profiler (such as perf) has to scan /proc/pid/maps at the
beginning of profiling, and monitor mmap2() calls afterwards. Given the
cost of maintaining the address map, this solution is not practical for
system wide profiling that is always on.
This patch tries to solve this problem with a variation of stackmap. This
variation is enabled by flag BPF_F_STACK_BUILD_ID, and only works for
user stack. Instead of storing addresses, the variation stores ELF file
build_id + offset.
Build ID is a 20-byte unique identifier for ELF files. The following
command shows the Build ID of /bin/bash:
[user@]$ readelf -n /bin/bash
...
Build ID: XXXXXXXXXX
...
With BPF_F_STACK_BUILD_ID, bpf_get_stackid() tries to parse Build ID
for each entry in the call trace, and translate it into the following
struct:
struct bpf_stack_build_id_offset {
__s32 status;
unsigned char build_id[BPF_BUILD_ID_SIZE];
__aligned_u64 offset;
};
Since the binary file is mapped to a vma (vm_area_struct), parsing
Build ID (after successful find_vma) is overall a cheap operation.
User space can access this struct with bpf syscall BPF_MAP_LOOKUP_ELEM.
It is necessary for user space to maintain mapping from build id to
binary files. This mostly static mapping is much easier to maintain
than per process address maps.
Signed-off-by: Song Liu <songliubraving@fb.com>
---
include/uapi/linux/bpf.h | 15 +++
kernel/bpf/stackmap.c | 261 +++++++++++++++++++++++++++++++++++++++++++----
2 files changed, 254 insertions(+), 22 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index db6bdc3..7df62c9 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -231,6 +231,21 @@ enum bpf_attach_type {
#define BPF_F_RDONLY (1U << 3)
#define BPF_F_WRONLY (1U << 4)
+/* Flag for stack_map, store build_id+offset instead of pointer */
+#define BPF_F_STACK_BUILD_ID (1U << 5)
+
+enum bpf_stack_build_id_status {
+ BPF_STACK_BUILD_ID_EMPTY = 0,
+ BPF_STACK_BUILD_ID_VALID = 1,
+};
+
+#define BPF_BUILD_ID_SIZE 20
+struct bpf_stack_build_id {
+ __s32 status;
+ unsigned char build_id[BPF_BUILD_ID_SIZE];
+ __u64 offset;
+};
+
union bpf_attr {
struct { /* anonymous struct used by BPF_MAP_CREATE command */
__u32 map_type; /* one of enum bpf_map_type */
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index b0ecf43..e6a48ca 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -9,16 +9,18 @@
#include <linux/filter.h>
#include <linux/stacktrace.h>
#include <linux/perf_event.h>
+#include <uapi/linux/elf.h>
#include "percpu_freelist.h"
-#define STACK_CREATE_FLAG_MASK \
- (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
+#define STACK_CREATE_FLAG_MASK \
+ (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY | \
+ BPF_F_STACK_BUILD_ID)
struct stack_map_bucket {
struct pcpu_freelist_node fnode;
u32 hash;
u32 nr;
- u64 ip[];
+ u64 data[];
};
struct bpf_stack_map {
@@ -29,6 +31,17 @@ struct bpf_stack_map {
struct stack_map_bucket *buckets[];
};
+static inline bool stack_map_use_build_id(struct bpf_map *map)
+{
+ return (map->map_flags & BPF_F_STACK_BUILD_ID);
+}
+
+static inline int stack_map_data_size(struct bpf_map *map)
+{
+ return stack_map_use_build_id(map) ?
+ sizeof(struct bpf_stack_build_id) : sizeof(u64);
+}
+
static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
{
u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size;
@@ -68,8 +81,16 @@ static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
/* check sanity of attributes */
if (attr->max_entries == 0 || attr->key_size != 4 ||
- value_size < 8 || value_size % 8 ||
- value_size / 8 > sysctl_perf_event_max_stack)
+ value_size < 8 || value_size % 8)
+ return ERR_PTR(-EINVAL);
+
+ BUILD_BUG_ON(sizeof(struct bpf_stack_build_id) % sizeof(u64));
+ if (attr->map_flags & BPF_F_STACK_BUILD_ID) {
+ if (value_size % sizeof(struct bpf_stack_build_id) ||
+ value_size / sizeof(struct bpf_stack_build_id)
+ > sysctl_perf_event_max_stack)
+ return ERR_PTR(-EINVAL);
+ } else if (value_size / 8 > sysctl_perf_event_max_stack)
return ERR_PTR(-EINVAL);
/* hash table size must be power of 2 */
@@ -114,13 +135,180 @@ static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
return ERR_PTR(err);
}
+#define BPF_BUILD_ID 3
+/*
+ * Parse build id from the note segment. This logic can be shared between
+ * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
+ * identical.
+ */
+static inline int stack_map_parse_build_id(struct vm_area_struct *vma,
+ unsigned char *build_id,
+ unsigned long note_start,
+ Elf32_Word note_size)
+{
+ Elf32_Word note_offs = 0, new_offs;
+
+ if (note_start + note_size >= vma->vm_end || /* note too big */
+ note_start + note_size < note_size) /* overflow */
+ return -EINVAL;
+
+ while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
+ Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
+
+ if (nhdr->n_type == BPF_BUILD_ID &&
+ nhdr->n_namesz == sizeof("GNU") &&
+ nhdr->n_descsz == BPF_BUILD_ID_SIZE) {
+ memcpy(build_id,
+ (void *)(note_start + note_offs +
+ ALIGN(sizeof("GNU"), 4) +
+ sizeof(Elf32_Nhdr)),
+ BPF_BUILD_ID_SIZE);
+ return 0;
+ }
+ new_offs = note_offs + sizeof(Elf32_Nhdr) +
+ ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
+ if (new_offs <= note_offs) /* overflow */
+ break;
+ note_offs = new_offs;
+ };
+ return -EINVAL;
+}
+
+/* Parse build ID from 32-bit ELF */
+static int stack_map_get_build_id_32(struct vm_area_struct *vma,
+ unsigned char *build_id)
+{
+ Elf32_Ehdr *ehdr = (Elf32_Ehdr *)vma->vm_start;
+ Elf32_Phdr *phdr;
+ int i;
+
+ /*
+ * e_phnum is __u16, so e_phnum * sizeof(Elf32_Phdr) will not
+ * overflow
+ */
+ if (vma->vm_end - vma->vm_start <
+ sizeof(Elf32_Ehdr) + ehdr->e_phnum * sizeof(Elf32_Phdr))
+ return -EINVAL;
+
+ phdr = (Elf32_Phdr *)(vma->vm_start + sizeof(Elf32_Ehdr));
+
+ for (i = 0; i < ehdr->e_phnum; ++i)
+ if (phdr[i].p_type == PT_NOTE) {
+ unsigned long note_start;
+
+ note_start = vma->vm_start + phdr[i].p_offset;
+ if (note_start < vma->vm_start) /* overflow */
+ return -EINVAL;
+ return stack_map_parse_build_id(
+ vma, build_id, note_start, phdr[i].p_filesz);
+ }
+ return -EINVAL;
+}
+
+/* Parse build ID from 64-bit ELF */
+static int stack_map_get_build_id_64(struct vm_area_struct *vma,
+ unsigned char *build_id)
+{
+ Elf64_Ehdr *ehdr = (Elf64_Ehdr *)vma->vm_start;
+ Elf64_Phdr *phdr;
+ int i;
+
+ /*
+ * e_phnum is __u16, so e_phnum * sizeof(Elf32_Phdr) will not
+ * overflow
+ */
+ if (vma->vm_end - vma->vm_start <
+ sizeof(Elf64_Ehdr) + ehdr->e_phnum * sizeof(Elf64_Phdr))
+ return -EINVAL;
+
+ phdr = (Elf64_Phdr *)(vma->vm_start + sizeof(Elf64_Ehdr));
+
+ for (i = 0; i < ehdr->e_phnum; ++i)
+ if (phdr[i].p_type == PT_NOTE) {
+ unsigned long note_start;
+
+ note_start = vma->vm_start + phdr[i].p_offset;
+ if (note_start < vma->vm_start) /* overflow */
+ return -EINVAL;
+ return stack_map_parse_build_id(
+ vma, build_id, note_start, phdr[i].p_filesz);
+ }
+ return -EINVAL;
+}
+
+/* Parse build ID of ELF file mapped to vma */
+static int stack_map_get_build_id(struct vm_area_struct *vma,
+ unsigned char *build_id)
+{
+ Elf32_Ehdr *ehdr = (Elf32_Ehdr *)vma->vm_start;
+
+ /* we need at least 1 file header and 1 program header */
+ if (vma->vm_end - vma->vm_start <
+ sizeof(Elf32_Ehdr) + sizeof(Elf32_Phdr))
+ return -EINVAL;
+
+ /* compare magic x7f "ELF" */
+ if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
+ return -EINVAL;
+
+ /* only support executable file and shared object file */
+ if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
+ return -EINVAL;
+
+ if (ehdr->e_ident[EI_CLASS] == 1)
+ return stack_map_get_build_id_32(vma, build_id);
+ else if (ehdr->e_ident[EI_CLASS] == 2)
+ return stack_map_get_build_id_64(vma, build_id);
+ return -EINVAL;
+}
+
+static int stack_map_get_build_id_offset(struct bpf_map *map,
+ struct stack_map_bucket *bucket,
+ u64 *ips, u32 trace_nr)
+{
+ int i;
+ struct vm_area_struct *vma;
+ struct bpf_stack_build_id *id_offs;
+ int err;
+ int successful_lookup = 0;
+
+ id_offs = (struct bpf_stack_build_id *)bucket->data;
+
+ if (!current || !current->mm)
+ return -ENOENT;
+
+ if (down_read_trylock(¤t->mm->mmap_sem) == 0)
+ return -EBUSY;
+
+ for (i = 0; i < trace_nr; i++) {
+ vma = find_vma(current->mm, ips[i]);
+ if (!vma) {
+ id_offs[i].status = -EFAULT;
+ continue;
+ }
+
+ err = stack_map_get_build_id(vma, id_offs[i].build_id);
+ if (err) {
+ id_offs[i].status = err;
+ continue;
+ }
+ id_offs[i].offset = ips[i] - vma->vm_start;
+ id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
+ successful_lookup++;
+ }
+ up_read(¤t->mm->mmap_sem);
+ bucket->nr = trace_nr;
+
+ return successful_lookup > 0 ? 0 : -EINVAL;
+}
+
BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
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 / 8;
+ 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;
u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
@@ -128,11 +316,17 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
bool user = flags & BPF_F_USER_STACK;
bool kernel = !user;
u64 *ips;
+ bool hash_matches;
+ int err;
if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
return -EINVAL;
+ /* build_id+offset stack map only supports user stack */
+ if (stack_map_use_build_id(map) && !user)
+ return -EINVAL;
+
trace = get_perf_callchain(regs, init_nr, kernel, user,
sysctl_perf_event_max_stack, false, false);
@@ -156,24 +350,47 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
id = hash & (smap->n_buckets - 1);
bucket = READ_ONCE(smap->buckets[id]);
- if (bucket && bucket->hash == hash) {
- if (flags & BPF_F_FAST_STACK_CMP)
+ hash_matches = bucket && bucket->hash == hash;
+ /* fast cmp */
+ if (hash_matches && flags & BPF_F_FAST_STACK_CMP)
+ return id;
+
+ if (stack_map_use_build_id(map)) {
+ /* for build_id+offset, pop a bucket before slow cmp */
+ new_bucket = (struct stack_map_bucket *)
+ pcpu_freelist_pop(&smap->freelist);
+ if (unlikely(!new_bucket))
+ return -ENOMEM;
+ err = stack_map_get_build_id_offset(map, new_bucket,
+ ips, trace_nr);
+ if (err) {
+ pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
+ return err;
+ }
+ trace_len = trace_nr * sizeof(struct bpf_stack_build_id);
+ if (hash_matches && bucket->nr == trace_nr &&
+ memcmp(bucket->data, new_bucket->data, trace_len) == 0) {
+ pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
return id;
- if (bucket->nr == trace_nr &&
- memcmp(bucket->ip, ips, trace_len) == 0)
+ }
+ if (bucket && !(flags & BPF_F_REUSE_STACKID)) {
+ pcpu_freelist_push(&smap->freelist, &new_bucket->fnode);
+ return -EEXIST;
+ }
+ } else {
+ if (hash_matches && bucket->nr == trace_nr &&
+ memcmp(bucket->data, ips, trace_len) == 0)
return id;
+ if (bucket && !(flags & BPF_F_REUSE_STACKID))
+ return -EEXIST;
+
+ new_bucket = (struct stack_map_bucket *)
+ pcpu_freelist_pop(&smap->freelist);
+ if (unlikely(!new_bucket))
+ return -ENOMEM;
+ memcpy(new_bucket->data, ips, trace_len);
}
- /* this call stack is not in the map, try to add it */
- if (bucket && !(flags & BPF_F_REUSE_STACKID))
- return -EEXIST;
-
- new_bucket = (struct stack_map_bucket *)
- pcpu_freelist_pop(&smap->freelist);
- if (unlikely(!new_bucket))
- return -ENOMEM;
-
- memcpy(new_bucket->ip, ips, trace_len);
new_bucket->hash = hash;
new_bucket->nr = trace_nr;
@@ -212,8 +429,8 @@ int bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
if (!bucket)
return -ENOENT;
- trace_len = bucket->nr * sizeof(u64);
- memcpy(value, bucket->ip, trace_len);
+ trace_len = bucket->nr * stack_map_data_size(map);
+ memcpy(value, bucket->data, trace_len);
memset(value + trace_len, 0, map->value_size - trace_len);
old_bucket = xchg(&smap->buckets[id], bucket);
--
2.9.5
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [RFC bpf-next 2/2] bpf: add selftest for stackmap with BPF_F_STACK_BUILD_ID
2018-02-02 22:53 [RFC bpf-next 0/2] stackmap with build_id+offset Song Liu
2018-02-02 22:53 ` [RFC bpf-next 1/2] bpf: extend stackmap to save binary_build_id+offset instead of address Song Liu
@ 2018-02-02 22:53 ` Song Liu
1 sibling, 0 replies; 3+ messages in thread
From: Song Liu @ 2018-02-02 22:53 UTC (permalink / raw)
To: netdev, ast, peterz, daniel; +Cc: kernel-team, hannes, Song Liu
test_stacktrace_build_id() is added. It accesses tracepoint urandom_read
with "dd" and "urandom_read" and gathers stack traces. Then it reads the
stack traces from the stackmap.
urandom_read is a statically link binary that reads from /dev/urandom.
test_stacktrace_build_id() calls readelf to read build ID of urandom_read
and compares it with build ID from the stackmap.
Signed-off-by: Song Liu <songliubraving@fb.com>
---
tools/include/uapi/linux/bpf.h | 15 ++
tools/testing/selftests/bpf/Makefile | 12 +-
tools/testing/selftests/bpf/test_progs.c | 164 ++++++++++++++++++++-
.../selftests/bpf/test_stacktrace_build_id.c | 60 ++++++++
tools/testing/selftests/bpf/urandom_read.c | 22 +++
5 files changed, 271 insertions(+), 2 deletions(-)
create mode 100644 tools/testing/selftests/bpf/test_stacktrace_build_id.c
create mode 100644 tools/testing/selftests/bpf/urandom_read.c
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index db6bdc3..7df62c9 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -231,6 +231,21 @@ enum bpf_attach_type {
#define BPF_F_RDONLY (1U << 3)
#define BPF_F_WRONLY (1U << 4)
+/* Flag for stack_map, store build_id+offset instead of pointer */
+#define BPF_F_STACK_BUILD_ID (1U << 5)
+
+enum bpf_stack_build_id_status {
+ BPF_STACK_BUILD_ID_EMPTY = 0,
+ BPF_STACK_BUILD_ID_VALID = 1,
+};
+
+#define BPF_BUILD_ID_SIZE 20
+struct bpf_stack_build_id {
+ __s32 status;
+ unsigned char build_id[BPF_BUILD_ID_SIZE];
+ __u64 offset;
+};
+
union bpf_attr {
struct { /* anonymous struct used by BPF_MAP_CREATE command */
__u32 map_type; /* one of enum bpf_map_type */
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index bf05bc5..cd5ccee 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -13,6 +13,14 @@ endif
CFLAGS += -Wall -O2 -I$(APIDIR) -I$(LIBDIR) -I$(GENDIR) $(GENFLAGS) -I../../../include
LDLIBS += -lcap -lelf -lrt -lpthread
+TEST_CUSTOM_PROGS = $(OUTPUT)/urandom_read
+all: $(TEST_CUSTOM_PROGS)
+
+$(TEST_CUSTOM_PROGS): urandom_read
+
+urandom_read: urandom_read.c
+ $(CC) -o $(TEST_CUSTOM_PROGS) -static $<
+
TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test_progs \
test_align test_verifier_log test_dev_cgroup test_tcpbpf_user
@@ -20,7 +28,7 @@ TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test
test_pkt_md_access.o test_xdp_redirect.o test_xdp_meta.o sockmap_parse_prog.o \
sockmap_verdict_prog.o dev_cgroup.o sample_ret0.o test_tracepoint.o \
test_l4lb_noinline.o test_xdp_noinline.o test_stacktrace_map.o \
- sample_map_ret0.o test_tcpbpf_kern.o
+ sample_map_ret0.o test_tcpbpf_kern.o test_stacktrace_build_id.o
TEST_PROGS := test_kmod.sh test_xdp_redirect.sh test_xdp_meta.sh \
test_offload.py
@@ -62,3 +70,5 @@ $(OUTPUT)/test_xdp_noinline.o: CLANG_FLAGS += -fno-inline
$(CLANG) $(CLANG_FLAGS) \
-O2 -target bpf -emit-llvm -c $< -o - | \
$(LLC) -march=bpf -mcpu=$(CPU) -filetype=obj -o $@
+
+EXTRA_CLEAN := $(TEST_CUSTOM_PROGS)
diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index b549308..d9f689a 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -840,7 +840,8 @@ static void test_tp_attach_query(void)
static int compare_map_keys(int map1_fd, int map2_fd)
{
__u32 key, next_key;
- char val_buf[PERF_MAX_STACK_DEPTH * sizeof(__u64)];
+ char val_buf[PERF_MAX_STACK_DEPTH *
+ sizeof(struct bpf_stack_build_id)];
int err;
err = bpf_map_get_next_key(map1_fd, NULL, &key);
@@ -963,6 +964,166 @@ static void test_stacktrace_map()
return;
}
+static int extract_build_id(char *build_id, size_t size)
+{
+ FILE *fp;
+ char *line = NULL;
+ size_t len = 0;
+
+ fp = popen("readelf -n ./urandom_read | grep 'Build ID'", "r");
+ if (fp == NULL)
+ return -1;
+
+ if (getline(&line, &len, fp) == -1)
+ goto err;
+ fclose(fp);
+
+ if (len > size)
+ len = size;
+ memcpy(build_id, line, len);
+ build_id[len] = '\0';
+ return 0;
+err:
+ fclose(fp);
+ return -1;
+}
+
+static void test_stacktrace_build_id(void)
+{
+ int control_map_fd, stackid_hmap_fd, stackmap_fd;
+ const char *file = "./test_stacktrace_build_id.o";
+ int bytes, efd, err, pmu_fd, prog_fd;
+ struct perf_event_attr attr = {};
+ __u32 key, previous_key, val, duration = 0;
+ struct bpf_object *obj;
+ char buf[256];
+ int i, j;
+ struct bpf_stack_build_id id_offs[PERF_MAX_STACK_DEPTH];
+ int build_id_matches = 0;
+
+ err = bpf_prog_load(file, BPF_PROG_TYPE_TRACEPOINT, &obj, &prog_fd);
+ if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
+ goto out;
+
+ /* Get the ID for the sched/sched_switch tracepoint */
+ snprintf(buf, sizeof(buf),
+ "/sys/kernel/debug/tracing/events/random/urandom_read/id");
+ efd = open(buf, O_RDONLY, 0);
+ if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
+ goto close_prog;
+
+ bytes = read(efd, buf, sizeof(buf));
+ close(efd);
+ if (CHECK(bytes <= 0 || bytes >= sizeof(buf),
+ "read", "bytes %d errno %d\n", bytes, errno))
+ goto close_prog;
+
+ /* Open the perf event and attach bpf progrram */
+ attr.config = strtol(buf, NULL, 0);
+ attr.type = PERF_TYPE_TRACEPOINT;
+ attr.sample_type = PERF_SAMPLE_RAW | PERF_SAMPLE_CALLCHAIN;
+ attr.sample_period = 1;
+ attr.wakeup_events = 1;
+ pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
+ 0 /* cpu 0 */, -1 /* group id */,
+ 0 /* flags */);
+ if (CHECK(pmu_fd < 0, "perf_event_open", "err %d errno %d\n",
+ pmu_fd, errno))
+ goto close_prog;
+
+ err = ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0);
+ if (CHECK(err, "perf_event_ioc_enable", "err %d errno %d\n",
+ err, errno))
+ goto close_pmu;
+
+ err = ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
+ if (CHECK(err, "perf_event_ioc_set_bpf", "err %d errno %d\n",
+ err, errno))
+ goto disable_pmu;
+
+ /* find map fds */
+ control_map_fd = bpf_find_map(__func__, obj, "control_map");
+ if (CHECK(control_map_fd < 0, "bpf_find_map control_map",
+ "err %d errno %d\n", err, errno))
+ goto disable_pmu;
+
+ stackid_hmap_fd = bpf_find_map(__func__, obj, "stackid_hmap");
+ if (CHECK(stackid_hmap_fd < 0, "bpf_find_map stackid_hmap",
+ "err %d errno %d\n", err, errno))
+ goto disable_pmu;
+
+ stackmap_fd = bpf_find_map(__func__, obj, "stackmap");
+ if (CHECK(stackmap_fd < 0, "bpf_find_map stackmap", "err %d errno %d\n",
+ err, errno))
+ goto disable_pmu;
+
+ assert(system("dd if=/dev/urandom of=/dev/zero count=4 2> /dev/null")
+ == 0);
+ assert(system("./urandom_read if=/dev/urandom of=/dev/zero count=4 2> /dev/null") == 0);
+ /* disable stack trace collection */
+ key = 0;
+ val = 1;
+ bpf_map_update_elem(control_map_fd, &key, &val, 0);
+
+ /* for every element in stackid_hmap, we can find a corresponding one
+ * in stackmap, and vise versa.
+ */
+ err = compare_map_keys(stackid_hmap_fd, stackmap_fd);
+ if (CHECK(err, "compare_map_keys stackid_hmap vs. stackmap",
+ "err %d errno %d\n", err, errno))
+ goto disable_pmu;
+
+ err = compare_map_keys(stackmap_fd, stackid_hmap_fd);
+ if (CHECK(err, "compare_map_keys stackmap vs. stackid_hmap",
+ "err %d errno %d\n", err, errno))
+ goto disable_pmu;
+
+ err = extract_build_id(buf, 256);
+
+ if (CHECK(err, "get build_id with readelf",
+ "err %d errno %d\n", err, errno))
+ goto disable_pmu;
+
+ err = bpf_map_get_next_key(stackmap_fd, NULL, &key);
+ if (CHECK(err, "get_next_key from stackmap",
+ "err %d, errno %d\n", err, errno))
+ goto disable_pmu;
+
+ do {
+ char build_id[64];
+
+ err = bpf_map_lookup_elem(stackmap_fd, &key, id_offs);
+ if (CHECK(err, "lookup_elem from stackmap",
+ "err %d, errno %d\n", err, errno))
+ goto disable_pmu;
+ for (i = 0; i < PERF_MAX_STACK_DEPTH; ++i)
+ if (id_offs[i].status == BPF_STACK_BUILD_ID_VALID &&
+ id_offs[i].offset != 0) {
+ for (j = 0; j < 20; ++j)
+ sprintf(build_id + 2 * j, "%02x",
+ id_offs[i].build_id[j] & 0xff);
+ if (strstr(buf, build_id) != NULL)
+ build_id_matches = 1;
+ }
+ previous_key = key;
+ } while (bpf_map_get_next_key(stackmap_fd, &previous_key, &key) == 0);
+
+ CHECK(build_id_matches < 1, "build id match",
+ "Didn't find expected build ID from the map");
+
+disable_pmu:
+ ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE);
+
+close_pmu:
+ close(pmu_fd);
+
+close_prog:
+ bpf_object__close(obj);
+
+out:
+ return;
+}
+
int main(void)
{
struct rlimit rinf = { RLIM_INFINITY, RLIM_INFINITY };
@@ -979,6 +1140,7 @@ int main(void)
test_obj_name();
test_tp_attach_query();
test_stacktrace_map();
+ test_stacktrace_build_id();
printf("Summary: %d PASSED, %d FAILED\n", pass_cnt, error_cnt);
return error_cnt ? EXIT_FAILURE : EXIT_SUCCESS;
diff --git a/tools/testing/selftests/bpf/test_stacktrace_build_id.c b/tools/testing/selftests/bpf/test_stacktrace_build_id.c
new file mode 100644
index 0000000..b755bd7
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_stacktrace_build_id.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Facebook
+
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+
+#ifndef PERF_MAX_STACK_DEPTH
+#define PERF_MAX_STACK_DEPTH 127
+#endif
+
+struct bpf_map_def SEC("maps") control_map = {
+ .type = BPF_MAP_TYPE_ARRAY,
+ .key_size = sizeof(__u32),
+ .value_size = sizeof(__u32),
+ .max_entries = 1,
+};
+
+struct bpf_map_def SEC("maps") stackid_hmap = {
+ .type = BPF_MAP_TYPE_HASH,
+ .key_size = sizeof(__u32),
+ .value_size = sizeof(__u32),
+ .max_entries = 10000,
+};
+
+struct bpf_map_def SEC("maps") stackmap = {
+ .type = BPF_MAP_TYPE_STACK_TRACE,
+ .key_size = sizeof(__u32),
+ .value_size = sizeof(struct bpf_stack_build_id)
+ * PERF_MAX_STACK_DEPTH,
+ .max_entries = 128,
+ .map_flags = BPF_F_STACK_BUILD_ID,
+};
+
+/* taken from /sys/kernel/debug/tracing/events/random/urandom_read/format */
+struct random_urandom_args {
+ unsigned long long pad;
+ int got_bits;
+ int pool_left;
+ int input_left;
+};
+
+SEC("tracepoint/random/urandom_read")
+int oncpu(struct random_urandom_args *args)
+{
+ __u32 key = 0, val = 0, *value_p;
+
+ value_p = bpf_map_lookup_elem(&control_map, &key);
+ if (value_p && *value_p)
+ return 0; /* skip if non-zero *value_p */
+
+ /* The size of stackmap and stackid_hmap should be the same */
+ key = bpf_get_stackid(args, &stackmap, BPF_F_USER_STACK);
+ if ((int)key >= 0)
+ bpf_map_update_elem(&stackid_hmap, &key, &val, 0);
+
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
+__u32 _version SEC("version") = 1; /* ignored by tracepoints, required by libbpf.a */
diff --git a/tools/testing/selftests/bpf/urandom_read.c b/tools/testing/selftests/bpf/urandom_read.c
new file mode 100644
index 0000000..4acfdeb
--- /dev/null
+++ b/tools/testing/selftests/bpf/urandom_read.c
@@ -0,0 +1,22 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdlib.h>
+
+#define BUF_SIZE 256
+int main(void)
+{
+ int fd = open("/dev/urandom", O_RDONLY);
+ int i;
+ char buf[BUF_SIZE];
+
+ if (fd < 0)
+ return 1;
+ for (i = 0; i < 4; ++i)
+ read(fd, buf, BUF_SIZE);
+
+ close(fd);
+ return 0;
+}
--
2.9.5
^ permalink raw reply related [flat|nested] 3+ messages in thread
end of thread, other threads:[~2018-02-02 22:53 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-02-02 22:53 [RFC bpf-next 0/2] stackmap with build_id+offset Song Liu
2018-02-02 22:53 ` [RFC bpf-next 1/2] bpf: extend stackmap to save binary_build_id+offset instead of address Song Liu
2018-02-02 22:53 ` [RFC bpf-next 2/2] bpf: add selftest for stackmap with BPF_F_STACK_BUILD_ID Song Liu
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