BCC is a compiler and a toolkit, containing powerful kernel tracing tools that trace at the lowest levels, including adding hooks to functions in kernel space and user space to deeply understand system behavior while being low in overhead. Here's a presentation with an overview and visit BCC's project page for the official BCC documentation.
adeb is the primary vehicle for running BCC on Android. It supports preparing the target Android device with necessary kernel headers, cloning and building BCC on device, and other setup. Take a look a quick look at adeb README so that you're familiar with what it is.
For setting up BCC on your Android device, you need the target device's kernel source and the sources should be built atleast once in-tree. Once it is built, run the following command pointing adeb to the kernel sources which will have it extract headers from there and push them to the device.
adeb prepare --build --bcc --kernelsrc /path/to/kernel-source/
This downloads and installs a pre-built adeb filesystem containing a recent
version of BCC onto the android device, extracts kernel headers from the source
tree pointed to and does other setup. Note that --download option will work
only if the target architecture is ARM64. For other architectures, see the
Other Architectures
section
Now to run BCC, just start an adeb shell: adeb shell. This uses adb
as the backend to start a shell into your adeb environment. Try running
opensnoop or any of the other BCC tracers to confirm that the setup worked
correctly.
If building your own kernel, following are the kernel requirements:
You need kernel 4.9 or newer. Anything less needs backports. Your kernel needs to be built with the following config options at the minimum:
CONFIG_KPROBES=y
CONFIG_KPROBE_EVENT=y
CONFIG_BPF_SYSCALL=y
Optionally,
CONFIG_UPROBES=y
CONFIG_UPROBE_EVENT=y
Additionally, for the criticalsection BCC tracer to work, you need:
CONFIG_DEBUG_PREEMPT=y
CONFIG_PREEMPTIRQ_EVENTS=y
If you would like the latest BCC installation on your Android device, we
recommend dropping the --download option from the adeb command above.
This will make adeb clone and build the latest version of BCC for the
target architecture. Note that this is much slower that --download.
adeb prepare --build --bcc --kernelsrc /path/to/kernel-source/
Note that the full adeb install already contains recent BCC:
adeb prepare --full
This downloads and installs a prebuilt FS and is faster than building locally
using --build.
By default adeb assumes the target Android device is based on ARM64 processor architecture. For other architectures, use the --arch option. For example for x86_64 architecture, run:
adeb prepare --arch amd64 --bcc --kernelsrc /path/to/kernel-source/
Note: The --download option ignores the --arch flag. This is because we only provide pre-built filesystems for ARM64 at the moment.
Here are some common issues you may face when running different BCC tools.
- Issue 1: Headers are missing on the target device.
Symptom: This will usually result in an error like the following:
root@localhost:/# criticalstat
In file included from <built-in>:2
In file included from /virtual/include/bcc/bpf.h:12:
In file included from include/linux/types.h:5:
include/uapi/linux/types.h:4:10: fatal error: 'asm/types.h' file not found
#include <asm/types.h>
^~~~~~~~~~~~~
1 error generated.
Traceback (most recent call last):
File "./criticalstat.py", line 138, in <module>
b = BPF(text=bpf_text)
File "/usr/lib/python2.7/dist-packages/bcc/__init__.py", line 297, in __init__
raise Exception("Failed to compile BPF text:\n%s" % text)
Exception: Failed to compile BPF text:
#include <uapi/linux/ptrace.h>
#include <uapi/linux/limits.h>
#include <linux/sched.h>
extern char _stext[];
- Issue 2:
CONFIG_KPROBESisn't enabled.
Symptom: This will result in an error like the following:
Traceback (most recent call last):
File "/usr/share/bcc/tools/cachetop", line 263, in <module>
curses.wrapper(handle_loop, args)
File "/usr/lib/python2.7/curses/wrapper.py", line 43, in wrapper
return func(stdscr, *args, **kwds)
File "/usr/share/bcc/tools/cachetop", line 172, in handle_loop
b.attach_kprobe(event="add_to_page_cache_lru", fn_name="do_count")
File "/usr/lib/python2.7/dist-packages/bcc/__init__.py", line 543, in
attach_kprobe
fn = self.load_func(fn_name, BPF.KPROBE)
File "/usr/lib/python2.7/dist-packages/bcc/__init__.py", line 355, in
load_func
(func_name, errstr))
Exception: Failed to load BPF program do_count: Invalid argument
- Issue 3:
CONFIG_BPF_SYSCALLisn't enabled.
Symptom: This may result in a compilation error like the following:
root@localhost:/# cachetop
Traceback (most recent call last):
File "/usr/share/bcc/tools/cachetop", line 263, in <module>
curses.wrapper(handle_loop, args)
File "/usr/lib/python2.7/curses/wrapper.py", line 43, in wrapper
return func(stdscr, *args, **kwds)
File "/usr/share/bcc/tools/cachetop", line 171, in handle_loop
b = BPF(text=bpf_text)
File "/usr/lib/python2.7/dist-packages/bcc/__init__.py", line 297, in __init__
raise Exception("Failed to compile BPF text:\n%s" % text)
Exception: Failed to compile BPF text:
#include <uapi/linux/ptrace.h>
struct key_t {
u64 ip;
u32 pid;
u32 uid;
char comm[16];
};
BPF_HASH(counts, struct key_t);
int do_count(struct pt_regs *ctx) {
struct key_t key = {};
u64 zero = 0 , *val;
u64 pid = bpf_get_current_pid_tgid();
u32 uid = bpf_get_current_uid_gid();
key.ip = PT_REGS_IP(ctx);
key.pid = pid & 0xFFFFFFFF;
key.uid = uid & 0xFFFFFFFF;
bpf_get_current_comm(&(key.comm), 16);
val = counts.lookup_or_init(&key, &zero); // update counter
(*val)++;
return 0;
}