[PATCH bpf-next v3 0/5] Separate error injection table from kprobes

Masami Hiramatsu
2018-01-10T10:16:34Z

Hi,

Here are the 3rd version of patches to moving error injection
table from kprobes. This series includes some fixes and error
type descriptions which we discussed in the previous thread.

Here is the previous version:

https://lkml.org/lkml/2017/12/26/26

There are 2 main reasons why I separate it from kprobes.

- kprobes users can modify execution path not only at
error-injection whitelist functions but also other
functions.

- This error injection information is also useful for
ftrace (function-hook) and livepatch. It should not
be limited by CONFIG_KPROBES.

So I introduced CONFIG_FUNCTION_ERROR_INJECTION for this feature.

Unfortunately currently CONFIG_FUNCTION_ERROR_INJECTION depends on
CONFIG_KPROBES because of arch_deref_entry_point(), which should
be provided by asm/types.h as ppc64 and ia64 do or kallsyms
subsystem. Anyway, since that is another story, I will make
another series to fix it.

For [1/5], I tested it by test_override_return.sh on the
kernel with CONFIG_DYNAMIC_FTRACE=n, and succeeded as below.
(actually I'v found some bugs and fixed, thanks Alexei!)

======
# LANG=C ./test_override_return.sh
1+0 records in
1+0 records out
1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.00200037 s, 524 MB/s
btrfs-progs v4.9.1
See http://btrfs.wiki.kernel.org for more information.

Performing full device TRIM /dev/loop1 (1001.00MiB) ...
Label: (null)
UUID: 02635ea7-f6d1-4ee8-a677-4354a38f6930
Node size: 16384
Sector size: 4096
Filesystem size: 1001.00MiB
Block group profiles:
Data: single 8.00MiB
Metadata: DUP 50.00MiB
System: DUP 8.00MiB
SSD detected: no
Incompat features: extref, skinny-metadata
Number of devices: 1
Devices:
ID SIZE PATH
1 1001.00MiB /dev/loop1

mount: /opt/samples/bpf/tmpmnt: mount(2) system call failed: Cannot allocate memory.
SUCCESS!
======

I've removed RFC from this series, but actually, [4/5] and [5/5]
will be need more discussion. So please feel free to merge
[1/5] to [3/5] separately.

[4/5] introduces error return types for describing what error
values the function callers must expect.
For the purpose of error injection test is to find out hidden
problems which caller doesn't handle errors correctly. So if the
caller is programmed correctly, even if we inject an error, it
continues to work as expected. However, if we inject a succeed
return value even though the callee doesn't do anything, the
caller does wrong processing (and end up with kernel panic, or
even worse data corruption). That is not what we want to do
with error injection.
[5/5] introduces function-based error injection interface via
debugfs, which can cause "success injection", So I coupled it
with [4/5] to ensure the expected error types for the target
function.

Changes in v3:
- [1/5] Move arch_ftrace_kprobe_override_function() to core.c
to remove CONFIG_KPROBE_ON_FTRACE dependency, and fix a
bug in trace_kprobe_on_func_entry().
- [3/5] Fix a build error and typos, separate CONFIG_MODULES
dependent code, add CONFIG_KPROBES dependency, and call
error-injection init function in late_initcall stage.
- [4/5] Newly added
- [5/5] Check and adjust error value for each target function
and add more documents and example.

Thank you,

---

Masami Hiramatsu (5):
tracing/kprobe: bpf: Check error injectable event is on function entry
tracing/kprobe: bpf: Compare instruction pointer with original one
error-injection: Separate error-injection from kprobe
error-injection: Add injectable error types
error-injection: Support fault injection framework

Documentation/fault-injection/fault-injection.txt | 62 +++++
arch/Kconfig | 2
arch/x86/Kconfig | 2
arch/x86/include/asm/error-injection.h | 13 +
arch/x86/include/asm/kprobes.h | 4
arch/x86/kernel/kprobes/ftrace.c | 14 -
arch/x86/lib/Makefile | 1
arch/x86/lib/error-inject.c | 19 ++
fs/btrfs/disk-io.c | 2
fs/btrfs/free-space-cache.c | 2
include/asm-generic/error-injection.h | 35 +++
include/asm-generic/vmlinux.lds.h | 14 +
include/linux/bpf.h | 12 -
include/linux/error-injection.h | 27 ++
include/linux/kprobes.h | 1
include/linux/module.h | 7 -
kernel/Makefile | 1
kernel/fail_function.c | 217 +++++++++++++++++++
kernel/kprobes.c | 163 --------------
kernel/module.c | 8 -
kernel/trace/Kconfig | 4
kernel/trace/bpf_trace.c | 9 -
kernel/trace/trace_kprobe.c | 33 +--
kernel/trace/trace_probe.h | 12 +
lib/Kconfig.debug | 14 +
lib/Makefile | 1
lib/error-inject.c | 242 +++++++++++++++++++++
27 files changed, 679 insertions(+), 242 deletions(-)
create mode 100644 arch/x86/include/asm/error-injection.h
create mode 100644 arch/x86/lib/error-inject.c
create mode 100644 include/asm-generic/error-injection.h
create mode 100644 include/linux/error-injection.h
create mode 100644 kernel/fail_function.c
create mode 100644 lib/error-inject.c

--
Masami Hiramatsu (Linaro)