Messages in this thread | | | Subject | Re: [PATCH v2 bpf-next 2/2] selftests: bpf: Add a new test for bare tracepoints | From | Yonghong Song <> | Date | Mon, 18 Jan 2021 09:48:53 -0800 |
| |
On 1/18/21 4:18 AM, Qais Yousef wrote: > On 01/16/21 18:11, Yonghong Song wrote: >> >> >> On 1/16/21 10:21 AM, Qais Yousef wrote: >>> Reuse module_attach infrastructure to add a new bare tracepoint to check >>> we can attach to it as a raw tracepoint. >>> >>> Signed-off-by: Qais Yousef <qais.yousef@arm.com> >>> --- >>> .../bpf/bpf_testmod/bpf_testmod-events.h | 6 +++++ >>> .../selftests/bpf/bpf_testmod/bpf_testmod.c | 21 ++++++++++++++- >>> .../selftests/bpf/bpf_testmod/bpf_testmod.h | 6 +++++ >>> .../selftests/bpf/prog_tests/module_attach.c | 27 +++++++++++++++++++ >>> .../selftests/bpf/progs/test_module_attach.c | 10 +++++++ >>> 5 files changed, 69 insertions(+), 1 deletion(-) >>> >>> diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h >>> index b83ea448bc79..89c6d58e5dd6 100644 >>> --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h >>> +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod-events.h >>> @@ -28,6 +28,12 @@ TRACE_EVENT(bpf_testmod_test_read, >>> __entry->pid, __entry->comm, __entry->off, __entry->len) >>> ); >>> +/* A bare tracepoint with no event associated with it */ >>> +DECLARE_TRACE(bpf_testmod_test_write_bare, >>> + TP_PROTO(struct task_struct *task, struct bpf_testmod_test_write_ctx *ctx), >>> + TP_ARGS(task, ctx) >>> +); >>> + >>> #endif /* _BPF_TESTMOD_EVENTS_H */ >>> #undef TRACE_INCLUDE_PATH >>> diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c >>> index 2df19d73ca49..e900adad2276 100644 >>> --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c >>> +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c >>> @@ -28,9 +28,28 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj, >>> EXPORT_SYMBOL(bpf_testmod_test_read); >>> ALLOW_ERROR_INJECTION(bpf_testmod_test_read, ERRNO); >>> +noinline ssize_t >>> +bpf_testmod_test_write(struct file *file, struct kobject *kobj, >>> + struct bin_attribute *bin_attr, >>> + char *buf, loff_t off, size_t len) >>> +{ >>> + struct bpf_testmod_test_write_ctx ctx = { >>> + .buf = buf, >>> + .off = off, >>> + .len = len, >>> + }; >>> + >>> + trace_bpf_testmod_test_write_bare(current, &ctx); >>> + >>> + return -EIO; /* always fail */ >>> +} >>> +EXPORT_SYMBOL(bpf_testmod_test_write); >>> +ALLOW_ERROR_INJECTION(bpf_testmod_test_write, ERRNO); >>> + >>> static struct bin_attribute bin_attr_bpf_testmod_file __ro_after_init = { >> >> Do we need to remove __ro_after_init? > > I don't think so. The structure should still remain RO AFAIU.
okay.
> >> >>> - .attr = { .name = "bpf_testmod", .mode = 0444, }, >>> + .attr = { .name = "bpf_testmod", .mode = 0666, }, >>> .read = bpf_testmod_test_read, >>> + .write = bpf_testmod_test_write, >>> }; >>> static int bpf_testmod_init(void) >>> diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h >>> index b81adfedb4f6..b3892dc40111 100644 >>> --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h >>> +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h >>> @@ -11,4 +11,10 @@ struct bpf_testmod_test_read_ctx { >>> size_t len; >>> }; >>> +struct bpf_testmod_test_write_ctx { >>> + char *buf; >>> + loff_t off; >>> + size_t len; >>> +}; >>> + >>> #endif /* _BPF_TESTMOD_H */ >>> diff --git a/tools/testing/selftests/bpf/prog_tests/module_attach.c b/tools/testing/selftests/bpf/prog_tests/module_attach.c >>> index 50796b651f72..e4605c0b5af1 100644 >>> --- a/tools/testing/selftests/bpf/prog_tests/module_attach.c >>> +++ b/tools/testing/selftests/bpf/prog_tests/module_attach.c >>> @@ -21,9 +21,34 @@ static int trigger_module_test_read(int read_sz) >>> return 0; >>> } >>> +static int trigger_module_test_write(int write_sz) >>> +{ >>> + int fd, err; >> >> Init err = 0? > > I don't see what difference this makes. > >> >>> + char *buf = malloc(write_sz); >>> + >>> + if (!buf) >>> + return -ENOMEM; >> >> Looks like we already non-negative value, so return ENOMEM? > > We already set err=-errno. So shouldn't we return negative too?
Oh, yes, return -ENOMEM sounds right here.
> >> >>> + >>> + memset(buf, 'a', write_sz); >>> + buf[write_sz-1] = '\0'; >>> + >>> + fd = open("/sys/kernel/bpf_testmod", O_WRONLY); >>> + err = -errno; >>> + if (CHECK(fd < 0, "testmod_file_open", "failed: %d\n", err)) >>> + goto out; >> >> Change the above to >> fd = open("/sys/kernel/bpf_testmod", O_WRONLY); >> if (CHECK(fd < 0, "testmod_file_open", "failed: %d\n", errno)) {
Here it should be ... "failed: %d\n", -errno.
>> err = -errno; >> goto out; >> } > > I kept the code consistent with the definition of trigger_module_test_read().
The original patch code:
+static int trigger_module_test_write(int write_sz) +{ + int fd, err; + char *buf = malloc(write_sz); + + if (!buf) + return -ENOMEM; + + memset(buf, 'a', write_sz); + buf[write_sz-1] = '\0'; + + fd = open("/sys/kernel/bpf_testmod", O_WRONLY); + err = -errno; + if (CHECK(fd < 0, "testmod_file_open", "failed: %d\n", err)) + goto out; + + write(fd, buf, write_sz); + close(fd); +out: + free(buf); + + return 0; +}
Even for "fd < 0" case, it "goto out" and "return 0". We should return error code here instead of 0.
Second, "err = -errno" is set before checking fd < 0. If fd >= 0, err might inherit an postive errno from previous failure. In trigger_module_test_write(), it is okay since the err is only used when fd < 0: err = -errno; if (CHECK(fd < 0, "testmod_file_open", "failed: %d\n", err)) return err;
My above rewrite intends to use "err" during final "return" statement, so I put assignment of "err = -errno" inside the CHECK branch. But there are different ways to implement this properly.
> > I'll leave it up to the maintainer to pick up the style changes if they prefer > it this way. > > Thanks for the ack and for the review.
No problem.
> > Cheers > > -- > Qais Yousef >
| |