From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Alan Maguire <alan.maguire@oracle.com>
Cc: ast@kernel.org, daniel@iogearbox.net, andriin@fb.com, yhs@fb.com,
linux@rasmusvillemoes.dk, andriy.shevchenko@linux.intel.com,
pmladek@suse.com, kafai@fb.com, songliubraving@fb.com,
john.fastabend@gmail.com, kpsingh@chromium.org, shuah@kernel.org,
rdna@fb.com, scott.branden@broadcom.com, quentin@isovalent.com,
cneirabustos@gmail.com, jakub@cloudflare.com, mingo@redhat.com,
rostedt@goodmis.org, bpf@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
acme@kernel.org
Subject: Re: [PATCH v6 bpf-next 4/6] selftests/bpf: add bpf_snprintf_btf helper tests
Date: Thu, 24 Sep 2020 17:50:51 -0700 [thread overview]
Message-ID: <20200925005051.nqf6ru46psex7oh4@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <1600883188-4831-5-git-send-email-alan.maguire@oracle.com>
On Wed, Sep 23, 2020 at 06:46:26PM +0100, Alan Maguire wrote:
> +static int __strncmp(const void *m1, const void *m2, size_t len)
> +{
> + const unsigned char *s1 = m1;
> + const unsigned char *s2 = m2;
> + int i, delta = 0;
> +
> +#pragma clang loop unroll(full)
Shouldn't be needed?
The verifier supports bounded loops.
> + for (i = 0; i < len; i++) {
> + delta = s1[i] - s2[i];
> + if (delta || s1[i] == 0 || s2[i] == 0)
> + break;
> + }
> + return delta;
> +}
> +
> +/* Use __builtin_btf_type_id to test snprintf_btf by type id instead of name */
> +#if __has_builtin(__builtin_btf_type_id)
> +#define TEST_BTF_BY_ID(_str, _typestr, _ptr, _hflags) \
> + do { \
> + int _expected_ret = ret; \
> + _ptr.type = 0; \
> + _ptr.type_id = __builtin_btf_type_id(_typestr, 0); \
The test is passing for me, but I don't understand why :)
__builtin_btf_type_id(, 0); means btf_id of the bpf program.
While bpf_snprintf_btf() is treating it as btf_id of vmlinux_btf.
So it really should have been __builtin_btf_type_id(,1);
The following diff works:
diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c
index b4f96f1f6830..bffa786e3b03 100644
--- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c
+++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c
@@ -45,7 +45,7 @@ static int __strncmp(const void *m1, const void *m2, size_t len)
do { \
int _expected_ret = ret; \
_ptr.type = 0; \
- _ptr.type_id = __builtin_btf_type_id(_typestr, 0); \
+ _ptr.type_id = __builtin_btf_type_id(_typestr, 1); \
ret = bpf_snprintf_btf(_str, STRSIZE, &_ptr, \
sizeof(_ptr), _hflags); \
if (ret != _expected_ret) { \
@@ -88,7 +88,7 @@ static int __strncmp(const void *m1, const void *m2, size_t len)
ret = -EBADMSG; \
break; \
} \
- TEST_BTF_BY_ID(_str, #_type, _ptr, _hflags); \
+ TEST_BTF_BY_ID(_str, _ptr, _ptr, _hflags); \
But still makes me suspicious of the test. I haven't debugged further.
next prev parent reply other threads:[~2020-09-25 0:50 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-23 17:46 [PATCH v6 bpf-next 0/6] bpf: add helpers to support BTF-based kernel data display Alan Maguire
2020-09-23 17:46 ` [PATCH v6 bpf-next 1/6] bpf: provide function to get vmlinux BTF information Alan Maguire
2020-09-23 17:46 ` [PATCH v6 bpf-next 2/6] bpf: move to generic BTF show support, apply it to seq files/strings Alan Maguire
2020-09-25 0:33 ` Alexei Starovoitov
2020-09-23 17:46 ` [PATCH v6 bpf-next 3/6] bpf: add bpf_snprintf_btf helper Alan Maguire
2020-09-25 0:42 ` Alexei Starovoitov
2020-09-23 17:46 ` [PATCH v6 bpf-next 4/6] selftests/bpf: add bpf_snprintf_btf helper tests Alan Maguire
2020-09-25 0:50 ` Alexei Starovoitov [this message]
2020-09-25 17:36 ` Andrii Nakryiko
2020-09-23 17:46 ` [PATCH v6 bpf-next 5/6] bpf: add bpf_seq_printf_btf helper Alan Maguire
2020-09-23 17:46 ` [PATCH v6 bpf-next 6/6] selftests/bpf: add test for " Alan Maguire
2020-09-25 1:26 ` Alexei Starovoitov
2020-09-28 14:12 ` Alan Maguire
2020-09-28 17:51 ` Andrii Nakryiko
2020-09-29 1:54 ` Alexei Starovoitov
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