* [PATCH bpf-next] libbpf: fix probe code to return EPERM if encountered
@ 2020-04-30 10:23 Eelco Chaudron
2020-04-30 10:49 ` Toke Høiland-Jørgensen
2020-04-30 18:12 ` Andrii Nakryiko
0 siblings, 2 replies; 6+ messages in thread
From: Eelco Chaudron @ 2020-04-30 10:23 UTC (permalink / raw)
To: bpf; +Cc: davem, netdev, ast, daniel, kafai, songliubraving, yhs, andriin, toke
When the probe code was failing for any reason ENOTSUP was returned, even
if this was due to no having enough lock space. This patch fixes this by
returning EPERM to the user application, so it can respond and increase
the RLIMIT_MEMLOCK size.
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
---
tools/lib/bpf/libbpf.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 8f480e29a6b0..a62388a151d4 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3381,8 +3381,13 @@ bpf_object__probe_caps(struct bpf_object *obj)
for (i = 0; i < ARRAY_SIZE(probe_fn); i++) {
ret = probe_fn[i](obj);
- if (ret < 0)
+ if (ret < 0) {
pr_debug("Probe #%d failed with %d.\n", i, ret);
+ if (ret == -EPERM) {
+ pr_perm_msg(ret);
+ return ret;
+ }
+ }
}
return 0;
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next] libbpf: fix probe code to return EPERM if encountered
2020-04-30 10:23 [PATCH bpf-next] libbpf: fix probe code to return EPERM if encountered Eelco Chaudron
@ 2020-04-30 10:49 ` Toke Høiland-Jørgensen
2020-04-30 18:12 ` Andrii Nakryiko
1 sibling, 0 replies; 6+ messages in thread
From: Toke Høiland-Jørgensen @ 2020-04-30 10:49 UTC (permalink / raw)
To: Eelco Chaudron, bpf
Cc: davem, netdev, ast, daniel, kafai, songliubraving, yhs, andriin
Eelco Chaudron <echaudro@redhat.com> writes:
> When the probe code was failing for any reason ENOTSUP was returned, even
> if this was due to no having enough lock space. This patch fixes this by
> returning EPERM to the user application, so it can respond and increase
> the RLIMIT_MEMLOCK size.
>
> Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
For context - we ran into this in xdp-tools where we've implemented
"fiddle rlimit and retry" logic in response to EPERM errors, and
suddenly we were seeing ENOTSUP errors instead. See discussion here:
https://github.com/xdp-project/xdp-tools/pull/16
-Toke
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next] libbpf: fix probe code to return EPERM if encountered
2020-04-30 10:23 [PATCH bpf-next] libbpf: fix probe code to return EPERM if encountered Eelco Chaudron
2020-04-30 10:49 ` Toke Høiland-Jørgensen
@ 2020-04-30 18:12 ` Andrii Nakryiko
2020-05-01 9:56 ` Eelco Chaudron
1 sibling, 1 reply; 6+ messages in thread
From: Andrii Nakryiko @ 2020-04-30 18:12 UTC (permalink / raw)
To: Eelco Chaudron
Cc: bpf, David S. Miller, Networking, Alexei Starovoitov,
Daniel Borkmann, Martin Lau, Song Liu, Yonghong Song,
Andrii Nakryiko, Toke Høiland-Jørgensen
On Thu, Apr 30, 2020 at 3:24 AM Eelco Chaudron <echaudro@redhat.com> wrote:
>
> When the probe code was failing for any reason ENOTSUP was returned, even
> if this was due to no having enough lock space. This patch fixes this by
> returning EPERM to the user application, so it can respond and increase
> the RLIMIT_MEMLOCK size.
>
> Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
> ---
> tools/lib/bpf/libbpf.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 8f480e29a6b0..a62388a151d4 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -3381,8 +3381,13 @@ bpf_object__probe_caps(struct bpf_object *obj)
>
> for (i = 0; i < ARRAY_SIZE(probe_fn); i++) {
> ret = probe_fn[i](obj);
> - if (ret < 0)
> + if (ret < 0) {
> pr_debug("Probe #%d failed with %d.\n", i, ret);
> + if (ret == -EPERM) {
> + pr_perm_msg(ret);
> + return ret;
I think this is dangerous to do. This detection loop is not supposed
to return error to user if any of the features are missing. I'd feel
more comfortable if we split bpf_object__probe_name() into two tests:
one testing trivial program and another testing same program with
name. If the first one fails with EPERM -- then we can return error to
user. If anything else fails -- that's ok. Thoughts?
> + }
> + }
> }
>
> return 0;
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next] libbpf: fix probe code to return EPERM if encountered
2020-04-30 18:12 ` Andrii Nakryiko
@ 2020-05-01 9:56 ` Eelco Chaudron
2020-05-01 19:16 ` Andrii Nakryiko
0 siblings, 1 reply; 6+ messages in thread
From: Eelco Chaudron @ 2020-05-01 9:56 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: bpf, David S. Miller, Networking, Alexei Starovoitov,
Daniel Borkmann, Martin Lau, Song Liu, Yonghong Song,
Andrii Nakryiko, Toke Høiland-Jørgensen
On 30 Apr 2020, at 20:12, Andrii Nakryiko wrote:
> On Thu, Apr 30, 2020 at 3:24 AM Eelco Chaudron <echaudro@redhat.com>
> wrote:
>>
>> When the probe code was failing for any reason ENOTSUP was returned,
>> even
>> if this was due to no having enough lock space. This patch fixes this
>> by
>> returning EPERM to the user application, so it can respond and
>> increase
>> the RLIMIT_MEMLOCK size.
>>
>> Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
>> ---
>> tools/lib/bpf/libbpf.c | 7 ++++++-
>> 1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index 8f480e29a6b0..a62388a151d4 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -3381,8 +3381,13 @@ bpf_object__probe_caps(struct bpf_object *obj)
>>
>> for (i = 0; i < ARRAY_SIZE(probe_fn); i++) {
>> ret = probe_fn[i](obj);
>> - if (ret < 0)
>> + if (ret < 0) {
>> pr_debug("Probe #%d failed with %d.\n", i,
>> ret);
>> + if (ret == -EPERM) {
>> + pr_perm_msg(ret);
>> + return ret;
>
> I think this is dangerous to do. This detection loop is not supposed
> to return error to user if any of the features are missing. I'd feel
> more comfortable if we split bpf_object__probe_name() into two tests:
> one testing trivial program and another testing same program with
> name. If the first one fails with EPERM -- then we can return error to
> user. If anything else fails -- that's ok. Thoughts?
Before sending the patch I briefly checked the existing probes and did
not see any other code path that could lead to EPERM. But you are right
that this might not be the case for previous kernels. So you suggest
something like this?
diff --git a/src/libbpf.c b/src/libbpf.c
index ff91742..fd5fdee 100644
--- a/src/libbpf.c
+++ b/src/libbpf.c
@@ -3130,7 +3130,7 @@ int bpf_map__resize(struct bpf_map *map, __u32
max_entries)
}
static int
-bpf_object__probe_name(struct bpf_object *obj)
+bpf_object__probe_loading(struct bpf_object *obj)
{
struct bpf_load_program_attr attr;
char *cp, errmsg[STRERR_BUFSIZE];
@@ -3157,8 +3157,26 @@ bpf_object__probe_name(struct bpf_object *obj)
}
close(ret);
- /* now try the same program, but with the name */
+ return 0;
+}
+static int
+bpf_object__probe_name(struct bpf_object *obj)
+{
+ struct bpf_load_program_attr attr;
+ struct bpf_insn insns[] = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ };
+ int ret;
+
+ /* make sure loading with name works */
+
+ memset(&attr, 0, sizeof(attr));
+ attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
+ attr.insns = insns;
+ attr.insns_cnt = ARRAY_SIZE(insns);
+ attr.license = "GPL";
attr.name = "test";
ret = bpf_load_program_xattr(&attr, NULL, 0);
if (ret >= 0) {
@@ -3328,6 +3346,11 @@ bpf_object__probe_caps(struct bpf_object *obj)
};
int i, ret;
+ if (bpf_object__probe_loading(obj) == -EPERM) {
+ pr_perm_msg(-EPERM);
+ return -EPERM;
+ }
+
for (i = 0; i < ARRAY_SIZE(probe_fn); i++) {
ret = probe_fn[i](obj);
if (ret < 0)
Let me know, and I sent out a v2.
Cheers,
Eelco
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next] libbpf: fix probe code to return EPERM if encountered
2020-05-01 9:56 ` Eelco Chaudron
@ 2020-05-01 19:16 ` Andrii Nakryiko
2020-05-04 8:57 ` Eelco Chaudron
0 siblings, 1 reply; 6+ messages in thread
From: Andrii Nakryiko @ 2020-05-01 19:16 UTC (permalink / raw)
To: Eelco Chaudron
Cc: bpf, David S. Miller, Networking, Alexei Starovoitov,
Daniel Borkmann, Martin Lau, Song Liu, Yonghong Song,
Andrii Nakryiko, Toke Høiland-Jørgensen
On Fri, May 1, 2020 at 2:56 AM Eelco Chaudron <echaudro@redhat.com> wrote:
>
>
>
> On 30 Apr 2020, at 20:12, Andrii Nakryiko wrote:
>
> > On Thu, Apr 30, 2020 at 3:24 AM Eelco Chaudron <echaudro@redhat.com>
> > wrote:
> >>
> >> When the probe code was failing for any reason ENOTSUP was returned,
> >> even
> >> if this was due to no having enough lock space. This patch fixes this
> >> by
> >> returning EPERM to the user application, so it can respond and
> >> increase
> >> the RLIMIT_MEMLOCK size.
> >>
> >> Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
> >> ---
> >> tools/lib/bpf/libbpf.c | 7 ++++++-
> >> 1 file changed, 6 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> >> index 8f480e29a6b0..a62388a151d4 100644
> >> --- a/tools/lib/bpf/libbpf.c
> >> +++ b/tools/lib/bpf/libbpf.c
> >> @@ -3381,8 +3381,13 @@ bpf_object__probe_caps(struct bpf_object *obj)
> >>
> >> for (i = 0; i < ARRAY_SIZE(probe_fn); i++) {
> >> ret = probe_fn[i](obj);
> >> - if (ret < 0)
> >> + if (ret < 0) {
> >> pr_debug("Probe #%d failed with %d.\n", i,
> >> ret);
> >> + if (ret == -EPERM) {
> >> + pr_perm_msg(ret);
> >> + return ret;
> >
> > I think this is dangerous to do. This detection loop is not supposed
> > to return error to user if any of the features are missing. I'd feel
> > more comfortable if we split bpf_object__probe_name() into two tests:
> > one testing trivial program and another testing same program with
> > name. If the first one fails with EPERM -- then we can return error to
> > user. If anything else fails -- that's ok. Thoughts?
>
> Before sending the patch I briefly checked the existing probes and did
> not see any other code path that could lead to EPERM. But you are right
> that this might not be the case for previous kernels. So you suggest
> something like this?
It both previous as well as future kernel version. We can never be
100% sure. While the idea of probe_caps() is to detect optional
features.
>
> diff --git a/src/libbpf.c b/src/libbpf.c
> index ff91742..fd5fdee 100644
> --- a/src/libbpf.c
> +++ b/src/libbpf.c
> @@ -3130,7 +3130,7 @@ int bpf_map__resize(struct bpf_map *map, __u32
> max_entries)
> }
>
> static int
> -bpf_object__probe_name(struct bpf_object *obj)
> +bpf_object__probe_loading(struct bpf_object *obj)
> {
> struct bpf_load_program_attr attr;
> char *cp, errmsg[STRERR_BUFSIZE];
> @@ -3157,8 +3157,26 @@ bpf_object__probe_name(struct bpf_object *obj)
> }
> close(ret);
>
> - /* now try the same program, but with the name */
> + return 0;
> +}
>
> +static int
> +bpf_object__probe_name(struct bpf_object *obj)
> +{
> + struct bpf_load_program_attr attr;
> + struct bpf_insn insns[] = {
> + BPF_MOV64_IMM(BPF_REG_0, 0),
> + BPF_EXIT_INSN(),
> + };
> + int ret;
> +
> + /* make sure loading with name works */
> +
> + memset(&attr, 0, sizeof(attr));
> + attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
> + attr.insns = insns;
> + attr.insns_cnt = ARRAY_SIZE(insns);
> + attr.license = "GPL";
> attr.name = "test";
> ret = bpf_load_program_xattr(&attr, NULL, 0);
> if (ret >= 0) {
> @@ -3328,6 +3346,11 @@ bpf_object__probe_caps(struct bpf_object *obj)
> };
> int i, ret;
>
> + if (bpf_object__probe_loading(obj) == -EPERM) {
> + pr_perm_msg(-EPERM);
> + return -EPERM;
> + }
> +
> for (i = 0; i < ARRAY_SIZE(probe_fn); i++) {
> ret = probe_fn[i](obj);
> if (ret < 0)
>
> Let me know, and I sent out a v2.
Yes, that's the split I had in mind, but I'd move
bpf_object__probe_loading() call directly into bpf_object__load() to
be the first thing to check. probe_caps() should still be non-failing
if any feature is missing. Does it make sense?
>
> Cheers,
>
> Eelco
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next] libbpf: fix probe code to return EPERM if encountered
2020-05-01 19:16 ` Andrii Nakryiko
@ 2020-05-04 8:57 ` Eelco Chaudron
0 siblings, 0 replies; 6+ messages in thread
From: Eelco Chaudron @ 2020-05-04 8:57 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: bpf, David S. Miller, Networking, Alexei Starovoitov,
Daniel Borkmann, Martin Lau, Song Liu, Yonghong Song,
Andrii Nakryiko, Toke Høiland-Jørgensen
On 1 May 2020, at 21:16, Andrii Nakryiko wrote:
> On Fri, May 1, 2020 at 2:56 AM Eelco Chaudron <echaudro@redhat.com> wrote:
<SNIP>
>>
>> Let me know, and I sent out a v2.
>
> Yes, that's the split I had in mind, but I'd move
> bpf_object__probe_loading() call directly into bpf_object__load() to
> be the first thing to check. probe_caps() should still be non-failing
> if any feature is missing. Does it make sense?
I think I got it :) I’ll send out a v2 soon…
//Eelco
^ permalink raw reply [flat|nested] 6+ messages in thread
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2020-04-30 10:23 [PATCH bpf-next] libbpf: fix probe code to return EPERM if encountered Eelco Chaudron
2020-04-30 10:49 ` Toke Høiland-Jørgensen
2020-04-30 18:12 ` Andrii Nakryiko
2020-05-01 9:56 ` Eelco Chaudron
2020-05-01 19:16 ` Andrii Nakryiko
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