* [PATCH bpf-next v2 1/2] libbpf: Probe for bounded loop support
@ 2021-12-17 13:52 Paul Chaignon
2021-12-17 13:52 ` [PATCH bpf-next v2 2/2] bpftool: " Paul Chaignon
0 siblings, 1 reply; 2+ messages in thread
From: Paul Chaignon @ 2021-12-17 13:52 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko; +Cc: bpf, Quentin Monnet
This patch introduces a new probe to check whether the verifier supports
bounded loops as introduced in commit 2589726d12a1 ("bpf: introduce
bounded loops"). This patch will allow BPF users such as Cilium to probe
for loop support on startup and only unconditionally unroll loops on
older kernels.
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Paul Chaignon <paul@isovalent.com>
---
Changes in v2:
- Resending to fix a format error. I had the good idea of saving the
patch in Gmail as a draft before sending with mutt, which caused
Gmail to remove the trailing space in the Git version signature.
That then caused pathwork to generate an incorrect mbox file.
tools/lib/bpf/libbpf.h | 1 +
tools/lib/bpf/libbpf.map | 1 +
tools/lib/bpf/libbpf_probes.c | 20 ++++++++++++++++++++
3 files changed, 22 insertions(+)
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 42b2f36fd9f0..3621aaaff67c 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -1058,6 +1058,7 @@ LIBBPF_API bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex);
LIBBPF_API bool bpf_probe_helper(enum bpf_func_id id,
enum bpf_prog_type prog_type, __u32 ifindex);
LIBBPF_API bool bpf_probe_large_insn_limit(__u32 ifindex);
+LIBBPF_API bool bpf_probe_bounded_loops(__u32 ifindex);
/*
* Get bpf_prog_info in continuous memory
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index b3938b3f8fc9..059d168452d7 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -423,6 +423,7 @@ LIBBPF_0.6.0 {
LIBBPF_0.7.0 {
global:
bpf_btf_load;
+ bpf_probe_bounded_loops;
bpf_program__log_buf;
bpf_program__log_level;
bpf_program__set_log_buf;
diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
index 4bdec69523a7..e5bd691059e4 100644
--- a/tools/lib/bpf/libbpf_probes.c
+++ b/tools/lib/bpf/libbpf_probes.c
@@ -356,3 +356,23 @@ bool bpf_probe_large_insn_limit(__u32 ifindex)
return errno != E2BIG && errno != EINVAL;
}
+
+/*
+ * Probe for bounded loop support introduced in commit 2589726d12a1
+ * ("bpf: introduce bounded loops").
+ */
+bool bpf_probe_bounded_loops(__u32 ifindex)
+{
+ struct bpf_insn insns[4] = {
+ BPF_MOV64_IMM(BPF_REG_0, 10),
+ BPF_ALU64_IMM(BPF_SUB, BPF_REG_0, 1),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, -2),
+ BPF_EXIT_INSN()
+ };
+
+ errno = 0;
+ probe_load(BPF_PROG_TYPE_SOCKET_FILTER, insns, ARRAY_SIZE(insns), NULL,
+ 0, ifindex);
+
+ return !errno;
+}
--
2.25.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [PATCH bpf-next v2 2/2] bpftool: Probe for bounded loop support
2021-12-17 13:52 [PATCH bpf-next v2 1/2] libbpf: Probe for bounded loop support Paul Chaignon
@ 2021-12-17 13:52 ` Paul Chaignon
0 siblings, 0 replies; 2+ messages in thread
From: Paul Chaignon @ 2021-12-17 13:52 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko; +Cc: bpf, Quentin Monnet
This patch probes for bounded loop support and displays the results as
part of the miscellaneous section, as shown below.
$ bpftool feature probe | grep loops
Bounded loop support is available
$ bpftool feature probe macro | grep LOOPS
#define HAVE_BOUNDED_LOOPS
$ bpftool feature probe -j | jq .misc
{
"have_large_insn_limit": true,
"have_bounded_loops": true
}
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Paul Chaignon <paul@isovalent.com>
---
Changes in v2:
- Resending to fix a format error.
tools/bpf/bpftool/feature.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c
index 5397077d0d9e..7aee920162e5 100644
--- a/tools/bpf/bpftool/feature.c
+++ b/tools/bpf/bpftool/feature.c
@@ -654,6 +654,18 @@ probe_large_insn_limit(const char *define_prefix, __u32 ifindex)
res, define_prefix);
}
+static void
+probe_bounded_loops(const char *define_prefix, __u32 ifindex)
+{
+ bool res;
+
+ res = bpf_probe_bounded_loops(ifindex);
+ print_bool_feature("have_bounded_loops",
+ "Bounded loop support",
+ "BOUNDED_LOOPS",
+ res, define_prefix);
+}
+
static void
section_system_config(enum probe_component target, const char *define_prefix)
{
@@ -768,6 +780,7 @@ static void section_misc(const char *define_prefix, __u32 ifindex)
"/*** eBPF misc features ***/",
define_prefix);
probe_large_insn_limit(define_prefix, ifindex);
+ probe_bounded_loops(define_prefix, ifindex);
print_end_section();
}
--
2.25.1
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