@@ -708,6 +708,48 @@ probe_bounded_loops(const char *define_prefix, __u32 ifindex)
"BOUNDED_LOOPS");
}
+/*
+ * Probe for the v2 instruction set extension introduced in commit 92b31a9af73b
+ * ("bpf: add BPF_J{LT,LE,SLT,SLE} instructions").
+ */
+static void
+probe_v2_isa_extension(const char *define_prefix, __u32 ifindex)
+{
+ struct bpf_insn insns[4] = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_JMP_IMM(BPF_JLT, BPF_REG_0, 0, 1),
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_EXIT_INSN()
+ };
+
+ probe_misc_feature(insns, ARRAY_SIZE(insns),
+ define_prefix, ifindex,
+ "have_v2_isa_extension",
+ "ISA extension v2",
+ "V2_ISA_EXTENSION");
+}
+
+/*
+ * Probe for the v3 instruction set extension introduced in commit 092ed0968bb6
+ * ("bpf: verifier support JMP32").
+ */
+static void
+probe_v3_isa_extension(const char *define_prefix, __u32 ifindex)
+{
+ struct bpf_insn insns[4] = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_JMP32_IMM(BPF_JLT, BPF_REG_0, 0, 1),
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_EXIT_INSN()
+ };
+
+ probe_misc_feature(insns, ARRAY_SIZE(insns),
+ define_prefix, ifindex,
+ "have_v3_isa_extension",
+ "ISA extension v3",
+ "V3_ISA_EXTENSION");
+}
+
static void
section_system_config(enum probe_component target, const char *define_prefix)
{
@@ -823,6 +865,8 @@ static void section_misc(const char *define_prefix, __u32 ifindex)
define_prefix);
probe_large_insn_limit(define_prefix, ifindex);
probe_bounded_loops(define_prefix, ifindex);
+ probe_v2_isa_extension(define_prefix, ifindex);
+ probe_v3_isa_extension(define_prefix, ifindex);
print_end_section();
}
This patch introduces new probes to check whether the kernel supports instruction set extensions v2 and v3. The first introduced eBPF instructions BPF_J{LT,LE,SLT,SLE} in commit 92b31a9af73b ("bpf: add BPF_J{LT,LE,SLT,SLE} instructions"). The second introduces 32-bit variants of all jump instructions in commit 092ed0968bb6 ("bpf: verifier support JMP32"). These probes are useful for userspace BPF projects that want to use newer instruction set extensions on newer kernels, to reduce the programs' sizes or their complexity. LLVM already provides an mcpu=probe option to automatically probe the kernel and select the newest-supported instruction set extension. That is however not flexible enough for all use cases. For example, in Cilium, we only want to use the v3 instruction set extension on v5.10+, even though it is supported on all kernels v5.1+. Reviewed-by: Quentin Monnet <quentin@isovalent.com> Signed-off-by: Paul Chaignon <paul@isovalent.com> --- tools/bpf/bpftool/feature.c | 44 +++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+)