From 0d45550a184cc5a9f10187a97b9ef8dc7fa13f31 Mon Sep 17 00:00:00 2001

From: Serhei Makarov <smakarov@redhat.com>

Date: Fri, 2 Nov 2018 16:49:23 -0400

Subject: [PATCH 19/32] PR23829 :: fallback defines __BPF_FUNC_MAPPER and

 BPF_J{LT,LE,SLT,SLE} for older kernels

---

 bpf-base.cxx   | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 bpf-internal.h | 11 +++++++++++

 2 files changed, 70 insertions(+)

diff --git a/bpf-base.cxx b/bpf-base.cxx

index 277927b72..210efa9aa 100644

--- a/bpf-base.cxx

+++ b/bpf-base.cxx

@@ -140,6 +140,65 @@ is_commutative(opcode code)

 std::map<unsigned, const char *> bpf_func_name_map;

 std::map<std::string, bpf_func_id> bpf_func_id_map;

+/* PR23829: On older kernels, bpf.h does not define __BPF_FUNC_MAPPER.

+   As a fallback, use the *earliest* __BPF_FUNC_MAPPER, so stapbpf

+   will not try helpers that only exist on subsequent kernels.

+

+   TODO: This isn't perfect since even older kernels don't have

+   some of these helpers.

+

+   XXX: Note the build limitation in that SystemTap must be compiled

+   against a recent kernel to be able to use the helpers from that

+   kernel. That's also the case when building against recent bpf.h

+   with __BPF_FUNC_MAPPER, so this workaround is not the source of the

+   problem. */

+#ifndef __BPF_FUNC_MAPPER

+#define __BPF_FUNC_MAPPER(FN)		\

+	FN(unspec),			\

+	FN(map_lookup_elem),		\

+	FN(map_update_elem),		\

+	FN(map_delete_elem),		\

+	FN(probe_read),			\

+	FN(ktime_get_ns),		\

+	FN(trace_printk),		\

+	FN(get_prandom_u32),		\

+	FN(get_smp_processor_id),	\

+	FN(skb_store_bytes),		\

+	FN(l3_csum_replace),		\

+	FN(l4_csum_replace),		\

+	FN(tail_call),			\

+	FN(clone_redirect),		\

+	FN(get_current_pid_tgid),	\

+	FN(get_current_uid_gid),	\

+	FN(get_current_comm),		\

+	FN(get_cgroup_classid),		\

+	FN(skb_vlan_push),		\

+	FN(skb_vlan_pop),		\

+	FN(skb_get_tunnel_key),		\

+	FN(skb_set_tunnel_key),		\

+	FN(perf_event_read),		\

+	FN(redirect),			\

+	FN(get_route_realm),		\

+	FN(perf_event_output),		\

+	FN(skb_load_bytes),		\

+	FN(get_stackid),		\

+	FN(csum_diff),			\

+	FN(skb_get_tunnel_opt),		\

+	FN(skb_set_tunnel_opt),		\

+	FN(skb_change_proto),		\

+	FN(skb_change_type),		\

+	FN(skb_under_cgroup),		\

+	FN(get_hash_recalc),		\

+	FN(get_current_task),		\

+	FN(probe_write_user),		\

+	FN(current_task_under_cgroup),	\

+	FN(skb_change_tail),		\

+	FN(skb_pull_data),		\

+	FN(csum_update),		\

+	FN(set_hash_invalid),           \

+

+#endif

+

 void

 init_bpf_helper_tables () // TODO call before script translation

 {

diff --git a/bpf-internal.h b/bpf-internal.h

index 3041bbdf5..82cba2c79 100644

--- a/bpf-internal.h

+++ b/bpf-internal.h

@@ -21,6 +21,17 @@ extern "C" {

 #include <linux/bpf.h>

 }

+/* PR23829: These eBPF opcodes were added in recent kernels, and the

+   following 'ad hoc' defines are only used by the embedded-code

+   assembler.  The code generator will convert these opcodes to

+   equivalent operations valid for earlier eBPF. */

+#ifndef BPF_JLT

+#define BPF_JLT		0xa0	/* LT is unsigned, '<' */

+#define BPF_JLE		0xb0	/* LE is unsigned, '<=' */

+#define BPF_JSLT	0xc0	/* SLT is signed, '<' */

+#define BPF_JSLE	0xd0	/* SLE is signed, '<=' */

+#endif

+

 struct systemtap_session;

 struct derived_probe;

 struct vardecl;

-- 

2.14.5