Merge branch 'move_BPF_PROG_to_libbpf'

Andrii Nakryiko says:

====================
Move BPF_PROG, BPF_KPROBE, and BPF_KRETPROBE helper macros from private
selftests helpers to public libbpf ones. These helpers are extremely helpful
for writing tracing BPF applications and have been requested to be exposed for
easy use (e.g., [0]).

As part of this move, fix up BPF_KRETPROBE to not allow for capturing input
arguments (as it's unreliable and they will be often clobbered). Also, add
vmlinux.h header guard to allow multi-time inclusion, if necessary; but also
to let PT_REGS_PARM do proper detection of struct pt_regs field names on x86
arch. See relevant patches for more details.

  [0] https://github.com/iovisor/bcc/pull/2778#issue-381642907
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/bpf/bpftool/btf.c

@@ -389,6 +389,9 @@ static int dump_btf_c(const struct btf *btf,
 	if (IS_ERR(d))
 		return PTR_ERR(d);
 
+	printf("#ifndef __VMLINUX_H__\n");
+	printf("#define __VMLINUX_H__\n");
+	printf("\n");
 	printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");
 	printf("#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)\n");
 	printf("#endif\n\n");
@@ -412,6 +415,8 @@ static int dump_btf_c(const struct btf *btf,
 	printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");
 	printf("#pragma clang attribute pop\n");
 	printf("#endif\n");
+	printf("\n");
+	printf("#endif /* __VMLINUX_H__ */\n");
 
 done:
 	btf_dump__free(d);

tools/lib/bpf/bpf_tracing.h

@@ -49,7 +49,7 @@
 
 #if defined(bpf_target_x86)
 
-#ifdef __KERNEL__
+#if defined(__KERNEL__) || defined(__VMLINUX_H__)
 #define PT_REGS_PARM1(x) ((x)->di)
 #define PT_REGS_PARM2(x) ((x)->si)
 #define PT_REGS_PARM3(x) ((x)->dx)
@@ -192,4 +192,122 @@ struct pt_regs;
 			  (void *)(PT_REGS_FP(ctx) + sizeof(ip))); })
 #endif
 
+#define ___bpf_concat(a, b) a ## b
+#define ___bpf_apply(fn, n) ___bpf_concat(fn, n)
+#define ___bpf_nth(_, _1, _2, _3, _4, _5, _6, _7, _8, _9, _a, _b, _c, N, ...) N
+#define ___bpf_narg(...) \
+	___bpf_nth(_, ##__VA_ARGS__, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
+#define ___bpf_empty(...) \
+	___bpf_nth(_, ##__VA_ARGS__, N, N, N, N, N, N, N, N, N, N, 0)
+
+#define ___bpf_ctx_cast0() ctx
+#define ___bpf_ctx_cast1(x) ___bpf_ctx_cast0(), (void *)ctx[0]
+#define ___bpf_ctx_cast2(x, args...) ___bpf_ctx_cast1(args), (void *)ctx[1]
+#define ___bpf_ctx_cast3(x, args...) ___bpf_ctx_cast2(args), (void *)ctx[2]
+#define ___bpf_ctx_cast4(x, args...) ___bpf_ctx_cast3(args), (void *)ctx[3]
+#define ___bpf_ctx_cast5(x, args...) ___bpf_ctx_cast4(args), (void *)ctx[4]
+#define ___bpf_ctx_cast6(x, args...) ___bpf_ctx_cast5(args), (void *)ctx[5]
+#define ___bpf_ctx_cast7(x, args...) ___bpf_ctx_cast6(args), (void *)ctx[6]
+#define ___bpf_ctx_cast8(x, args...) ___bpf_ctx_cast7(args), (void *)ctx[7]
+#define ___bpf_ctx_cast9(x, args...) ___bpf_ctx_cast8(args), (void *)ctx[8]
+#define ___bpf_ctx_cast10(x, args...) ___bpf_ctx_cast9(args), (void *)ctx[9]
+#define ___bpf_ctx_cast11(x, args...) ___bpf_ctx_cast10(args), (void *)ctx[10]
+#define ___bpf_ctx_cast12(x, args...) ___bpf_ctx_cast11(args), (void *)ctx[11]
+#define ___bpf_ctx_cast(args...) \
+	___bpf_apply(___bpf_ctx_cast, ___bpf_narg(args))(args)
+
+/*
+ * BPF_PROG is a convenience wrapper for generic tp_btf/fentry/fexit and
+ * similar kinds of BPF programs, that accept input arguments as a single
+ * pointer to untyped u64 array, where each u64 can actually be a typed
+ * pointer or integer of different size. Instead of requring user to write
+ * manual casts and work with array elements by index, BPF_PROG macro
+ * allows user to declare a list of named and typed input arguments in the
+ * same syntax as for normal C function. All the casting is hidden and
+ * performed transparently, while user code can just assume working with
+ * function arguments of specified type and name.
+ *
+ * Original raw context argument is preserved as well as 'ctx' argument.
+ * This is useful when using BPF helpers that expect original context
+ * as one of the parameters (e.g., for bpf_perf_event_output()).
+ */
+#define BPF_PROG(name, args...)						    \
+name(unsigned long long *ctx);						    \
+static __attribute__((always_inline)) typeof(name(0))			    \
+____##name(unsigned long long *ctx, ##args);				    \
+typeof(name(0)) name(unsigned long long *ctx)				    \
+{									    \
+	_Pragma("GCC diagnostic push")					    \
+	_Pragma("GCC diagnostic ignored \"-Wint-conversion\"")		    \
+	return ____##name(___bpf_ctx_cast(args));			    \
+	_Pragma("GCC diagnostic pop")					    \
+}									    \
+static __attribute__((always_inline)) typeof(name(0))			    \
+____##name(unsigned long long *ctx, ##args)
+
+struct pt_regs;
+
+#define ___bpf_kprobe_args0() ctx
+#define ___bpf_kprobe_args1(x) \
+	___bpf_kprobe_args0(), (void *)PT_REGS_PARM1(ctx)
+#define ___bpf_kprobe_args2(x, args...) \
+	___bpf_kprobe_args1(args), (void *)PT_REGS_PARM2(ctx)
+#define ___bpf_kprobe_args3(x, args...) \
+	___bpf_kprobe_args2(args), (void *)PT_REGS_PARM3(ctx)
+#define ___bpf_kprobe_args4(x, args...) \
+	___bpf_kprobe_args3(args), (void *)PT_REGS_PARM4(ctx)
+#define ___bpf_kprobe_args5(x, args...) \
+	___bpf_kprobe_args4(args), (void *)PT_REGS_PARM5(ctx)
+#define ___bpf_kprobe_args(args...) \
+	___bpf_apply(___bpf_kprobe_args, ___bpf_narg(args))(args)
+
+/*
+ * BPF_KPROBE serves the same purpose for kprobes as BPF_PROG for
+ * tp_btf/fentry/fexit BPF programs. It hides the underlying platform-specific
+ * low-level way of getting kprobe input arguments from struct pt_regs, and
+ * provides a familiar typed and named function arguments syntax and
+ * semantics of accessing kprobe input paremeters.
+ *
+ * Original struct pt_regs* context is preserved as 'ctx' argument. This might
+ * be necessary when using BPF helpers like bpf_perf_event_output().
+ */
+#define BPF_KPROBE(name, args...)					    \
+name(struct pt_regs *ctx);						    \
+static __attribute__((always_inline)) typeof(name(0))			    \
+____##name(struct pt_regs *ctx, ##args);				    \
+typeof(name(0)) name(struct pt_regs *ctx)				    \
+{									    \
+	_Pragma("GCC diagnostic push")					    \
+	_Pragma("GCC diagnostic ignored \"-Wint-conversion\"")		    \
+	return ____##name(___bpf_kprobe_args(args));			    \
+	_Pragma("GCC diagnostic pop")					    \
+}									    \
+static __attribute__((always_inline)) typeof(name(0))			    \
+____##name(struct pt_regs *ctx, ##args)
+
+#define ___bpf_kretprobe_args0() ctx
+#define ___bpf_kretprobe_args1(x) \
+	___bpf_kretprobe_args0(), (void *)PT_REGS_RET(ctx)
+#define ___bpf_kretprobe_args(args...) \
+	___bpf_apply(___bpf_kretprobe_args, ___bpf_narg(args))(args)
+
+/*
+ * BPF_KRETPROBE is similar to BPF_KPROBE, except, it only provides optional
+ * return value (in addition to `struct pt_regs *ctx`), but no input
+ * arguments, because they will be clobbered by the time probed function
+ * returns.
+ */
+#define BPF_KRETPROBE(name, args...)					    \
+name(struct pt_regs *ctx);						    \
+static __attribute__((always_inline)) typeof(name(0))			    \
+____##name(struct pt_regs *ctx, ##args);				    \
+typeof(name(0)) name(struct pt_regs *ctx)				    \
+{									    \
+	_Pragma("GCC diagnostic push")					    \
+	_Pragma("GCC diagnostic ignored \"-Wint-conversion\"")		    \
+	return ____##name(___bpf_kretprobe_args(args));			    \
+	_Pragma("GCC diagnostic pop")					    \
+}									    \
+static __always_inline typeof(name(0)) ____##name(struct pt_regs *ctx, ##args)
+
 #endif

tools/testing/selftests/bpf/bpf_tcp_helpers.h

@@ -6,7 +6,7 @@
 #include <linux/types.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_core_read.h>
-#include "bpf_trace_helpers.h"
+#include <bpf/bpf_tracing.h>
 
 #define BPF_STRUCT_OPS(name, args...) \
 SEC("struct_ops/"#name) \

tools/testing/selftests/bpf/progs/bpf_dctcp.c

@@ -9,7 +9,7 @@
 #include <linux/bpf.h>
 #include <linux/types.h>
 #include <bpf/bpf_helpers.h>
-#include "bpf_trace_helpers.h"
+#include <bpf/bpf_tracing.h>
 #include "bpf_tcp_helpers.h"
 
 char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/fentry_test.c

@@ -2,7 +2,7 @@
 /* Copyright (c) 2019 Facebook */
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
-#include "bpf_trace_helpers.h"
+#include <bpf/bpf_tracing.h>
 
 char _license[] SEC("license") = "GPL";
 

tools/testing/selftests/bpf/progs/fexit_bpf2bpf.c

@@ -5,7 +5,7 @@
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_endian.h>
-#include "bpf_trace_helpers.h"
+#include <bpf/bpf_tracing.h>
 
 struct sk_buff {
 	unsigned int len;

tools/testing/selftests/bpf/progs/fexit_bpf2bpf_simple.c

@@ -2,7 +2,7 @@
 /* Copyright (c) 2019 Facebook */
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
-#include "bpf_trace_helpers.h"
+#include <bpf/bpf_tracing.h>
 
 struct sk_buff {
 	unsigned int len;

tools/testing/selftests/bpf/progs/fexit_test.c

@@ -2,7 +2,7 @@
 /* Copyright (c) 2019 Facebook */
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
-#include "bpf_trace_helpers.h"
+#include <bpf/bpf_tracing.h>
 
 char _license[] SEC("license") = "GPL";
 

tools/testing/selftests/bpf/progs/kfree_skb.c

@@ -4,7 +4,7 @@
 #include <stdbool.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_endian.h>
-#include "bpf_trace_helpers.h"
+#include <bpf/bpf_tracing.h>
 
 char _license[] SEC("license") = "GPL";
 struct {

tools/testing/selftests/bpf/progs/test_attach_probe.c

@@ -4,6 +4,7 @@
 #include <linux/ptrace.h>
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
 
 int kprobe_res = 0;
 int kretprobe_res = 0;
@@ -18,7 +19,7 @@ int handle_kprobe(struct pt_regs *ctx)
 }
 
 SEC("kretprobe/sys_nanosleep")
-int handle_kretprobe(struct pt_regs *ctx)
+int BPF_KRETPROBE(handle_kretprobe)
 {
 	kretprobe_res = 2;
 	return 0;

tools/testing/selftests/bpf/progs/test_overhead.c

@@ -6,7 +6,6 @@
 #include <linux/ptrace.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
-#include "bpf_trace_helpers.h"
 
 struct task_struct;
 
@@ -17,11 +16,9 @@ int BPF_KPROBE(prog1, struct task_struct *tsk, const char *buf, bool exec)
 }
 
 SEC("kretprobe/__set_task_comm")
-int BPF_KRETPROBE(prog2,
-		  struct task_struct *tsk, const char *buf, bool exec,
-		  int ret)
+int BPF_KRETPROBE(prog2, int ret)
 {
-	return !PT_REGS_PARM1(ctx) && ret;
+	return ret;
 }
 
 SEC("raw_tp/task_rename")

tools/testing/selftests/bpf/progs/test_perf_branches.c

@@ -5,7 +5,7 @@
 #include <linux/ptrace.h>
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
-#include "bpf_trace_helpers.h"
+#include <bpf/bpf_tracing.h>
 
 int valid = 0;
 int required_size_out = 0;

tools/testing/selftests/bpf/progs/test_perf_buffer.c

@@ -4,7 +4,7 @@
 #include <linux/ptrace.h>
 #include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>
-#include "bpf_trace_helpers.h"
+#include <bpf/bpf_tracing.h>
 
 struct {
 	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);

tools/testing/selftests/bpf/progs/test_probe_user.c

@@ -7,7 +7,6 @@
 
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
-#include "bpf_trace_helpers.h"
 
 static struct sockaddr_in old;