libbpf: Improve BPF_PROG2 macro code quality and description

Commit 34586d29f8df ("libbpf: Add new BPF_PROG2 macro") added BPF_PROG2
macro for trampoline based programs with struct arguments. Andrii
made a few suggestions to improve code quality and description.
This patch implemented these suggestions including better internal
macro name, consistent usage pattern for __builtin_choose_expr(),
simpler macro definition for always-inline func arguments and
better macro description.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20220910025214.1536510-1-yhs@fb.com

diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
index 8d4bdd18cb3df28817bb0eb6d9f6db8da2085fbe..2972dc25ff72226b9938106c950a2cd000b393d5 100644 (file)
--- a/tools/lib/bpf/bpf_tracing.h
+++ b/tools/lib/bpf/bpf_tracing.h
@@ -438,84 +438,112 @@ typeof(name(0)) name(unsigned long long *ctx)                                \
 static __always_inline typeof(name(0))                                     \
 ____##name(unsigned long long *ctx, ##args)
 
-#ifndef ____bpf_nth
-#define ____bpf_nth(_, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, _16, _17, _18, _19, _20, _21, _22, _23, _24, N, ...) N
+#ifndef ___bpf_nth2
+#define ___bpf_nth2(_, _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, \
+                   _14, _15, _16, _17, _18, _19, _20, _21, _22, _23, _24, N, ...) N
 #endif
-#ifndef ____bpf_narg
-#define ____bpf_narg(...) ____bpf_nth(_, ##__VA_ARGS__, 12, 12, 11, 11, 10, 10, 9, 9, 8, 8, 7, 7, 6, 6, 5, 5, 4, 4, 3, 3, 2, 2, 1, 1, 0)
+#ifndef ___bpf_narg2
+#define ___bpf_narg2(...)      \
+       ___bpf_nth2(_, ##__VA_ARGS__, 12, 12, 11, 11, 10, 10, 9, 9, 8, 8, 7, 7, \
+                   6, 6, 5, 5, 4, 4, 3, 3, 2, 2, 1, 1, 0)
 #endif
 
-#define BPF_REG_CNT(t) \
-       (__builtin_choose_expr(sizeof(t) == 1 || sizeof(t) == 2 || sizeof(t) == 4 || sizeof(t) == 8, 1, \
-        __builtin_choose_expr(sizeof(t) == 16, 2,                                                      \
-                              (void)0)))
-
-#define ____bpf_reg_cnt0()                     (0)
-#define ____bpf_reg_cnt1(t, x)                 (____bpf_reg_cnt0() + BPF_REG_CNT(t))
-#define ____bpf_reg_cnt2(t, x, args...)                (____bpf_reg_cnt1(args) + BPF_REG_CNT(t))
-#define ____bpf_reg_cnt3(t, x, args...)                (____bpf_reg_cnt2(args) + BPF_REG_CNT(t))
-#define ____bpf_reg_cnt4(t, x, args...)                (____bpf_reg_cnt3(args) + BPF_REG_CNT(t))
-#define ____bpf_reg_cnt5(t, x, args...)                (____bpf_reg_cnt4(args) + BPF_REG_CNT(t))
-#define ____bpf_reg_cnt6(t, x, args...)                (____bpf_reg_cnt5(args) + BPF_REG_CNT(t))
-#define ____bpf_reg_cnt7(t, x, args...)                (____bpf_reg_cnt6(args) + BPF_REG_CNT(t))
-#define ____bpf_reg_cnt8(t, x, args...)                (____bpf_reg_cnt7(args) + BPF_REG_CNT(t))
-#define ____bpf_reg_cnt9(t, x, args...)                (____bpf_reg_cnt8(args) + BPF_REG_CNT(t))
-#define ____bpf_reg_cnt10(t, x, args...)       (____bpf_reg_cnt9(args) + BPF_REG_CNT(t))
-#define ____bpf_reg_cnt11(t, x, args...)       (____bpf_reg_cnt10(args) + BPF_REG_CNT(t))
-#define ____bpf_reg_cnt12(t, x, args...)       (____bpf_reg_cnt11(args) + BPF_REG_CNT(t))
-#define ____bpf_reg_cnt(args...)        ___bpf_apply(____bpf_reg_cnt, ____bpf_narg(args))(args)
-
-#define ____bpf_union_arg(t, x, n) \
-       __builtin_choose_expr(sizeof(t) == 1, ({ union { struct { __u8 x; } ___z; t x; } ___tmp = { .___z = {ctx[n]}}; ___tmp.x; }), \
-       __builtin_choose_expr(sizeof(t) == 2, ({ union { struct { __u16 x; } ___z; t x; } ___tmp = { .___z = {ctx[n]} }; ___tmp.x; }), \
-       __builtin_choose_expr(sizeof(t) == 4, ({ union { struct { __u32 x; } ___z; t x; } ___tmp = { .___z = {ctx[n]} }; ___tmp.x; }), \
-       __builtin_choose_expr(sizeof(t) == 8, ({ union { struct { __u64 x; } ___z; t x; } ___tmp = {.___z = {ctx[n]} }; ___tmp.x; }), \
-       __builtin_choose_expr(sizeof(t) == 16, ({ union { struct { __u64 x, y; } ___z; t x; } ___tmp = {.___z = {ctx[n], ctx[n + 1]} }; ___tmp.x; }), \
+#define ___bpf_treg_cnt(t) \
+       __builtin_choose_expr(sizeof(t) == 1, 1,        \
+       __builtin_choose_expr(sizeof(t) == 2, 1,        \
+       __builtin_choose_expr(sizeof(t) == 4, 1,        \
+       __builtin_choose_expr(sizeof(t) == 8, 1,        \
+       __builtin_choose_expr(sizeof(t) == 16, 2,       \
                              (void)0)))))
 
-#define ____bpf_ctx_arg0(n, args...)
-#define ____bpf_ctx_arg1(n, t, x)              , ____bpf_union_arg(t, x, n - ____bpf_reg_cnt1(t, x))
-#define ____bpf_ctx_arg2(n, t, x, args...)     , ____bpf_union_arg(t, x, n - ____bpf_reg_cnt2(t, x, args)) ____bpf_ctx_arg1(n, args)
-#define ____bpf_ctx_arg3(n, t, x, args...)     , ____bpf_union_arg(t, x, n - ____bpf_reg_cnt3(t, x, args)) ____bpf_ctx_arg2(n, args)
-#define ____bpf_ctx_arg4(n, t, x, args...)     , ____bpf_union_arg(t, x, n - ____bpf_reg_cnt4(t, x, args)) ____bpf_ctx_arg3(n, args)
-#define ____bpf_ctx_arg5(n, t, x, args...)     , ____bpf_union_arg(t, x, n - ____bpf_reg_cnt5(t, x, args)) ____bpf_ctx_arg4(n, args)
-#define ____bpf_ctx_arg6(n, t, x, args...)     , ____bpf_union_arg(t, x, n - ____bpf_reg_cnt6(t, x, args)) ____bpf_ctx_arg5(n, args)
-#define ____bpf_ctx_arg7(n, t, x, args...)     , ____bpf_union_arg(t, x, n - ____bpf_reg_cnt7(t, x, args)) ____bpf_ctx_arg6(n, args)
-#define ____bpf_ctx_arg8(n, t, x, args...)     , ____bpf_union_arg(t, x, n - ____bpf_reg_cnt8(t, x, args)) ____bpf_ctx_arg7(n, args)
-#define ____bpf_ctx_arg9(n, t, x, args...)     , ____bpf_union_arg(t, x, n - ____bpf_reg_cnt9(t, x, args)) ____bpf_ctx_arg8(n, args)
-#define ____bpf_ctx_arg10(n, t, x, args...)    , ____bpf_union_arg(t, x, n - ____bpf_reg_cnt10(t, x, args)) ____bpf_ctx_arg9(n, args)
-#define ____bpf_ctx_arg11(n, t, x, args...)    , ____bpf_union_arg(t, x, n - ____bpf_reg_cnt11(t, x, args)) ____bpf_ctx_arg10(n, args)
-#define ____bpf_ctx_arg12(n, t, x, args...)    , ____bpf_union_arg(t, x, n - ____bpf_reg_cnt12(t, x, args)) ____bpf_ctx_arg11(n, args)
-#define ____bpf_ctx_arg(n, args...)    ___bpf_apply(____bpf_ctx_arg, ____bpf_narg(args))(n, args)
-
-#define ____bpf_ctx_decl0()
-#define ____bpf_ctx_decl1(t, x)                        , t x
-#define ____bpf_ctx_decl2(t, x, args...)       , t x ____bpf_ctx_decl1(args)
-#define ____bpf_ctx_decl3(t, x, args...)       , t x ____bpf_ctx_decl2(args)
-#define ____bpf_ctx_decl4(t, x, args...)       , t x ____bpf_ctx_decl3(args)
-#define ____bpf_ctx_decl5(t, x, args...)       , t x ____bpf_ctx_decl4(args)
-#define ____bpf_ctx_decl6(t, x, args...)       , t x ____bpf_ctx_decl5(args)
-#define ____bpf_ctx_decl7(t, x, args...)       , t x ____bpf_ctx_decl6(args)
-#define ____bpf_ctx_decl8(t, x, args...)       , t x ____bpf_ctx_decl7(args)
-#define ____bpf_ctx_decl9(t, x, args...)       , t x ____bpf_ctx_decl8(args)
-#define ____bpf_ctx_decl10(t, x, args...)      , t x ____bpf_ctx_decl9(args)
-#define ____bpf_ctx_decl11(t, x, args...)      , t x ____bpf_ctx_decl10(args)
-#define ____bpf_ctx_decl12(t, x, args...)      , t x ____bpf_ctx_decl11(args)
-#define ____bpf_ctx_decl(args...)      ___bpf_apply(____bpf_ctx_decl, ____bpf_narg(args))(args)
+#define ___bpf_reg_cnt0()              (0)
+#define ___bpf_reg_cnt1(t, x)          (___bpf_reg_cnt0() + ___bpf_treg_cnt(t))
+#define ___bpf_reg_cnt2(t, x, args...) (___bpf_reg_cnt1(args) + ___bpf_treg_cnt(t))
+#define ___bpf_reg_cnt3(t, x, args...) (___bpf_reg_cnt2(args) + ___bpf_treg_cnt(t))
+#define ___bpf_reg_cnt4(t, x, args...) (___bpf_reg_cnt3(args) + ___bpf_treg_cnt(t))
+#define ___bpf_reg_cnt5(t, x, args...) (___bpf_reg_cnt4(args) + ___bpf_treg_cnt(t))
+#define ___bpf_reg_cnt6(t, x, args...) (___bpf_reg_cnt5(args) + ___bpf_treg_cnt(t))
+#define ___bpf_reg_cnt7(t, x, args...) (___bpf_reg_cnt6(args) + ___bpf_treg_cnt(t))
+#define ___bpf_reg_cnt8(t, x, args...) (___bpf_reg_cnt7(args) + ___bpf_treg_cnt(t))
+#define ___bpf_reg_cnt9(t, x, args...) (___bpf_reg_cnt8(args) + ___bpf_treg_cnt(t))
+#define ___bpf_reg_cnt10(t, x, args...)        (___bpf_reg_cnt9(args) + ___bpf_treg_cnt(t))
+#define ___bpf_reg_cnt11(t, x, args...)        (___bpf_reg_cnt10(args) + ___bpf_treg_cnt(t))
+#define ___bpf_reg_cnt12(t, x, args...)        (___bpf_reg_cnt11(args) + ___bpf_treg_cnt(t))
+#define ___bpf_reg_cnt(args...)         ___bpf_apply(___bpf_reg_cnt, ___bpf_narg2(args))(args)
+
+#define ___bpf_union_arg(t, x, n) \
+       __builtin_choose_expr(sizeof(t) == 1, ({ union { __u8 z[1]; t x; } ___t = { .z = {ctx[n]}}; ___t.x; }), \
+       __builtin_choose_expr(sizeof(t) == 2, ({ union { __u16 z[1]; t x; } ___t = { .z = {ctx[n]} }; ___t.x; }), \
+       __builtin_choose_expr(sizeof(t) == 4, ({ union { __u32 z[1]; t x; } ___t = { .z = {ctx[n]} }; ___t.x; }), \
+       __builtin_choose_expr(sizeof(t) == 8, ({ union { __u64 z[1]; t x; } ___t = {.z = {ctx[n]} }; ___t.x; }), \
+       __builtin_choose_expr(sizeof(t) == 16, ({ union { __u64 z[2]; t x; } ___t = {.z = {ctx[n], ctx[n + 1]} }; ___t.x; }), \
+                             (void)0)))))
+
+#define ___bpf_ctx_arg0(n, args...)
+#define ___bpf_ctx_arg1(n, t, x)               , ___bpf_union_arg(t, x, n - ___bpf_reg_cnt1(t, x))
+#define ___bpf_ctx_arg2(n, t, x, args...)      , ___bpf_union_arg(t, x, n - ___bpf_reg_cnt2(t, x, args)) ___bpf_ctx_arg1(n, args)
+#define ___bpf_ctx_arg3(n, t, x, args...)      , ___bpf_union_arg(t, x, n - ___bpf_reg_cnt3(t, x, args)) ___bpf_ctx_arg2(n, args)
+#define ___bpf_ctx_arg4(n, t, x, args...)      , ___bpf_union_arg(t, x, n - ___bpf_reg_cnt4(t, x, args)) ___bpf_ctx_arg3(n, args)
+#define ___bpf_ctx_arg5(n, t, x, args...)      , ___bpf_union_arg(t, x, n - ___bpf_reg_cnt5(t, x, args)) ___bpf_ctx_arg4(n, args)
+#define ___bpf_ctx_arg6(n, t, x, args...)      , ___bpf_union_arg(t, x, n - ___bpf_reg_cnt6(t, x, args)) ___bpf_ctx_arg5(n, args)
+#define ___bpf_ctx_arg7(n, t, x, args...)      , ___bpf_union_arg(t, x, n - ___bpf_reg_cnt7(t, x, args)) ___bpf_ctx_arg6(n, args)
+#define ___bpf_ctx_arg8(n, t, x, args...)      , ___bpf_union_arg(t, x, n - ___bpf_reg_cnt8(t, x, args)) ___bpf_ctx_arg7(n, args)
+#define ___bpf_ctx_arg9(n, t, x, args...)      , ___bpf_union_arg(t, x, n - ___bpf_reg_cnt9(t, x, args)) ___bpf_ctx_arg8(n, args)
+#define ___bpf_ctx_arg10(n, t, x, args...)     , ___bpf_union_arg(t, x, n - ___bpf_reg_cnt10(t, x, args)) ___bpf_ctx_arg9(n, args)
+#define ___bpf_ctx_arg11(n, t, x, args...)     , ___bpf_union_arg(t, x, n - ___bpf_reg_cnt11(t, x, args)) ___bpf_ctx_arg10(n, args)
+#define ___bpf_ctx_arg12(n, t, x, args...)     , ___bpf_union_arg(t, x, n - ___bpf_reg_cnt12(t, x, args)) ___bpf_ctx_arg11(n, args)
+#define ___bpf_ctx_arg(args...)        ___bpf_apply(___bpf_ctx_arg, ___bpf_narg2(args))(___bpf_reg_cnt(args), args)
+
+#define ___bpf_ctx_decl0()
+#define ___bpf_ctx_decl1(t, x)                 , t x
+#define ___bpf_ctx_decl2(t, x, args...)                , t x ___bpf_ctx_decl1(args)
+#define ___bpf_ctx_decl3(t, x, args...)                , t x ___bpf_ctx_decl2(args)
+#define ___bpf_ctx_decl4(t, x, args...)                , t x ___bpf_ctx_decl3(args)
+#define ___bpf_ctx_decl5(t, x, args...)                , t x ___bpf_ctx_decl4(args)
+#define ___bpf_ctx_decl6(t, x, args...)                , t x ___bpf_ctx_decl5(args)
+#define ___bpf_ctx_decl7(t, x, args...)                , t x ___bpf_ctx_decl6(args)
+#define ___bpf_ctx_decl8(t, x, args...)                , t x ___bpf_ctx_decl7(args)
+#define ___bpf_ctx_decl9(t, x, args...)                , t x ___bpf_ctx_decl8(args)
+#define ___bpf_ctx_decl10(t, x, args...)       , t x ___bpf_ctx_decl9(args)
+#define ___bpf_ctx_decl11(t, x, args...)       , t x ___bpf_ctx_decl10(args)
+#define ___bpf_ctx_decl12(t, x, args...)       , t x ___bpf_ctx_decl11(args)
+#define ___bpf_ctx_decl(args...)       ___bpf_apply(___bpf_ctx_decl, ___bpf_narg2(args))(args)
 
 /*
- * BPF_PROG2 can handle struct arguments.
+ * BPF_PROG2 is an enhanced version of BPF_PROG in order to handle struct
+ * arguments. Since each struct argument might take one or two u64 values
+ * in the trampoline stack, argument type size is needed to place proper number
+ * of u64 values for each argument. Therefore, BPF_PROG2 has different
+ * syntax from BPF_PROG. For example, for the following BPF_PROG syntax:
+ *
+ *   int BPF_PROG(test2, int a, int b) { ... }
+ *
+ * the corresponding BPF_PROG2 syntax is:
+ *
+ *   int BPF_PROG2(test2, int, a, int, b) { ... }
+ *
+ * where type and the corresponding argument name are separated by comma.
+ *
+ * Use BPF_PROG2 macro if one of the arguments might be a struct/union larger
+ * than 8 bytes:
+ *
+ *   int BPF_PROG2(test_struct_arg, struct bpf_testmod_struct_arg_1, a, int, b,
+ *                int, c, int, d, struct bpf_testmod_struct_arg_2, e, int, ret)
+ *   {
+ *        // access a, b, c, d, e, and ret directly
+ *        ...
+ *   }
  */
 #define BPF_PROG2(name, args...)                                               \
 name(unsigned long long *ctx);                                                 \
 static __always_inline typeof(name(0))                                         \
-____##name(unsigned long long *ctx ____bpf_ctx_decl(args));                    \
+____##name(unsigned long long *ctx ___bpf_ctx_decl(args));                     \
 typeof(name(0)) name(unsigned long long *ctx)                                  \
 {                                                                              \
-       return ____##name(ctx ____bpf_ctx_arg(____bpf_reg_cnt(args), args));    \
+       return ____##name(ctx ___bpf_ctx_arg(args));                            \
 }                                                                              \
 static __always_inline typeof(name(0))                                         \
-____##name(unsigned long long *ctx ____bpf_ctx_decl(args))
+____##name(unsigned long long *ctx ___bpf_ctx_decl(args))
 
 struct pt_regs;