From bd428b7b200cedca0dc94294188937c1df40e787 Mon Sep 17 00:00:00 2001 From: Leon Hwang Date: Thu, 18 Sep 2025 11:42:42 +0800 Subject: [PATCH 1/2] bpf: Allow union argument in trampoline based programs Currently, functions with 'union' arguments cannot be traced with fentry/fexit: bpftrace -e 'fentry:release_pages { exit(); }' -v AST node count: 6 Attaching 1 probe... ERROR: Error loading BPF program for fentry_vmlinux_release_pages_1. Kernel error log: The function release_pages arg0 type UNION is unsupported. processed 0 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0 ERROR: Loading BPF object(s) failed. The type of the 'release_pages' argument is defined as: typedef union { struct page **pages; struct folio **folios; struct encoded_page **encoded_pages; } release_pages_arg __attribute__ ((__transparent_union__)); This patch relaxes the restriction by allowing function arguments of type 'union' to be traced in verifier. Reviewed-by: Amery Hung Signed-off-by: Leon Hwang --- include/linux/bpf.h | 2 +- kernel/bpf/btf.c | 8 ++++---- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 41f776071ff51..42242e238757a 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1113,7 +1113,7 @@ struct bpf_prog_offload { */ #define MAX_BPF_FUNC_REG_ARGS 5 -/* The argument is a structure. */ +/* The argument is a structure or a union. */ #define BTF_FMODEL_STRUCT_ARG BIT(0) /* The argument is signed. */ diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 64739308902f7..bfd83e9e79798 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6762,7 +6762,7 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, /* skip modifiers */ while (btf_type_is_modifier(t)) t = btf_type_by_id(btf, t->type); - if (btf_type_is_small_int(t) || btf_is_any_enum(t) || __btf_type_is_struct(t)) + if (btf_type_is_small_int(t) || btf_is_any_enum(t) || btf_type_is_struct(t)) /* accessing a scalar */ return true; if (!btf_type_is_ptr(t)) { @@ -7334,7 +7334,7 @@ static int __get_type_size(struct btf *btf, u32 btf_id, if (btf_type_is_ptr(t)) /* kernel size of pointer. Not BPF's size of pointer*/ return sizeof(void *); - if (btf_type_is_int(t) || btf_is_any_enum(t) || __btf_type_is_struct(t)) + if (btf_type_is_int(t) || btf_is_any_enum(t) || btf_type_is_struct(t)) return t->size; return -EINVAL; } @@ -7343,7 +7343,7 @@ static u8 __get_type_fmodel_flags(const struct btf_type *t) { u8 flags = 0; - if (__btf_type_is_struct(t)) + if (btf_type_is_struct(t)) flags |= BTF_FMODEL_STRUCT_ARG; if (btf_type_is_signed_int(t)) flags |= BTF_FMODEL_SIGNED_ARG; @@ -7384,7 +7384,7 @@ int btf_distill_func_proto(struct bpf_verifier_log *log, return -EINVAL; } ret = __get_type_size(btf, func->type, &t); - if (ret < 0 || __btf_type_is_struct(t)) { + if (ret < 0 || btf_type_is_struct(t)) { bpf_log(log, "The function %s return type %s is unsupported.\n", tname, btf_type_str(t)); From 86a17e472a5d9717a3df6fd8aa50ee4d464ce1ed Mon Sep 17 00:00:00 2001 From: Leon Hwang Date: Thu, 18 Sep 2025 11:42:43 +0800 Subject: [PATCH 2/2] selftests/bpf: Add union argument tests using fexit programs By referencing commit 1642a3945e223 ("selftests/bpf: Add struct argument tests with fentry/fexit programs."), test the following cases for union argument support: * 8B union argument. * 16B union argument. cd tools/testing/selftests/bpf ./test_progs -t tracing_struct/union_args 472/3 tracing_struct/union_args:OK 472 tracing_struct:OK Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Leon Hwang --- .../selftests/bpf/prog_tests/tracing_struct.c | 29 ++++++++++++++++ .../selftests/bpf/progs/tracing_struct.c | 33 +++++++++++++++++++ .../selftests/bpf/test_kmods/bpf_testmod.c | 31 +++++++++++++++++ 3 files changed, 93 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/tracing_struct.c b/tools/testing/selftests/bpf/prog_tests/tracing_struct.c index 19e68d4b35327..6f8c0bfb04155 100644 --- a/tools/testing/selftests/bpf/prog_tests/tracing_struct.c +++ b/tools/testing/selftests/bpf/prog_tests/tracing_struct.c @@ -112,10 +112,39 @@ static void test_struct_many_args(void) tracing_struct_many_args__destroy(skel); } +static void test_union_args(void) +{ + struct tracing_struct *skel; + int err; + + skel = tracing_struct__open_and_load(); + if (!ASSERT_OK_PTR(skel, "tracing_struct__open_and_load")) + return; + + err = tracing_struct__attach(skel); + if (!ASSERT_OK(err, "tracing_struct__attach")) + goto out; + + ASSERT_OK(trigger_module_test_read(256), "trigger_read"); + + ASSERT_EQ(skel->bss->ut1_a_a, 1, "ut1:a.arg.a"); + ASSERT_EQ(skel->bss->ut1_b, 4, "ut1:b"); + ASSERT_EQ(skel->bss->ut1_c, 5, "ut1:c"); + + ASSERT_EQ(skel->bss->ut2_a, 6, "ut2:a"); + ASSERT_EQ(skel->bss->ut2_b_a, 2, "ut2:b.arg.a"); + ASSERT_EQ(skel->bss->ut2_b_b, 3, "ut2:b.arg.b"); + +out: + tracing_struct__destroy(skel); +} + void test_tracing_struct(void) { if (test__start_subtest("struct_args")) test_struct_args(); if (test__start_subtest("struct_many_args")) test_struct_many_args(); + if (test__start_subtest("union_args")) + test_union_args(); } diff --git a/tools/testing/selftests/bpf/progs/tracing_struct.c b/tools/testing/selftests/bpf/progs/tracing_struct.c index c435a3a8328ab..d460732e20239 100644 --- a/tools/testing/selftests/bpf/progs/tracing_struct.c +++ b/tools/testing/selftests/bpf/progs/tracing_struct.c @@ -18,6 +18,18 @@ struct bpf_testmod_struct_arg_3 { int b[]; }; +union bpf_testmod_union_arg_1 { + char a; + short b; + struct bpf_testmod_struct_arg_1 arg; +}; + +union bpf_testmod_union_arg_2 { + int a; + long b; + struct bpf_testmod_struct_arg_2 arg; +}; + long t1_a_a, t1_a_b, t1_b, t1_c, t1_ret, t1_nregs; __u64 t1_reg0, t1_reg1, t1_reg2, t1_reg3; long t2_a, t2_b_a, t2_b_b, t2_c, t2_ret; @@ -26,6 +38,9 @@ long t4_a_a, t4_b, t4_c, t4_d, t4_e_a, t4_e_b, t4_ret; long t5_ret; int t6; +long ut1_a_a, ut1_b, ut1_c; +long ut2_a, ut2_b_a, ut2_b_b; + SEC("fentry/bpf_testmod_test_struct_arg_1") int BPF_PROG2(test_struct_arg_1, struct bpf_testmod_struct_arg_2, a, int, b, int, c) { @@ -130,4 +145,22 @@ int BPF_PROG2(test_struct_arg_11, struct bpf_testmod_struct_arg_3 *, a) return 0; } +SEC("fexit/bpf_testmod_test_union_arg_1") +int BPF_PROG2(test_union_arg_1, union bpf_testmod_union_arg_1, a, int, b, int, c) +{ + ut1_a_a = a.arg.a; + ut1_b = b; + ut1_c = c; + return 0; +} + +SEC("fexit/bpf_testmod_test_union_arg_2") +int BPF_PROG2(test_union_arg_2, int, a, union bpf_testmod_union_arg_2, b) +{ + ut2_a = a; + ut2_b_a = b.arg.a; + ut2_b_b = b.arg.b; + return 0; +} + char _license[] SEC("license") = "GPL"; diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c index d6ce51df9ed4a..6df6475f5dbc2 100644 --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c @@ -62,6 +62,18 @@ struct bpf_testmod_struct_arg_5 { long d; }; +union bpf_testmod_union_arg_1 { + char a; + short b; + struct bpf_testmod_struct_arg_1 arg; +}; + +union bpf_testmod_union_arg_2 { + int a; + long b; + struct bpf_testmod_struct_arg_2 arg; +}; + __bpf_hook_start(); noinline int @@ -128,6 +140,20 @@ bpf_testmod_test_struct_arg_9(u64 a, void *b, short c, int d, void *e, char f, return bpf_testmod_test_struct_arg_result; } +noinline int +bpf_testmod_test_union_arg_1(union bpf_testmod_union_arg_1 a, int b, int c) +{ + bpf_testmod_test_struct_arg_result = a.arg.a + b + c; + return bpf_testmod_test_struct_arg_result; +} + +noinline int +bpf_testmod_test_union_arg_2(int a, union bpf_testmod_union_arg_2 b) +{ + bpf_testmod_test_struct_arg_result = a + b.arg.a + b.arg.b; + return bpf_testmod_test_struct_arg_result; +} + noinline int bpf_testmod_test_arg_ptr_to_struct(struct bpf_testmod_struct_arg_1 *a) { bpf_testmod_test_struct_arg_result = a->a; @@ -408,6 +434,8 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj, struct bpf_testmod_struct_arg_3 *struct_arg3; struct bpf_testmod_struct_arg_4 struct_arg4 = {21, 22}; struct bpf_testmod_struct_arg_5 struct_arg5 = {23, 24, 25, 26}; + union bpf_testmod_union_arg_1 union_arg1 = { .arg = {1} }; + union bpf_testmod_union_arg_2 union_arg2 = { .arg = {2, 3} }; int i = 1; while (bpf_testmod_return_ptr(i)) @@ -425,6 +453,9 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj, (void)bpf_testmod_test_struct_arg_9(16, (void *)17, 18, 19, (void *)20, 21, 22, struct_arg5, 27); + (void)bpf_testmod_test_union_arg_1(union_arg1, 4, 5); + (void)bpf_testmod_test_union_arg_2(6, union_arg2); + (void)bpf_testmod_test_arg_ptr_to_struct(&struct_arg1_2); (void)trace_bpf_testmod_test_raw_tp_null_tp(NULL);