Merge branch 'bpf-libbpf-bitfield-size-relo'

Andrii Nakryiko says:

====================
This patch set adds support for reading bitfields in a relocatable manner
through a set of relocations emitted by Clang, corresponding libbpf support
for those relocations, as well as abstracting details into
BPF_CORE_READ_BITFIELD/BPF_CORE_READ_BITFIELD_PROBED macro.

We also add support for capturing relocatable field size, so that BPF program
code can adjust its logic to actual amount of data it needs to operate on,
even if it changes between kernels. New convenience macro is added to
bpf_core_read.h (bpf_core_field_size(), in the same family of macro as
bpf_core_read() and bpf_core_field_exists()). Corresponding set of selftests
are added to excercise this logic and validate correctness in a variety of
scenarios.

Some of the overly strict logic of matching fields is relaxed to support wider
variety of scenarios. See patch #1 for that.

Patch #1 removes few overly strict test cases.
Patch #2 adds support for bitfield-related relocations.
Patch #3 adds some further adjustments to support generic field size
relocations and introduces bpf_core_field_size() macro.
Patch #4 tests bitfield reading.
Patch #5 tests field size relocations.

v1 -> v2:
  - added direct memory read-based macro and tests for bitfield reads.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 116 insertions, 7 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
index 09dfa75fe948..00f1f3229542 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -174,21 +174,82 @@
 	.fails = true,							\
 }
 
-#define EXISTENCE_DATA(struct_name) STRUCT_TO_CHAR_PTR(struct_name) {	\
-	.a = 42,							\
-}
-
 #define EXISTENCE_CASE_COMMON(name)					\
 	.case_name = #name,						\
 	.bpf_obj_file = "test_core_reloc_existence.o",			\
 	.btf_src_file = "btf__core_reloc_" #name ".o",			\
-	.relaxed_core_relocs = true					\
+	.relaxed_core_relocs = true
 
 #define EXISTENCE_ERR_CASE(name) {					\
 	EXISTENCE_CASE_COMMON(name),					\
 	.fails = true,							\
 }
 
+#define BITFIELDS_CASE_COMMON(objfile, test_name_prefix,  name)		\
+	.case_name = test_name_prefix#name,				\
+	.bpf_obj_file = objfile,					\
+	.btf_src_file = "btf__core_reloc_" #name ".o"
+
+#define BITFIELDS_CASE(name, ...) {					\
+	BITFIELDS_CASE_COMMON("test_core_reloc_bitfields_probed.o",	\
+			      "direct:", name),				\
+	.input = STRUCT_TO_CHAR_PTR(core_reloc_##name) __VA_ARGS__,	\
+	.input_len = sizeof(struct core_reloc_##name),			\
+	.output = STRUCT_TO_CHAR_PTR(core_reloc_bitfields_output)	\
+		__VA_ARGS__,						\
+	.output_len = sizeof(struct core_reloc_bitfields_output),	\
+}, {									\
+	BITFIELDS_CASE_COMMON("test_core_reloc_bitfields_direct.o",	\
+			      "probed:", name),				\
+	.input = STRUCT_TO_CHAR_PTR(core_reloc_##name) __VA_ARGS__,	\
+	.input_len = sizeof(struct core_reloc_##name),			\
+	.output = STRUCT_TO_CHAR_PTR(core_reloc_bitfields_output)	\
+		__VA_ARGS__,						\
+	.output_len = sizeof(struct core_reloc_bitfields_output),	\
+	.direct_raw_tp = true,						\
+}
+
+
+#define BITFIELDS_ERR_CASE(name) {					\
+	BITFIELDS_CASE_COMMON("test_core_reloc_bitfields_probed.o",	\
+			      "probed:", name),				\
+	.fails = true,							\
+}, {									\
+	BITFIELDS_CASE_COMMON("test_core_reloc_bitfields_direct.o",	\
+			      "direct:", name),				\
+	.direct_raw_tp = true,						\
+	.fails = true,							\
+}
+
+#define SIZE_CASE_COMMON(name)						\
+	.case_name = #name,						\
+	.bpf_obj_file = "test_core_reloc_size.o",			\
+	.btf_src_file = "btf__core_reloc_" #name ".o",			\
+	.relaxed_core_relocs = true
+
+#define SIZE_OUTPUT_DATA(type)						\
+	STRUCT_TO_CHAR_PTR(core_reloc_size_output) {			\
+		.int_sz = sizeof(((type *)0)->int_field),		\
+		.struct_sz = sizeof(((type *)0)->struct_field),		\
+		.union_sz = sizeof(((type *)0)->union_field),		\
+		.arr_sz = sizeof(((type *)0)->arr_field),		\
+		.arr_elem_sz = sizeof(((type *)0)->arr_field[0]),	\
+		.ptr_sz = sizeof(((type *)0)->ptr_field),		\
+		.enum_sz = sizeof(((type *)0)->enum_field),	\
+	}
+
+#define SIZE_CASE(name) {						\
+	SIZE_CASE_COMMON(name),						\
+	.input_len = 0,							\
+	.output = SIZE_OUTPUT_DATA(struct core_reloc_##name),		\
+	.output_len = sizeof(struct core_reloc_size_output),		\
+}
+
+#define SIZE_ERR_CASE(name) {						\
+	SIZE_CASE_COMMON(name),						\
+	.fails = true,							\
+}
+
 struct core_reloc_test_case {
 	const char *case_name;
 	const char *bpf_obj_file;
@@ -199,6 +260,7 @@ struct core_reloc_test_case {
 	int output_len;
 	bool fails;
 	bool relaxed_core_relocs;
+	bool direct_raw_tp;
 };
 
 static struct core_reloc_test_case test_cases[] = {
@@ -352,6 +414,44 @@ static struct core_reloc_test_case test_cases[] = {
 	EXISTENCE_ERR_CASE(existence__err_arr_kind),
 	EXISTENCE_ERR_CASE(existence__err_arr_value_type),
 	EXISTENCE_ERR_CASE(existence__err_struct_type),
+
+	/* bitfield relocation checks */
+	BITFIELDS_CASE(bitfields, {
+		.ub1 = 1,
+		.ub2 = 2,
+		.ub7 = 96,
+		.sb4 = -7,
+		.sb20 = -0x76543,
+		.u32 = 0x80000000,
+		.s32 = -0x76543210,
+	}),
+	BITFIELDS_CASE(bitfields___bit_sz_change, {
+		.ub1 = 6,
+		.ub2 = 0xABCDE,
+		.ub7 = 1,
+		.sb4 = -1,
+		.sb20 = -0x17654321,
+		.u32 = 0xBEEF,
+		.s32 = -0x3FEDCBA987654321,
+	}),
+	BITFIELDS_CASE(bitfields___bitfield_vs_int, {
+		.ub1 = 0xFEDCBA9876543210,
+		.ub2 = 0xA6,
+		.ub7 = -0x7EDCBA987654321,
+		.sb4 = -0x6123456789ABCDE,
+		.sb20 = 0xD00D,
+		.u32 = -0x76543,
+		.s32 = 0x0ADEADBEEFBADB0B,
+	}),
+	BITFIELDS_CASE(bitfields___just_big_enough, {
+		.ub1 = 0xF,
+		.ub2 = 0x0812345678FEDCBA,
+	}),
+	BITFIELDS_ERR_CASE(bitfields___err_too_big_bitfield),
+
+	/* size relocation checks */
+	SIZE_CASE(size),
+	SIZE_CASE(size___diff_sz),
 };
 
 struct data {
@@ -361,9 +461,9 @@ struct data {
 
 void test_core_reloc(void)
 {
-	const char *probe_name = "raw_tracepoint/sys_enter";
 	struct bpf_object_load_attr load_attr = {};
 	struct core_reloc_test_case *test_case;
+	const char *tp_name, *probe_name;
 	int err, duration = 0, i, equal;
 	struct bpf_link *link = NULL;
 	struct bpf_map *data_map;
@@ -387,6 +487,15 @@ void test_core_reloc(void)
 			  test_case->bpf_obj_file, PTR_ERR(obj)))
 			continue;
 
+		/* for typed raw tracepoints, NULL should be specified */
+		if (test_case->direct_raw_tp) {
+			probe_name = "tp_btf/sys_enter";
+			tp_name = NULL;
+		} else {
+			probe_name = "raw_tracepoint/sys_enter";
+			tp_name = "sys_enter";
+		}
+
 		prog = bpf_object__find_program_by_title(obj, probe_name);
 		if (CHECK(!prog, "find_probe",
 			  "prog '%s' not found\n", probe_name))
@@ -407,7 +516,7 @@ void test_core_reloc(void)
 				goto cleanup;
 		}
 
-		link = bpf_program__attach_raw_tracepoint(prog, "sys_enter");
+		link = bpf_program__attach_raw_tracepoint(prog, tp_name);
 		if (CHECK(IS_ERR(link), "attach_raw_tp", "err %ld\n",
 			  PTR_ERR(link)))
 			goto cleanup;