Merge branch 'Introduce type match support'

Daniel Müller says:

====================

This patch set proposes the addition of a new way for performing type queries to
BPF. It introduces the "type matches" relation, similar to what is already
present with "type exists" (in the form of bpf_core_type_exists).

"type exists" performs fairly superficial checking, mostly concerned with
whether a type exists in the kernel and is of the same kind (enum/struct/...).
Notably, compatibility checks for members of composite types is lacking.

The newly introduced "type matches" (bpf_core_type_matches) fills this gap in
that it performs stricter checks: compatibility of members and existence of
similarly named enum variants is checked as well. E.g., given these definitions:

	struct task_struct___og { int pid; int tgid; };

	struct task_struct___foo { int foo; }

'task_struct___og' would "match" the kernel type 'task_struct', because the
members match up, while 'task_struct___foo' would not match, because the
kernel's 'task_struct' has no member named 'foo'.

More precisely, the "type match" relation is defined as follows (copied from
source):
- modifiers and typedefs are stripped (and, hence, effectively ignored)
- generally speaking types need to be of same kind (struct vs. struct, union
  vs. union, etc.)
  - exceptions are struct/union behind a pointer which could also match a
    forward declaration of a struct or union, respectively, and enum vs.
    enum64 (see below)
Then, depending on type:
- integers:
  - match if size and signedness match
- arrays & pointers:
  - target types are recursively matched
- structs & unions:
  - local members need to exist in target with the same name
  - for each member we recursively check match unless it is already behind a
    pointer, in which case we only check matching names and compatible kind
- enums:
  - local variants have to have a match in target by symbolic name (but not
    numeric value)
  - size has to match (but enum may match enum64 and vice versa)
- function pointers:
  - number and position of arguments in local type has to match target
  - for each argument and the return value we recursively check match

Enabling this feature requires a new relocation to be made known to the
compiler. This is being taken care of for LLVM as part of
https://reviews.llvm.org/D126838.

If applied, among other things, usage of this functionality could have helped
flag issues such as the one discussed here
https://lore.kernel.org/all/93a20759600c05b6d9e4359a1517c88e06b44834.camel@fb.com/
earlier.

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
---
Changelog:
v2 -> v3:
- renamed btfgen_mark_types_match
- covered BTF_KIND_RESTRICT in type match marking logic
- used bpf_core_names_match in more places
- reworked "behind pointer" logic
- added test using live task_struct

v1 -> v2:
- deduplicated and moved core algorithm into relo_core.c
- adjusted bpf_core_names_match to get btf_type passed in
- removed some length equality checks before strncmp usage
- correctly use kflag from targ_t instead of local_t
- added comment for meaning of kflag w/ FWD kind
- __u32 -> u32
- handle BTF_KIND_FWD properly in bpftool marking logic
- rebased
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

1 files changed, 71 insertions, 2 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
index 2f92feb809be..a6f65e2236f4 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -543,7 +543,6 @@ static int __trigger_module_test_read(const struct core_reloc_test_case *test)
 	return 0;
 }
 
-
 static const struct core_reloc_test_case test_cases[] = {
 	/* validate we can find kernel image and use its BTF for relocs */
 	{
@@ -556,6 +555,7 @@ static const struct core_reloc_test_case test_cases[] = {
 			.valid = { 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, },
 			.comm = "test_progs",
 			.comm_len = sizeof("test_progs"),
+			.local_task_struct_matches = true,
 		},
 		.output_len = sizeof(struct core_reloc_kernel_output),
 		.raw_tp_name = "sys_enter",
@@ -752,9 +752,10 @@ static const struct core_reloc_test_case test_cases[] = {
 	SIZE_CASE(size___diff_offs),
 	SIZE_ERR_CASE(size___err_ambiguous),
 
-	/* validate type existence and size relocations */
+	/* validate type existence, match, and size relocations */
 	TYPE_BASED_CASE(type_based, {
 		.struct_exists = 1,
+		.complex_struct_exists = 1,
 		.union_exists = 1,
 		.enum_exists = 1,
 		.typedef_named_struct_exists = 1,
@@ -765,6 +766,20 @@ static const struct core_reloc_test_case test_cases[] = {
 		.typedef_void_ptr_exists = 1,
 		.typedef_func_proto_exists = 1,
 		.typedef_arr_exists = 1,
+
+		.struct_matches = 1,
+		.complex_struct_matches = 1,
+		.union_matches = 1,
+		.enum_matches = 1,
+		.typedef_named_struct_matches = 1,
+		.typedef_anon_struct_matches = 1,
+		.typedef_struct_ptr_matches = 1,
+		.typedef_int_matches = 1,
+		.typedef_enum_matches = 1,
+		.typedef_void_ptr_matches = 1,
+		.typedef_func_proto_matches = 1,
+		.typedef_arr_matches = 1,
+
 		.struct_sz = sizeof(struct a_struct),
 		.union_sz = sizeof(union a_union),
 		.enum_sz = sizeof(enum an_enum),
@@ -780,6 +795,45 @@ static const struct core_reloc_test_case test_cases[] = {
 	TYPE_BASED_CASE(type_based___all_missing, {
 		/* all zeros */
 	}),
+	TYPE_BASED_CASE(type_based___diff, {
+		.struct_exists = 1,
+		.complex_struct_exists = 1,
+		.union_exists = 1,
+		.enum_exists = 1,
+		.typedef_named_struct_exists = 1,
+		.typedef_anon_struct_exists = 1,
+		.typedef_struct_ptr_exists = 1,
+		.typedef_int_exists = 1,
+		.typedef_enum_exists = 1,
+		.typedef_void_ptr_exists = 1,
+		.typedef_func_proto_exists = 1,
+		.typedef_arr_exists = 1,
+
+		.struct_matches = 1,
+		.complex_struct_matches = 1,
+		.union_matches = 1,
+		.enum_matches = 1,
+		.typedef_named_struct_matches = 1,
+		.typedef_anon_struct_matches = 1,
+		.typedef_struct_ptr_matches = 1,
+		.typedef_int_matches = 0,
+		.typedef_enum_matches = 1,
+		.typedef_void_ptr_matches = 1,
+		.typedef_func_proto_matches = 0,
+		.typedef_arr_matches = 0,
+
+		.struct_sz = sizeof(struct a_struct___diff),
+		.union_sz = sizeof(union a_union___diff),
+		.enum_sz = sizeof(enum an_enum___diff),
+		.typedef_named_struct_sz = sizeof(named_struct_typedef___diff),
+		.typedef_anon_struct_sz = sizeof(anon_struct_typedef___diff),
+		.typedef_struct_ptr_sz = sizeof(struct_ptr_typedef___diff),
+		.typedef_int_sz = sizeof(int_typedef___diff),
+		.typedef_enum_sz = sizeof(enum_typedef___diff),
+		.typedef_void_ptr_sz = sizeof(void_ptr_typedef___diff),
+		.typedef_func_proto_sz = sizeof(func_proto_typedef___diff),
+		.typedef_arr_sz = sizeof(arr_typedef___diff),
+	}),
 	TYPE_BASED_CASE(type_based___diff_sz, {
 		.struct_exists = 1,
 		.union_exists = 1,
@@ -792,6 +846,19 @@ static const struct core_reloc_test_case test_cases[] = {
 		.typedef_void_ptr_exists = 1,
 		.typedef_func_proto_exists = 1,
 		.typedef_arr_exists = 1,
+
+		.struct_matches = 0,
+		.union_matches = 0,
+		.enum_matches = 0,
+		.typedef_named_struct_matches = 0,
+		.typedef_anon_struct_matches = 0,
+		.typedef_struct_ptr_matches = 1,
+		.typedef_int_matches = 0,
+		.typedef_enum_matches = 0,
+		.typedef_void_ptr_matches = 1,
+		.typedef_func_proto_matches = 0,
+		.typedef_arr_matches = 0,
+
 		.struct_sz = sizeof(struct a_struct___diff_sz),
 		.union_sz = sizeof(union a_union___diff_sz),
 		.enum_sz = sizeof(enum an_enum___diff_sz),
@@ -806,10 +873,12 @@ static const struct core_reloc_test_case test_cases[] = {
 	}),
 	TYPE_BASED_CASE(type_based___incompat, {
 		.enum_exists = 1,
+		.enum_matches = 1,
 		.enum_sz = sizeof(enum an_enum),
 	}),
 	TYPE_BASED_CASE(type_based___fn_wrong_args, {
 		.struct_exists = 1,
+		.struct_matches = 1,
 		.struct_sz = sizeof(struct a_struct),
 	}),