diff mbox series

[bpf-next,v3,08/18] libbpf: Add enum64 sanitization

Message ID 20220526185514.2549806-1-yhs@fb.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: Add 64bit enum value support | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-PR fail PR summary
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count fail Series longer than 15 patches (and no cover letter)
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers warning 5 maintainers not CCed: netdev@vger.kernel.org songliubraving@fb.com john.fastabend@gmail.com kafai@fb.com kpsingh@kernel.org
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch fail ERROR: code indent should use tabs where possible WARNING: line length of 102 exceeds 80 columns WARNING: line length of 81 exceeds 80 columns WARNING: please, no spaces at the start of a line
netdev/kdoc success Errors and warnings before: 12 this patch: 12
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-VM_Test-1 fail Logs for Kernel LATEST on ubuntu-latest with gcc
bpf/vmtest-bpf-next-VM_Test-2 fail Logs for Kernel LATEST on ubuntu-latest with llvm-15
bpf/vmtest-bpf-next-VM_Test-3 fail Logs for Kernel LATEST on z15 with gcc

Commit Message

Yonghong Song May 26, 2022, 6:55 p.m. UTC 
When old kernel does not support enum64 but user space btf
contains non-zero enum kflag or enum64, libbpf needs to
do proper sanitization so modified btf can be accepted
by the kernel.

Sanitization for enum kflag can be achieved by clearing
the kflag bit. For enum64, the type is replaced with an
union of integer member types and the integer member size
must be smaller than enum64 size. If such an integer
type cannot be found, a new type is created and used
for union members.

Signed-off-by: Yonghong Song <yhs@fb.com>
---
 tools/lib/bpf/btf.h             |  3 +-
 tools/lib/bpf/libbpf.c          | 56 ++++++++++++++++++++++++++++++---
 tools/lib/bpf/libbpf_internal.h |  2 ++
 3 files changed, 56 insertions(+), 5 deletions(-)

Comments

Andrii Nakryiko May 31, 2022, 11:59 p.m. UTC | #1 
On Thu, May 26, 2022 at 11:55 AM Yonghong Song <yhs@fb.com> wrote:
>
> When old kernel does not support enum64 but user space btf
> contains non-zero enum kflag or enum64, libbpf needs to
> do proper sanitization so modified btf can be accepted
> by the kernel.
>
> Sanitization for enum kflag can be achieved by clearing
> the kflag bit. For enum64, the type is replaced with an
> union of integer member types and the integer member size
> must be smaller than enum64 size. If such an integer
> type cannot be found, a new type is created and used
> for union members.
>
> Signed-off-by: Yonghong Song <yhs@fb.com>
> ---

LGTM!

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

>  tools/lib/bpf/btf.h             |  3 +-
>  tools/lib/bpf/libbpf.c          | 56 ++++++++++++++++++++++++++++++---
>  tools/lib/bpf/libbpf_internal.h |  2 ++
>  3 files changed, 56 insertions(+), 5 deletions(-)
>

[...]
diff mbox series

Patch

diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 7da6970b8c9f..d4fe1300ed33 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -395,9 +395,10 @@  btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
 #ifndef BTF_KIND_FLOAT
 #define BTF_KIND_FLOAT		16	/* Floating point	*/
 #endif
-/* The kernel header switched to enums, so these two were never #defined */
+/* The kernel header switched to enums, so the following were never #defined */
 #define BTF_KIND_DECL_TAG	17	/* Decl Tag */
 #define BTF_KIND_TYPE_TAG	18	/* Type Tag */
+#define BTF_KIND_ENUM64		19	/* Enum for up-to 64bit values */
 
 static inline __u16 btf_kind(const struct btf_type *t)
 {
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e89cc9c885b3..a9667b49b838 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2114,6 +2114,7 @@  static const char *__btf_kind_str(__u16 kind)
 	case BTF_KIND_FLOAT: return "float";
 	case BTF_KIND_DECL_TAG: return "decl_tag";
 	case BTF_KIND_TYPE_TAG: return "type_tag";
+	case BTF_KIND_ENUM64: return "enum64";
 	default: return "unknown";
 	}
 }
@@ -2642,12 +2643,13 @@  static bool btf_needs_sanitization(struct bpf_object *obj)
 	bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);
 	bool has_decl_tag = kernel_supports(obj, FEAT_BTF_DECL_TAG);
 	bool has_type_tag = kernel_supports(obj, FEAT_BTF_TYPE_TAG);
+	bool has_enum64 = kernel_supports(obj, FEAT_BTF_ENUM64);
 
 	return !has_func || !has_datasec || !has_func_global || !has_float ||
-	       !has_decl_tag || !has_type_tag;
+	       !has_decl_tag || !has_type_tag || !has_enum64;
 }
 
-static void bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
+static int bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
 {
 	bool has_func_global = kernel_supports(obj, FEAT_BTF_GLOBAL_FUNC);
 	bool has_datasec = kernel_supports(obj, FEAT_BTF_DATASEC);
@@ -2655,6 +2657,8 @@  static void bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
 	bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);
 	bool has_decl_tag = kernel_supports(obj, FEAT_BTF_DECL_TAG);
 	bool has_type_tag = kernel_supports(obj, FEAT_BTF_TYPE_TAG);
+	bool has_enum64 = kernel_supports(obj, FEAT_BTF_ENUM64);
+	__u32 enum64_placeholder_id = 0;
 	struct btf_type *t;
 	int i, j, vlen;
 
@@ -2717,8 +2721,32 @@  static void bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
 			/* replace TYPE_TAG with a CONST */
 			t->name_off = 0;
 			t->info = BTF_INFO_ENC(BTF_KIND_CONST, 0, 0);
-		}
+		} else if (!has_enum64 && btf_is_enum(t)) {
+			/* clear the kflag */
+			t->info = btf_type_info(btf_kind(t), btf_vlen(t), false);
+		} else if (!has_enum64 && btf_is_enum64(t)) {
+			/* replace ENUM64 with a union */
+			struct btf_member *m;
+
+			if (enum64_placeholder_id == 0) {
+				enum64_placeholder_id = btf__add_int(btf, "enum64_placeholder", 1, 0);
+				if (enum64_placeholder_id < 0)
+					return enum64_placeholder_id;
+
+				t = (struct btf_type *)btf__type_by_id(btf, i);
+			}
+
+			m = btf_members(t);
+			vlen = btf_vlen(t);
+			t->info = BTF_INFO_ENC(BTF_KIND_UNION, 0, vlen);
+			for (j = 0; j < vlen; j++, m++) {
+				m->type = enum64_placeholder_id;
+				m->offset = 0;
+			}
+                }
 	}
+
+	return 0;
 }
 
 static bool libbpf_needs_btf(const struct bpf_object *obj)
@@ -3056,7 +3084,9 @@  static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
 
 		/* enforce 8-byte pointers for BPF-targeted BTFs */
 		btf__set_pointer_size(obj->btf, 8);
-		bpf_object__sanitize_btf(obj, kern_btf);
+		err = bpf_object__sanitize_btf(obj, kern_btf);
+		if (err)
+			return err;
 	}
 
 	if (obj->gen_loader) {
@@ -3563,6 +3593,10 @@  static enum kcfg_type find_kcfg_type(const struct btf *btf, int id,
 		if (strcmp(name, "libbpf_tristate"))
 			return KCFG_UNKNOWN;
 		return KCFG_TRISTATE;
+	case BTF_KIND_ENUM64:
+		if (strcmp(name, "libbpf_tristate"))
+			return KCFG_UNKNOWN;
+		return KCFG_TRISTATE;
 	case BTF_KIND_ARRAY:
 		if (btf_array(t)->nelems == 0)
 			return KCFG_UNKNOWN;
@@ -4746,6 +4780,17 @@  static int probe_kern_bpf_cookie(void)
 	return probe_fd(ret);
 }
 
+static int probe_kern_btf_enum64(void)
+{
+	static const char strs[] = "\0enum64";
+	__u32 types[] = {
+		BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_ENUM64, 0, 0), 8),
+	};
+
+	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),
+					     strs, sizeof(strs)));
+}
+
 enum kern_feature_result {
 	FEAT_UNKNOWN = 0,
 	FEAT_SUPPORTED = 1,
@@ -4811,6 +4856,9 @@  static struct kern_feature_desc {
 	[FEAT_BPF_COOKIE] = {
 		"BPF cookie support", probe_kern_bpf_cookie,
 	},
+	[FEAT_BTF_ENUM64] = {
+		"BTF_KIND_ENUM64 support", probe_kern_btf_enum64,
+	},
 };
 
 bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 4abdbe2fea9d..10c16acfa8ae 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -351,6 +351,8 @@  enum kern_feature_id {
 	FEAT_MEMCG_ACCOUNT,
 	/* BPF cookie (bpf_get_attach_cookie() BPF helper) support */
 	FEAT_BPF_COOKIE,
+	/* BTF_KIND_ENUM64 support and BTF_KIND_ENUM kflag support */
+	FEAT_BTF_ENUM64,
 	__FEAT_CNT,
 };