Merge branch 'bpf: Add 64bit enum value support'

Yonghong Song says:

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

Currently, btf only supports upto 32bit enum value with BTF_KIND_ENUM.
But in kernel, some enum has 64bit values, e.g., in uapi bpf.h, we have
  enum {
        BPF_F_INDEX_MASK                = 0xffffffffULL,
        BPF_F_CURRENT_CPU               = BPF_F_INDEX_MASK,
        BPF_F_CTXLEN_MASK               = (0xfffffULL << 32),
  };
With BTF_KIND_ENUM, the value for BPF_F_CTXLEN_MASK will be encoded
as 0 which is incorrect.

To solve this problem, BTF_KIND_ENUM64 is proposed in this patch set
to support enum 64bit values. Also, since sometimes there is a need
to generate C code from btf, e.g., vmlinux.h, btf kflag support
is also added for BTF_KIND_ENUM and BTF_KIND_ENUM64 to indicate
signedness, helping proper value printout.

Changelog:
  v4 -> v5:
    - skip newly-added enum64 C test if clang version <= 14.
  v3 -> v4:
    - rename btf_type_is_any_enum() to btf_is_any_enum() to favor
      consistency in libbpf.
    - fix sign extension issue in btf_dump_get_enum_value().
    - fix BPF_CORE_FIELD_SIGNED signedness issue in bpf_core_calc_field_relo().
  v2 -> v3:
    - Implement separate btf_equal_enum()/btf_equal_enum64() and
      btf_compat_enum()/btf_compat_enum64().
    - Add a new enum64 placeholder type dynamicly for enum64 sanitization.
    - For bpftool output and unit selftest, printed out signed/unsigned
      encoding as well.
    - fix some issues with BTF_KIND_ENUM is doc and clarified sign extension
      rules for enum values.
  v1 -> v2:
    - Changed kflag default from signed to unsigned
    - Fixed sanitization issue
    - Broke down libbpf related patches for easier review
    - Added more tests
    - More code refactorization
    - Corresponding llvm patch (to support enum64) is also updated
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: Alexei Starovoitov

Documentation/bpf/btf.rst

@@ -74,7 +74,7 @@ sequentially and type id is assigned to each recognized type starting from id
     #define BTF_KIND_ARRAY          3       /* Array        */
     #define BTF_KIND_STRUCT         4       /* Struct       */
     #define BTF_KIND_UNION          5       /* Union        */
-    #define BTF_KIND_ENUM           6       /* Enumeration  */
+    #define BTF_KIND_ENUM           6       /* Enumeration up to 32-bit values */
     #define BTF_KIND_FWD            7       /* Forward      */
     #define BTF_KIND_TYPEDEF        8       /* Typedef      */
     #define BTF_KIND_VOLATILE       9       /* Volatile     */
@@ -87,6 +87,7 @@ sequentially and type id is assigned to each recognized type starting from id
     #define BTF_KIND_FLOAT          16      /* Floating point       */
     #define BTF_KIND_DECL_TAG       17      /* Decl Tag     */
     #define BTF_KIND_TYPE_TAG       18      /* Type Tag     */
+    #define BTF_KIND_ENUM64         19      /* Enumeration up to 64-bit values */
 
 Note that the type section encodes debug info, not just pure types.
 ``BTF_KIND_FUNC`` is not a type, and it represents a defined subprogram.
@@ -101,10 +102,10 @@ Each type contains the following common data::
          * bits 24-28: kind (e.g. int, ptr, array...etc)
          * bits 29-30: unused
          * bit     31: kind_flag, currently used by
-         *             struct, union and fwd
+         *             struct, union, fwd, enum and enum64.
          */
         __u32 info;
-        /* "size" is used by INT, ENUM, STRUCT and UNION.
+        /* "size" is used by INT, ENUM, STRUCT, UNION and ENUM64.
          * "size" tells the size of the type it is describing.
          *
          * "type" is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT,
@@ -281,10 +282,10 @@ modes exist:
 
 ``struct btf_type`` encoding requirement:
   * ``name_off``: 0 or offset to a valid C identifier
-  * ``info.kind_flag``: 0
+  * ``info.kind_flag``: 0 for unsigned, 1 for signed
   * ``info.kind``: BTF_KIND_ENUM
   * ``info.vlen``: number of enum values
-  * ``size``: 4
+  * ``size``: 1/2/4/8
 
 ``btf_type`` is followed by ``info.vlen`` number of ``struct btf_enum``.::
 
@@ -297,6 +298,10 @@ The ``btf_enum`` encoding:
   * ``name_off``: offset to a valid C identifier
   * ``val``: any value
 
+If the original enum value is signed and the size is less than 4,
+that value will be sign extended into 4 bytes. If the size is 8,
+the value will be truncated into 4 bytes.
+
 2.2.7 BTF_KIND_FWD
 ~~~~~~~~~~~~~~~~~~
 
@@ -493,7 +498,7 @@ the attribute is applied to a ``struct``/``union`` member or
 a ``func`` argument, and ``btf_decl_tag.component_idx`` should be a
 valid index (starting from 0) pointing to a member or an argument.
 
-2.2.17 BTF_KIND_TYPE_TAG
+2.2.18 BTF_KIND_TYPE_TAG
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
 ``struct btf_type`` encoding requirement:
@@ -516,6 +521,32 @@ type_tag, then zero or more const/volatile/restrict/typedef
 and finally the base type. The base type is one of
 int, ptr, array, struct, union, enum, func_proto and float types.
 
+2.2.19 BTF_KIND_ENUM64
+~~~~~~~~~~~~~~~~~~~~~~
+
+``struct btf_type`` encoding requirement:
+  * ``name_off``: 0 or offset to a valid C identifier
+  * ``info.kind_flag``: 0 for unsigned, 1 for signed
+  * ``info.kind``: BTF_KIND_ENUM64
+  * ``info.vlen``: number of enum values
+  * ``size``: 1/2/4/8
+
+``btf_type`` is followed by ``info.vlen`` number of ``struct btf_enum64``.::
+
+    struct btf_enum64 {
+        __u32   name_off;
+        __u32   val_lo32;
+        __u32   val_hi32;
+    };
+
+The ``btf_enum64`` encoding:
+  * ``name_off``: offset to a valid C identifier
+  * ``val_lo32``: lower 32-bit value for a 64-bit value
+  * ``val_hi32``: high 32-bit value for a 64-bit value
+
+If the original enum value is signed and the size is less than 8,
+that value will be sign extended into 8 bytes.
+
 3. BTF Kernel API
 =================
 

include/linux/btf.h

@@ -177,6 +177,19 @@ static inline bool btf_type_is_enum(const struct btf_type *t)
 	return BTF_INFO_KIND(t->info) == BTF_KIND_ENUM;
 }
 
+static inline bool btf_is_any_enum(const struct btf_type *t)
+{
+	return BTF_INFO_KIND(t->info) == BTF_KIND_ENUM ||
+	       BTF_INFO_KIND(t->info) == BTF_KIND_ENUM64;
+}
+
+static inline bool btf_kind_core_compat(const struct btf_type *t1,
+					const struct btf_type *t2)
+{
+	return BTF_INFO_KIND(t1->info) == BTF_INFO_KIND(t2->info) ||
+	       (btf_is_any_enum(t1) && btf_is_any_enum(t2));
+}
+
 static inline bool str_is_empty(const char *s)
 {
 	return !s || !s[0];
@@ -192,6 +205,16 @@ static inline bool btf_is_enum(const struct btf_type *t)
 	return btf_kind(t) == BTF_KIND_ENUM;
 }
 
+static inline bool btf_is_enum64(const struct btf_type *t)
+{
+	return btf_kind(t) == BTF_KIND_ENUM64;
+}
+
+static inline u64 btf_enum64_value(const struct btf_enum64 *e)
+{
+	return ((u64)e->val_hi32 << 32) | e->val_lo32;
+}
+
 static inline bool btf_is_composite(const struct btf_type *t)
 {
 	u16 kind = btf_kind(t);
@@ -332,6 +355,11 @@ static inline struct btf_enum *btf_enum(const struct btf_type *t)
 	return (struct btf_enum *)(t + 1);
 }
 
+static inline struct btf_enum64 *btf_enum64(const struct btf_type *t)
+{
+	return (struct btf_enum64 *)(t + 1);
+}
+
 static inline const struct btf_var_secinfo *btf_type_var_secinfo(
 		const struct btf_type *t)
 {

include/uapi/linux/btf.h

@@ -36,10 +36,10 @@ struct btf_type {
 	 * bits 24-28: kind (e.g. int, ptr, array...etc)
 	 * bits 29-30: unused
 	 * bit     31: kind_flag, currently used by
-	 *             struct, union and fwd
+	 *             struct, union, enum, fwd and enum64
 	 */
 	__u32 info;
-	/* "size" is used by INT, ENUM, STRUCT, UNION and DATASEC.
+	/* "size" is used by INT, ENUM, STRUCT, UNION, DATASEC and ENUM64.
 	 * "size" tells the size of the type it is describing.
 	 *
 	 * "type" is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT,
@@ -63,7 +63,7 @@ enum {
 	BTF_KIND_ARRAY		= 3,	/* Array	*/
 	BTF_KIND_STRUCT		= 4,	/* Struct	*/
 	BTF_KIND_UNION		= 5,	/* Union	*/
-	BTF_KIND_ENUM		= 6,	/* Enumeration	*/
+	BTF_KIND_ENUM		= 6,	/* Enumeration up to 32-bit values */
 	BTF_KIND_FWD		= 7,	/* Forward	*/
 	BTF_KIND_TYPEDEF	= 8,	/* Typedef	*/
 	BTF_KIND_VOLATILE	= 9,	/* Volatile	*/
@@ -76,6 +76,7 @@ enum {
 	BTF_KIND_FLOAT		= 16,	/* Floating point	*/
 	BTF_KIND_DECL_TAG	= 17,	/* Decl Tag */
 	BTF_KIND_TYPE_TAG	= 18,	/* Type Tag */
+	BTF_KIND_ENUM64		= 19,	/* Enumeration up to 64-bit values */
 
 	NR_BTF_KINDS,
 	BTF_KIND_MAX		= NR_BTF_KINDS - 1,
@@ -186,4 +187,14 @@ struct btf_decl_tag {
        __s32   component_idx;
 };
 
+/* BTF_KIND_ENUM64 is followed by multiple "struct btf_enum64".
+ * The exact number of btf_enum64 is stored in the vlen (of the
+ * info in "struct btf_type").
+ */
+struct btf_enum64 {
+	__u32	name_off;
+	__u32	val_lo32;
+	__u32	val_hi32;
+};
+
 #endif /* _UAPI__LINUX_BTF_H__ */