/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
#ifndef __BPF_CORE_READ_H__
#define __BPF_CORE_READ_H__
/*
* enum bpf_field_info_kind is passed as a second argument into
* __builtin_preserve_field_info() built-in to get a specific aspect of
* a field, captured as a first argument. __builtin_preserve_field_info(field,
* info_kind) returns __u32 integer and produces BTF field relocation, which
* is understood and processed by libbpf during BPF object loading. See
* selftests/bpf for examples.
*/
enum bpf_field_info_kind {
BPF_FIELD_BYTE_OFFSET = 0, /* field byte offset */
BPF_FIELD_BYTE_SIZE = 1,
BPF_FIELD_EXISTS = 2, /* field existence in target kernel */
BPF_FIELD_SIGNED = 3,
BPF_FIELD_LSHIFT_U64 = 4,
BPF_FIELD_RSHIFT_U64 = 5,
};
/* second argument to __builtin_btf_type_id() built-in */
enum bpf_type_id_kind {
BPF_TYPE_ID_LOCAL = 0, /* BTF type ID in local program */
BPF_TYPE_ID_TARGET = 1, /* BTF type ID in target kernel */
};
/* second argument to __builtin_preserve_type_info() built-in */
enum bpf_type_info_kind {
BPF_TYPE_EXISTS = 0, /* type existence in target kernel */
BPF_TYPE_SIZE = 1, /* type size in target kernel */
BPF_TYPE_MATCHES = 2, /* type match in target kernel */
};
/* second argument to __builtin_preserve_enum_value() built-in */
enum bpf_enum_value_kind {
BPF_ENUMVAL_EXISTS = 0, /* enum value existence in kernel */
BPF_ENUMVAL_VALUE = 1, /* enum value value relocation */
};
#define __CORE_RELO(src, field, info) \
__builtin_preserve_field_info((src)->field, BPF_FIELD_##info)
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
#define __CORE_BITFIELD_PROBE_READ(dst, src, fld) \
bpf_probe_read_kernel( \
(void *)dst, \
__CORE_RELO(src, fld, BYTE_SIZE), \
(const void *)src + __CORE_RELO(src, fld, BYTE_OFFSET))
#else
/* semantics of LSHIFT_64 assumes loading values into low-ordered bytes, so
* for big-endian we need to adjust destination pointer accordingly, based on
* field byte size
*/
#define __CORE_BITFIELD_PROBE_READ(dst, src, fld) \
bpf_probe_read_kernel( \
(void *)dst + (8 - __CORE_RELO(src, fld, BYTE_SIZE)), \
__CORE_RELO(src, fld, BYTE_SIZE), \
(const void *)src + __CORE_RELO(src, fld, BYTE_OFFSET))
#endif
/*
* Extract bitfield, identified by s->field, and return its value as u64.
* All this is done in relocatable manner, so bitfield changes such as
* signedness, bit size, offset changes, this will be handled automatically.
* This version of macro is using bpf_probe_read_kernel() to read underlying
* integer storage. Macro functions as an expression and its return type is
* bpf_probe_read_kernel()'s return value: 0, on success, <0 on error.
*/
#define BPF_CORE_READ_BITFIELD_PROBED(s, field) ({ \
unsigned long long val = 0; \
\
__CORE_BITFIELD_PROBE_READ(&val, s, field); \
val <<= __CORE_RELO(s, field, LSHIFT_U64); \
if (__CORE_RELO(s, field, SIGNED)) \
val = ((long long)val) >> __CORE_RELO(s, field, RSHIFT_U64); \
else \
val = val >> __CORE_RELO(s, field, RSHIFT_U64); \
val; \
})
/*
* Extract bitfield, identified by s->field, and return its value as u64.
* This version of macro is using direct memory reads and should be used from
* BPF program types that support such functionality (e.g., typed raw
* tracepoints).
*/
#define BPF_CORE_READ_BITFIELD(s, field) ({ \
const void *p = (const void *)s + __CORE_RELO(s, field, BYTE_OFFSET); \
unsigned long long val; \
\
/* This is a so-called barrier_var() operation that makes specified \
* variable "a black box" for optimizing compiler. \
* It forces compiler to perform BYTE_OFFSET relocation on p and use \
* its calculated value in the switch below, instead of applying \
* the same relocation 4 times for each individual memory load. \
*/ \
asm volatile("" : "=r"(p) : "0"(p)); \
\
switch (__CORE_RELO(s, field, BYTE_SIZE)) { \
case 1: val = *(const unsigned char *)p; break; \
case 2: val = *(const unsigned short *)p; break; \
case 4: val = *(const unsigned int *)p; break; \
case 8: val = *(const unsigned long long *)p; break; \
} \
val <<= __CORE_RELO(s, field, LSHIFT_U64); \
if (__CORE_RELO(s, field, SIGNED)) \
val = ((long long)val) >> __CORE_RELO(s, field, RSHIFT_U64); \
else \
val = val >> __CORE_RELO(s, field, RSHIFT_U64); \
val; \
})
#define ___bpf_field_ref1(field) (field)
#define ___bpf_field_ref2(type, field) (((typeof(type) *)0)->field)
#define ___bpf_field_ref(args...) \
___bpf_apply(___bpf_field_ref, ___bpf_narg(args))(args)
/*
* Convenience macro to check that field actually exists in target kernel's.
* Returns:
* 1, if matching field is present in target kernel;
* 0, if no matching field found.
*
* Supports two forms:
* - field reference through variable access:
* bpf_core_field_exists(p->my_field);
* - field reference through type and field names:
* bpf_core_field_exists(struct my_type, my_field).
*/
#define bpf_core_field_exists(field...) \
__builtin_preserve_field_info(___bpf_field_ref(field), BPF_FIELD_EXISTS)
/*
* Convenience macro to get the byte size of a field. Works for integers,
* struct/unions, pointers, arrays, and enums.
*
* Supports two forms:
* - field reference through variable access:
* bpf_core_field_size(p->my_field);
* - field reference through type and field names:
* bpf_core_field_size(struct my_type, my_field).
*/
#define bpf_core_field_size(field...) \
__builtin_preserve_field_info(___bpf_field_ref(field), BPF_FIELD_BYTE_SIZE)
/*
* Convenience macro to get field's byte offset.
*
* Supports two forms:
* - field reference through variable access:
* bpf_core_field_offset(p->my_field);
* - field reference through type and field names:
* bpf_core_field_offset(struct my_type, my_field).
*/
#define bpf_core_field_offset(field...) \
__builtin_preserve_field_info(___bpf_field_ref(field), BPF_FIELD_BYTE_OFFSET)
/*
* Convenience macro to get BTF type ID of a specified type, using a local BTF
* information. Return 32-bit unsigned integer with type ID from program's own
* BTF. Always succeeds.
*/
#define bpf_core_type_id_local(type) \
__builtin_btf_type_id(*(typeof(type) *)0, BPF_TYPE_ID_LOCAL)
/*
* Convenience macro to get BTF type ID of a target kernel's type that matches
* specified local type.
* Returns:
* - valid 32-bit unsigned type ID in kernel BTF;
* - 0, if no matching type was found in a target kernel BTF.
*/
#define bpf_core_type_id_kernel(type) \
__builtin_btf_type_id(*(typeof(type) *)0, BPF_TYPE_ID_TARGET)
/*
* Convenience macro to check that provided named type
* (struct/union/enum/typedef) exists in a target kernel.
* Returns:
* 1, if such type is present in target kernel's BTF;
* 0, if no matching type is found.
*/
#define bpf_core_type_exists(type) \
__builtin_preserve_type_info(*(typeof(type) *)0, BPF_TYPE_EXISTS)
/*
* Convenience macro to check that provided named type
* (struct/union/enum/typedef) "matches" that in a target kernel.
* Returns:
* 1, if the type matches in the target kernel's BTF;
* 0, if the type does not match any in the target kernel
*/
#define bpf_core_type_matches(type) \
__builtin_preserve_type_info(*(typeof(type) *)0, BPF_TYPE_MATCHES)
/*
* Convenience macro to get the byte size of a provided named type
* (struct/union/enum/typedef) in a target kernel.
* Returns:
* >= 0 size (in bytes), if type is present in target kernel's BTF;
* 0, if no matching type is found.
*/
#define bpf_core_type_size(type) \
__builtin_preserve_type_info(*(typeof(type) *)0, BPF_TYPE_SIZE)
/*
* Convenience macro to check that provided enumerator value is defined in
* a target kernel.
* Returns:
* 1, if specified enum type and its enumerator value are present in target
* kernel's BTF;
* 0, if no matching enum and/or enum value within that enum is found.
*/
#define bpf_core_enum_value_exists(enum_type, enum_value) \
__builtin_preserve_enum_value(*(typeof(enum_type) *)enum_value, BPF_ENUMVAL_EXISTS)
/*
* Convenience macro to get the integer value of an enumerator value in
* a target kernel.
* Returns:
* 64-bit value, if specified enum type and its enumerator value are
* present in target kernel's BTF;
* 0, if no matching enum and/or enum value within that enum is found.
*/
#define bpf_core_enum_value(enum_type, enum_value) \
__builtin_preserve_enum_value(*(typeof(enum_type) *)enum_value, BPF_ENUMVAL_VALUE)
/*
* bpf_core_read() abstracts away bpf_probe_read_kernel() call and captures
* offset relocation for source address using __builtin_preserve_access_index()
* built-in, provided by Clang.
*
* __builtin_preserve_access_index() takes as an argument an expression of
* taking an address of a field within struct/union. It makes compiler emit
* a relocation, which records BTF type ID describing root struct/union and an
* accessor string which describes exact embedded field that was used to take
* an address. See detailed description of this relocation format and
* semantics in comments to struct bpf_field_reloc in libbpf_internal.h.
*
* This relocation allows libbpf to adjust BPF instruction to use correct
* actual field offset, based on target kernel BTF type that matches original
* (local) BTF, used to record relocation.
*/
#define bpf_core_read(dst, sz, src) \
bpf_probe_read_kernel(dst, sz, (const void *)__builtin_preserve_access_index(src))
/* NOTE: see comments for BPF_CORE_READ_USER() about the proper types use. */
#define bpf_core_read_user(dst, sz, src) \
bpf_probe_read_user(dst, sz, (const void *)__builtin_preserve_access_index(src))
/*
* bpf_core_read_str() is a thin wrapper around bpf_probe_read_str()
* additionally emitting BPF CO-RE field relocation for specified source
* argument.
*/
#define bpf_core_read_str(dst, sz, src) \
bpf_probe_read_kernel_str(dst, sz, (const void *)__builtin_preserve_access_index(src))
/* NOTE: see comments for BPF_CORE_READ_USER() about the proper types use. */
#define bpf_core_read_user_str(dst, sz, src) \
bpf_probe_read_user_str(dst, sz, (const void *)__builtin_preserve_access_index(src))
#define ___concat(a, b) a ## b
#define ___apply(fn, n) ___concat(fn, n)
#define ___nth(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, __11, N, ...) N
/*
* return number of provided arguments; used for switch-based variadic macro
* definitions (see ___last, ___arrow, etc below)
*/
#define ___narg(...) ___nth(_, ##__VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
/*
* return 0 if no arguments are passed, N - otherwise; used for
* recursively-defined macros to specify termination (0) case, and generic
* (N) case (e.g., ___read_ptrs, ___core_read)
*/
#define ___empty(...) ___nth(_, ##__VA_ARGS__, N, N, N, N, N, N, N, N, N, N, 0)
#define ___last1(x) x
#define ___last2(a, x) x
#define ___last3(a, b, x) x
#define ___last4(a, b, c, x) x
#define ___last5(a, b, c, d, x) x
#define ___last6(a, b, c, d, e, x) x
#define ___last7(a, b, c, d, e, f, x) x
#define ___last8(a, b, c, d, e, f, g, x) x
#define ___last9(a, b, c, d, e, f, g, h, x) x
#define ___last10(a, b, c, d, e, f, g, h, i, x) x
#define ___last(...) ___apply(___last, ___narg(__VA_ARGS__))(__VA_ARGS__)
#define ___nolast2(a, _) a
#define ___nolast3(a, b, _) a, b
#define ___nolast4(a, b, c, _) a, b, c
#define ___nolast5(a, b, c, d, _) a, b, c, d
#define ___nolast6(a, b, c, d, e, _) a, b, c, d, e
#define ___nolast7(a, b, c, d, e, f, _) a, b, c, d, e, f
#define ___nolast8(a, b, c, d, e, f, g, _) a, b, c, d, e, f, g
#define ___nolast9(a, b, c, d, e, f, g, h, _) a, b, c, d, e, f, g, h
#define ___nolast10(a, b, c, d, e, f, g, h, i, _) a, b, c, d, e, f, g, h, i
#define ___nolast(...) ___apply(___nolast, ___narg(__VA_ARGS__))(__VA_ARGS__)
#define ___arrow1(a) a
#define ___arrow2(a, b) a->b
#define ___arrow3(a, b, c) a->b->c
#define ___arrow4(a, b, c, d) a->b->c->d
#define ___arrow5(a, b, c, d, e) a->b->c->d->e
#define ___arrow6(a, b, c, d, e, f) a->b->c->d->e->f
#define ___arrow7(a, b, c, d, e, f, g) a->b->c->d->e->f->g
#define ___arrow8(a, b, c, d, e, f, g, h) a->b->c->d->e->f->g->h
#define ___arrow9(a, b, c, d, e, f, g, h, i) a->b->c->d->e->f->g->h->i
#define ___arrow10(a, b, c, d, e, f, g, h, i, j) a->b->c->d->e->f->g->h->i->j
#define ___arrow(...) ___apply(___arrow, ___narg(__VA_ARGS__))(__VA_ARGS__)
#define ___type(...) typeof(___arrow(__VA_ARGS__))
#define ___read(read_fn, dst, src_type, src, accessor) \
read_fn((void *)(dst), sizeof(*(dst)), &((src_type)(src))->accessor)
/* "recursively" read a sequence of inner pointers using local __t var */
#define ___rd_first(fn, src, a) ___read(fn, &__t, ___type(src), src, a);
#define ___rd_last(fn, ...) \
___read(fn, &__t, ___type(___nolast(__VA_ARGS__)), __t, ___last(__VA_ARGS__));
#define ___rd_p1(fn, ...) const void *__t; ___rd_first(fn, __VA_ARGS__)
#define ___rd_p2(fn, ...) ___rd_p1(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__)
#define ___rd_p3(fn, ...) ___rd_p2(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__)
#define ___rd_p4(fn, ...) ___rd_p3(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__)
#define ___rd_p5(fn, ...) ___rd_p4(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__)
#define ___rd_p6(fn, ...) ___rd_p5(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__)
#define ___rd_p7(fn, ...) ___rd_p6(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__)
#define ___rd_p8(fn, ...) ___rd_p7(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__)
#define ___rd_p9(fn, ...) ___rd_p8(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__)
#define ___read_ptrs(fn, src, ...) \
___apply(___rd_p, ___narg(__VA_ARGS__))(fn, src, __VA_ARGS__)
#define ___core_read0(fn, fn_ptr, dst, src, a) \
___read(fn, dst, ___type(src), src, a);
#define ___core_readN(fn, fn_ptr, dst, src, ...) \
___read_ptrs(fn_ptr, src, ___nolast(__VA_ARGS__)) \
___read(fn, dst, ___type(src, ___nolast(__VA_ARGS__)), __t, \
___last(__VA_ARGS__));
#define ___core_read(fn, fn_ptr, dst, src, a, ...) \
___apply(___core_read, ___empty(__VA_ARGS__))(fn, fn_ptr, dst, \
src, a, ##__VA_ARGS__)
/*
* BPF_CORE_READ_INTO() is a more performance-conscious variant of
* BPF_CORE_READ(), in which final field is read into user-provided storage.
* See BPF_CORE_READ() below for more details on general usage.
*/
#define BPF_CORE_READ_INTO(dst, src, a, ...) ({ \
___core_read(bpf_core_read, bpf_core_read, \
dst, (src), a, ##__VA_ARGS__) \
})
/*
* Variant of BPF_CORE_READ_INTO() for reading from user-space memory.
*
* NOTE: see comments for BPF_CORE_READ_USER() about the proper types use.
*/
#define BPF_CORE_READ_USER_INTO(dst, src, a, ...) ({ \
___core_read(bpf_core_read_user, bpf_core_read_user, \
dst, (src), a, ##__VA_ARGS__) \
})
/* Non-CO-RE variant of BPF_CORE_READ_INTO() */
#define BPF_PROBE_READ_INTO(dst, src, a, ...) ({ \
___core_read(bpf_probe_read_kernel, bpf_probe_read_kernel, \
dst, (src), a, ##__VA_ARGS__) \
})
/* Non-CO-RE variant of BPF_CORE_READ_USER_INTO().
*
* As no CO-RE relocations are emitted, source types can be arbitrary and are
* not restricted to kernel types only.
*/
#define BPF_PROBE_READ_USER_INTO(dst, src, a, ...) ({ \
___core_read(bpf_probe_read_user, bpf_probe_read_user, \
dst, (src), a, ##__VA_ARGS__) \
})
/*
* BPF_CORE_READ_STR_INTO() does same "pointer chasing" as
* BPF_CORE_READ() for intermediate pointers, but then executes (and returns
* corresponding error code) bpf_core_read_str() for final string read.
*/
#define BPF_CORE_READ_STR_INTO(dst, src, a, ...) ({ \
___core_read(bpf_core_read_str, bpf_core_read, \
dst, (src), a, ##__VA_ARGS__) \
})
/*
* Variant of BPF_CORE_READ_STR_INTO() for reading from user-space memory.
*
* NOTE: see comments for BPF_CORE_READ_USER() about the proper types use.
*/
#define BPF_CORE_READ_USER_STR_INTO(dst, src, a, ...) ({ \
___core_read(bpf_core_read_user_str, bpf_core_read_user, \
dst, (src), a, ##__VA_ARGS__) \
})
/* Non-CO-RE variant of BPF_CORE_READ_STR_INTO() */
#define BPF_PROBE_READ_STR_INTO(dst, src, a, ...) ({ \
___core_read(bpf_probe_read_kernel_str, bpf_probe_read_kernel, \
dst, (src), a, ##__VA_ARGS__) \
})
/*
* Non-CO-RE variant of BPF_CORE_READ_USER_STR_INTO().
*
* As no CO-RE relocations are emitted, source types can be arbitrary and are
* not restricted to kernel types only.
*/
#define BPF_PROBE_READ_USER_STR_INTO(dst, src, a, ...) ({ \
___core_read(bpf_probe_read_user_str, bpf_probe_read_user, \
dst, (src), a, ##__VA_ARGS__) \
})
/*
* BPF_CORE_READ() is used to simplify BPF CO-RE relocatable read, especially
* when there are few pointer chasing steps.
* E.g., what in non-BPF world (or in BPF w/ BCC) would be something like:
* int x = s->a.b.c->d.e->f->g;
* can be succinctly achieved using BPF_CORE_READ as:
* int x = BPF_CORE_READ(s, a.b.c, d.e, f, g);
*
* BPF_CORE_READ will decompose above statement into 4 bpf_core_read (BPF
* CO-RE relocatable bpf_probe_read_kernel() wrapper) calls, logically
* equivalent to:
* 1. const void *__t = s->a.b.c;
* 2. __t = __t->d.e;
* 3. __t = __t->f;
* 4. return __t->g;
*
* Equivalence is logical, because there is a heavy type casting/preservation
* involved, as well as all the reads are happening through
* bpf_probe_read_kernel() calls using __builtin_preserve_access_index() to
* emit CO-RE relocations.
*
* N.B. Only up to 9 "field accessors" are supported, which should be more
* than enough for any practical purpose.
*/
#define BPF_CORE_READ(src, a, ...) ({ \
___type((src), a, ##__VA_ARGS__) __r; \
BPF_CORE_READ_INTO(&__r, (src), a, ##__VA_ARGS__); \
__r; \
})
/*
* Variant of BPF_CORE_READ() for reading from user-space memory.
*
* NOTE: all the source types involved are still *kernel types* and need to
* exist in kernel (or kernel module) BTF, otherwise CO-RE relocation will
* fail. Custom user types are not relocatable with CO-RE.
* The typical situation in which BPF_CORE_READ_USER() might be used is to
* read kernel UAPI types from the user-space memory passed in as a syscall
* input argument.
*/
#define BPF_CORE_READ_USER(src, a, ...) ({ \
___type((src), a, ##__VA_ARGS__) __r; \
BPF_CORE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \
__r; \
})
/* Non-CO-RE variant of BPF_CORE_READ() */
#define BPF_PROBE_READ(src, a, ...) ({ \
___type((src), a, ##__VA_ARGS__) __r; \
BPF_PROBE_READ_INTO(&__r, (src), a, ##__VA_ARGS__); \
__r; \
})
/*
* Non-CO-RE variant of BPF_CORE_READ_USER().
*
* As no CO-RE relocations are emitted, source types can be arbitrary and are
* not restricted to kernel types only.
*/
#define BPF_PROBE_READ_USER(src, a, ...) ({ \
___type((src), a, ##__VA_ARGS__) __r; \
BPF_PROBE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \
__r; \
})
#endif