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편집 파일: usdt.bpf.h

/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ /* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */ #ifndef __USDT_BPF_H__ #define __USDT_BPF_H__ #include <linux/errno.h> #include "bpf_helpers.h" #include "bpf_tracing.h" /* Below types and maps are internal implementation details of libbpf's USDT * support and are subjects to change. Also, bpf_usdt_xxx() API helpers should * be considered an unstable API as well and might be adjusted based on user * feedback from using libbpf's USDT support in production. */ /* User can override BPF_USDT_MAX_SPEC_CNT to change default size of internal * map that keeps track of USDT argument specifications. This might be * necessary if there are a lot of USDT attachments. */ #ifndef BPF_USDT_MAX_SPEC_CNT #define BPF_USDT_MAX_SPEC_CNT 256 #endif /* User can override BPF_USDT_MAX_IP_CNT to change default size of internal * map that keeps track of IP (memory address) mapping to USDT argument * specification. * Note, if kernel supports BPF cookies, this map is not used and could be * resized all the way to 1 to save a bit of memory. */ #ifndef BPF_USDT_MAX_IP_CNT #define BPF_USDT_MAX_IP_CNT (4 * BPF_USDT_MAX_SPEC_CNT) #endif enum __bpf_usdt_arg_type { BPF_USDT_ARG_CONST, BPF_USDT_ARG_REG, BPF_USDT_ARG_REG_DEREF, }; struct __bpf_usdt_arg_spec { /* u64 scalar interpreted depending on arg_type, see below */ __u64 val_off; /* arg location case, see bpf_usdt_arg() for details */ enum __bpf_usdt_arg_type arg_type; /* offset of referenced register within struct pt_regs */ short reg_off; /* whether arg should be interpreted as signed value */ bool arg_signed; /* number of bits that need to be cleared and, optionally, * sign-extended to cast arguments that are 1, 2, or 4 bytes * long into final 8-byte u64/s64 value returned to user */ char arg_bitshift; }; /* should match USDT_MAX_ARG_CNT in usdt.c exactly */ #define BPF_USDT_MAX_ARG_CNT 12 struct __bpf_usdt_spec { struct __bpf_usdt_arg_spec args[BPF_USDT_MAX_ARG_CNT]; __u64 usdt_cookie; short arg_cnt; }; struct { __uint(type, BPF_MAP_TYPE_ARRAY); __uint(max_entries, BPF_USDT_MAX_SPEC_CNT); __type(key, int); __type(value, struct __bpf_usdt_spec); } __bpf_usdt_specs SEC(".maps") __weak; struct { __uint(type, BPF_MAP_TYPE_HASH); __uint(max_entries, BPF_USDT_MAX_IP_CNT); __type(key, long); __type(value, __u32); } __bpf_usdt_ip_to_spec_id SEC(".maps") __weak; extern const _Bool LINUX_HAS_BPF_COOKIE __kconfig; static __always_inline int __bpf_usdt_spec_id(struct pt_regs *ctx) { if (!LINUX_HAS_BPF_COOKIE) { long ip = PT_REGS_IP(ctx); int *spec_id_ptr; spec_id_ptr = bpf_map_lookup_elem(&__bpf_usdt_ip_to_spec_id, &ip); return spec_id_ptr ? *spec_id_ptr : -ESRCH; } return bpf_get_attach_cookie(ctx); } /* Return number of USDT arguments defined for currently traced USDT. */ __weak __hidden int bpf_usdt_arg_cnt(struct pt_regs *ctx) { struct __bpf_usdt_spec *spec; int spec_id; spec_id = __bpf_usdt_spec_id(ctx); if (spec_id < 0) return -ESRCH; spec = bpf_map_lookup_elem(&__bpf_usdt_specs, &spec_id); if (!spec) return -ESRCH; return spec->arg_cnt; } /* Fetch USDT argument #*arg_num* (zero-indexed) and put its value into *res. * Returns 0 on success; negative error, otherwise. * On error *res is guaranteed to be set to zero. */ __weak __hidden int bpf_usdt_arg(struct pt_regs *ctx, __u64 arg_num, long *res) { struct __bpf_usdt_spec *spec; struct __bpf_usdt_arg_spec *arg_spec; unsigned long val; int err, spec_id; *res = 0; spec_id = __bpf_usdt_spec_id(ctx); if (spec_id < 0) return -ESRCH; spec = bpf_map_lookup_elem(&__bpf_usdt_specs, &spec_id); if (!spec) return -ESRCH; if (arg_num >= BPF_USDT_MAX_ARG_CNT) return -ENOENT; barrier_var(arg_num); if (arg_num >= spec->arg_cnt) return -ENOENT; arg_spec = &spec->args[arg_num]; switch (arg_spec->arg_type) { case BPF_USDT_ARG_CONST: /* Arg is just a constant ("-4@$-9" in USDT arg spec). * value is recorded in arg_spec->val_off directly. */ val = arg_spec->val_off; break; case BPF_USDT_ARG_REG: /* Arg is in a register (e.g, "8@%rax" in USDT arg spec), * so we read the contents of that register directly from * struct pt_regs. To keep things simple user-space parts * record offsetof(struct pt_regs, <regname>) in arg_spec->reg_off. */ err = bpf_probe_read_kernel(&val, sizeof(val), (void *)ctx + arg_spec->reg_off); if (err) return err; break; case BPF_USDT_ARG_REG_DEREF: /* Arg is in memory addressed by register, plus some offset * (e.g., "-4@-1204(%rbp)" in USDT arg spec). Register is * identified like with BPF_USDT_ARG_REG case, and the offset * is in arg_spec->val_off. We first fetch register contents * from pt_regs, then do another user-space probe read to * fetch argument value itself. */ err = bpf_probe_read_kernel(&val, sizeof(val), (void *)ctx + arg_spec->reg_off); if (err) return err; err = bpf_probe_read_user(&val, sizeof(val), (void *)val + arg_spec->val_off); if (err) return err; #if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ val >>= arg_spec->arg_bitshift; #endif break; default: return -EINVAL; } /* cast arg from 1, 2, or 4 bytes to final 8 byte size clearing * necessary upper arg_bitshift bits, with sign extension if argument * is signed */ val <<= arg_spec->arg_bitshift; if (arg_spec->arg_signed) val = ((long)val) >> arg_spec->arg_bitshift; else val = val >> arg_spec->arg_bitshift; *res = val; return 0; } /* Retrieve user-specified cookie value provided during attach as * bpf_usdt_opts.usdt_cookie. This serves the same purpose as BPF cookie * returned by bpf_get_attach_cookie(). Libbpf's support for USDT is itself * utilizing BPF cookies internally, so user can't use BPF cookie directly * for USDT programs and has to use bpf_usdt_cookie() API instead. */ __weak __hidden long bpf_usdt_cookie(struct pt_regs *ctx) { struct __bpf_usdt_spec *spec; int spec_id; spec_id = __bpf_usdt_spec_id(ctx); if (spec_id < 0) return 0; spec = bpf_map_lookup_elem(&__bpf_usdt_specs, &spec_id); if (!spec) return 0; return spec->usdt_cookie; } /* we rely on ___bpf_apply() and ___bpf_narg() macros already defined in bpf_tracing.h */ #define ___bpf_usdt_args0() ctx #define ___bpf_usdt_args1(x) ___bpf_usdt_args0(), ({ long _x; bpf_usdt_arg(ctx, 0, &_x); _x; }) #define ___bpf_usdt_args2(x, args...) ___bpf_usdt_args1(args), ({ long _x; bpf_usdt_arg(ctx, 1, &_x); _x; }) #define ___bpf_usdt_args3(x, args...) ___bpf_usdt_args2(args), ({ long _x; bpf_usdt_arg(ctx, 2, &_x); _x; }) #define ___bpf_usdt_args4(x, args...) ___bpf_usdt_args3(args), ({ long _x; bpf_usdt_arg(ctx, 3, &_x); _x; }) #define ___bpf_usdt_args5(x, args...) ___bpf_usdt_args4(args), ({ long _x; bpf_usdt_arg(ctx, 4, &_x); _x; }) #define ___bpf_usdt_args6(x, args...) ___bpf_usdt_args5(args), ({ long _x; bpf_usdt_arg(ctx, 5, &_x); _x; }) #define ___bpf_usdt_args7(x, args...) ___bpf_usdt_args6(args), ({ long _x; bpf_usdt_arg(ctx, 6, &_x); _x; }) #define ___bpf_usdt_args8(x, args...) ___bpf_usdt_args7(args), ({ long _x; bpf_usdt_arg(ctx, 7, &_x); _x; }) #define ___bpf_usdt_args9(x, args...) ___bpf_usdt_args8(args), ({ long _x; bpf_usdt_arg(ctx, 8, &_x); _x; }) #define ___bpf_usdt_args10(x, args...) ___bpf_usdt_args9(args), ({ long _x; bpf_usdt_arg(ctx, 9, &_x); _x; }) #define ___bpf_usdt_args11(x, args...) ___bpf_usdt_args10(args), ({ long _x; bpf_usdt_arg(ctx, 10, &_x); _x; }) #define ___bpf_usdt_args12(x, args...) ___bpf_usdt_args11(args), ({ long _x; bpf_usdt_arg(ctx, 11, &_x); _x; }) #define ___bpf_usdt_args(args...) ___bpf_apply(___bpf_usdt_args, ___bpf_narg(args))(args) /* * BPF_USDT serves the same purpose for USDT handlers as BPF_PROG for * tp_btf/fentry/fexit BPF programs and BPF_KPROBE for kprobes. * Original struct pt_regs * context is preserved as 'ctx' argument. */ #define BPF_USDT(name, args...) \ name(struct pt_regs *ctx); \ static __always_inline typeof(name(0)) \ ____##name(struct pt_regs *ctx, ##args); \ typeof(name(0)) name(struct pt_regs *ctx) \ { \ _Pragma("GCC diagnostic push") \ _Pragma("GCC diagnostic ignored \"-Wint-conversion\"") \ return ____##name(___bpf_usdt_args(args)); \ _Pragma("GCC diagnostic pop") \ } \ static __always_inline typeof(name(0)) \ ____##name(struct pt_regs *ctx, ##args) #endif /* __USDT_BPF_H__ */