bianbu-linux-6.6/tools/bpf/bpftool/main.h
Quentin Monnet eb9d1acf63 bpftool: Add LLVM as default library for disassembling JIT-ed programs
To disassemble instructions for JIT-ed programs, bpftool has relied on
the libbfd library. This has been problematic in the past: libbfd's
interface is not meant to be stable and has changed several times. For
building bpftool, we have to detect how the libbfd version on the system
behaves, which is why we have to handle features disassembler-four-args
and disassembler-init-styled in the Makefile. When it comes to shipping
bpftool, this has also caused issues with several distribution
maintainers unwilling to support the feature (see for example Debian's
page for binutils-dev, which ships libbfd: "Note that building Debian
packages which depend on the shared libbfd is Not Allowed." [0]).

For these reasons, we add support for LLVM as an alternative to libbfd
for disassembling instructions of JIT-ed programs. Thanks to the
preparation work in the previous commits, it's easy to add the library
by passing the relevant compilation options in the Makefile, and by
adding the functions for setting up the LLVM disassembler in file
jit_disasm.c.

The LLVM disassembler requires the LLVM development package (usually
llvm-dev or llvm-devel).

The expectation is that the interface for this disassembler will be more
stable. There is a note in LLVM's Developer Policy [1] stating that the
stability for the C API is "best effort" and not guaranteed, but at
least there is some effort to keep compatibility when possible (which
hasn't really been the case for libbfd so far). Furthermore, the Debian
page for the related LLVM package does not caution against linking to
the lib, as binutils-dev page does.

Naturally, the display of disassembled instructions comes with a few
minor differences. Here is a sample output with libbfd (already
supported before this patch):

    # bpftool prog dump jited id 56
    bpf_prog_6deef7357e7b4530:
       0:   nopl   0x0(%rax,%rax,1)
       5:   xchg   %ax,%ax
       7:   push   %rbp
       8:   mov    %rsp,%rbp
       b:   push   %rbx
       c:   push   %r13
       e:   push   %r14
      10:   mov    %rdi,%rbx
      13:   movzwq 0xb4(%rbx),%r13
      1b:   xor    %r14d,%r14d
      1e:   or     $0x2,%r14d
      22:   mov    $0x1,%eax
      27:   cmp    $0x2,%r14
      2b:   jne    0x000000000000002f
      2d:   xor    %eax,%eax
      2f:   pop    %r14
      31:   pop    %r13
      33:   pop    %rbx
      34:   leave
      35:   ret

LLVM supports several variants that we could set when initialising the
disassembler, for example with:

    LLVMSetDisasmOptions(*ctx,
                         LLVMDisassembler_Option_AsmPrinterVariant);

but the default printer is used for now. Here is the output with LLVM:

    # bpftool prog dump jited id 56
    bpf_prog_6deef7357e7b4530:
       0:   nopl    (%rax,%rax)
       5:   nop
       7:   pushq   %rbp
       8:   movq    %rsp, %rbp
       b:   pushq   %rbx
       c:   pushq   %r13
       e:   pushq   %r14
      10:   movq    %rdi, %rbx
      13:   movzwq  180(%rbx), %r13
      1b:   xorl    %r14d, %r14d
      1e:   orl     $2, %r14d
      22:   movl    $1, %eax
      27:   cmpq    $2, %r14
      2b:   jne     0x2f
      2d:   xorl    %eax, %eax
      2f:   popq    %r14
      31:   popq    %r13
      33:   popq    %rbx
      34:   leave
      35:   retq

The LLVM disassembler comes as the default choice, with libbfd as a
fall-back.

Of course, we could replace libbfd entirely and avoid supporting two
different libraries. One reason for keeping libbfd is that, right now,
it works well, we have all we need in terms of features detection in the
Makefile, so it provides a fallback for disassembling JIT-ed programs if
libbfd is installed but LLVM is not. The other motivation is that libbfd
supports nfp instruction for Netronome's SmartNICs and can be used to
disassemble offloaded programs, something that LLVM cannot do. If
libbfd's interface breaks again in the future, we might reconsider
keeping support for it.

[0] https://packages.debian.org/buster/binutils-dev
[1] https://llvm.org/docs/DeveloperPolicy.html#c-api-changes

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Tested-by: Niklas Söderlund <niklas.soderlund@corigine.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221025150329.97371-7-quentin@isovalent.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2022-10-25 10:11:56 -07:00

276 lines
8.3 KiB
C

/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
/* Copyright (C) 2017-2018 Netronome Systems, Inc. */
#ifndef __BPF_TOOL_H
#define __BPF_TOOL_H
/* BFD and kernel.h both define GCC_VERSION, differently */
#undef GCC_VERSION
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <linux/bpf.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <bpf/hashmap.h>
#include <bpf/libbpf.h>
#include "json_writer.h"
/* Make sure we do not use kernel-only integer typedefs */
#pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64
static inline __u64 ptr_to_u64(const void *ptr)
{
return (__u64)(unsigned long)ptr;
}
static inline void *u64_to_ptr(__u64 ptr)
{
return (void *)(unsigned long)ptr;
}
#define NEXT_ARG() ({ argc--; argv++; if (argc < 0) usage(); })
#define NEXT_ARGP() ({ (*argc)--; (*argv)++; if (*argc < 0) usage(); })
#define BAD_ARG() ({ p_err("what is '%s'?", *argv); -1; })
#define GET_ARG() ({ argc--; *argv++; })
#define REQ_ARGS(cnt) \
({ \
int _cnt = (cnt); \
bool _res; \
\
if (argc < _cnt) { \
p_err("'%s' needs at least %d arguments, %d found", \
argv[-1], _cnt, argc); \
_res = false; \
} else { \
_res = true; \
} \
_res; \
})
#define ERR_MAX_LEN 1024
#define BPF_TAG_FMT "%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx"
#define HELP_SPEC_PROGRAM \
"PROG := { id PROG_ID | pinned FILE | tag PROG_TAG | name PROG_NAME }"
#define HELP_SPEC_OPTIONS \
"OPTIONS := { {-j|--json} [{-p|--pretty}] | {-d|--debug} | {-l|--legacy}"
#define HELP_SPEC_MAP \
"MAP := { id MAP_ID | pinned FILE | name MAP_NAME }"
#define HELP_SPEC_LINK \
"LINK := { id LINK_ID | pinned FILE }"
/* keep in sync with the definition in skeleton/pid_iter.bpf.c */
enum bpf_obj_type {
BPF_OBJ_UNKNOWN,
BPF_OBJ_PROG,
BPF_OBJ_MAP,
BPF_OBJ_LINK,
BPF_OBJ_BTF,
};
extern const char *bin_name;
extern json_writer_t *json_wtr;
extern bool json_output;
extern bool show_pinned;
extern bool show_pids;
extern bool block_mount;
extern bool verifier_logs;
extern bool relaxed_maps;
extern bool use_loader;
extern bool legacy_libbpf;
extern struct btf *base_btf;
extern struct hashmap *refs_table;
void __printf(1, 2) p_err(const char *fmt, ...);
void __printf(1, 2) p_info(const char *fmt, ...);
bool is_prefix(const char *pfx, const char *str);
int detect_common_prefix(const char *arg, ...);
void fprint_hex(FILE *f, void *arg, unsigned int n, const char *sep);
void usage(void) __noreturn;
void set_max_rlimit(void);
int mount_tracefs(const char *target);
struct obj_ref {
int pid;
char comm[16];
};
struct obj_refs {
int ref_cnt;
bool has_bpf_cookie;
struct obj_ref *refs;
__u64 bpf_cookie;
};
struct btf;
struct bpf_line_info;
int build_pinned_obj_table(struct hashmap *table,
enum bpf_obj_type type);
void delete_pinned_obj_table(struct hashmap *table);
__weak int build_obj_refs_table(struct hashmap **table,
enum bpf_obj_type type);
__weak void delete_obj_refs_table(struct hashmap *table);
__weak void emit_obj_refs_json(struct hashmap *table, __u32 id,
json_writer_t *json_wtr);
__weak void emit_obj_refs_plain(struct hashmap *table, __u32 id,
const char *prefix);
void print_dev_plain(__u32 ifindex, __u64 ns_dev, __u64 ns_inode);
void print_dev_json(__u32 ifindex, __u64 ns_dev, __u64 ns_inode);
struct cmd {
const char *cmd;
int (*func)(int argc, char **argv);
};
int cmd_select(const struct cmd *cmds, int argc, char **argv,
int (*help)(int argc, char **argv));
#define MAX_PROG_FULL_NAME 128
void get_prog_full_name(const struct bpf_prog_info *prog_info, int prog_fd,
char *name_buff, size_t buff_len);
int get_fd_type(int fd);
const char *get_fd_type_name(enum bpf_obj_type type);
char *get_fdinfo(int fd, const char *key);
int open_obj_pinned(const char *path, bool quiet);
int open_obj_pinned_any(const char *path, enum bpf_obj_type exp_type);
int mount_bpffs_for_pin(const char *name);
int do_pin_any(int argc, char **argv, int (*get_fd_by_id)(int *, char ***));
int do_pin_fd(int fd, const char *name);
/* commands available in bootstrap mode */
int do_gen(int argc, char **argv);
int do_btf(int argc, char **argv);
/* non-bootstrap only commands */
int do_prog(int argc, char **arg) __weak;
int do_map(int argc, char **arg) __weak;
int do_link(int argc, char **arg) __weak;
int do_event_pipe(int argc, char **argv) __weak;
int do_cgroup(int argc, char **arg) __weak;
int do_perf(int argc, char **arg) __weak;
int do_net(int argc, char **arg) __weak;
int do_tracelog(int argc, char **arg) __weak;
int do_feature(int argc, char **argv) __weak;
int do_struct_ops(int argc, char **argv) __weak;
int do_iter(int argc, char **argv) __weak;
int parse_u32_arg(int *argc, char ***argv, __u32 *val, const char *what);
int prog_parse_fd(int *argc, char ***argv);
int prog_parse_fds(int *argc, char ***argv, int **fds);
int map_parse_fd(int *argc, char ***argv);
int map_parse_fds(int *argc, char ***argv, int **fds);
int map_parse_fd_and_info(int *argc, char ***argv, void *info, __u32 *info_len);
struct bpf_prog_linfo;
#if defined(HAVE_LLVM_SUPPORT) || defined(HAVE_LIBBFD_SUPPORT)
int disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
const char *arch, const char *disassembler_options,
const struct btf *btf,
const struct bpf_prog_linfo *prog_linfo,
__u64 func_ksym, unsigned int func_idx,
bool linum);
int disasm_init(void);
#else
static inline
int disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
const char *arch, const char *disassembler_options,
const struct btf *btf,
const struct bpf_prog_linfo *prog_linfo,
__u64 func_ksym, unsigned int func_idx,
bool linum)
{
return 0;
}
static inline int disasm_init(void)
{
p_err("No JIT disassembly support");
return -1;
}
#endif
void print_data_json(uint8_t *data, size_t len);
void print_hex_data_json(uint8_t *data, size_t len);
unsigned int get_page_size(void);
unsigned int get_possible_cpus(void);
const char *
ifindex_to_bfd_params(__u32 ifindex, __u64 ns_dev, __u64 ns_ino,
const char **opt);
struct btf_dumper {
const struct btf *btf;
json_writer_t *jw;
bool is_plain_text;
bool prog_id_as_func_ptr;
};
/* btf_dumper_type - print data along with type information
* @d: an instance containing context for dumping types
* @type_id: index in btf->types array. this points to the type to be dumped
* @data: pointer the actual data, i.e. the values to be printed
*
* Returns zero on success and negative error code otherwise
*/
int btf_dumper_type(const struct btf_dumper *d, __u32 type_id,
const void *data);
void btf_dumper_type_only(const struct btf *btf, __u32 func_type_id,
char *func_only, int size);
void btf_dump_linfo_plain(const struct btf *btf,
const struct bpf_line_info *linfo,
const char *prefix, bool linum);
void btf_dump_linfo_json(const struct btf *btf,
const struct bpf_line_info *linfo, bool linum);
struct nlattr;
struct ifinfomsg;
struct tcmsg;
int do_xdp_dump(struct ifinfomsg *ifinfo, struct nlattr **tb);
int do_filter_dump(struct tcmsg *ifinfo, struct nlattr **tb, const char *kind,
const char *devname, int ifindex);
int print_all_levels(__maybe_unused enum libbpf_print_level level,
const char *format, va_list args);
size_t hash_fn_for_key_as_id(const void *key, void *ctx);
bool equal_fn_for_key_as_id(const void *k1, const void *k2, void *ctx);
/* bpf_attach_type_input_str - convert the provided attach type value into a
* textual representation that we accept for input purposes.
*
* This function is similar in nature to libbpf_bpf_attach_type_str, but
* recognizes some attach type names that have been used by the program in the
* past and which do not follow the string inference scheme that libbpf uses.
* These textual representations should only be used for user input.
*
* @t: The attach type
* Returns a pointer to a static string identifying the attach type. NULL is
* returned for unknown bpf_attach_type values.
*/
const char *bpf_attach_type_input_str(enum bpf_attach_type t);
static inline void *u32_as_hash_field(__u32 x)
{
return (void *)(uintptr_t)x;
}
static inline __u32 hash_field_as_u32(const void *x)
{
return (__u32)(uintptr_t)x;
}
static inline bool hashmap__empty(struct hashmap *map)
{
return map ? hashmap__size(map) == 0 : true;
}
#endif