1/* Main simulator entry points specific to the eBPF.
2   Copyright (C) 2020 Free Software Foundation, Inc.
3
4   This file is part of GDB, the GNU debugger.
5
6   This program is free software; you can redistribute it and/or modify
7   it under the terms of the GNU General Public License as published by
8   the Free Software Foundation; either version 3 of the License, or
9   (at your option) any later version.
10
11   This program is distributed in the hope that it will be useful,
12   but WITHOUT ANY WARRANTY; without even the implied warranty of
13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14   GNU General Public License for more details.
15
16   You should have received a copy of the GNU General Public License
17   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
18
19#include <stdlib.h>
20
21#include "sim-main.h"
22#include "sim-options.h"
23#include "libiberty.h"
24#include "bfd.h"
25
26/* Globals.  */
27
28/* String with the name of the section containing the BPF program to
29   run.  */
30static char *bpf_program_section = NULL;
31
32extern uint64_t skb_data_offset;
33
34
35/* Handle BPF-specific options.  */
36
37static SIM_RC bpf_option_handler (SIM_DESC, sim_cpu *, int, char *, int);
38
39typedef enum
40{
41 OPTION_BPF_SET_PROGRAM = OPTION_START,
42 OPTION_BPF_LIST_PROGRAMS,
43 OPTION_BPF_VERIFY_PROGRAM,
44 OPTION_BPF_SKB_DATA_OFFSET,
45} BPF_OPTION;
46
47static const OPTION bpf_options[] =
48{
49 { {"bpf-set-program", required_argument, NULL, OPTION_BPF_SET_PROGRAM},
50   '\0', "SECTION_NAME", "Set the entry point",
51   bpf_option_handler },
52 { {"bpf-list-programs", no_argument, NULL, OPTION_BPF_LIST_PROGRAMS},
53   '\0', "", "List loaded bpf programs",
54   bpf_option_handler },
55 { {"bpf-verify-program", required_argument, NULL, OPTION_BPF_VERIFY_PROGRAM},
56   '\0', "PROGRAM", "Run the verifier on the given BPF program",
57   bpf_option_handler },
58 { {"skb-data-offset", required_argument, NULL, OPTION_BPF_SKB_DATA_OFFSET},
59   '\0', "OFFSET", "Configure offsetof(struct sk_buff, data)",
60   bpf_option_handler },
61
62 { {NULL, no_argument, NULL, 0}, '\0', NULL, NULL, NULL, NULL }
63};
64
65static SIM_RC
66bpf_option_handler (SIM_DESC sd, sim_cpu *cpu ATTRIBUTE_UNUSED, int opt,
67                    char *arg, int is_command ATTRIBUTE_UNUSED)
68{
69  switch ((BPF_OPTION) opt)
70    {
71    case OPTION_BPF_VERIFY_PROGRAM:
72      /* XXX call the verifier. */
73      sim_io_printf (sd, "Verifying BPF program %s...\n", arg);
74      break;
75
76    case OPTION_BPF_LIST_PROGRAMS:
77      /* XXX list programs.  */
78      sim_io_printf (sd, "BPF programs available:\n");
79      break;
80
81    case OPTION_BPF_SET_PROGRAM:
82      /* XXX: check that the section exists and tell the user about a
83         new start_address.  */
84      bpf_program_section = xstrdup (arg);
85      break;
86
87    case OPTION_BPF_SKB_DATA_OFFSET:
88      skb_data_offset = strtoul (arg, NULL, 0);
89      break;
90
91    default:
92      sim_io_eprintf (sd, "Unknown option `%s'\n", arg);
93      return SIM_RC_FAIL;
94    }
95
96  return SIM_RC_OK;
97}
98
99/* Like sim_state_free, but free the cpu buffers as well.  */
100
101static void
102bpf_free_state (SIM_DESC sd)
103{
104  if (STATE_MODULES (sd) != NULL)
105    sim_module_uninstall (sd);
106
107  sim_cpu_free_all (sd);
108  sim_state_free (sd);
109}
110
111/* Create an instance of the simulator.  */
112
113SIM_DESC
114sim_open (SIM_OPEN_KIND kind,
115          host_callback *callback,
116          struct bfd *abfd,
117	  char * const *argv)
118{
119  /* XXX Analyze the program, and collect per-function information
120     like the kernel verifier does.  The implementation of the CALL
121     instruction will need that information, to update %fp.  */
122
123  SIM_DESC sd = sim_state_alloc (kind, callback);
124
125  if (sim_cpu_alloc_all (sd, 1, cgen_cpu_max_extra_bytes ())
126      != SIM_RC_OK)
127    goto error;
128
129  if (sim_pre_argv_init (sd, argv[0]) != SIM_RC_OK)
130    goto error;
131
132  /* Add the BPF-specific option list to the simulator.  */
133  if (sim_add_option_table (sd, NULL, bpf_options) != SIM_RC_OK)
134    {
135      bpf_free_state (sd);
136      return 0;
137    }
138
139  if (sim_parse_args (sd, argv) != SIM_RC_OK)
140    goto error;
141
142  if (sim_analyze_program (sd,
143                           (STATE_PROG_ARGV (sd) != NULL
144                            ? *STATE_PROG_ARGV (sd)
145                            : NULL), abfd) != SIM_RC_OK)
146    goto error;
147
148  if (sim_config (sd) != SIM_RC_OK)
149    goto error;
150
151  if (sim_post_argv_init (sd) != SIM_RC_OK)
152    goto error;
153
154  /* ... */
155
156  /* Initialize the CPU descriptors and the disassemble in the cpu
157     descriptor table entries.  */
158  {
159    int i;
160    CGEN_CPU_DESC cd = bpf_cgen_cpu_open_1 (STATE_ARCHITECTURE (sd)->printable_name,
161                                            CGEN_ENDIAN_LITTLE);
162
163    /* We have one cpu per installed program! MAX_NR_PROCESSORS is an
164       arbitrary upper limit.  XXX where is it defined?  */
165    for (i = 0; i < MAX_NR_PROCESSORS; ++i)
166      {
167        SIM_CPU *cpu = STATE_CPU (sd, i);
168
169        CPU_CPU_DESC (cpu) = cd;
170        CPU_DISASSEMBLER (cpu) = sim_cgen_disassemble_insn;
171      }
172
173    bpf_cgen_init_dis (cd);
174  }
175
176  /* Initialize various cgen things not done by common framework.
177     Must be done after bpf_cgen_cpu_open.  */
178  cgen_init (sd);
179
180  /* XXX do eBPF sim specific initializations.  */
181
182  return sd;
183
184 error:
185      bpf_free_state (sd);
186      return NULL;
187}
188
189
190SIM_RC
191sim_create_inferior (SIM_DESC sd, struct bfd *abfd,
192		     char *const *argv, char *const *envp)
193{
194  SIM_CPU *current_cpu = STATE_CPU (sd, 0);
195  SIM_ADDR addr;
196
197  /* Determine the start address.
198
199     XXX acknowledge bpf_program_section.  If it is NULL, emit a
200     warning explaining that we are using the ELF file start address,
201     which often is not what is actually wanted.  */
202  if (abfd != NULL)
203    addr = bfd_get_start_address (abfd);
204  else
205    addr = 0;
206
207  sim_pc_set (current_cpu, addr);
208
209  if (STATE_PROG_ARGV (sd) != argv)
210    {
211      freeargv (STATE_PROG_ARGV (sd));
212      STATE_PROG_ARGV (sd) = dupargv (argv);
213    }
214
215  return SIM_RC_OK;
216}
217