1/* Emulation of eBPF helpers.
2   Copyright (C) 2020-2023 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/* BPF programs rely on the existence of several helper functions,
20   which are provided by the kernel.  This simulator provides an
21   implementation of the helpers, which can be customized by the
22   user.  */
23
24/* This must come before any other includes.  */
25#include "defs.h"
26
27#define WANT_CPU_BPFBF
28#define WANT_CPU bpfbf
29
30#include "sim-main.h"
31#include "cgen-mem.h"
32#include "cgen-ops.h"
33#include "cpu.h"
34
35#include "bpf-helpers.h"
36
37/* bpf_trace_printk is a printk-like facility for debugging.
38
39   In the kernel, it appends a line to the Linux's tracing debugging
40   interface.
41
42   In this simulator, it uses the simulator's tracing interface
43   instead.
44
45   The format tags recognized by this helper are:
46   %d, %i, %u, %x, %ld, %li, %lu, %lx, %lld, %lli, %llu, %llx,
47   %p, %s
48
49   A maximum of three tags are supported.
50
51   This helper returns the number of bytes written, or a negative
52   value in case of failure.  */
53
54int
55bpf_trace_printk (SIM_CPU *current_cpu)
56{
57  va_list ap;
58  SIM_DESC sd = CPU_STATE (current_cpu);
59
60  DI fmt_address;
61  uint32_t size, tags_processed;
62  size_t i, bytes_written = 0;
63
64  /* The first argument is the format string, which is passed as a
65     pointer in %r1.  */
66  fmt_address = GET_H_GPR (1);
67
68  /* The second argument is the length of the format string, as an
69     unsigned 32-bit number in %r2.  */
70  size = GET_H_GPR (2);
71
72  /* Read the format string from the memory pointed by %r2, printing
73     out the stuff as we go.  There is a maximum of three format tags
74     supported, which are read from %r3, %r4 and %r5 respectively.  */
75  for (i = 0, tags_processed = 0; i < size;)
76    {
77      UDI value;
78      QI c = GETMEMUQI (current_cpu, CPU_PC_GET (current_cpu),
79                        fmt_address + i);
80
81      switch (c)
82        {
83        case '%':
84          /* Check we are not exceeding the limit of three format
85             tags.  */
86          if (tags_processed > 2)
87            return -1; /* XXX look for kernel error code.  */
88
89          /* Depending on the kind of tag, extract the value from the
90             proper argument.  */
91          if (i++ >= size)
92            return -1; /* XXX look for kernel error code.  */
93
94          value = GET_H_GPR (3 + tags_processed);
95
96          switch ((GETMEMUQI (current_cpu, CPU_PC_GET (current_cpu),
97                             fmt_address + i)))
98            {
99            case 'd':
100              trace_printf (sd, current_cpu, "%d", (int) value);
101              break;
102            case 'i':
103              trace_printf (sd, current_cpu, "%i", (int) value);
104              break;
105            case 'u':
106              trace_printf (sd, current_cpu, "%u", (unsigned int) value);
107              break;
108            case 'x':
109              trace_printf (sd, current_cpu, "%x", (unsigned int) value);
110              break;
111            case 'l':
112              {
113                if (i++ >= size)
114                  return -1;
115                switch (GETMEMUQI (current_cpu, CPU_PC_GET (current_cpu),
116                             fmt_address + i))
117                  {
118                  case 'd':
119                    trace_printf (sd, current_cpu, "%ld", (long) value);
120                    break;
121                  case 'i':
122                    trace_printf (sd, current_cpu, "%li", (long) value);
123                    break;
124                  case 'u':
125                    trace_printf (sd, current_cpu, "%lu", (unsigned long) value);
126                    break;
127                  case 'x':
128                    trace_printf (sd, current_cpu, "%lx", (unsigned long) value);
129                    break;
130                  case 'l':
131                    {
132                      if (i++ >= size)
133                        return -1;
134                      switch (GETMEMUQI (current_cpu, CPU_PC_GET (current_cpu),
135                                fmt_address + i)) {
136                        case 'd':
137                          trace_printf (sd, current_cpu, "%lld", (long long) value);
138                          break;
139                        case 'i':
140                          trace_printf (sd, current_cpu, "%lli", (long long) value);
141                          break;
142                        case 'u':
143                          trace_printf (sd, current_cpu, "%llu", (unsigned long long) value);
144                          break;
145                        case 'x':
146                          trace_printf (sd, current_cpu, "%llx", (unsigned long long) value);
147                          break;
148                        default:
149                          assert (0);
150                          break;
151                      }
152                      break;
153                    }
154                  default:
155                    assert (0);
156                    break;
157                }
158                break;
159              }
160            default:
161              /* XXX completeme */
162              assert (0);
163              break;
164            }
165
166          tags_processed++;
167          i++;
168          break;
169        case '\0':
170          i = size;
171          break;
172        default:
173          trace_printf (sd, current_cpu, "%c", c);
174          bytes_written++;
175          i++;
176          break;
177        }
178    }
179
180  return bytes_written;
181}
182