1/* Target-dependent code for GNU/Linux on Nios II.
2   Copyright (C) 2012-2020 Free Software Foundation, Inc.
3   Contributed by Mentor Graphics, Inc.
4
5   This file is part of GDB.
6
7   This program is free software; you can redistribute it and/or modify
8   it under the terms of the GNU General Public License as published by
9   the Free Software Foundation; either version 3 of the License, or
10   (at your option) any later version.
11
12   This program is distributed in the hope that it will be useful,
13   but WITHOUT ANY WARRANTY; without even the implied warranty of
14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15   GNU General Public License for more details.
16
17   You should have received a copy of the GNU General Public License
18   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
19
20#include "defs.h"
21#include "frame.h"
22#include "osabi.h"
23#include "solib-svr4.h"
24#include "trad-frame.h"
25#include "tramp-frame.h"
26#include "symtab.h"
27#include "regset.h"
28#include "regcache.h"
29#include "linux-tdep.h"
30#include "glibc-tdep.h"
31#include "nios2-tdep.h"
32#include "gdbarch.h"
33
34/* Core file and register set support.  */
35
36/* Map from the normal register enumeration order to the order that
37   registers appear in core files, which corresponds to the order
38   of the register slots in the kernel's struct pt_regs.  */
39
40static const int reg_offsets[NIOS2_NUM_REGS] =
41{
42  -1,  8,  9, 10, 11, 12, 13, 14,	/* r0 - r7 */
43  0,  1,  2,  3,  4,  5,  6,  7,	/* r8 - r15 */
44  23, 24, 25, 26, 27, 28, 29, 30,	/* r16 - r23 */
45  -1, -1, 19, 18, 17, 21, -1, 16,	/* et bt gp sp fp ea sstatus ra */
46  21,					/* pc */
47  -1, 20, -1, -1, -1, -1, -1, -1,	/* status estatus ...  */
48  -1, -1, -1, -1, -1, -1, -1, -1
49};
50
51/* General register set size.  Should match sizeof (struct pt_regs) +
52   sizeof (struct switch_stack) from the NIOS2 Linux kernel patch.  */
53
54#define NIOS2_GREGS_SIZE (4 * 34)
55
56/* Implement the supply_regset hook for core files.  */
57
58static void
59nios2_supply_gregset (const struct regset *regset,
60		      struct regcache *regcache,
61		      int regnum, const void *gregs_buf, size_t len)
62{
63  const gdb_byte *gregs = (const gdb_byte *) gregs_buf;
64  int regno;
65  static const gdb_byte zero_buf[4] = {0, 0, 0, 0};
66
67  for (regno = NIOS2_Z_REGNUM; regno <= NIOS2_MPUACC_REGNUM; regno++)
68    if (regnum == -1 || regnum == regno)
69      {
70	if (reg_offsets[regno] != -1)
71	  regcache->raw_supply (regno, gregs + 4 * reg_offsets[regno]);
72	else
73	  regcache->raw_supply (regno, zero_buf);
74      }
75}
76
77/* Implement the collect_regset hook for core files.  */
78
79static void
80nios2_collect_gregset (const struct regset *regset,
81		       const struct regcache *regcache,
82		       int regnum, void *gregs_buf, size_t len)
83{
84  gdb_byte *gregs = (gdb_byte *) gregs_buf;
85  int regno;
86
87  for (regno = NIOS2_Z_REGNUM; regno <= NIOS2_MPUACC_REGNUM; regno++)
88    if (regnum == -1 || regnum == regno)
89      {
90	if (reg_offsets[regno] != -1)
91	  regcache->raw_collect (regno, gregs + 4 * reg_offsets[regno]);
92      }
93}
94
95static const struct regset nios2_core_regset =
96{
97  NULL,
98  nios2_supply_gregset,
99  nios2_collect_gregset
100};
101
102/* Iterate over core file register note sections.  */
103
104static void
105nios2_iterate_over_regset_sections (struct gdbarch *gdbarch,
106				    iterate_over_regset_sections_cb *cb,
107				    void *cb_data,
108				    const struct regcache *regcache)
109{
110  cb (".reg", NIOS2_GREGS_SIZE, NIOS2_GREGS_SIZE, &nios2_core_regset, NULL,
111      cb_data);
112}
113
114/* Initialize a trad-frame cache corresponding to the tramp-frame.
115   FUNC is the address of the instruction TRAMP[0] in memory.
116
117   This ABI is not documented.  It corresponds to rt_setup_ucontext in
118   the kernel arch/nios2/kernel/signal.c file.
119
120   The key points are:
121   - The kernel creates a trampoline at the hard-wired address 0x1044.
122   - The stack pointer points to an object of type struct rt_sigframe.
123     The definition of this structure is not exported from the kernel.
124     The register save area is located at offset 152 bytes (as determined
125     by inspection of the stack contents in the debugger), and the
126     registers are saved as r1-r23, ra, fp, gp, ea, sp.
127
128   This interface was implemented with kernel version 3.19 (the first
129   official mainline kernel).  Older unofficial kernel versions used
130   incompatible conventions; we do not support those here.  */
131
132#define NIOS2_SIGRETURN_TRAMP_ADDR 0x1044
133#define NIOS2_SIGRETURN_REGSAVE_OFFSET 152
134
135static void
136nios2_linux_rt_sigreturn_init (const struct tramp_frame *self,
137			       struct frame_info *next_frame,
138			       struct trad_frame_cache *this_cache,
139			       CORE_ADDR func)
140{
141  CORE_ADDR sp = get_frame_register_unsigned (next_frame, NIOS2_SP_REGNUM);
142  CORE_ADDR base = sp + NIOS2_SIGRETURN_REGSAVE_OFFSET;
143  int i;
144
145  for (i = 0; i < 23; i++)
146    trad_frame_set_reg_addr (this_cache, i + 1, base + i * 4);
147  trad_frame_set_reg_addr (this_cache, NIOS2_RA_REGNUM, base + 23 * 4);
148  trad_frame_set_reg_addr (this_cache, NIOS2_FP_REGNUM, base + 24 * 4);
149  trad_frame_set_reg_addr (this_cache, NIOS2_GP_REGNUM, base + 25 * 4);
150  trad_frame_set_reg_addr (this_cache, NIOS2_PC_REGNUM, base + 27 * 4);
151  trad_frame_set_reg_addr (this_cache, NIOS2_SP_REGNUM, base + 28 * 4);
152
153  /* Save a frame ID.  */
154  trad_frame_set_id (this_cache, frame_id_build (base, func));
155}
156
157/* Trampoline for sigreturn.  This has the form
158     movi r2, __NR_rt_sigreturn
159     trap 0
160   appropriately encoded for R1 or R2.  */
161
162static struct tramp_frame nios2_r1_linux_rt_sigreturn_tramp_frame =
163{
164  SIGTRAMP_FRAME,
165  4,
166  {
167    { MATCH_R1_MOVI | SET_IW_I_B (2) | SET_IW_I_IMM16 (139), ULONGEST_MAX },
168    { MATCH_R1_TRAP | SET_IW_R_IMM5 (0), ULONGEST_MAX},
169    { TRAMP_SENTINEL_INSN }
170  },
171  nios2_linux_rt_sigreturn_init
172};
173
174static struct tramp_frame nios2_r2_linux_rt_sigreturn_tramp_frame =
175{
176  SIGTRAMP_FRAME,
177  4,
178  {
179    { MATCH_R2_MOVI | SET_IW_F2I16_B (2) | SET_IW_F2I16_IMM16 (139), ULONGEST_MAX },
180    { MATCH_R2_TRAP | SET_IW_X2L5_IMM5 (0), ULONGEST_MAX},
181    { TRAMP_SENTINEL_INSN }
182  },
183  nios2_linux_rt_sigreturn_init
184};
185
186/* When FRAME is at a syscall instruction, return the PC of the next
187   instruction to be executed.  */
188
189static CORE_ADDR
190nios2_linux_syscall_next_pc (struct frame_info *frame,
191			     const struct nios2_opcode *op)
192{
193  CORE_ADDR pc = get_frame_pc (frame);
194  ULONGEST syscall_nr = get_frame_register_unsigned (frame, NIOS2_R2_REGNUM);
195
196  /* If we are about to make a sigreturn syscall, use the unwinder to
197     decode the signal frame.  */
198  if (syscall_nr == 139 /* rt_sigreturn */)
199    return frame_unwind_caller_pc (frame);
200
201  return pc + op->size;
202}
203
204/* Return true if PC is a kernel helper, a function mapped by the kernel
205   into user space on an unwritable page.  Currently the only such function
206   is __kuser_cmpxchg at 0x1004.  See arch/nios2/kernel/entry.S in the Linux
207   kernel sources and sysdeps/unix/sysv/linux/nios2/atomic-machine.h in
208   GLIBC.  */
209static bool
210nios2_linux_is_kernel_helper (CORE_ADDR pc)
211{
212  return pc == 0x1004;
213}
214
215/* Hook function for gdbarch_register_osabi.  */
216
217static void
218nios2_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
219{
220  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
221
222  linux_init_abi (info, gdbarch);
223
224  /* Shared library handling.  */
225  set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target);
226  set_gdbarch_skip_solib_resolver (gdbarch, glibc_skip_solib_resolver);
227
228  set_solib_svr4_fetch_link_map_offsets (gdbarch,
229					 svr4_ilp32_fetch_link_map_offsets);
230  /* Enable TLS support.  */
231  set_gdbarch_fetch_tls_load_module_address (gdbarch,
232                                             svr4_fetch_objfile_link_map);
233  /* Core file support.  */
234  set_gdbarch_iterate_over_regset_sections
235    (gdbarch, nios2_iterate_over_regset_sections);
236  /* Linux signal frame unwinders.  */
237  if (gdbarch_bfd_arch_info (gdbarch)->mach == bfd_mach_nios2r2)
238    tramp_frame_prepend_unwinder (gdbarch,
239				  &nios2_r2_linux_rt_sigreturn_tramp_frame);
240  else
241    tramp_frame_prepend_unwinder (gdbarch,
242				  &nios2_r1_linux_rt_sigreturn_tramp_frame);
243
244  tdep->syscall_next_pc = nios2_linux_syscall_next_pc;
245  tdep->is_kernel_helper = nios2_linux_is_kernel_helper;
246
247  /* Index of target address word in glibc jmp_buf.  */
248  tdep->jb_pc = 10;
249}
250
251void _initialize_nios2_linux_tdep ();
252void
253_initialize_nios2_linux_tdep ()
254{
255
256  const struct bfd_arch_info *arch_info;
257
258  for (arch_info = bfd_lookup_arch (bfd_arch_nios2, 0);
259       arch_info != NULL;
260       arch_info = arch_info->next)
261    gdbarch_register_osabi (bfd_arch_nios2, arch_info->mach,
262			    GDB_OSABI_LINUX, nios2_linux_init_abi);
263}
264