1 /* GNU/Linux on ARM target support.
3 Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
4 Free Software Foundation, Inc.
6 This file is part of GDB.
8 This program is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3 of the License, or
11 (at your option) any later version.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with this program. If not, see <http://www.gnu.org/licenses/>. */
25 #include "floatformat.h"
30 #include "solib-svr4.h"
33 #include "trad-frame.h"
34 #include "tramp-frame.h"
37 #include "arm-linux-tdep.h"
38 #include "glibc-tdep.h"
40 #include "gdb_string.h"
42 extern int arm_apcs_32
;
44 /* Under ARM GNU/Linux the traditional way of performing a breakpoint
45 is to execute a particular software interrupt, rather than use a
46 particular undefined instruction to provoke a trap. Upon exection
47 of the software interrupt the kernel stops the inferior with a
48 SIGTRAP, and wakes the debugger. */
50 static const char arm_linux_arm_le_breakpoint
[] = { 0x01, 0x00, 0x9f, 0xef };
52 static const char arm_linux_arm_be_breakpoint
[] = { 0xef, 0x9f, 0x00, 0x01 };
54 /* However, the EABI syscall interface (new in Nov. 2005) does not look at
55 the operand of the swi if old-ABI compatibility is disabled. Therefore,
56 use an undefined instruction instead. This is supported as of kernel
57 version 2.5.70 (May 2003), so should be a safe assumption for EABI
60 static const char eabi_linux_arm_le_breakpoint
[] = { 0xf0, 0x01, 0xf0, 0xe7 };
62 static const char eabi_linux_arm_be_breakpoint
[] = { 0xe7, 0xf0, 0x01, 0xf0 };
64 /* All the kernels which support Thumb support using a specific undefined
65 instruction for the Thumb breakpoint. */
67 static const char arm_linux_thumb_be_breakpoint
[] = {0xde, 0x01};
69 static const char arm_linux_thumb_le_breakpoint
[] = {0x01, 0xde};
71 /* Description of the longjmp buffer. */
72 #define ARM_LINUX_JB_ELEMENT_SIZE INT_REGISTER_SIZE
73 #define ARM_LINUX_JB_PC 21
76 Dynamic Linking on ARM GNU/Linux
77 --------------------------------
79 Note: PLT = procedure linkage table
80 GOT = global offset table
82 As much as possible, ELF dynamic linking defers the resolution of
83 jump/call addresses until the last minute. The technique used is
84 inspired by the i386 ELF design, and is based on the following
87 1) The calling technique should not force a change in the assembly
88 code produced for apps; it MAY cause changes in the way assembly
89 code is produced for position independent code (i.e. shared
92 2) The technique must be such that all executable areas must not be
93 modified; and any modified areas must not be executed.
95 To do this, there are three steps involved in a typical jump:
99 3) using a pointer from the GOT
101 When the executable or library is first loaded, each GOT entry is
102 initialized to point to the code which implements dynamic name
103 resolution and code finding. This is normally a function in the
104 program interpreter (on ARM GNU/Linux this is usually
105 ld-linux.so.2, but it does not have to be). On the first
106 invocation, the function is located and the GOT entry is replaced
107 with the real function address. Subsequent calls go through steps
108 1, 2 and 3 and end up calling the real code.
115 This is typical ARM code using the 26 bit relative branch or branch
116 and link instructions. The target of the instruction
117 (function_call is usually the address of the function to be called.
118 In position independent code, the target of the instruction is
119 actually an entry in the PLT when calling functions in a shared
120 library. Note that this call is identical to a normal function
121 call, only the target differs.
125 The PLT is a synthetic area, created by the linker. It exists in
126 both executables and libraries. It is an array of stubs, one per
127 imported function call. It looks like this:
130 str lr, [sp, #-4]! @push the return address (lr)
131 ldr lr, [pc, #16] @load from 6 words ahead
132 add lr, pc, lr @form an address for GOT[0]
133 ldr pc, [lr, #8]! @jump to the contents of that addr
135 The return address (lr) is pushed on the stack and used for
136 calculations. The load on the second line loads the lr with
137 &GOT[3] - . - 20. The addition on the third leaves:
139 lr = (&GOT[3] - . - 20) + (. + 8)
143 On the fourth line, the pc and lr are both updated, so that:
149 NOTE: PLT[0] borrows an offset .word from PLT[1]. This is a little
150 "tight", but allows us to keep all the PLT entries the same size.
153 ldr ip, [pc, #4] @load offset from gotoff
154 add ip, pc, ip @add the offset to the pc
155 ldr pc, [ip] @jump to that address
156 gotoff: .word GOT[n+3] - .
158 The load on the first line, gets an offset from the fourth word of
159 the PLT entry. The add on the second line makes ip = &GOT[n+3],
160 which contains either a pointer to PLT[0] (the fixup trampoline) or
161 a pointer to the actual code.
165 The GOT contains helper pointers for both code (PLT) fixups and
166 data fixups. The first 3 entries of the GOT are special. The next
167 M entries (where M is the number of entries in the PLT) belong to
168 the PLT fixups. The next D (all remaining) entries belong to
169 various data fixups. The actual size of the GOT is 3 + M + D.
171 The GOT is also a synthetic area, created by the linker. It exists
172 in both executables and libraries. When the GOT is first
173 initialized , all the GOT entries relating to PLT fixups are
174 pointing to code back at PLT[0].
176 The special entries in the GOT are:
178 GOT[0] = linked list pointer used by the dynamic loader
179 GOT[1] = pointer to the reloc table for this module
180 GOT[2] = pointer to the fixup/resolver code
182 The first invocation of function call comes through and uses the
183 fixup/resolver code. On the entry to the fixup/resolver code:
187 stack[0] = return address (lr) of the function call
188 [r0, r1, r2, r3] are still the arguments to the function call
190 This is enough information for the fixup/resolver code to work
191 with. Before the fixup/resolver code returns, it actually calls
192 the requested function and repairs &GOT[n+3]. */
194 /* The constants below were determined by examining the following files
195 in the linux kernel sources:
197 arch/arm/kernel/signal.c
198 - see SWI_SYS_SIGRETURN and SWI_SYS_RT_SIGRETURN
199 include/asm-arm/unistd.h
200 - see __NR_sigreturn, __NR_rt_sigreturn, and __NR_SYSCALL_BASE */
202 #define ARM_LINUX_SIGRETURN_INSTR 0xef900077
203 #define ARM_LINUX_RT_SIGRETURN_INSTR 0xef9000ad
205 /* For ARM EABI, the syscall number is not in the SWI instruction
206 (instead it is loaded into r7). We recognize the pattern that
207 glibc uses... alternatively, we could arrange to do this by
208 function name, but they are not always exported. */
209 #define ARM_SET_R7_SIGRETURN 0xe3a07077
210 #define ARM_SET_R7_RT_SIGRETURN 0xe3a070ad
211 #define ARM_EABI_SYSCALL 0xef000000
214 arm_linux_sigtramp_cache (struct frame_info
*next_frame
,
215 struct trad_frame_cache
*this_cache
,
216 CORE_ADDR func
, int regs_offset
)
218 CORE_ADDR sp
= frame_unwind_register_unsigned (next_frame
, ARM_SP_REGNUM
);
219 CORE_ADDR base
= sp
+ regs_offset
;
222 for (i
= 0; i
< 16; i
++)
223 trad_frame_set_reg_addr (this_cache
, i
, base
+ i
* 4);
225 trad_frame_set_reg_addr (this_cache
, ARM_PS_REGNUM
, base
+ 16 * 4);
227 /* The VFP or iWMMXt registers may be saved on the stack, but there's
228 no reliable way to restore them (yet). */
230 /* Save a frame ID. */
231 trad_frame_set_id (this_cache
, frame_id_build (sp
, func
));
234 /* There are a couple of different possible stack layouts that
237 Before version 2.6.18, the kernel used completely independent
238 layouts for non-RT and RT signals. For non-RT signals the stack
239 began directly with a struct sigcontext. For RT signals the stack
240 began with two redundant pointers (to the siginfo and ucontext),
241 and then the siginfo and ucontext.
243 As of version 2.6.18, the non-RT signal frame layout starts with
244 a ucontext and the RT signal frame starts with a siginfo and then
245 a ucontext. Also, the ucontext now has a designated save area
246 for coprocessor registers.
248 For RT signals, it's easy to tell the difference: we look for
249 pinfo, the pointer to the siginfo. If it has the expected
250 value, we have an old layout. If it doesn't, we have the new
253 For non-RT signals, it's a bit harder. We need something in one
254 layout or the other with a recognizable offset and value. We can't
255 use the return trampoline, because ARM usually uses SA_RESTORER,
256 in which case the stack return trampoline is not filled in.
257 We can't use the saved stack pointer, because sigaltstack might
258 be in use. So for now we guess the new layout... */
260 /* There are three words (trap_no, error_code, oldmask) in
261 struct sigcontext before r0. */
262 #define ARM_SIGCONTEXT_R0 0xc
264 /* There are five words (uc_flags, uc_link, and three for uc_stack)
265 in the ucontext_t before the sigcontext. */
266 #define ARM_UCONTEXT_SIGCONTEXT 0x14
268 /* There are three elements in an rt_sigframe before the ucontext:
269 pinfo, puc, and info. The first two are pointers and the third
270 is a struct siginfo, with size 128 bytes. We could follow puc
271 to the ucontext, but it's simpler to skip the whole thing. */
272 #define ARM_OLD_RT_SIGFRAME_SIGINFO 0x8
273 #define ARM_OLD_RT_SIGFRAME_UCONTEXT 0x88
275 #define ARM_NEW_RT_SIGFRAME_UCONTEXT 0x80
277 #define ARM_NEW_SIGFRAME_MAGIC 0x5ac3c35a
280 arm_linux_sigreturn_init (const struct tramp_frame
*self
,
281 struct frame_info
*next_frame
,
282 struct trad_frame_cache
*this_cache
,
285 CORE_ADDR sp
= frame_unwind_register_unsigned (next_frame
, ARM_SP_REGNUM
);
286 ULONGEST uc_flags
= read_memory_unsigned_integer (sp
, 4);
288 if (uc_flags
== ARM_NEW_SIGFRAME_MAGIC
)
289 arm_linux_sigtramp_cache (next_frame
, this_cache
, func
,
290 ARM_UCONTEXT_SIGCONTEXT
291 + ARM_SIGCONTEXT_R0
);
293 arm_linux_sigtramp_cache (next_frame
, this_cache
, func
,
298 arm_linux_rt_sigreturn_init (const struct tramp_frame
*self
,
299 struct frame_info
*next_frame
,
300 struct trad_frame_cache
*this_cache
,
303 CORE_ADDR sp
= frame_unwind_register_unsigned (next_frame
, ARM_SP_REGNUM
);
304 ULONGEST pinfo
= read_memory_unsigned_integer (sp
, 4);
306 if (pinfo
== sp
+ ARM_OLD_RT_SIGFRAME_SIGINFO
)
307 arm_linux_sigtramp_cache (next_frame
, this_cache
, func
,
308 ARM_OLD_RT_SIGFRAME_UCONTEXT
309 + ARM_UCONTEXT_SIGCONTEXT
310 + ARM_SIGCONTEXT_R0
);
312 arm_linux_sigtramp_cache (next_frame
, this_cache
, func
,
313 ARM_NEW_RT_SIGFRAME_UCONTEXT
314 + ARM_UCONTEXT_SIGCONTEXT
315 + ARM_SIGCONTEXT_R0
);
318 static struct tramp_frame arm_linux_sigreturn_tramp_frame
= {
322 { ARM_LINUX_SIGRETURN_INSTR
, -1 },
323 { TRAMP_SENTINEL_INSN
}
325 arm_linux_sigreturn_init
328 static struct tramp_frame arm_linux_rt_sigreturn_tramp_frame
= {
332 { ARM_LINUX_RT_SIGRETURN_INSTR
, -1 },
333 { TRAMP_SENTINEL_INSN
}
335 arm_linux_rt_sigreturn_init
338 static struct tramp_frame arm_eabi_linux_sigreturn_tramp_frame
= {
342 { ARM_SET_R7_SIGRETURN
, -1 },
343 { ARM_EABI_SYSCALL
, -1 },
344 { TRAMP_SENTINEL_INSN
}
346 arm_linux_sigreturn_init
349 static struct tramp_frame arm_eabi_linux_rt_sigreturn_tramp_frame
= {
353 { ARM_SET_R7_RT_SIGRETURN
, -1 },
354 { ARM_EABI_SYSCALL
, -1 },
355 { TRAMP_SENTINEL_INSN
}
357 arm_linux_rt_sigreturn_init
360 /* Core file and register set support. */
362 #define ARM_LINUX_SIZEOF_GREGSET (18 * INT_REGISTER_SIZE)
365 arm_linux_supply_gregset (const struct regset
*regset
,
366 struct regcache
*regcache
,
367 int regnum
, const void *gregs_buf
, size_t len
)
369 const gdb_byte
*gregs
= gregs_buf
;
372 gdb_byte pc_buf
[INT_REGISTER_SIZE
];
374 for (regno
= ARM_A1_REGNUM
; regno
< ARM_PC_REGNUM
; regno
++)
375 if (regnum
== -1 || regnum
== regno
)
376 regcache_raw_supply (regcache
, regno
,
377 gregs
+ INT_REGISTER_SIZE
* regno
);
379 if (regnum
== ARM_PS_REGNUM
|| regnum
== -1)
382 regcache_raw_supply (regcache
, ARM_PS_REGNUM
,
383 gregs
+ INT_REGISTER_SIZE
* ARM_CPSR_REGNUM
);
385 regcache_raw_supply (regcache
, ARM_PS_REGNUM
,
386 gregs
+ INT_REGISTER_SIZE
* ARM_PC_REGNUM
);
389 if (regnum
== ARM_PC_REGNUM
|| regnum
== -1)
391 reg_pc
= extract_unsigned_integer (gregs
392 + INT_REGISTER_SIZE
* ARM_PC_REGNUM
,
394 reg_pc
= gdbarch_addr_bits_remove (current_gdbarch
, reg_pc
);
395 store_unsigned_integer (pc_buf
, INT_REGISTER_SIZE
, reg_pc
);
396 regcache_raw_supply (regcache
, ARM_PC_REGNUM
, pc_buf
);
401 arm_linux_collect_gregset (const struct regset
*regset
,
402 const struct regcache
*regcache
,
403 int regnum
, void *gregs_buf
, size_t len
)
405 gdb_byte
*gregs
= gregs_buf
;
408 for (regno
= ARM_A1_REGNUM
; regno
< ARM_PC_REGNUM
; regno
++)
409 if (regnum
== -1 || regnum
== regno
)
410 regcache_raw_collect (regcache
, regno
,
411 gregs
+ INT_REGISTER_SIZE
* regno
);
413 if (regnum
== ARM_PS_REGNUM
|| regnum
== -1)
416 regcache_raw_collect (regcache
, ARM_PS_REGNUM
,
417 gregs
+ INT_REGISTER_SIZE
* ARM_CPSR_REGNUM
);
419 regcache_raw_collect (regcache
, ARM_PS_REGNUM
,
420 gregs
+ INT_REGISTER_SIZE
* ARM_PC_REGNUM
);
423 if (regnum
== ARM_PC_REGNUM
|| regnum
== -1)
424 regcache_raw_collect (regcache
, ARM_PC_REGNUM
,
425 gregs
+ INT_REGISTER_SIZE
* ARM_PC_REGNUM
);
428 /* Support for register format used by the NWFPE FPA emulator. */
430 #define typeNone 0x00
431 #define typeSingle 0x01
432 #define typeDouble 0x02
433 #define typeExtended 0x03
436 supply_nwfpe_register (struct regcache
*regcache
, int regno
,
437 const gdb_byte
*regs
)
439 const gdb_byte
*reg_data
;
441 gdb_byte buf
[FP_REGISTER_SIZE
];
443 reg_data
= regs
+ (regno
- ARM_F0_REGNUM
) * FP_REGISTER_SIZE
;
444 reg_tag
= regs
[(regno
- ARM_F0_REGNUM
) + NWFPE_TAGS_OFFSET
];
445 memset (buf
, 0, FP_REGISTER_SIZE
);
450 memcpy (buf
, reg_data
, 4);
453 memcpy (buf
, reg_data
+ 4, 4);
454 memcpy (buf
+ 4, reg_data
, 4);
457 /* We want sign and exponent, then least significant bits,
458 then most significant. NWFPE does sign, most, least. */
459 memcpy (buf
, reg_data
, 4);
460 memcpy (buf
+ 4, reg_data
+ 8, 4);
461 memcpy (buf
+ 8, reg_data
+ 4, 4);
467 regcache_raw_supply (regcache
, regno
, buf
);
471 collect_nwfpe_register (const struct regcache
*regcache
, int regno
,
476 gdb_byte buf
[FP_REGISTER_SIZE
];
478 regcache_raw_collect (regcache
, regno
, buf
);
480 /* NOTE drow/2006-06-07: This code uses the tag already in the
481 register buffer. I've preserved that when moving the code
482 from the native file to the target file. But this doesn't
483 always make sense. */
485 reg_data
= regs
+ (regno
- ARM_F0_REGNUM
) * FP_REGISTER_SIZE
;
486 reg_tag
= regs
[(regno
- ARM_F0_REGNUM
) + NWFPE_TAGS_OFFSET
];
491 memcpy (reg_data
, buf
, 4);
494 memcpy (reg_data
, buf
+ 4, 4);
495 memcpy (reg_data
+ 4, buf
, 4);
498 memcpy (reg_data
, buf
, 4);
499 memcpy (reg_data
+ 4, buf
+ 8, 4);
500 memcpy (reg_data
+ 8, buf
+ 4, 4);
508 arm_linux_supply_nwfpe (const struct regset
*regset
,
509 struct regcache
*regcache
,
510 int regnum
, const void *regs_buf
, size_t len
)
512 const gdb_byte
*regs
= regs_buf
;
515 if (regnum
== ARM_FPS_REGNUM
|| regnum
== -1)
516 regcache_raw_supply (regcache
, ARM_FPS_REGNUM
,
517 regs
+ NWFPE_FPSR_OFFSET
);
519 for (regno
= ARM_F0_REGNUM
; regno
<= ARM_F7_REGNUM
; regno
++)
520 if (regnum
== -1 || regnum
== regno
)
521 supply_nwfpe_register (regcache
, regno
, regs
);
525 arm_linux_collect_nwfpe (const struct regset
*regset
,
526 const struct regcache
*regcache
,
527 int regnum
, void *regs_buf
, size_t len
)
529 gdb_byte
*regs
= regs_buf
;
532 for (regno
= ARM_F0_REGNUM
; regno
<= ARM_F7_REGNUM
; regno
++)
533 if (regnum
== -1 || regnum
== regno
)
534 collect_nwfpe_register (regcache
, regno
, regs
);
536 if (regnum
== ARM_FPS_REGNUM
|| regnum
== -1)
537 regcache_raw_collect (regcache
, ARM_FPS_REGNUM
,
538 regs
+ INT_REGISTER_SIZE
* ARM_FPS_REGNUM
);
541 /* Return the appropriate register set for the core section identified
542 by SECT_NAME and SECT_SIZE. */
544 static const struct regset
*
545 arm_linux_regset_from_core_section (struct gdbarch
*gdbarch
,
546 const char *sect_name
, size_t sect_size
)
548 struct gdbarch_tdep
*tdep
= gdbarch_tdep (gdbarch
);
550 if (strcmp (sect_name
, ".reg") == 0
551 && sect_size
== ARM_LINUX_SIZEOF_GREGSET
)
553 if (tdep
->gregset
== NULL
)
554 tdep
->gregset
= regset_alloc (gdbarch
, arm_linux_supply_gregset
,
555 arm_linux_collect_gregset
);
556 return tdep
->gregset
;
559 if (strcmp (sect_name
, ".reg2") == 0
560 && sect_size
== ARM_LINUX_SIZEOF_NWFPE
)
562 if (tdep
->fpregset
== NULL
)
563 tdep
->fpregset
= regset_alloc (gdbarch
, arm_linux_supply_nwfpe
,
564 arm_linux_collect_nwfpe
);
565 return tdep
->fpregset
;
572 arm_linux_init_abi (struct gdbarch_info info
,
573 struct gdbarch
*gdbarch
)
575 struct gdbarch_tdep
*tdep
= gdbarch_tdep (gdbarch
);
577 tdep
->lowest_pc
= 0x8000;
578 if (info
.byte_order
== BFD_ENDIAN_BIG
)
580 if (tdep
->arm_abi
== ARM_ABI_AAPCS
)
581 tdep
->arm_breakpoint
= eabi_linux_arm_be_breakpoint
;
583 tdep
->arm_breakpoint
= arm_linux_arm_be_breakpoint
;
584 tdep
->thumb_breakpoint
= arm_linux_thumb_be_breakpoint
;
588 if (tdep
->arm_abi
== ARM_ABI_AAPCS
)
589 tdep
->arm_breakpoint
= eabi_linux_arm_le_breakpoint
;
591 tdep
->arm_breakpoint
= arm_linux_arm_le_breakpoint
;
592 tdep
->thumb_breakpoint
= arm_linux_thumb_le_breakpoint
;
594 tdep
->arm_breakpoint_size
= sizeof (arm_linux_arm_le_breakpoint
);
595 tdep
->thumb_breakpoint_size
= sizeof (arm_linux_thumb_le_breakpoint
);
597 if (tdep
->fp_model
== ARM_FLOAT_AUTO
)
598 tdep
->fp_model
= ARM_FLOAT_FPA
;
600 tdep
->jb_pc
= ARM_LINUX_JB_PC
;
601 tdep
->jb_elt_size
= ARM_LINUX_JB_ELEMENT_SIZE
;
603 set_solib_svr4_fetch_link_map_offsets
604 (gdbarch
, svr4_ilp32_fetch_link_map_offsets
);
606 /* Single stepping. */
607 set_gdbarch_software_single_step (gdbarch
, arm_software_single_step
);
609 /* Shared library handling. */
610 set_gdbarch_skip_trampoline_code (gdbarch
, find_solib_trampoline_target
);
611 set_gdbarch_skip_solib_resolver (gdbarch
, glibc_skip_solib_resolver
);
613 /* Enable TLS support. */
614 set_gdbarch_fetch_tls_load_module_address (gdbarch
,
615 svr4_fetch_objfile_link_map
);
617 tramp_frame_prepend_unwinder (gdbarch
,
618 &arm_linux_sigreturn_tramp_frame
);
619 tramp_frame_prepend_unwinder (gdbarch
,
620 &arm_linux_rt_sigreturn_tramp_frame
);
621 tramp_frame_prepend_unwinder (gdbarch
,
622 &arm_eabi_linux_sigreturn_tramp_frame
);
623 tramp_frame_prepend_unwinder (gdbarch
,
624 &arm_eabi_linux_rt_sigreturn_tramp_frame
);
626 /* Core file support. */
627 set_gdbarch_regset_from_core_section (gdbarch
,
628 arm_linux_regset_from_core_section
);
632 _initialize_arm_linux_tdep (void)
634 gdbarch_register_osabi (bfd_arch_arm
, 0, GDB_OSABI_LINUX
,