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c877c8e6 | 1 | /* Target-dependent code for GDB, the GNU debugger. |
4e052eda | 2 | |
ca557f44 AC |
3 | Copyright 1986, 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, |
4 | 1997, 2000, 2001, 2002 Free Software Foundation, Inc. | |
c877c8e6 KB |
5 | |
6 | This file is part of GDB. | |
7 | ||
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 2 of the License, or | |
11 | (at your option) any later version. | |
12 | ||
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. | |
17 | ||
18 | You should have received a copy of the GNU General Public License | |
19 | along with this program; if not, write to the Free Software | |
20 | Foundation, Inc., 59 Temple Place - Suite 330, | |
21 | Boston, MA 02111-1307, USA. */ | |
22 | ||
23 | #include "defs.h" | |
24 | #include "frame.h" | |
25 | #include "inferior.h" | |
26 | #include "symtab.h" | |
27 | #include "target.h" | |
28 | #include "gdbcore.h" | |
29 | #include "gdbcmd.h" | |
30 | #include "symfile.h" | |
31 | #include "objfiles.h" | |
4e052eda | 32 | #include "regcache.h" |
fd0407d6 | 33 | #include "value.h" |
c877c8e6 | 34 | |
6ded7999 | 35 | #include "solib-svr4.h" |
9aa1e687 KB |
36 | #include "ppc-tdep.h" |
37 | ||
c877c8e6 | 38 | /* The following two instructions are used in the signal trampoline |
ca557f44 | 39 | code on GNU/Linux PPC. */ |
c877c8e6 KB |
40 | #define INSTR_LI_R0_0x7777 0x38007777 |
41 | #define INSTR_SC 0x44000002 | |
42 | ||
43 | /* Since the *-tdep.c files are platform independent (i.e, they may be | |
44 | used to build cross platform debuggers), we can't include system | |
45 | headers. Therefore, details concerning the sigcontext structure | |
46 | must be painstakingly rerecorded. What's worse, if these details | |
47 | ever change in the header files, they'll have to be changed here | |
48 | as well. */ | |
49 | ||
50 | /* __SIGNAL_FRAMESIZE from <asm/ptrace.h> */ | |
51 | #define PPC_LINUX_SIGNAL_FRAMESIZE 64 | |
52 | ||
53 | /* From <asm/sigcontext.h>, offsetof(struct sigcontext_struct, regs) == 0x1c */ | |
54 | #define PPC_LINUX_REGS_PTR_OFFSET (PPC_LINUX_SIGNAL_FRAMESIZE + 0x1c) | |
55 | ||
56 | /* From <asm/sigcontext.h>, | |
57 | offsetof(struct sigcontext_struct, handler) == 0x14 */ | |
58 | #define PPC_LINUX_HANDLER_PTR_OFFSET (PPC_LINUX_SIGNAL_FRAMESIZE + 0x14) | |
59 | ||
60 | /* From <asm/ptrace.h>, values for PT_NIP, PT_R1, and PT_LNK */ | |
61 | #define PPC_LINUX_PT_R0 0 | |
62 | #define PPC_LINUX_PT_R1 1 | |
63 | #define PPC_LINUX_PT_R2 2 | |
64 | #define PPC_LINUX_PT_R3 3 | |
65 | #define PPC_LINUX_PT_R4 4 | |
66 | #define PPC_LINUX_PT_R5 5 | |
67 | #define PPC_LINUX_PT_R6 6 | |
68 | #define PPC_LINUX_PT_R7 7 | |
69 | #define PPC_LINUX_PT_R8 8 | |
70 | #define PPC_LINUX_PT_R9 9 | |
71 | #define PPC_LINUX_PT_R10 10 | |
72 | #define PPC_LINUX_PT_R11 11 | |
73 | #define PPC_LINUX_PT_R12 12 | |
74 | #define PPC_LINUX_PT_R13 13 | |
75 | #define PPC_LINUX_PT_R14 14 | |
76 | #define PPC_LINUX_PT_R15 15 | |
77 | #define PPC_LINUX_PT_R16 16 | |
78 | #define PPC_LINUX_PT_R17 17 | |
79 | #define PPC_LINUX_PT_R18 18 | |
80 | #define PPC_LINUX_PT_R19 19 | |
81 | #define PPC_LINUX_PT_R20 20 | |
82 | #define PPC_LINUX_PT_R21 21 | |
83 | #define PPC_LINUX_PT_R22 22 | |
84 | #define PPC_LINUX_PT_R23 23 | |
85 | #define PPC_LINUX_PT_R24 24 | |
86 | #define PPC_LINUX_PT_R25 25 | |
87 | #define PPC_LINUX_PT_R26 26 | |
88 | #define PPC_LINUX_PT_R27 27 | |
89 | #define PPC_LINUX_PT_R28 28 | |
90 | #define PPC_LINUX_PT_R29 29 | |
91 | #define PPC_LINUX_PT_R30 30 | |
92 | #define PPC_LINUX_PT_R31 31 | |
93 | #define PPC_LINUX_PT_NIP 32 | |
94 | #define PPC_LINUX_PT_MSR 33 | |
95 | #define PPC_LINUX_PT_CTR 35 | |
96 | #define PPC_LINUX_PT_LNK 36 | |
97 | #define PPC_LINUX_PT_XER 37 | |
98 | #define PPC_LINUX_PT_CCR 38 | |
99 | #define PPC_LINUX_PT_MQ 39 | |
100 | #define PPC_LINUX_PT_FPR0 48 /* each FP reg occupies 2 slots in this space */ | |
101 | #define PPC_LINUX_PT_FPR31 (PPC_LINUX_PT_FPR0 + 2*31) | |
102 | #define PPC_LINUX_PT_FPSCR (PPC_LINUX_PT_FPR0 + 2*32 + 1) | |
103 | ||
9aa1e687 | 104 | static int ppc_linux_at_sigtramp_return_path (CORE_ADDR pc); |
50c9bd31 | 105 | |
c877c8e6 KB |
106 | /* Determine if pc is in a signal trampoline... |
107 | ||
ca557f44 | 108 | Ha! That's not what this does at all. wait_for_inferior in |
d7bd68ca AC |
109 | infrun.c calls PC_IN_SIGTRAMP in order to detect entry into a |
110 | signal trampoline just after delivery of a signal. But on | |
111 | GNU/Linux, signal trampolines are used for the return path only. | |
112 | The kernel sets things up so that the signal handler is called | |
113 | directly. | |
c877c8e6 KB |
114 | |
115 | If we use in_sigtramp2() in place of in_sigtramp() (see below) | |
116 | we'll (often) end up with stop_pc in the trampoline and prev_pc in | |
117 | the (now exited) handler. The code there will cause a temporary | |
118 | breakpoint to be set on prev_pc which is not very likely to get hit | |
119 | again. | |
120 | ||
121 | If this is confusing, think of it this way... the code in | |
122 | wait_for_inferior() needs to be able to detect entry into a signal | |
123 | trampoline just after a signal is delivered, not after the handler | |
124 | has been run. | |
125 | ||
126 | So, we define in_sigtramp() below to return 1 if the following is | |
127 | true: | |
128 | ||
129 | 1) The previous frame is a real signal trampoline. | |
130 | ||
131 | - and - | |
132 | ||
133 | 2) pc is at the first or second instruction of the corresponding | |
134 | handler. | |
135 | ||
136 | Why the second instruction? It seems that wait_for_inferior() | |
137 | never sees the first instruction when single stepping. When a | |
138 | signal is delivered while stepping, the next instruction that | |
139 | would've been stepped over isn't, instead a signal is delivered and | |
140 | the first instruction of the handler is stepped over instead. That | |
141 | puts us on the second instruction. (I added the test for the | |
142 | first instruction long after the fact, just in case the observed | |
143 | behavior is ever fixed.) | |
144 | ||
d7bd68ca | 145 | PC_IN_SIGTRAMP is called from blockframe.c as well in order to set |
c877c8e6 | 146 | the signal_handler_caller flag. Because of our strange definition |
d7bd68ca AC |
147 | of in_sigtramp below, we can't rely on signal_handler_caller |
148 | getting set correctly from within blockframe.c. This is why we | |
149 | take pains to set it in init_extra_frame_info(). */ | |
c877c8e6 KB |
150 | |
151 | int | |
152 | ppc_linux_in_sigtramp (CORE_ADDR pc, char *func_name) | |
153 | { | |
154 | CORE_ADDR lr; | |
155 | CORE_ADDR sp; | |
156 | CORE_ADDR tramp_sp; | |
157 | char buf[4]; | |
158 | CORE_ADDR handler; | |
159 | ||
2188cbdd | 160 | lr = read_register (gdbarch_tdep (current_gdbarch)->ppc_lr_regnum); |
c877c8e6 KB |
161 | if (!ppc_linux_at_sigtramp_return_path (lr)) |
162 | return 0; | |
163 | ||
164 | sp = read_register (SP_REGNUM); | |
165 | ||
166 | if (target_read_memory (sp, buf, sizeof (buf)) != 0) | |
167 | return 0; | |
168 | ||
169 | tramp_sp = extract_unsigned_integer (buf, 4); | |
170 | ||
171 | if (target_read_memory (tramp_sp + PPC_LINUX_HANDLER_PTR_OFFSET, buf, | |
172 | sizeof (buf)) != 0) | |
173 | return 0; | |
174 | ||
175 | handler = extract_unsigned_integer (buf, 4); | |
176 | ||
177 | return (pc == handler || pc == handler + 4); | |
178 | } | |
179 | ||
180 | /* | |
181 | * The signal handler trampoline is on the stack and consists of exactly | |
182 | * two instructions. The easiest and most accurate way of determining | |
183 | * whether the pc is in one of these trampolines is by inspecting the | |
184 | * instructions. It'd be faster though if we could find a way to do this | |
185 | * via some simple address comparisons. | |
186 | */ | |
9aa1e687 | 187 | static int |
c877c8e6 KB |
188 | ppc_linux_at_sigtramp_return_path (CORE_ADDR pc) |
189 | { | |
190 | char buf[12]; | |
191 | unsigned long pcinsn; | |
192 | if (target_read_memory (pc - 4, buf, sizeof (buf)) != 0) | |
193 | return 0; | |
194 | ||
195 | /* extract the instruction at the pc */ | |
196 | pcinsn = extract_unsigned_integer (buf + 4, 4); | |
197 | ||
198 | return ( | |
199 | (pcinsn == INSTR_LI_R0_0x7777 | |
200 | && extract_unsigned_integer (buf + 8, 4) == INSTR_SC) | |
201 | || | |
202 | (pcinsn == INSTR_SC | |
203 | && extract_unsigned_integer (buf, 4) == INSTR_LI_R0_0x7777)); | |
204 | } | |
205 | ||
206 | CORE_ADDR | |
207 | ppc_linux_skip_trampoline_code (CORE_ADDR pc) | |
208 | { | |
209 | char buf[4]; | |
210 | struct obj_section *sect; | |
211 | struct objfile *objfile; | |
212 | unsigned long insn; | |
213 | CORE_ADDR plt_start = 0; | |
214 | CORE_ADDR symtab = 0; | |
215 | CORE_ADDR strtab = 0; | |
216 | int num_slots = -1; | |
217 | int reloc_index = -1; | |
218 | CORE_ADDR plt_table; | |
219 | CORE_ADDR reloc; | |
220 | CORE_ADDR sym; | |
221 | long symidx; | |
222 | char symname[1024]; | |
223 | struct minimal_symbol *msymbol; | |
224 | ||
225 | /* Find the section pc is in; return if not in .plt */ | |
226 | sect = find_pc_section (pc); | |
227 | if (!sect || strcmp (sect->the_bfd_section->name, ".plt") != 0) | |
228 | return 0; | |
229 | ||
230 | objfile = sect->objfile; | |
231 | ||
232 | /* Pick up the instruction at pc. It had better be of the | |
233 | form | |
234 | li r11, IDX | |
235 | ||
236 | where IDX is an index into the plt_table. */ | |
237 | ||
238 | if (target_read_memory (pc, buf, 4) != 0) | |
239 | return 0; | |
240 | insn = extract_unsigned_integer (buf, 4); | |
241 | ||
242 | if ((insn & 0xffff0000) != 0x39600000 /* li r11, VAL */ ) | |
243 | return 0; | |
244 | ||
245 | reloc_index = (insn << 16) >> 16; | |
246 | ||
247 | /* Find the objfile that pc is in and obtain the information | |
248 | necessary for finding the symbol name. */ | |
249 | for (sect = objfile->sections; sect < objfile->sections_end; ++sect) | |
250 | { | |
251 | const char *secname = sect->the_bfd_section->name; | |
252 | if (strcmp (secname, ".plt") == 0) | |
253 | plt_start = sect->addr; | |
254 | else if (strcmp (secname, ".rela.plt") == 0) | |
255 | num_slots = ((int) sect->endaddr - (int) sect->addr) / 12; | |
256 | else if (strcmp (secname, ".dynsym") == 0) | |
257 | symtab = sect->addr; | |
258 | else if (strcmp (secname, ".dynstr") == 0) | |
259 | strtab = sect->addr; | |
260 | } | |
261 | ||
262 | /* Make sure we have all the information we need. */ | |
263 | if (plt_start == 0 || num_slots == -1 || symtab == 0 || strtab == 0) | |
264 | return 0; | |
265 | ||
266 | /* Compute the value of the plt table */ | |
267 | plt_table = plt_start + 72 + 8 * num_slots; | |
268 | ||
269 | /* Get address of the relocation entry (Elf32_Rela) */ | |
270 | if (target_read_memory (plt_table + reloc_index, buf, 4) != 0) | |
271 | return 0; | |
272 | reloc = extract_address (buf, 4); | |
273 | ||
274 | sect = find_pc_section (reloc); | |
275 | if (!sect) | |
276 | return 0; | |
277 | ||
278 | if (strcmp (sect->the_bfd_section->name, ".text") == 0) | |
279 | return reloc; | |
280 | ||
281 | /* Now get the r_info field which is the relocation type and symbol | |
282 | index. */ | |
283 | if (target_read_memory (reloc + 4, buf, 4) != 0) | |
284 | return 0; | |
285 | symidx = extract_unsigned_integer (buf, 4); | |
286 | ||
287 | /* Shift out the relocation type leaving just the symbol index */ | |
288 | /* symidx = ELF32_R_SYM(symidx); */ | |
289 | symidx = symidx >> 8; | |
290 | ||
291 | /* compute the address of the symbol */ | |
292 | sym = symtab + symidx * 4; | |
293 | ||
294 | /* Fetch the string table index */ | |
295 | if (target_read_memory (sym, buf, 4) != 0) | |
296 | return 0; | |
297 | symidx = extract_unsigned_integer (buf, 4); | |
298 | ||
299 | /* Fetch the string; we don't know how long it is. Is it possible | |
300 | that the following will fail because we're trying to fetch too | |
301 | much? */ | |
302 | if (target_read_memory (strtab + symidx, symname, sizeof (symname)) != 0) | |
303 | return 0; | |
304 | ||
305 | /* This might not work right if we have multiple symbols with the | |
306 | same name; the only way to really get it right is to perform | |
307 | the same sort of lookup as the dynamic linker. */ | |
308 | msymbol = lookup_minimal_symbol_text (symname, NULL, NULL); | |
309 | if (!msymbol) | |
310 | return 0; | |
311 | ||
312 | return SYMBOL_VALUE_ADDRESS (msymbol); | |
313 | } | |
314 | ||
315 | /* The rs6000 version of FRAME_SAVED_PC will almost work for us. The | |
316 | signal handler details are different, so we'll handle those here | |
317 | and call the rs6000 version to do the rest. */ | |
9aa1e687 | 318 | CORE_ADDR |
c877c8e6 KB |
319 | ppc_linux_frame_saved_pc (struct frame_info *fi) |
320 | { | |
321 | if (fi->signal_handler_caller) | |
322 | { | |
323 | CORE_ADDR regs_addr = | |
50c9bd31 | 324 | read_memory_integer (fi->frame + PPC_LINUX_REGS_PTR_OFFSET, 4); |
c877c8e6 KB |
325 | /* return the NIP in the regs array */ |
326 | return read_memory_integer (regs_addr + 4 * PPC_LINUX_PT_NIP, 4); | |
327 | } | |
50c9bd31 KB |
328 | else if (fi->next && fi->next->signal_handler_caller) |
329 | { | |
330 | CORE_ADDR regs_addr = | |
331 | read_memory_integer (fi->next->frame + PPC_LINUX_REGS_PTR_OFFSET, 4); | |
332 | /* return LNK in the regs array */ | |
333 | return read_memory_integer (regs_addr + 4 * PPC_LINUX_PT_LNK, 4); | |
334 | } | |
335 | else | |
336 | return rs6000_frame_saved_pc (fi); | |
c877c8e6 KB |
337 | } |
338 | ||
339 | void | |
340 | ppc_linux_init_extra_frame_info (int fromleaf, struct frame_info *fi) | |
341 | { | |
342 | rs6000_init_extra_frame_info (fromleaf, fi); | |
343 | ||
344 | if (fi->next != 0) | |
345 | { | |
346 | /* We're called from get_prev_frame_info; check to see if | |
347 | this is a signal frame by looking to see if the pc points | |
348 | at trampoline code */ | |
349 | if (ppc_linux_at_sigtramp_return_path (fi->pc)) | |
350 | fi->signal_handler_caller = 1; | |
351 | else | |
352 | fi->signal_handler_caller = 0; | |
353 | } | |
354 | } | |
355 | ||
356 | int | |
357 | ppc_linux_frameless_function_invocation (struct frame_info *fi) | |
358 | { | |
359 | /* We'll find the wrong thing if we let | |
360 | rs6000_frameless_function_invocation () search for a signal trampoline */ | |
361 | if (ppc_linux_at_sigtramp_return_path (fi->pc)) | |
362 | return 0; | |
363 | else | |
364 | return rs6000_frameless_function_invocation (fi); | |
365 | } | |
366 | ||
367 | void | |
368 | ppc_linux_frame_init_saved_regs (struct frame_info *fi) | |
369 | { | |
370 | if (fi->signal_handler_caller) | |
371 | { | |
372 | CORE_ADDR regs_addr; | |
373 | int i; | |
374 | if (fi->saved_regs) | |
375 | return; | |
376 | ||
377 | frame_saved_regs_zalloc (fi); | |
378 | ||
379 | regs_addr = | |
380 | read_memory_integer (fi->frame + PPC_LINUX_REGS_PTR_OFFSET, 4); | |
381 | fi->saved_regs[PC_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_NIP; | |
2188cbdd EZ |
382 | fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_ps_regnum] = |
383 | regs_addr + 4 * PPC_LINUX_PT_MSR; | |
384 | fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_cr_regnum] = | |
385 | regs_addr + 4 * PPC_LINUX_PT_CCR; | |
386 | fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_lr_regnum] = | |
387 | regs_addr + 4 * PPC_LINUX_PT_LNK; | |
388 | fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_ctr_regnum] = | |
389 | regs_addr + 4 * PPC_LINUX_PT_CTR; | |
390 | fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_xer_regnum] = | |
391 | regs_addr + 4 * PPC_LINUX_PT_XER; | |
392 | fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_mq_regnum] = | |
393 | regs_addr + 4 * PPC_LINUX_PT_MQ; | |
c877c8e6 | 394 | for (i = 0; i < 32; i++) |
2188cbdd EZ |
395 | fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_gp0_regnum + i] = |
396 | regs_addr + 4 * PPC_LINUX_PT_R0 + 4 * i; | |
c877c8e6 KB |
397 | for (i = 0; i < 32; i++) |
398 | fi->saved_regs[FP0_REGNUM + i] = regs_addr + 4 * PPC_LINUX_PT_FPR0 + 8 * i; | |
399 | } | |
400 | else | |
401 | rs6000_frame_init_saved_regs (fi); | |
402 | } | |
403 | ||
404 | CORE_ADDR | |
405 | ppc_linux_frame_chain (struct frame_info *thisframe) | |
406 | { | |
407 | /* Kernel properly constructs the frame chain for the handler */ | |
408 | if (thisframe->signal_handler_caller) | |
409 | return read_memory_integer ((thisframe)->frame, 4); | |
410 | else | |
411 | return rs6000_frame_chain (thisframe); | |
412 | } | |
413 | ||
414 | /* FIXME: Move the following to rs6000-tdep.c (or some other file where | |
415 | it may be used generically by ports which use either the SysV ABI or | |
416 | the EABI */ | |
417 | ||
ace1378a EZ |
418 | /* Until November 2001, gcc was not complying to the SYSV ABI for |
419 | returning structures less than or equal to 8 bytes in size. It was | |
420 | returning everything in memory. When this was corrected, it wasn't | |
421 | fixed for native platforms. */ | |
422 | int | |
423 | ppc_sysv_abi_broken_use_struct_convention (int gcc_p, struct type *value_type) | |
424 | { | |
425 | if (TYPE_LENGTH (value_type) == 16 | |
426 | && TYPE_VECTOR (value_type)) | |
427 | return 0; | |
428 | ||
429 | return generic_use_struct_convention (gcc_p, value_type); | |
430 | } | |
431 | ||
8e0662df EZ |
432 | /* Structures 8 bytes or less long are returned in the r3 & r4 |
433 | registers, according to the SYSV ABI. */ | |
434 | int | |
435 | ppc_sysv_abi_use_struct_convention (int gcc_p, struct type *value_type) | |
436 | { | |
ace1378a EZ |
437 | if (TYPE_LENGTH (value_type) == 16 |
438 | && TYPE_VECTOR (value_type)) | |
439 | return 0; | |
440 | ||
8e0662df EZ |
441 | return (TYPE_LENGTH (value_type) > 8); |
442 | } | |
443 | ||
c877c8e6 KB |
444 | /* round2 rounds x up to the nearest multiple of s assuming that s is a |
445 | power of 2 */ | |
446 | ||
447 | #undef round2 | |
448 | #define round2(x,s) ((((long) (x) - 1) & ~(long)((s)-1)) + (s)) | |
449 | ||
450 | /* Pass the arguments in either registers, or in the stack. Using the | |
451 | ppc sysv ABI, the first eight words of the argument list (that might | |
452 | be less than eight parameters if some parameters occupy more than one | |
453 | word) are passed in r3..r10 registers. float and double parameters are | |
454 | passed in fpr's, in addition to that. Rest of the parameters if any | |
455 | are passed in user stack. | |
456 | ||
457 | If the function is returning a structure, then the return address is passed | |
458 | in r3, then the first 7 words of the parametes can be passed in registers, | |
459 | starting from r4. */ | |
460 | ||
461 | CORE_ADDR | |
ea7c478f | 462 | ppc_sysv_abi_push_arguments (int nargs, struct value **args, CORE_ADDR sp, |
fba45db2 | 463 | int struct_return, CORE_ADDR struct_addr) |
c877c8e6 KB |
464 | { |
465 | int argno; | |
ace1378a EZ |
466 | /* Next available general register for non-float, non-vector arguments. */ |
467 | int greg; | |
468 | /* Next available floating point register for float arguments. */ | |
469 | int freg; | |
470 | /* Next available vector register for vector arguments. */ | |
471 | int vreg; | |
c877c8e6 KB |
472 | int argstkspace; |
473 | int structstkspace; | |
474 | int argoffset; | |
475 | int structoffset; | |
ea7c478f | 476 | struct value *arg; |
c877c8e6 KB |
477 | struct type *type; |
478 | int len; | |
479 | char old_sp_buf[4]; | |
480 | CORE_ADDR saved_sp; | |
481 | ||
482 | greg = struct_return ? 4 : 3; | |
483 | freg = 1; | |
ace1378a | 484 | vreg = 2; |
c877c8e6 KB |
485 | argstkspace = 0; |
486 | structstkspace = 0; | |
487 | ||
488 | /* Figure out how much new stack space is required for arguments | |
489 | which don't fit in registers. Unlike the PowerOpen ABI, the | |
490 | SysV ABI doesn't reserve any extra space for parameters which | |
491 | are put in registers. */ | |
492 | for (argno = 0; argno < nargs; argno++) | |
493 | { | |
494 | arg = args[argno]; | |
495 | type = check_typedef (VALUE_TYPE (arg)); | |
496 | len = TYPE_LENGTH (type); | |
497 | ||
498 | if (TYPE_CODE (type) == TYPE_CODE_FLT) | |
499 | { | |
500 | if (freg <= 8) | |
501 | freg++; | |
502 | else | |
503 | { | |
504 | /* SysV ABI converts floats to doubles when placed in | |
505 | memory and requires 8 byte alignment */ | |
506 | if (argstkspace & 0x4) | |
507 | argstkspace += 4; | |
508 | argstkspace += 8; | |
509 | } | |
510 | } | |
511 | else if (TYPE_CODE (type) == TYPE_CODE_INT && len == 8) /* long long */ | |
512 | { | |
513 | if (greg > 9) | |
514 | { | |
515 | greg = 11; | |
516 | if (argstkspace & 0x4) | |
517 | argstkspace += 4; | |
518 | argstkspace += 8; | |
519 | } | |
520 | else | |
521 | { | |
522 | if ((greg & 1) == 0) | |
523 | greg++; | |
524 | greg += 2; | |
525 | } | |
526 | } | |
ace1378a EZ |
527 | else if (!TYPE_VECTOR (type)) |
528 | { | |
c877c8e6 KB |
529 | if (len > 4 |
530 | || TYPE_CODE (type) == TYPE_CODE_STRUCT | |
531 | || TYPE_CODE (type) == TYPE_CODE_UNION) | |
532 | { | |
533 | /* Rounding to the nearest multiple of 8 may not be necessary, | |
ace1378a EZ |
534 | but it is safe. Particularly since we don't know the |
535 | field types of the structure */ | |
c877c8e6 KB |
536 | structstkspace += round2 (len, 8); |
537 | } | |
538 | if (greg <= 10) | |
539 | greg++; | |
540 | else | |
541 | argstkspace += 4; | |
ace1378a EZ |
542 | } |
543 | else | |
544 | { | |
545 | if (len == 16 | |
546 | && TYPE_CODE (type) == TYPE_CODE_ARRAY | |
547 | && TYPE_VECTOR (type)) | |
548 | { | |
549 | if (vreg <= 13) | |
550 | vreg++; | |
551 | else | |
552 | { | |
553 | /* Vector arguments must be aligned to 16 bytes on | |
554 | the stack. */ | |
555 | argstkspace += round2 (argstkspace, 16); | |
556 | argstkspace += 16; | |
557 | } | |
558 | } | |
c877c8e6 KB |
559 | } |
560 | } | |
561 | ||
562 | /* Get current SP location */ | |
563 | saved_sp = read_sp (); | |
564 | ||
565 | sp -= argstkspace + structstkspace; | |
566 | ||
567 | /* Allocate space for backchain and callee's saved lr */ | |
568 | sp -= 8; | |
569 | ||
570 | /* Make sure that we maintain 16 byte alignment */ | |
571 | sp &= ~0x0f; | |
572 | ||
573 | /* Update %sp before proceeding any further */ | |
574 | write_register (SP_REGNUM, sp); | |
575 | ||
576 | /* write the backchain */ | |
577 | store_address (old_sp_buf, 4, saved_sp); | |
578 | write_memory (sp, old_sp_buf, 4); | |
579 | ||
580 | argoffset = 8; | |
581 | structoffset = argoffset + argstkspace; | |
582 | freg = 1; | |
583 | greg = 3; | |
ace1378a | 584 | vreg = 2; |
482ca3f5 KB |
585 | /* Fill in r3 with the return structure, if any */ |
586 | if (struct_return) | |
587 | { | |
588 | char val_buf[4]; | |
589 | store_address (val_buf, 4, struct_addr); | |
590 | memcpy (®isters[REGISTER_BYTE (greg)], val_buf, 4); | |
591 | greg++; | |
592 | } | |
c877c8e6 KB |
593 | /* Now fill in the registers and stack... */ |
594 | for (argno = 0; argno < nargs; argno++) | |
595 | { | |
596 | arg = args[argno]; | |
597 | type = check_typedef (VALUE_TYPE (arg)); | |
598 | len = TYPE_LENGTH (type); | |
599 | ||
600 | if (TYPE_CODE (type) == TYPE_CODE_FLT) | |
601 | { | |
602 | if (freg <= 8) | |
603 | { | |
604 | if (len > 8) | |
605 | printf_unfiltered ( | |
ace1378a | 606 | "Fatal Error: a floating point parameter #%d with a size > 8 is found!\n", argno); |
c877c8e6 KB |
607 | memcpy (®isters[REGISTER_BYTE (FP0_REGNUM + freg)], |
608 | VALUE_CONTENTS (arg), len); | |
609 | freg++; | |
610 | } | |
611 | else | |
612 | { | |
613 | /* SysV ABI converts floats to doubles when placed in | |
614 | memory and requires 8 byte alignment */ | |
615 | /* FIXME: Convert floats to doubles */ | |
616 | if (argoffset & 0x4) | |
617 | argoffset += 4; | |
618 | write_memory (sp + argoffset, (char *) VALUE_CONTENTS (arg), len); | |
619 | argoffset += 8; | |
620 | } | |
621 | } | |
622 | else if (TYPE_CODE (type) == TYPE_CODE_INT && len == 8) /* long long */ | |
623 | { | |
624 | if (greg > 9) | |
625 | { | |
626 | greg = 11; | |
627 | if (argoffset & 0x4) | |
628 | argoffset += 4; | |
629 | write_memory (sp + argoffset, (char *) VALUE_CONTENTS (arg), len); | |
630 | argoffset += 8; | |
631 | } | |
632 | else | |
633 | { | |
634 | if ((greg & 1) == 0) | |
635 | greg++; | |
636 | ||
637 | memcpy (®isters[REGISTER_BYTE (greg)], | |
638 | VALUE_CONTENTS (arg), 4); | |
639 | memcpy (®isters[REGISTER_BYTE (greg + 1)], | |
640 | VALUE_CONTENTS (arg) + 4, 4); | |
641 | greg += 2; | |
642 | } | |
643 | } | |
ace1378a | 644 | else if (!TYPE_VECTOR (type)) |
c877c8e6 KB |
645 | { |
646 | char val_buf[4]; | |
647 | if (len > 4 | |
648 | || TYPE_CODE (type) == TYPE_CODE_STRUCT | |
649 | || TYPE_CODE (type) == TYPE_CODE_UNION) | |
650 | { | |
651 | write_memory (sp + structoffset, VALUE_CONTENTS (arg), len); | |
652 | store_address (val_buf, 4, sp + structoffset); | |
653 | structoffset += round2 (len, 8); | |
654 | } | |
655 | else | |
656 | { | |
657 | memset (val_buf, 0, 4); | |
658 | memcpy (val_buf, VALUE_CONTENTS (arg), len); | |
659 | } | |
660 | if (greg <= 10) | |
661 | { | |
c877c8e6 KB |
662 | memcpy (®isters[REGISTER_BYTE (greg)], val_buf, 4); |
663 | greg++; | |
664 | } | |
665 | else | |
666 | { | |
667 | write_memory (sp + argoffset, val_buf, 4); | |
668 | argoffset += 4; | |
669 | } | |
670 | } | |
ace1378a EZ |
671 | else |
672 | { | |
673 | if (len == 16 | |
674 | && TYPE_CODE (type) == TYPE_CODE_ARRAY | |
675 | && TYPE_VECTOR (type)) | |
676 | { | |
677 | struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch); | |
678 | char *v_val_buf = alloca (16); | |
679 | memset (v_val_buf, 0, 16); | |
680 | memcpy (v_val_buf, VALUE_CONTENTS (arg), len); | |
681 | if (vreg <= 13) | |
682 | { | |
683 | memcpy (®isters[REGISTER_BYTE (tdep->ppc_vr0_regnum | |
684 | + vreg)], | |
685 | v_val_buf, 16); | |
686 | vreg++; | |
687 | } | |
688 | else | |
689 | { | |
690 | write_memory (sp + argoffset, v_val_buf, 16); | |
691 | argoffset += 16; | |
692 | } | |
693 | } | |
694 | } | |
c877c8e6 KB |
695 | } |
696 | ||
697 | target_store_registers (-1); | |
698 | return sp; | |
699 | } | |
482ca3f5 | 700 | |
122a33de KB |
701 | /* ppc_linux_memory_remove_breakpoints attempts to remove a breakpoint |
702 | in much the same fashion as memory_remove_breakpoint in mem-break.c, | |
703 | but is careful not to write back the previous contents if the code | |
704 | in question has changed in between inserting the breakpoint and | |
705 | removing it. | |
706 | ||
707 | Here is the problem that we're trying to solve... | |
708 | ||
709 | Once upon a time, before introducing this function to remove | |
710 | breakpoints from the inferior, setting a breakpoint on a shared | |
711 | library function prior to running the program would not work | |
712 | properly. In order to understand the problem, it is first | |
713 | necessary to understand a little bit about dynamic linking on | |
714 | this platform. | |
715 | ||
716 | A call to a shared library function is accomplished via a bl | |
717 | (branch-and-link) instruction whose branch target is an entry | |
718 | in the procedure linkage table (PLT). The PLT in the object | |
719 | file is uninitialized. To gdb, prior to running the program, the | |
720 | entries in the PLT are all zeros. | |
721 | ||
722 | Once the program starts running, the shared libraries are loaded | |
723 | and the procedure linkage table is initialized, but the entries in | |
724 | the table are not (necessarily) resolved. Once a function is | |
725 | actually called, the code in the PLT is hit and the function is | |
726 | resolved. In order to better illustrate this, an example is in | |
727 | order; the following example is from the gdb testsuite. | |
728 | ||
729 | We start the program shmain. | |
730 | ||
731 | [kev@arroyo testsuite]$ ../gdb gdb.base/shmain | |
732 | [...] | |
733 | ||
734 | We place two breakpoints, one on shr1 and the other on main. | |
735 | ||
736 | (gdb) b shr1 | |
737 | Breakpoint 1 at 0x100409d4 | |
738 | (gdb) b main | |
739 | Breakpoint 2 at 0x100006a0: file gdb.base/shmain.c, line 44. | |
740 | ||
741 | Examine the instruction (and the immediatly following instruction) | |
742 | upon which the breakpoint was placed. Note that the PLT entry | |
743 | for shr1 contains zeros. | |
744 | ||
745 | (gdb) x/2i 0x100409d4 | |
746 | 0x100409d4 <shr1>: .long 0x0 | |
747 | 0x100409d8 <shr1+4>: .long 0x0 | |
748 | ||
749 | Now run 'til main. | |
750 | ||
751 | (gdb) r | |
752 | Starting program: gdb.base/shmain | |
753 | Breakpoint 1 at 0xffaf790: file gdb.base/shr1.c, line 19. | |
754 | ||
755 | Breakpoint 2, main () | |
756 | at gdb.base/shmain.c:44 | |
757 | 44 g = 1; | |
758 | ||
759 | Examine the PLT again. Note that the loading of the shared | |
760 | library has initialized the PLT to code which loads a constant | |
761 | (which I think is an index into the GOT) into r11 and then | |
762 | branchs a short distance to the code which actually does the | |
763 | resolving. | |
764 | ||
765 | (gdb) x/2i 0x100409d4 | |
766 | 0x100409d4 <shr1>: li r11,4 | |
767 | 0x100409d8 <shr1+4>: b 0x10040984 <sg+4> | |
768 | (gdb) c | |
769 | Continuing. | |
770 | ||
771 | Breakpoint 1, shr1 (x=1) | |
772 | at gdb.base/shr1.c:19 | |
773 | 19 l = 1; | |
774 | ||
775 | Now we've hit the breakpoint at shr1. (The breakpoint was | |
776 | reset from the PLT entry to the actual shr1 function after the | |
777 | shared library was loaded.) Note that the PLT entry has been | |
778 | resolved to contain a branch that takes us directly to shr1. | |
779 | (The real one, not the PLT entry.) | |
780 | ||
781 | (gdb) x/2i 0x100409d4 | |
782 | 0x100409d4 <shr1>: b 0xffaf76c <shr1> | |
783 | 0x100409d8 <shr1+4>: b 0x10040984 <sg+4> | |
784 | ||
785 | The thing to note here is that the PLT entry for shr1 has been | |
786 | changed twice. | |
787 | ||
788 | Now the problem should be obvious. GDB places a breakpoint (a | |
789 | trap instruction) on the zero value of the PLT entry for shr1. | |
790 | Later on, after the shared library had been loaded and the PLT | |
791 | initialized, GDB gets a signal indicating this fact and attempts | |
792 | (as it always does when it stops) to remove all the breakpoints. | |
793 | ||
794 | The breakpoint removal was causing the former contents (a zero | |
795 | word) to be written back to the now initialized PLT entry thus | |
796 | destroying a portion of the initialization that had occurred only a | |
797 | short time ago. When execution continued, the zero word would be | |
798 | executed as an instruction an an illegal instruction trap was | |
799 | generated instead. (0 is not a legal instruction.) | |
800 | ||
801 | The fix for this problem was fairly straightforward. The function | |
802 | memory_remove_breakpoint from mem-break.c was copied to this file, | |
803 | modified slightly, and renamed to ppc_linux_memory_remove_breakpoint. | |
804 | In tm-linux.h, MEMORY_REMOVE_BREAKPOINT is defined to call this new | |
805 | function. | |
806 | ||
807 | The differences between ppc_linux_memory_remove_breakpoint () and | |
808 | memory_remove_breakpoint () are minor. All that the former does | |
809 | that the latter does not is check to make sure that the breakpoint | |
810 | location actually contains a breakpoint (trap instruction) prior | |
811 | to attempting to write back the old contents. If it does contain | |
812 | a trap instruction, we allow the old contents to be written back. | |
813 | Otherwise, we silently do nothing. | |
814 | ||
815 | The big question is whether memory_remove_breakpoint () should be | |
816 | changed to have the same functionality. The downside is that more | |
817 | traffic is generated for remote targets since we'll have an extra | |
818 | fetch of a memory word each time a breakpoint is removed. | |
819 | ||
820 | For the time being, we'll leave this self-modifying-code-friendly | |
821 | version in ppc-linux-tdep.c, but it ought to be migrated somewhere | |
822 | else in the event that some other platform has similar needs with | |
823 | regard to removing breakpoints in some potentially self modifying | |
824 | code. */ | |
482ca3f5 KB |
825 | int |
826 | ppc_linux_memory_remove_breakpoint (CORE_ADDR addr, char *contents_cache) | |
827 | { | |
f4f9705a | 828 | const unsigned char *bp; |
482ca3f5 KB |
829 | int val; |
830 | int bplen; | |
831 | char old_contents[BREAKPOINT_MAX]; | |
832 | ||
833 | /* Determine appropriate breakpoint contents and size for this address. */ | |
834 | bp = BREAKPOINT_FROM_PC (&addr, &bplen); | |
835 | if (bp == NULL) | |
836 | error ("Software breakpoints not implemented for this target."); | |
837 | ||
838 | val = target_read_memory (addr, old_contents, bplen); | |
839 | ||
840 | /* If our breakpoint is no longer at the address, this means that the | |
841 | program modified the code on us, so it is wrong to put back the | |
842 | old value */ | |
843 | if (val == 0 && memcmp (bp, old_contents, bplen) == 0) | |
844 | val = target_write_memory (addr, contents_cache, bplen); | |
845 | ||
846 | return val; | |
847 | } | |
6ded7999 KB |
848 | |
849 | /* Fetch (and possibly build) an appropriate link_map_offsets | |
ca557f44 | 850 | structure for GNU/Linux PPC targets using the struct offsets |
6ded7999 KB |
851 | defined in link.h (but without actual reference to that file). |
852 | ||
ca557f44 AC |
853 | This makes it possible to access GNU/Linux PPC shared libraries |
854 | from a GDB that was not built on an GNU/Linux PPC host (for cross | |
855 | debugging). */ | |
6ded7999 KB |
856 | |
857 | struct link_map_offsets * | |
858 | ppc_linux_svr4_fetch_link_map_offsets (void) | |
859 | { | |
860 | static struct link_map_offsets lmo; | |
861 | static struct link_map_offsets *lmp = NULL; | |
862 | ||
863 | if (lmp == NULL) | |
864 | { | |
865 | lmp = &lmo; | |
866 | ||
867 | lmo.r_debug_size = 8; /* The actual size is 20 bytes, but | |
868 | this is all we need. */ | |
869 | lmo.r_map_offset = 4; | |
870 | lmo.r_map_size = 4; | |
871 | ||
872 | lmo.link_map_size = 20; /* The actual size is 560 bytes, but | |
873 | this is all we need. */ | |
874 | lmo.l_addr_offset = 0; | |
875 | lmo.l_addr_size = 4; | |
876 | ||
877 | lmo.l_name_offset = 4; | |
878 | lmo.l_name_size = 4; | |
879 | ||
880 | lmo.l_next_offset = 12; | |
881 | lmo.l_next_size = 4; | |
882 | ||
883 | lmo.l_prev_offset = 16; | |
884 | lmo.l_prev_size = 4; | |
885 | } | |
886 | ||
887 | return lmp; | |
888 | } |