1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//
8// Implements gcc extensions to the C++ ABI Exception Handling Level 1.
9//
10//===----------------------------------------------------------------------===//
11
12#include <inttypes.h>
13#include <stdbool.h>
14#include <stdint.h>
15#include <stdio.h>
16#include <stdlib.h>
17#include <string.h>
18
19#include "config.h"
20#include "libunwind_ext.h"
21#include "libunwind.h"
22#include "Unwind-EHABI.h"
23#include "unwind.h"
24
25#if defined(_AIX)
26#include <sys/debug.h>
27#endif
28
29#if defined(_LIBUNWIND_BUILD_ZERO_COST_APIS)
30
31#if defined(_LIBUNWIND_SUPPORT_SEH_UNWIND)
32#define PRIVATE_1 private_[0]
33#elif defined(_LIBUNWIND_ARM_EHABI)
34#define PRIVATE_1 unwinder_cache.reserved1
35#else
36#define PRIVATE_1 private_1
37#endif
38
39/// Called by __cxa_rethrow().
40_LIBUNWIND_EXPORT _Unwind_Reason_Code
41_Unwind_Resume_or_Rethrow(_Unwind_Exception *exception_object) {
42 _LIBUNWIND_TRACE_API(
43 "_Unwind_Resume_or_Rethrow(ex_obj=%p), private_1=%" PRIdPTR,
44 (void *)exception_object, (intptr_t)exception_object->PRIVATE_1);
45
46 // If this is non-forced and a stopping place was found, then this is a
47 // re-throw.
48 // Call _Unwind_RaiseException() as if this was a new exception
49 if (exception_object->PRIVATE_1 == 0) {
50 return _Unwind_RaiseException(exception_object);
51 // Will return if there is no catch clause, so that __cxa_rethrow can call
52 // std::terminate().
53 }
54
55 // Call through to _Unwind_Resume() which distinguishes between forced and
56 // regular exceptions.
57 _Unwind_Resume(exception_object);
58 _LIBUNWIND_ABORT("_Unwind_Resume_or_Rethrow() called _Unwind_RaiseException()"
59 " which unexpectedly returned");
60}
61
62/// Called by personality handler during phase 2 to get base address for data
63/// relative encodings.
64_LIBUNWIND_EXPORT uintptr_t
65_Unwind_GetDataRelBase(struct _Unwind_Context *context) {
66 _LIBUNWIND_TRACE_API("_Unwind_GetDataRelBase(context=%p)", (void *)context);
67#if defined(_AIX)
68 return unw_get_data_rel_base((unw_cursor_t *)context);
69#else
70 (void)context;
71 _LIBUNWIND_ABORT("_Unwind_GetDataRelBase() not implemented");
72#endif
73}
74
75/// Called by personality handler during phase 2 to get base address for text
76/// relative encodings.
77_LIBUNWIND_EXPORT uintptr_t
78_Unwind_GetTextRelBase(struct _Unwind_Context *context) {
79 (void)context;
80 _LIBUNWIND_TRACE_API("_Unwind_GetTextRelBase(context=%p)", (void *)context);
81 _LIBUNWIND_ABORT("_Unwind_GetTextRelBase() not implemented");
82}
83
84
85/// Scans unwind information to find the function that contains the
86/// specified code address "pc".
87_LIBUNWIND_EXPORT void *_Unwind_FindEnclosingFunction(void *pc) {
88 _LIBUNWIND_TRACE_API("_Unwind_FindEnclosingFunction(pc=%p)", pc);
89#if defined(_AIX)
90 if (pc == NULL)
91 return NULL;
92
93 // Get the start address of the enclosing function from the function's
94 // traceback table.
95 uint32_t *p = (uint32_t *)pc;
96
97 // Keep looking forward until a word of 0 is found. The traceback
98 // table starts at the following word.
99 while (*p)
100 ++p;
101 struct tbtable *TBTable = (struct tbtable *)(p + 1);
102
103 // Get the address of the traceback table extension.
104 p = (uint32_t *)&TBTable->tb_ext;
105
106 // Skip field parminfo if it exists.
107 if (TBTable->tb.fixedparms || TBTable->tb.floatparms)
108 ++p;
109
110 if (TBTable->tb.has_tboff)
111 // *p contains the offset from the function start to traceback table.
112 return (void *)((uintptr_t)TBTable - *p - sizeof(uint32_t));
113 return NULL;
114#else
115 // This is slow, but works.
116 // We create an unwind cursor then alter the IP to be pc
117 unw_cursor_t cursor;
118 unw_context_t uc;
119 unw_proc_info_t info;
120 __unw_getcontext(&uc);
121 __unw_init_local(&cursor, &uc);
122 __unw_set_reg(&cursor, UNW_REG_IP, (unw_word_t)(intptr_t)pc);
123 if (__unw_get_proc_info(&cursor, &info) == UNW_ESUCCESS)
124 return (void *)(intptr_t) info.start_ip;
125 else
126 return NULL;
127#endif
128}
129
130/// Walk every frame and call trace function at each one. If trace function
131/// returns anything other than _URC_NO_REASON, then walk is terminated.
132_LIBUNWIND_EXPORT _Unwind_Reason_Code
133_Unwind_Backtrace(_Unwind_Trace_Fn callback, void *ref) {
134 unw_cursor_t cursor;
135 unw_context_t uc;
136 __unw_getcontext(&uc);
137 __unw_init_local(&cursor, &uc);
138
139 _LIBUNWIND_TRACE_API("_Unwind_Backtrace(callback=%p)",
140 (void *)(uintptr_t)callback);
141
142#if defined(_LIBUNWIND_ARM_EHABI)
143 // Create a mock exception object for force unwinding.
144 _Unwind_Exception ex;
145 memset(&ex, '\0', sizeof(ex));
146 memcpy(&ex.exception_class, "CLNGUNW", sizeof(ex.exception_class));
147#endif
148
149 // walk each frame
150 while (true) {
151 _Unwind_Reason_Code result;
152
153#if !defined(_LIBUNWIND_ARM_EHABI)
154 // ask libunwind to get next frame (skip over first frame which is
155 // _Unwind_Backtrace())
156 if (__unw_step(&cursor) <= 0) {
157 _LIBUNWIND_TRACE_UNWINDING(" _backtrace: ended because cursor reached "
158 "bottom of stack, returning %d",
159 _URC_END_OF_STACK);
160 return _URC_END_OF_STACK;
161 }
162#else
163 // Get the information for this frame.
164 unw_proc_info_t frameInfo;
165 if (__unw_get_proc_info(&cursor, &frameInfo) != UNW_ESUCCESS) {
166 return _URC_END_OF_STACK;
167 }
168
169 // Update the pr_cache in the mock exception object.
170 uint32_t *unwindInfo = (uint32_t *)frameInfo.unwind_info;
171 ex.pr_cache.fnstart = frameInfo.start_ip;
172 ex.pr_cache.ehtp = (_Unwind_EHT_Header *) unwindInfo;
173 ex.pr_cache.additional= frameInfo.flags;
174
175 struct _Unwind_Context *context = (struct _Unwind_Context *)&cursor;
176 // Get and call the personality function to unwind the frame.
177 _Unwind_Personality_Fn handler = (_Unwind_Personality_Fn)frameInfo.handler;
178 if (handler == NULL) {
179 return _URC_END_OF_STACK;
180 }
181 if (handler(_US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND, &ex, context) !=
182 _URC_CONTINUE_UNWIND) {
183 return _URC_END_OF_STACK;
184 }
185#endif // defined(_LIBUNWIND_ARM_EHABI)
186
187 // debugging
188 if (_LIBUNWIND_TRACING_UNWINDING) {
189 char functionName[512];
190 unw_proc_info_t frame;
191 unw_word_t offset;
192 __unw_get_proc_name(&cursor, functionName, 512, &offset);
193 __unw_get_proc_info(&cursor, &frame);
194 _LIBUNWIND_TRACE_UNWINDING(
195 " _backtrace: start_ip=0x%" PRIxPTR ", func=%s, lsda=0x%" PRIxPTR ", context=%p",
196 frame.start_ip, functionName, frame.lsda,
197 (void *)&cursor);
198 }
199
200 // call trace function with this frame
201 result = (*callback)((struct _Unwind_Context *)(&cursor), ref);
202 if (result != _URC_NO_REASON) {
203 _LIBUNWIND_TRACE_UNWINDING(
204 " _backtrace: ended because callback returned %d", result);
205 return result;
206 }
207 }
208}
209
210
211/// Find DWARF unwind info for an address 'pc' in some function.
212_LIBUNWIND_EXPORT const void *_Unwind_Find_FDE(const void *pc,
213 struct dwarf_eh_bases *bases) {
214 // This is slow, but works.
215 // We create an unwind cursor then alter the IP to be pc
216 unw_cursor_t cursor;
217 unw_context_t uc;
218 unw_proc_info_t info;
219 __unw_getcontext(&uc);
220 __unw_init_local(&cursor, &uc);
221 __unw_set_reg(&cursor, UNW_REG_IP, (unw_word_t)(intptr_t)pc);
222 __unw_get_proc_info(&cursor, &info);
223 bases->tbase = (uintptr_t)info.extra;
224 bases->dbase = 0; // dbase not used on Mac OS X
225 bases->func = (uintptr_t)info.start_ip;
226 _LIBUNWIND_TRACE_API("_Unwind_Find_FDE(pc=%p) => %p", pc,
227 (void *)(intptr_t) info.unwind_info);
228 return (void *)(intptr_t) info.unwind_info;
229}
230
231/// Returns the CFA (call frame area, or stack pointer at start of function)
232/// for the current context.
233_LIBUNWIND_EXPORT uintptr_t _Unwind_GetCFA(struct _Unwind_Context *context) {
234 unw_cursor_t *cursor = (unw_cursor_t *)context;
235 unw_word_t result;
236 __unw_get_reg(cursor, UNW_REG_SP, &result);
237 _LIBUNWIND_TRACE_API("_Unwind_GetCFA(context=%p) => 0x%" PRIxPTR,
238 (void *)context, result);
239 return (uintptr_t)result;
240}
241
242
243/// Called by personality handler during phase 2 to get instruction pointer.
244/// ipBefore is a boolean that says if IP is already adjusted to be the call
245/// site address. Normally IP is the return address.
246_LIBUNWIND_EXPORT uintptr_t _Unwind_GetIPInfo(struct _Unwind_Context *context,
247 int *ipBefore) {
248 _LIBUNWIND_TRACE_API("_Unwind_GetIPInfo(context=%p)", (void *)context);
249 int isSignalFrame = __unw_is_signal_frame((unw_cursor_t *)context);
250 // Negative means some kind of error (probably UNW_ENOINFO), but we have no
251 // good way to report that, and this maintains backward compatibility with the
252 // implementation that hard-coded zero in every case, even signal frames.
253 if (isSignalFrame <= 0)
254 *ipBefore = 0;
255 else
256 *ipBefore = 1;
257 return _Unwind_GetIP(context);
258}
259
260#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
261
262/// Called by programs with dynamic code generators that want
263/// to register a dynamically generated FDE.
264/// This function has existed on Mac OS X since 10.4, but
265/// was broken until 10.6.
266_LIBUNWIND_EXPORT void __register_frame(const void *fde) {
267 _LIBUNWIND_TRACE_API("__register_frame(%p)", fde);
268 __unw_add_dynamic_fde(fde: (unw_word_t)(uintptr_t)fde);
269}
270
271
272/// Called by programs with dynamic code generators that want
273/// to unregister a dynamically generated FDE.
274/// This function has existed on Mac OS X since 10.4, but
275/// was broken until 10.6.
276_LIBUNWIND_EXPORT void __deregister_frame(const void *fde) {
277 _LIBUNWIND_TRACE_API("__deregister_frame(%p)", fde);
278 __unw_remove_dynamic_fde(fde: (unw_word_t)(uintptr_t)fde);
279}
280
281
282// The following register/deregister functions are gcc extensions.
283// They have existed on Mac OS X, but have never worked because Mac OS X
284// before 10.6 used keymgr to track known FDEs, but these functions
285// never got updated to use keymgr.
286// For now, we implement these as do-nothing functions to keep any existing
287// applications working. We also add the not in 10.6 symbol so that nwe
288// application won't be able to use them.
289
290#if defined(_LIBUNWIND_SUPPORT_FRAME_APIS)
291_LIBUNWIND_EXPORT void __register_frame_info_bases(const void *fde, void *ob,
292 void *tb, void *db) {
293 (void)fde;
294 (void)ob;
295 (void)tb;
296 (void)db;
297 _LIBUNWIND_TRACE_API("__register_frame_info_bases(%p,%p, %p, %p)",
298 fde, ob, tb, db);
299 // do nothing, this function never worked in Mac OS X
300}
301
302_LIBUNWIND_EXPORT void __register_frame_info(const void *fde, void *ob) {
303 (void)fde;
304 (void)ob;
305 _LIBUNWIND_TRACE_API("__register_frame_info(%p, %p)", fde, ob);
306 // do nothing, this function never worked in Mac OS X
307}
308
309_LIBUNWIND_EXPORT void __register_frame_info_table_bases(const void *fde,
310 void *ob, void *tb,
311 void *db) {
312 (void)fde;
313 (void)ob;
314 (void)tb;
315 (void)db;
316 _LIBUNWIND_TRACE_API("__register_frame_info_table_bases"
317 "(%p,%p, %p, %p)", fde, ob, tb, db);
318 // do nothing, this function never worked in Mac OS X
319}
320
321_LIBUNWIND_EXPORT void __register_frame_info_table(const void *fde, void *ob) {
322 (void)fde;
323 (void)ob;
324 _LIBUNWIND_TRACE_API("__register_frame_info_table(%p, %p)", fde, ob);
325 // do nothing, this function never worked in Mac OS X
326}
327
328_LIBUNWIND_EXPORT void __register_frame_table(const void *fde) {
329 (void)fde;
330 _LIBUNWIND_TRACE_API("__register_frame_table(%p)", fde);
331 // do nothing, this function never worked in Mac OS X
332}
333
334_LIBUNWIND_EXPORT void *__deregister_frame_info(const void *fde) {
335 (void)fde;
336 _LIBUNWIND_TRACE_API("__deregister_frame_info(%p)", fde);
337 // do nothing, this function never worked in Mac OS X
338 return NULL;
339}
340
341_LIBUNWIND_EXPORT void *__deregister_frame_info_bases(const void *fde) {
342 (void)fde;
343 _LIBUNWIND_TRACE_API("__deregister_frame_info_bases(%p)", fde);
344 // do nothing, this function never worked in Mac OS X
345 return NULL;
346}
347#endif // defined(_LIBUNWIND_SUPPORT_FRAME_APIS)
348
349#endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
350
351#endif // defined(_LIBUNWIND_BUILD_ZERO_COST_APIS)
352

source code of libunwind/src/UnwindLevel1-gcc-ext.c