nptl/unwind.c

   1 /* Copyright (C) 2003-2023 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <setjmp.h>
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <string.h>
  22 #include <unistd.h>
  23 #include "pthreadP.h"
  24 #include <libc-diag.h>
  25 #include <jmpbuf-unwind.h>
  26 #include <shlib-compat.h>
  27
  28 #if _STACK_GROWS_DOWN
  29 # define FRAME_LEFT(frame, other, adj) \
  30   ((uintptr_t) frame - adj >= (uintptr_t) other - adj)
  31 #elif _STACK_GROWS_UP
  32 # define FRAME_LEFT(frame, other, adj) \
  33   ((uintptr_t) frame - adj <= (uintptr_t) other - adj)
  34 #else
  35 # error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
  36 #endif
  37
  38 static _Unwind_Reason_Code
  39 unwind_stop (int version, _Unwind_Action actions,
  40              _Unwind_Exception_Class exc_class,
  41              struct _Unwind_Exception *exc_obj,
  42              struct _Unwind_Context *context, void *stop_parameter)
  43 {
  44   struct pthread_unwind_buf *buf = stop_parameter;
  45   struct pthread *self = THREAD_SELF;
  46   struct _pthread_cleanup_buffer *curp = THREAD_GETMEM (self, cleanup);
  47   int do_longjump = 0;
  48
  49   /* Adjust all pointers used in comparisons, so that top of thread's
  50      stack is at the top of address space.  Without that, things break
  51      if stack is allocated above the main stack.  */
  52   uintptr_t adj = (uintptr_t) self->stackblock + self->stackblock_size;
  53
  54   /* Do longjmp if we're at "end of stack", aka "end of unwind data".
  55      We assume there are only C frame without unwind data in between
  56      here and the jmp_buf target.  Otherwise simply note that the CFA
  57      of a function is NOT within it's stack frame; it's the SP of the
  58      previous frame.  */
  59   if ((actions & _UA_END_OF_STACK)
  60       || ! _JMPBUF_CFA_UNWINDS_ADJ (buf->cancel_jmp_buf[0].jmp_buf, context,
  61                                     adj))
  62     do_longjump = 1;
  63
  64   if (__glibc_unlikely (curp != NULL))
  65     {
  66       /* Handle the compatibility stuff.  Execute all handlers
  67          registered with the old method which would be unwound by this
  68          step.  */
  69       struct _pthread_cleanup_buffer *oldp = buf->priv.data.cleanup;
  70       void *cfa = (void *) (_Unwind_Ptr) _Unwind_GetCFA (context);
  71
  72       if (curp != oldp && (do_longjump || FRAME_LEFT (cfa, curp, adj)))
  73         {
  74           do
  75             {
  76               /* Pointer to the next element.  */
  77               struct _pthread_cleanup_buffer *nextp = curp->__prev;
  78
  79               /* Call the handler.  */
  80               curp->__routine (curp->__arg);
  81
  82               /* To the next.  */
  83               curp = nextp;
  84             }
  85           while (curp != oldp
  86                  && (do_longjump || FRAME_LEFT (cfa, curp, adj)));
  87
  88           /* Mark the current element as handled.  */
  89           THREAD_SETMEM (self, cleanup, curp);
  90         }
  91     }
  92
  93   DIAG_PUSH_NEEDS_COMMENT;
  94 #if __GNUC_PREREQ (7, 0)
  95   /* This call results in a -Wstringop-overflow warning because struct
  96      pthread_unwind_buf is smaller than jmp_buf.  setjmp and longjmp
  97      do not use anything beyond the common prefix (they never access
  98      the saved signal mask), so that is a false positive.  */
  99   DIAG_IGNORE_NEEDS_COMMENT (11, "-Wstringop-overflow=");
 100 #endif
 101   if (do_longjump)
 102     __libc_unwind_longjmp ((struct __jmp_buf_tag *) buf->cancel_jmp_buf, 1);
 103   DIAG_POP_NEEDS_COMMENT;
 104
 105   return _URC_NO_REASON;
 106 }
 107
 108
 109 static void
 110 unwind_cleanup (_Unwind_Reason_Code reason, struct _Unwind_Exception *exc)
 111 {
 112   /* When we get here a C++ catch block didn't rethrow the object.  We
 113      cannot handle this case and therefore abort.  */
 114   __libc_fatal ("FATAL: exception not rethrown\n");
 115 }
 116
 117
 118 void
 119 __cleanup_fct_attribute __attribute ((noreturn))
 120 __pthread_unwind (__pthread_unwind_buf_t *buf)
 121 {
 122   struct pthread_unwind_buf *ibuf = (struct pthread_unwind_buf *) buf;
 123   struct pthread *self = THREAD_SELF;
 124
 125   /* This is not a catchable exception, so don't provide any details about
 126      the exception type.  We do need to initialize the field though.  */
 127   THREAD_SETMEM (self, exc.exception_class, 0);
 128   THREAD_SETMEM (self, exc.exception_cleanup, &unwind_cleanup);
 129
 130   _Unwind_ForcedUnwind (&self->exc, unwind_stop, ibuf);
 131   /* NOTREACHED */
 132
 133   /* We better do not get here.  */
 134   abort ();
 135 }
 136 libc_hidden_def (__pthread_unwind)
 137
 138 void
 139 __cleanup_fct_attribute __attribute ((noreturn))
 140 ___pthread_unwind_next (__pthread_unwind_buf_t *buf)
 141 {
 142   struct pthread_unwind_buf *ibuf = (struct pthread_unwind_buf *) buf;
 143
 144   __pthread_unwind ((__pthread_unwind_buf_t *) ibuf->priv.data.prev);
 145 }
 146 versioned_symbol (libc, ___pthread_unwind_next, __pthread_unwind_next,
 147                   GLIBC_2_34);
 148 #if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_3_3, GLIBC_2_34)
 149 compat_symbol (libpthread, ___pthread_unwind_next, __pthread_unwind_next,
 150                GLIBC_2_3_3);
 151 #endif