nptl/unwind.c

   1 /* Copyright (C) 2003-2021 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>
   4    and Richard Henderson <rth@redhat.com>, 2003.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 #include <setjmp.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include "pthreadP.h"
  26 #include <libc-diag.h>
  27 #include <jmpbuf-unwind.h>
  28
  29 #ifdef _STACK_GROWS_DOWN
  30 # define FRAME_LEFT(frame, other, adj) \
  31   ((uintptr_t) frame - adj >= (uintptr_t) other - adj)
  32 #elif _STACK_GROWS_UP
  33 # define FRAME_LEFT(frame, other, adj) \
  34   ((uintptr_t) frame - adj <= (uintptr_t) other - adj)
  35 #else
  36 # error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
  37 #endif
  38
  39 static _Unwind_Reason_Code
  40 unwind_stop (int version, _Unwind_Action actions,
  41              _Unwind_Exception_Class exc_class,
  42              struct _Unwind_Exception *exc_obj,
  43              struct _Unwind_Context *context, void *stop_parameter)
  44 {
  45   struct pthread_unwind_buf *buf = stop_parameter;
  46   struct pthread *self = THREAD_SELF;
  47   struct _pthread_cleanup_buffer *curp = THREAD_GETMEM (self, cleanup);
  48   int do_longjump = 0;
  49
  50   /* Adjust all pointers used in comparisons, so that top of thread's
  51      stack is at the top of address space.  Without that, things break
  52      if stack is allocated above the main stack.  */
  53   uintptr_t adj = (uintptr_t) self->stackblock + self->stackblock_size;
  54
  55   /* Do longjmp if we're at "end of stack", aka "end of unwind data".
  56      We assume there are only C frame without unwind data in between
  57      here and the jmp_buf target.  Otherwise simply note that the CFA
  58      of a function is NOT within it's stack frame; it's the SP of the
  59      previous frame.  */
  60   if ((actions & _UA_END_OF_STACK)
  61       || ! _JMPBUF_CFA_UNWINDS_ADJ (buf->cancel_jmp_buf[0].jmp_buf, context,
  62                                     adj))
  63     do_longjump = 1;
  64
  65   if (__glibc_unlikely (curp != NULL))
  66     {
  67       /* Handle the compatibility stuff.  Execute all handlers
  68          registered with the old method which would be unwound by this
  69          step.  */
  70       struct _pthread_cleanup_buffer *oldp = buf->priv.data.cleanup;
  71       void *cfa = (void *) (_Unwind_Ptr) _Unwind_GetCFA (context);
  72
  73       if (curp != oldp && (do_longjump || FRAME_LEFT (cfa, curp, adj)))
  74         {
  75           do
  76             {
  77               /* Pointer to the next element.  */
  78               struct _pthread_cleanup_buffer *nextp = curp->__prev;
  79
  80               /* Call the handler.  */
  81               curp->__routine (curp->__arg);
  82
  83               /* To the next.  */
  84               curp = nextp;
  85             }
  86           while (curp != oldp
  87                  && (do_longjump || FRAME_LEFT (cfa, curp, adj)));
  88
  89           /* Mark the current element as handled.  */
  90           THREAD_SETMEM (self, cleanup, curp);
  91         }
  92     }
  93
  94   DIAG_PUSH_NEEDS_COMMENT;
  95 #if __GNUC_PREREQ (7, 0)
  96   /* This call results in a -Wstringop-overflow warning because struct
  97      pthread_unwind_buf is smaller than jmp_buf.  setjmp and longjmp
  98      do not use anything beyond the common prefix (they never access
  99      the saved signal mask), so that is a false positive.  */
 100   DIAG_IGNORE_NEEDS_COMMENT (11, "-Wstringop-overflow=");
 101 #endif
 102   if (do_longjump)
 103     __libc_unwind_longjmp ((struct __jmp_buf_tag *) buf->cancel_jmp_buf, 1);
 104   DIAG_POP_NEEDS_COMMENT;
 105
 106   return _URC_NO_REASON;
 107 }
 108
 109
 110 static void
 111 unwind_cleanup (_Unwind_Reason_Code reason, struct _Unwind_Exception *exc)
 112 {
 113   /* When we get here a C++ catch block didn't rethrow the object.  We
 114      cannot handle this case and therefore abort.  */
 115   __libc_fatal ("FATAL: exception not rethrown\n");
 116 }
 117
 118
 119 void
 120 __cleanup_fct_attribute __attribute ((noreturn))
 121 __pthread_unwind (__pthread_unwind_buf_t *buf)
 122 {
 123   struct pthread_unwind_buf *ibuf = (struct pthread_unwind_buf *) buf;
 124   struct pthread *self = THREAD_SELF;
 125
 126   /* This is not a catchable exception, so don't provide any details about
 127      the exception type.  We do need to initialize the field though.  */
 128   THREAD_SETMEM (self, exc.exception_class, 0);
 129   THREAD_SETMEM (self, exc.exception_cleanup, &unwind_cleanup);
 130
 131   _Unwind_ForcedUnwind (&self->exc, unwind_stop, ibuf);
 132   /* NOTREACHED */
 133
 134   /* We better do not get here.  */
 135   abort ();
 136 }
 137 hidden_def (__pthread_unwind)
 138
 139
 140 void
 141 __cleanup_fct_attribute __attribute ((noreturn))
 142 __pthread_unwind_next (__pthread_unwind_buf_t *buf)
 143 {
 144   struct pthread_unwind_buf *ibuf = (struct pthread_unwind_buf *) buf;
 145
 146   __pthread_unwind ((__pthread_unwind_buf_t *) ibuf->priv.data.prev);
 147 }
 148 hidden_def (__pthread_unwind_next)