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33d5188ab1
But PR gdb/20126 highlights a case where GDB emits a large number of
warnings like:
warning: Can't open file /anon_hugepage (deleted) during file-backed mapping note processing
warning: Can't open file /dev/shm/PostgreSQL.1150234652 during file-backed mapping note processing
warning: Can't open file /dev/shm/PostgreSQL.535700290 during file-backed mapping note processing
warning: Can't open file /SYSV604b7d00 (deleted) during file-backed mapping note processing
... etc ...
when opening a core file. This commit aims to avoid at least some of
these warnings.
What we know is that, for at least some of these cases, (e.g. the
'(deleted)' mappings), the content of the mapping will have been
written into the core file itself. As such, the fact that the file
isn't available ('/SYSV604b7d00' at least is a shared memory mapping),
isn't really relevant, GDB can still provide access to the mapping, by
reading the content from the core file itself.
What I propose is that, when processing the file backed mappings, if
all of the mappings for a file are covered by segments within the core
file itself, then there is no need to warn the user that the file
can't be opened again. The debug experience should be unchanged, as
GDB would have read from the in-core mapping anyway.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30126
119 lines
3.0 KiB
C
119 lines
3.0 KiB
C
/* Copyright 1992-2025 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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/* This file is based on coremaker.c. */
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#include <stdio.h>
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#include <sys/types.h>
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#include <fcntl.h>
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#include <sys/mman.h>
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#include <signal.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <assert.h>
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#include <sys/ipc.h>
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#include <sys/shm.h>
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#define MAPSIZE (8 * 1024)
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/* Global pointers so it's easier to access them from GDB. */
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char *rw_mapping = NULL;
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char *malloc_buffer = NULL;
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char *anon_mapping = NULL;
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char *shm_mapping = NULL;
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/* Create mappings within this process. */
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void
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mmapdata ()
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{
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/* Allocate and initialize a buffer that will be used to write the file
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that is later mapped in. */
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malloc_buffer = (char *) malloc (MAPSIZE);
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for (int j = 0; j < MAPSIZE; ++j)
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malloc_buffer[j] = j;
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/* Write the file to map in. */
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int fd = open ("coremmap.data", O_CREAT | O_RDWR, 0666);
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assert (fd != -1);
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write (fd, malloc_buffer, MAPSIZE);
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/* Now map the file into our address space as RW_MAPPING. */
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rw_mapping
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= (char *) mmap (0, MAPSIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
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assert (rw_mapping != (char *) MAP_FAILED);
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/* Verify that the original data and the mapped data are identical. If
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not, we'd rather fail now than when trying to access the mapped data
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from the core file. */
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for (int j = 0; j < MAPSIZE; ++j)
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assert (malloc_buffer[j] == rw_mapping[j]);
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/* Touch RW_MAPPING so the kernel writes it out into 'core'. */
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rw_mapping[0] = malloc_buffer[0];
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/* Create yet another region which is allocated, but not written to. */
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anon_mapping = mmap (NULL, MAPSIZE, PROT_READ | PROT_WRITE,
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MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
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assert (anon_mapping != MAP_FAILED);
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/* Create a shared memory mapping. */
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int sid = shmget (IPC_PRIVATE, MAPSIZE, IPC_CREAT | IPC_EXCL | 0777);
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assert (sid != -1);
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shm_mapping = (char *) shmat (sid, NULL, 0);
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int res = shmctl (sid, IPC_RMID, NULL);
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assert (res == 0);
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assert (shm_mapping != MAP_FAILED);
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}
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void
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func2 ()
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{
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#ifdef SA_FULLDUMP
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/* Force a corefile that includes the data section for AIX. */
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{
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struct sigaction sa;
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sigaction (SIGABRT, (struct sigaction *)0, &sa);
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sa.sa_flags |= SA_FULLDUMP;
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sigaction (SIGABRT, &sa, (struct sigaction *)0);
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}
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#endif
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abort ();
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}
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void
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func1 ()
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{
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func2 ();
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}
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int
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main (void)
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{
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mmapdata ();
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func1 ();
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return 0;
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}
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