Squashed 'third_party/elfutils/' content from commit 555e15e
Change-Id: I61cde98949e47e5c8c09c33260de17f30921be79
git-subtree-dir: third_party/elfutils
git-subtree-split: 555e15ebe8bf1eb33d00747173cfc80cc65648a4
diff --git a/libdw/dwarf_getalt.c b/libdw/dwarf_getalt.c
new file mode 100644
index 0000000..3e5af15
--- /dev/null
+++ b/libdw/dwarf_getalt.c
@@ -0,0 +1,196 @@
+/* Retrieves the DWARF descriptor for debugaltlink data.
+ Copyright (C) 2014, 2018 Red Hat, Inc.
+ This file is part of elfutils.
+
+ This file is free software; you can redistribute it and/or modify
+ it under the terms of either
+
+ * the GNU Lesser General Public License as published by the Free
+ Software Foundation; either version 3 of the License, or (at
+ your option) any later version
+
+ or
+
+ * the GNU General Public License as published by the Free
+ Software Foundation; either version 2 of the License, or (at
+ your option) any later version
+
+ or both in parallel, as here.
+
+ elfutils is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ General Public License for more details.
+
+ You should have received copies of the GNU General Public License and
+ the GNU Lesser General Public License along with this program. If
+ not, see <http://www.gnu.org/licenses/>. */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include "libdwP.h"
+#include "libelfP.h"
+#include "libdwelfP.h"
+#include "system.h"
+
+#include <inttypes.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+
+char *
+internal_function
+__libdw_filepath (int fd, const char *dir, const char *file)
+{
+ if (file == NULL)
+ return NULL;
+
+ if (file[0] == '/')
+ return strdup (file);
+
+ if (dir != NULL && dir[0] == '/')
+ {
+ size_t dirlen = strlen (dir);
+ size_t filelen = strlen (file);
+ size_t len = dirlen + 1 + filelen + 1;
+ char *path = malloc (len);
+ if (path != NULL)
+ {
+ char *c = mempcpy (path, dir, dirlen);
+ if (dir[dirlen - 1] != '/')
+ *c++ = '/';
+ mempcpy (c, file, filelen + 1);
+ }
+ return path;
+ }
+
+ if (fd >= 0)
+ {
+ /* strlen ("/proc/self/fd/") = 14 + strlen (<MAXINT>) = 10 + 1 = 25. */
+ char devfdpath[25];
+ sprintf (devfdpath, "/proc/self/fd/%u", fd);
+ char *fdpath = realpath (devfdpath, NULL);
+ char *path = NULL;
+ char *fddir;
+ if (fdpath != NULL && fdpath[0] == '/'
+ && (fddir = strrchr (fdpath, '/')) != NULL)
+ {
+ *++fddir = '\0';
+ size_t fdpathlen = strlen (fdpath);
+ size_t dirlen = dir != NULL ? strlen (dir) : 0;
+ size_t filelen = strlen (file);
+ size_t len = fdpathlen + 1 + dirlen + 1 + filelen + 1;
+ path = malloc (len);
+ if (path != NULL)
+ {
+ char *c = mempcpy (path, fdpath, fdpathlen);
+ if (dirlen > 0)
+ {
+ c = mempcpy (c, dir, dirlen);
+ if (dir[dirlen - 1] != '/')
+ *c++ = '/';
+ }
+ mempcpy (c, file, filelen + 1);
+ }
+ }
+ free (fdpath);
+ return path;
+ }
+
+ return NULL;
+}
+
+static void
+find_debug_altlink (Dwarf *dbg)
+{
+ const char *altname;
+ const void *build_id;
+ ssize_t build_id_len = INTUSE(dwelf_dwarf_gnu_debugaltlink) (dbg,
+ &altname,
+ &build_id);
+
+ /* Couldn't even get the debugaltlink. It probably doesn't exist. */
+ if (build_id_len <= 0)
+ return;
+
+ const uint8_t *id = (const uint8_t *) build_id;
+ size_t id_len = build_id_len;
+ int fd = -1;
+
+ /* We only look in the standard path. And relative to the dbg file. */
+#define DEBUGINFO_PATH "/usr/lib/debug"
+
+ /* We don't handle very short or really large build-ids. We need at
+ at least 3 and allow for up to 64 (normally ids are 20 long). */
+#define MIN_BUILD_ID_BYTES 3
+#define MAX_BUILD_ID_BYTES 64
+ if (id_len >= MIN_BUILD_ID_BYTES && id_len <= MAX_BUILD_ID_BYTES)
+ {
+ /* Note sizeof a string literal includes the trailing zero. */
+ char id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1
+ + 2 + 1 + (MAX_BUILD_ID_BYTES - 2) * 2 + sizeof ".debug"];
+ sprintf (&id_path[0], "%s%s", DEBUGINFO_PATH, "/.build-id/");
+ sprintf (&id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1],
+ "%02" PRIx8 "/", (uint8_t) id[0]);
+ for (size_t i = 1; i < id_len; ++i)
+ sprintf (&id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1
+ + 3 + (i - 1) * 2], "%02" PRIx8, (uint8_t) id[i]);
+ strcpy (&id_path[sizeof DEBUGINFO_PATH - 1 + sizeof "/.build-id/" - 1
+ + 3 + (id_len - 1) * 2], ".debug");
+
+ fd = TEMP_FAILURE_RETRY (open (id_path, O_RDONLY));
+ }
+
+ /* Fall back on (possible relative) alt file path. */
+ if (fd < 0)
+ {
+ char *altpath = __libdw_filepath (dbg->elf->fildes, NULL, altname);
+ if (altpath != NULL)
+ {
+ fd = TEMP_FAILURE_RETRY (open (altpath, O_RDONLY));
+ free (altpath);
+ }
+ }
+
+ if (fd >= 0)
+ {
+ Dwarf *alt = dwarf_begin (fd, O_RDONLY);
+ if (alt != NULL)
+ {
+ dbg->alt_dwarf = alt;
+ dbg->alt_fd = fd;
+ }
+ else
+ close (fd);
+ }
+}
+
+Dwarf *
+dwarf_getalt (Dwarf *main)
+{
+ /* Only try once. */
+ if (main == NULL || main->alt_dwarf == (void *) -1)
+ return NULL;
+
+ if (main->alt_dwarf != NULL)
+ return main->alt_dwarf;
+
+ find_debug_altlink (main);
+
+ /* If we found nothing, make sure we don't try again. */
+ if (main->alt_dwarf == NULL)
+ {
+ main->alt_dwarf = (void *) -1;
+ return NULL;
+ }
+
+ return main->alt_dwarf;
+}
+INTDEF (dwarf_getalt)