[13/13] dlfcn,elf: impl DLMEM_DONTREPLACE dlmem() flag

diff --git a/dlfcn/Makefile b/dlfcn/Makefile
index 8bca644168..755020af1e 100644
--- a/dlfcn/Makefile
+++ b/dlfcn/Makefile
@@ -52,8 +52,10 @@  endif
 ifeq (yes,$(build-shared))
 tests = glrefmain failtest tst-dladdr default errmsg1 tstcxaatexit \
 	bug-dlopen1 bug-dlsym1 tst-dlinfo bug-atexit1 bug-atexit2 \
-	bug-atexit3 tstatexit bug-dl-leaf tst-rec-dlopen tst-dlmem-fdlopen
+	bug-atexit3 tstatexit bug-dl-leaf tst-rec-dlopen tst-dlmem-fdlopen \
+	tst-dlmem-shm
 CPPFLAGS-tst-dlmem-fdlopen.c += -DBUILDDIR=\"$(objpfx)\"
+CPPFLAGS-tst-dlmem-shm.c += -DBUILDDIR=\"$(objpfx)\"
 endif
 modules-names = glreflib1 glreflib2 glreflib3 failtestmod defaultmod1 \
 		defaultmod2 errmsg1mod modatexit modcxaatexit \
@@ -105,6 +107,7 @@  $(objpfx)failtest.out: $(objpfx)failtestmod.so
 
 $(objpfx)tst-dladdr.out: $(objpfx)glreflib1.so
 $(objpfx)tst-dlmem-fdlopen.out: $(objpfx)glreflib1.so
+$(objpfx)tst-dlmem-shm.out: $(objpfx)glreflib1.so
 
 $(objpfx)tst-dlinfo.out: $(objpfx)glreflib3.so
 LDFLAGS-glreflib3.so = -Wl,-rpath,:
diff --git a/dlfcn/dlfcn.h b/dlfcn/dlfcn.h
index 87dc4932fd..30bb532709 100644
--- a/dlfcn/dlfcn.h
+++ b/dlfcn/dlfcn.h
@@ -73,6 +73,9 @@  typedef void *
 (dlmem_premap_t) (void *mappref, size_t maplength, size_t mapalign,
 	          void *cookie);
 
+/* Do not replace destination mapping. dlmem() will then use memcpy(). */
+#define DLMEM_DONTREPLACE 1
+
 struct dlmem_args {
   /* Optional name to associate with the loaded object. */
   const char *soname;
diff --git a/dlfcn/glreflib1.c b/dlfcn/glreflib1.c
index f26832fabe..bab3fcd1b0 100644
--- a/dlfcn/glreflib1.c
+++ b/dlfcn/glreflib1.c
@@ -22,3 +22,5 @@  ref1 (void)
 {
   return 42;
 }
+
+int bar = 35;
diff --git a/dlfcn/tst-dlmem-shm.c b/dlfcn/tst-dlmem-shm.c
new file mode 100644
index 0000000000..7899dfc909
--- /dev/null
+++ b/dlfcn/tst-dlmem-shm.c
@@ -0,0 +1,169 @@ 
+/* Test for dlmem into shm.
+   Copyright (C) 2000-2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <dlfcn.h>
+#include <link.h>
+#include <errno.h>
+#include <error.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <support/check.h>
+
+static size_t maplen;
+
+static void *
+premap_dlmem (void *mappref, size_t maplength, size_t mapalign, void *cookie)
+{
+  int fd = * (int *) cookie;
+  int prot = PROT_READ | PROT_WRITE;
+  int err;
+
+  /* See if we support such parameters. */
+  if (mappref || mapalign > 4096)
+    return MAP_FAILED;
+
+  fprintf (stderr, "%s\n", __func__);
+
+  err = ftruncate (fd, maplength);
+  if (err)
+    error (EXIT_FAILURE, 0, "ftruncate() failed");
+  maplen = maplength;
+  return mmap (NULL, maplength, prot, MAP_SHARED | MAP_FILE
+#ifdef MAP_32BIT
+                                      | MAP_32BIT
+#endif
+                                      , fd, 0);
+}
+
+#define TEST_FUNCTION do_test
+extern int do_test (void);
+
+int
+do_test (void)
+{
+  void *handle;
+  void *addr;
+  int (*sym) (void); /* We load ref1 from glreflib1.c.  */
+  int *bar, *bar2;
+  unsigned char *addr2;
+  Dl_info info;
+  int ret;
+  int fd;
+  int num;
+  off_t len;
+  struct link_map *lm;
+  const char *shm_name = "/tst-dlmem";
+  int shm_fd;
+  struct dlmem_args a;
+
+  shm_fd = memfd_create (shm_name, 0);
+  if (shm_fd == -1)
+    error (EXIT_FAILURE, 0, "shm_open() failed");
+
+  fd = open (BUILDDIR "glreflib1.so", O_RDONLY);
+  if (fd == -1)
+    error (EXIT_FAILURE, 0, "cannot open: glreflib1.so");
+  len = lseek (fd, 0, SEEK_END);
+  lseek (fd, 0, SEEK_SET);
+  addr = mmap (NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);
+  if (addr == MAP_FAILED)
+    error (EXIT_FAILURE, 0, "cannot mmap: glreflib1.so");
+  a.soname = "glreflib1.so";
+  a.flags = DLMEM_DONTREPLACE;
+  a.nsid = LM_ID_BASE;
+  a.premap = premap_dlmem;
+  a.cookie = &shm_fd;
+  handle = dlmem (addr, len, RTLD_NOW | RTLD_LOCAL, &a);
+  if (handle == NULL)
+    error (EXIT_FAILURE, 0, "cannot load: glreflib1.so");
+  munmap (addr, len);
+  close (fd);
+  /* Check if premap was called. */
+  TEST_VERIFY (maplen != 0);
+
+  sym = dlsym (handle, "ref1");
+  if (sym == NULL)
+    error (EXIT_FAILURE, 0, "dlsym failed");
+
+  memset (&info, 0, sizeof (info));
+  ret = dladdr (sym, &info);
+  if (ret == 0)
+    error (EXIT_FAILURE, 0, "dladdr failed");
+#ifdef MAP_32BIT
+  /* Make sure MAP_32BIT worked. */
+  if ((unsigned long) info.dli_fbase >= 0x100000000)
+    error (EXIT_FAILURE, 0, "premap audit didn't work");
+#endif
+  ret = dlinfo (handle, RTLD_DI_LINKMAP, &lm);
+  if (ret != 0)
+    error (EXIT_FAILURE, 0, "dlinfo failed");
+
+  printf ("info.dli_fname = %p (\"%s\")\n", info.dli_fname, info.dli_fname);
+  printf ("info.dli_fbase = %p\n", info.dli_fbase);
+  printf ("info.dli_sname = %p (\"%s\")\n", info.dli_sname, info.dli_sname);
+  printf ("info.dli_saddr = %p\n", info.dli_saddr);
+  printf ("lm->l_addr = %lx\n", lm->l_addr);
+
+  if (info.dli_fname == NULL)
+    error (EXIT_FAILURE, 0, "dli_fname is NULL");
+  if (info.dli_fbase == NULL)
+    error (EXIT_FAILURE, 0, "dli_fbase is NULL");
+  if (info.dli_sname == NULL)
+    error (EXIT_FAILURE, 0, "dli_sname is NULL");
+  if (info.dli_saddr == NULL)
+    error (EXIT_FAILURE, 0, "dli_saddr is NULL");
+
+  num = sym ();
+  if (num != 42)
+    error (EXIT_FAILURE, 0, "bad return from ref1");
+
+  /* Now try symbol duplication. */
+  bar = dlsym (handle, "bar");
+  if (bar == NULL)
+    error (EXIT_FAILURE, 0, "dlsym failed");
+  TEST_COMPARE (*bar, 35);
+  /* write another value */
+#define TEST_BAR_VAL 48
+  *bar = TEST_BAR_VAL;
+
+  /* Create second instance of the solib. */
+  addr2 = mmap (NULL, maplen, PROT_READ | PROT_WRITE | PROT_EXEC,
+               MAP_SHARED, shm_fd, 0);
+  if (addr2 == MAP_FAILED)
+    error (EXIT_FAILURE, 0, "cannot mmap shm\n");
+  /* Find our bar symbol duplicate. */
+  ret = dladdr (bar, &info);
+  if (ret == 0)
+    error (EXIT_FAILURE, 0, "dladdr failed");
+  bar2 = (int *) (addr2 + (info.dli_saddr - info.dli_fbase));
+  /* See if we found the right one. */
+  TEST_COMPARE (*bar2, TEST_BAR_VAL);
+
+  munmap (addr2, maplen);
+  close (shm_fd);
+  dlclose (handle);
+
+  return 0;
+}
+
+
+#include <support/test-driver.c>
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 2550173f48..e7216c74c3 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -2385,6 +2385,25 @@  do_memremap (void *addr, size_t length, int prot, int flags,
   return addr;
 }
 
+static void *
+do_mmapcpy (void *addr, size_t length, int prot, int flags,
+            void *arg, off_t offset)
+{
+  const struct dlmem_fbuf *fb = arg;
+
+  assert (flags & MAP_FIXED);
+  if (offset < fb->len)
+    {
+      size_t to_copy = length;
+      if (offset + to_copy > fb->len)
+        to_copy = fb->len - offset;
+      memcpy (addr, fb->buf + offset, to_copy);
+    }
+  if (__mprotect (addr, length, prot) == -1)
+    return MAP_FAILED;
+  return addr;
+}
+
 static void *
 do_dlmem_premap (void *mappref, size_t maplength, size_t mapalign,
 		 void *cookie)
@@ -2428,6 +2447,10 @@  ___dl_map_object_from_mem (struct link_map *loader, const char *name,
   struct r_debug *r = _dl_debug_update (nsid);
   bool make_consistent = false;
   struct r_file_id id = {};
+  const struct dlmem_fbuf *fb = private;
+  unsigned dlmem_flags = fb->dlm_args ? fb->dlm_args->flags : 0;
+  __typeof (do_mmap) *m_map = (dlmem_flags & DLMEM_DONTREPLACE)
+                             ? do_mmapcpy : do_memremap;
 
   assert (nsid >= 0);
   assert (nsid < GL(dl_nns));
@@ -2478,7 +2501,7 @@  ___dl_map_object_from_mem (struct link_map *loader, const char *name,
 
   void *stack_end = __libc_stack_end;
   if (_ld_map_object_1 (l, private, fbp, mode, loader, &stack_end, &errval,
-                        &errstring, do_memremap, do_dlmem_premap))
+                        &errstring, m_map, do_dlmem_premap))
     goto lose;
 
   _ld_map_object_2 (l, mode, id, NULL, nsid, r, &make_consistent);