File gdb-6.6-buildid-locate.patch of Package gdb

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File gdb-6.6-buildid-locate.patch of Package gdb (Revision b14e3ea05919fa8bab2669f9bc0d280d)

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From FEDORA_PATCHES Mon Sep 17 00:00:00 2001
From: Fedora GDB patches <invalid@email.com>
Date: Fri, 27 Oct 2017 21:07:50 +0200
Subject: gdb-6.6-buildid-locate.patch

;; New locating of the matching binaries from the pure core file (build-id).
;;=push+jan

diff --git a/bfd/libbfd-in.h b/bfd/libbfd-in.h
index 1f7e22186ec..ec757bf1161 100644
--- a/bfd/libbfd-in.h
+++ b/bfd/libbfd-in.h
@@ -115,7 +115,7 @@ static inline char *
 bfd_strdup (const char *str)
 {
   size_t len = strlen (str) + 1;
-  char *buf = bfd_malloc (len);
+  char *buf = (char *) bfd_malloc (len);
   if (buf != NULL)
     memcpy (buf, str, len);
   return buf;
@@ -921,7 +921,7 @@ _bfd_alloc_and_read (bfd *abfd, bfd_size_type asize, bfd_size_type rsize)
 	  return NULL;
 	}
     }
-  mem = bfd_alloc (abfd, asize);
+  mem = (bfd_byte *) bfd_alloc (abfd, asize);
   if (mem != NULL)
     {
       if (bfd_bread (mem, rsize, abfd) == rsize)
@@ -944,7 +944,7 @@ _bfd_malloc_and_read (bfd *abfd, bfd_size_type asize, bfd_size_type rsize)
 	  return NULL;
 	}
     }
-  mem = bfd_malloc (asize);
+  mem = (bfd_byte *) bfd_malloc (asize);
   if (mem != NULL)
     {
       if (bfd_bread (mem, rsize, abfd) == rsize)
diff --git a/bfd/libbfd.h b/bfd/libbfd.h
index c37ddc03cfd..cba43417da5 100644
--- a/bfd/libbfd.h
+++ b/bfd/libbfd.h
@@ -120,7 +120,7 @@ static inline char *
 bfd_strdup (const char *str)
 {
   size_t len = strlen (str) + 1;
-  char *buf = bfd_malloc (len);
+  char *buf = (char *) bfd_malloc (len);
   if (buf != NULL)
     memcpy (buf, str, len);
   return buf;
@@ -926,7 +926,7 @@ _bfd_alloc_and_read (bfd *abfd, bfd_size_type asize, bfd_size_type rsize)
 	  return NULL;
 	}
     }
-  mem = bfd_alloc (abfd, asize);
+  mem = (bfd_byte *) bfd_alloc (abfd, asize);
   if (mem != NULL)
     {
       if (bfd_bread (mem, rsize, abfd) == rsize)
@@ -949,7 +949,7 @@ _bfd_malloc_and_read (bfd *abfd, bfd_size_type asize, bfd_size_type rsize)
 	  return NULL;
 	}
     }
-  mem = bfd_malloc (asize);
+  mem = (bfd_byte *) bfd_malloc (asize);
   if (mem != NULL)
     {
       if (bfd_bread (mem, rsize, abfd) == rsize)
diff --git a/gdb/build-id.c b/gdb/build-id.c
index d2f2576d96d..e2b3082b5d0 100644
--- a/gdb/build-id.c
+++ b/gdb/build-id.c
@@ -24,13 +24,71 @@
 #include "gdbsupport/gdb_vecs.h"
 #include "symfile.h"
 #include "objfiles.h"
+#include <sys/stat.h>
+#include "elf-bfd.h"
+#include "elf/common.h"
+#include "elf/external.h"
+#include "elf/internal.h"
 #include "filenames.h"
+#include "gdb_bfd.h"
+#include "gdbcmd.h"
 #include "gdbcore.h"
+#include "libbfd.h"
+#include "objfiles.h"
+#include "observable.h"
+#include "symfile.h"
+
+#define BUILD_ID_VERBOSE_NONE 0
+#define BUILD_ID_VERBOSE_FILENAMES 1
+#define BUILD_ID_VERBOSE_BINARY_PARSE 2
+static int build_id_verbose = BUILD_ID_VERBOSE_FILENAMES;
+static void
+show_build_id_verbose (struct ui_file *file, int from_tty,
+		       struct cmd_list_element *c, const char *value)
+{
+  fprintf_filtered (file, _("Verbosity level of the build-id locator is %s.\n"),
+		    value);
+}
+/* Locate NT_GNU_BUILD_ID and return its matching debug filename.
+   FIXME: NOTE decoding should be unified with the BFD core notes decoding.  */
+
+static struct bfd_build_id *
+build_id_buf_get (bfd *templ, gdb_byte *buf, bfd_size_type size)
+{
+  bfd_byte *p;
+
+  p = buf;
+  while (p < buf + size)
+    {
+      /* FIXME: bad alignment assumption.  */
+      Elf_External_Note *xnp = (Elf_External_Note *) p;
+      size_t namesz = H_GET_32 (templ, xnp->namesz);
+      size_t descsz = H_GET_32 (templ, xnp->descsz);
+      bfd_byte *descdata = (gdb_byte *) xnp->name + BFD_ALIGN (namesz, 4);
+
+      if (H_GET_32 (templ, xnp->type) == NT_GNU_BUILD_ID
+	  && namesz == sizeof "GNU"
+	  && memcmp (xnp->name, "GNU", sizeof "GNU") == 0)
+	{
+	  size_t sz = descsz;
+	  gdb_byte *data = (gdb_byte *) descdata;
+	  struct bfd_build_id *retval;
+
+	  retval = (struct bfd_build_id *) xmalloc (sizeof *retval - 1 + sz);
+	  retval->size = sz;
+	  memcpy (retval->data, data, sz);
+
+	  return retval;
+	}
+      p = descdata + BFD_ALIGN (descsz, 4);
+    }
+  return NULL;
+}
 
 /* See build-id.h.  */
 
 const struct bfd_build_id *
-build_id_bfd_get (bfd *abfd)
+build_id_bfd_shdr_get (bfd *abfd)
 {
   if (!bfd_check_format (abfd, bfd_object)
       && !bfd_check_format (abfd, bfd_core))
@@ -43,6 +101,348 @@ build_id_bfd_get (bfd *abfd)
   return NULL;
 }
 
+/* Core files may have missing (corrupt) SHDR but PDHR is correct there.
+   bfd_elf_bfd_from_remote_memory () has too much overhead by
+   allocating/reading all the available ELF PT_LOADs.  */
+
+static struct bfd_build_id *
+build_id_phdr_get (bfd *templ, bfd_vma loadbase, unsigned e_phnum,
+		   Elf_Internal_Phdr *i_phdr)
+{
+  int i;
+  struct bfd_build_id *retval = NULL;
+
+  for (i = 0; i < e_phnum; i++)
+    if (i_phdr[i].p_type == PT_NOTE && i_phdr[i].p_filesz > 0)
+      {
+	Elf_Internal_Phdr *hdr = &i_phdr[i];
+	gdb_byte *buf;
+	int err;
+
+	buf = (gdb_byte *) xmalloc (hdr->p_filesz);
+	err = target_read_memory (loadbase + i_phdr[i].p_vaddr, buf,
+				  hdr->p_filesz);
+	if (err == 0)
+	  retval = build_id_buf_get (templ, buf, hdr->p_filesz);
+	else
+	  retval = NULL;
+	xfree (buf);
+	if (retval != NULL)
+	  break;
+      }
+  return retval;
+}
+
+/* First we validate the file by reading in the ELF header and checking
+   the magic number.  */
+
+static inline bfd_boolean
+elf_file_p (Elf64_External_Ehdr *x_ehdrp64)
+{
+  gdb_assert (sizeof (Elf64_External_Ehdr) >= sizeof (Elf32_External_Ehdr));
+  gdb_assert (offsetof (Elf64_External_Ehdr, e_ident)
+	      == offsetof (Elf32_External_Ehdr, e_ident));
+  gdb_assert (sizeof (((Elf64_External_Ehdr *) 0)->e_ident)
+	      == sizeof (((Elf32_External_Ehdr *) 0)->e_ident));
+
+  return ((x_ehdrp64->e_ident[EI_MAG0] == ELFMAG0)
+	  && (x_ehdrp64->e_ident[EI_MAG1] == ELFMAG1)
+	  && (x_ehdrp64->e_ident[EI_MAG2] == ELFMAG2)
+	  && (x_ehdrp64->e_ident[EI_MAG3] == ELFMAG3));
+}
+
+/* Translate an ELF file header in external format into an ELF file header in
+   internal format.  */
+
+#define H_GET_WORD(bfd, ptr) (is64 ? H_GET_64 (bfd, (ptr))		\
+				   : H_GET_32 (bfd, (ptr)))
+#define H_GET_SIGNED_WORD(bfd, ptr) (is64 ? H_GET_S64 (bfd, (ptr))	\
+					  : H_GET_S32 (bfd, (ptr)))
+
+static void
+elf_swap_ehdr_in (bfd *abfd,
+		  const Elf64_External_Ehdr *src64,
+		  Elf_Internal_Ehdr *dst)
+{
+  int is64 = bfd_get_arch_size (abfd) == 64;
+#define SRC(field) (is64 ? src64->field \
+			 : ((const Elf32_External_Ehdr *) src64)->field)
+
+  int signed_vma = get_elf_backend_data (abfd)->sign_extend_vma;
+  memcpy (dst->e_ident, SRC (e_ident), EI_NIDENT);
+  dst->e_type = H_GET_16 (abfd, SRC (e_type));
+  dst->e_machine = H_GET_16 (abfd, SRC (e_machine));
+  dst->e_version = H_GET_32 (abfd, SRC (e_version));
+  if (signed_vma)
+    dst->e_entry = H_GET_SIGNED_WORD (abfd, SRC (e_entry));
+  else
+    dst->e_entry = H_GET_WORD (abfd, SRC (e_entry));
+  dst->e_phoff = H_GET_WORD (abfd, SRC (e_phoff));
+  dst->e_shoff = H_GET_WORD (abfd, SRC (e_shoff));
+  dst->e_flags = H_GET_32 (abfd, SRC (e_flags));
+  dst->e_ehsize = H_GET_16 (abfd, SRC (e_ehsize));
+  dst->e_phentsize = H_GET_16 (abfd, SRC (e_phentsize));
+  dst->e_phnum = H_GET_16 (abfd, SRC (e_phnum));
+  dst->e_shentsize = H_GET_16 (abfd, SRC (e_shentsize));
+  dst->e_shnum = H_GET_16 (abfd, SRC (e_shnum));
+  dst->e_shstrndx = H_GET_16 (abfd, SRC (e_shstrndx));
+
+#undef SRC
+}
+
+/* Translate an ELF program header table entry in external format into an
+   ELF program header table entry in internal format.  */
+
+static void
+elf_swap_phdr_in (bfd *abfd,
+		  const Elf64_External_Phdr *src64,
+		  Elf_Internal_Phdr *dst)
+{
+  int is64 = bfd_get_arch_size (abfd) == 64;
+#define SRC(field) (is64 ? src64->field					\
+			 : ((const Elf32_External_Phdr *) src64)->field)
+
+  int signed_vma = get_elf_backend_data (abfd)->sign_extend_vma;
+
+  dst->p_type = H_GET_32 (abfd, SRC (p_type));
+  dst->p_flags = H_GET_32 (abfd, SRC (p_flags));
+  dst->p_offset = H_GET_WORD (abfd, SRC (p_offset));
+  if (signed_vma)
+    {
+      dst->p_vaddr = H_GET_SIGNED_WORD (abfd, SRC (p_vaddr));
+      dst->p_paddr = H_GET_SIGNED_WORD (abfd, SRC (p_paddr));
+    }
+  else
+    {
+      dst->p_vaddr = H_GET_WORD (abfd, SRC (p_vaddr));
+      dst->p_paddr = H_GET_WORD (abfd, SRC (p_paddr));
+    }
+  dst->p_filesz = H_GET_WORD (abfd, SRC (p_filesz));
+  dst->p_memsz = H_GET_WORD (abfd, SRC (p_memsz));
+  dst->p_align = H_GET_WORD (abfd, SRC (p_align));
+
+#undef SRC
+}
+
+#undef H_GET_SIGNED_WORD
+#undef H_GET_WORD
+
+static Elf_Internal_Phdr *
+elf_get_phdr (bfd *templ, bfd_vma ehdr_vma, unsigned *e_phnum_pointer,
+              bfd_vma *loadbase_pointer)
+{
+  /* sizeof (Elf64_External_Ehdr) >= sizeof (Elf32_External_Ehdr)  */
+  Elf64_External_Ehdr x_ehdr64;	/* Elf file header, external form */
+  Elf_Internal_Ehdr i_ehdr;	/* Elf file header, internal form */
+  bfd_size_type x_phdrs_size;
+  gdb_byte *x_phdrs_ptr;
+  Elf_Internal_Phdr *i_phdrs;
+  int err;
+  unsigned int i;
+  bfd_vma loadbase;
+  int loadbase_set;
+
+  gdb_assert (templ != NULL);
+  gdb_assert (sizeof (Elf64_External_Ehdr) >= sizeof (Elf32_External_Ehdr));
+
+  /* Read in the ELF header in external format.  */
+  err = target_read_memory (ehdr_vma, (bfd_byte *) &x_ehdr64, sizeof x_ehdr64);
+  if (err)
+    {
+      if (build_id_verbose >= BUILD_ID_VERBOSE_BINARY_PARSE)
+        warning (_("build-id: Error reading ELF header at address 0x%lx"),
+		 (unsigned long) ehdr_vma);
+      return NULL;
+    }
+
+  /* Now check to see if we have a valid ELF file, and one that BFD can
+     make use of.  The magic number must match, the address size ('class')
+     and byte-swapping must match our XVEC entry.  */
+
+  if (! elf_file_p (&x_ehdr64)
+      || x_ehdr64.e_ident[EI_VERSION] != EV_CURRENT
+      || !((bfd_get_arch_size (templ) == 64
+            && x_ehdr64.e_ident[EI_CLASS] == ELFCLASS64)
+           || (bfd_get_arch_size (templ) == 32
+	       && x_ehdr64.e_ident[EI_CLASS] == ELFCLASS32)))
+    {
+      if (build_id_verbose >= BUILD_ID_VERBOSE_BINARY_PARSE)
+        warning (_("build-id: Unrecognized ELF header at address 0x%lx"),
+		 (unsigned long) ehdr_vma);
+      return NULL;
+    }
+
+  /* Check that file's byte order matches xvec's */
+  switch (x_ehdr64.e_ident[EI_DATA])
+    {
+    case ELFDATA2MSB:		/* Big-endian */
+      if (! bfd_header_big_endian (templ))
+	{
+	  if (build_id_verbose >= BUILD_ID_VERBOSE_BINARY_PARSE)
+	    warning (_("build-id: Unrecognized "
+		       "big-endian ELF header at address 0x%lx"),
+		     (unsigned long) ehdr_vma);
+	  return NULL;
+	}
+      break;
+    case ELFDATA2LSB:		/* Little-endian */
+      if (! bfd_header_little_endian (templ))
+	{
+	  if (build_id_verbose >= BUILD_ID_VERBOSE_BINARY_PARSE)
+	    warning (_("build-id: Unrecognized "
+		       "little-endian ELF header at address 0x%lx"),
+		     (unsigned long) ehdr_vma);
+	  return NULL;
+	}
+      break;
+    case ELFDATANONE:		/* No data encoding specified */
+    default:			/* Unknown data encoding specified */
+      if (build_id_verbose >= BUILD_ID_VERBOSE_BINARY_PARSE)
+	warning (_("build-id: Unrecognized "
+		   "ELF header endianity at address 0x%lx"),
+		 (unsigned long) ehdr_vma);
+      return NULL;
+    }
+
+  elf_swap_ehdr_in (templ, &x_ehdr64, &i_ehdr);
+
+  /* The file header tells where to find the program headers.
+     These are what we use to actually choose what to read.  */
+
+  if (i_ehdr.e_phentsize != (bfd_get_arch_size (templ) == 64
+                             ? sizeof (Elf64_External_Phdr)
+			     : sizeof (Elf32_External_Phdr))
+      || i_ehdr.e_phnum == 0)
+    {
+      if (build_id_verbose >= BUILD_ID_VERBOSE_BINARY_PARSE)
+	warning (_("build-id: Invalid ELF program headers from the ELF header "
+		   "at address 0x%lx"), (unsigned long) ehdr_vma);
+      return NULL;
+    }
+
+  x_phdrs_size = (bfd_get_arch_size (templ) == 64 ? sizeof (Elf64_External_Phdr)
+						: sizeof (Elf32_External_Phdr));
+
+  i_phdrs = (Elf_Internal_Phdr *) xmalloc (i_ehdr.e_phnum * (sizeof *i_phdrs + x_phdrs_size));
+  x_phdrs_ptr = (gdb_byte *) &i_phdrs[i_ehdr.e_phnum];
+  err = target_read_memory (ehdr_vma + i_ehdr.e_phoff, (bfd_byte *) x_phdrs_ptr,
+			    i_ehdr.e_phnum * x_phdrs_size);
+  if (err)
+    {
+      free (i_phdrs);
+      if (build_id_verbose >= BUILD_ID_VERBOSE_BINARY_PARSE)
+        warning (_("build-id: Error reading "
+		   "ELF program headers at address 0x%lx"),
+		 (unsigned long) (ehdr_vma + i_ehdr.e_phoff));
+      return NULL;
+    }
+
+  loadbase = ehdr_vma;
+  loadbase_set = 0;
+  for (i = 0; i < i_ehdr.e_phnum; ++i)
+    {
+      elf_swap_phdr_in (templ, (Elf64_External_Phdr *)
+			       (x_phdrs_ptr + i * x_phdrs_size), &i_phdrs[i]);
+      /* IA-64 vDSO may have two mappings for one segment, where one mapping
+	 is executable only, and one is read only.  We must not use the
+	 executable one (PF_R is the first one, PF_X the second one).  */
+      if (i_phdrs[i].p_type == PT_LOAD && (i_phdrs[i].p_flags & PF_R))
+	{
+	  /* Only the first PT_LOAD segment indicates the file bias.
+	     Next segments may have P_VADDR arbitrarily higher.
+	     If the first segment has P_VADDR zero any next segment must not
+	     confuse us, the first one sets LOADBASE certainly enough.  */
+	  if (!loadbase_set && i_phdrs[i].p_offset == 0)
+	    {
+	      loadbase = ehdr_vma - i_phdrs[i].p_vaddr;
+	      loadbase_set = 1;
+	    }
+	}
+    }
+
+  if (build_id_verbose >= BUILD_ID_VERBOSE_BINARY_PARSE)
+    warning (_("build-id: Found ELF header at address 0x%lx, loadbase 0x%lx"),
+	     (unsigned long) ehdr_vma, (unsigned long) loadbase);
+
+  *e_phnum_pointer = i_ehdr.e_phnum;
+  *loadbase_pointer = loadbase;
+  return i_phdrs;
+}
+
+/* BUILD_ID_ADDR_GET gets ADDR located somewhere in the object.
+   Find the first section before ADDR containing an ELF header.
+   We rely on the fact the sections from multiple files do not mix.
+   FIXME: We should check ADDR is contained _inside_ the section with possibly
+   missing content (P_FILESZ < P_MEMSZ).  These omitted sections are currently
+   hidden by _BFD_ELF_MAKE_SECTION_FROM_PHDR.  */
+
+static CORE_ADDR build_id_addr;
+struct build_id_addr_sect
+  {
+    struct build_id_addr_sect *next;
+    asection *sect;
+  };
+static struct build_id_addr_sect *build_id_addr_sect;
+
+static void build_id_addr_candidate (bfd *abfd, asection *sect, void *obj)
+{
+  if (build_id_addr >= bfd_section_vma (sect))
+    {
+      struct build_id_addr_sect *candidate;
+
+      candidate = (struct build_id_addr_sect *) xmalloc (sizeof *candidate);
+      candidate->next = build_id_addr_sect;
+      build_id_addr_sect = candidate;
+      candidate->sect = sect;
+    }
+}
+
+struct bfd_build_id *
+build_id_addr_get (CORE_ADDR addr)
+{
+  struct build_id_addr_sect *candidate;
+  struct bfd_build_id *retval = NULL;
+  Elf_Internal_Phdr *i_phdr = NULL;
+  bfd_vma loadbase = 0;
+  unsigned e_phnum = 0;
+
+  if (core_bfd == NULL)
+    return NULL;
+
+  build_id_addr = addr;
+  gdb_assert (build_id_addr_sect == NULL);
+  bfd_map_over_sections (core_bfd, build_id_addr_candidate, NULL);
+
+  /* Sections are sorted in the high-to-low VMAs order.
+     Stop the search on the first ELF header we find.
+     Do not continue the search even if it does not contain NT_GNU_BUILD_ID.  */
+
+  for (candidate = build_id_addr_sect; candidate != NULL;
+       candidate = candidate->next)
+    {
+      i_phdr = elf_get_phdr (core_bfd,
+			     bfd_section_vma (candidate->sect),
+			     &e_phnum, &loadbase);
+      if (i_phdr != NULL)
+	break;
+    }
+
+  if (i_phdr != NULL)
+    {
+      retval = build_id_phdr_get (core_bfd, loadbase, e_phnum, i_phdr);
+      xfree (i_phdr);
+    }
+
+  while (build_id_addr_sect != NULL)
+    {
+      candidate = build_id_addr_sect;
+      build_id_addr_sect = candidate->next;
+      xfree (candidate);
+    }
+
+  return retval;
+}
+
 /* See build-id.h.  */
 
 int
@@ -51,7 +451,7 @@ build_id_verify (bfd *abfd, size_t check_len, const bfd_byte *check)
   const struct bfd_build_id *found;
   int retval = 0;
 
-  found = build_id_bfd_get (abfd);
+  found = build_id_bfd_shdr_get (abfd);
 
   if (found == NULL)
     warning (_("File \"%s\" has no build-id, file skipped"),
@@ -66,56 +466,164 @@ build_id_verify (bfd *abfd, size_t check_len, const bfd_byte *check)
   return retval;
 }
 
+static char *
+link_resolve (const char *symlink, int level)
+{
+  char buf[PATH_MAX + 1], *target, *retval;
+  ssize_t got;
+
+  if (level > 10)
+    return xstrdup (symlink);
+
+  got = readlink (symlink, buf, sizeof (buf));
+  if (got < 0 || got >= sizeof (buf))
+    return xstrdup (symlink);
+  buf[got] = '\0';
+
+  if (IS_ABSOLUTE_PATH (buf))
+    target = xstrdup (buf);
+  else
+    {
+      const std::string dir (ldirname (symlink));
+
+      target = xstrprintf ("%s"
+#ifndef HAVE_DOS_BASED_FILE_SYSTEM
+			   "/"
+#else /* HAVE_DOS_BASED_FILE_SYSTEM */
+			   "\\"
+#endif /* HAVE_DOS_BASED_FILE_SYSTEM */
+			   "%s", dir.c_str(), buf);
+    }
+
+  retval = link_resolve (target, level + 1);
+  xfree (target);
+  return retval;
+}
+
 /* Helper for build_id_to_debug_bfd.  LINK is a path to a potential
    build-id-based separate debug file, potentially a symlink to the real file.
    If the file exists and matches BUILD_ID, return a BFD reference to it.  */
 
 static gdb_bfd_ref_ptr
-build_id_to_debug_bfd_1 (const std::string &link, size_t build_id_len,
-			 const bfd_byte *build_id)
+build_id_to_debug_bfd_1 (const std::string &orig_link, size_t build_id_len,
+			 const bfd_byte *build_id, char **link_return,
+			 const char *suffix)
 {
+  gdb_bfd_ref_ptr ret_bfd = {};
+  std::string ret_link;
+
   if (separate_debug_file_debug)
     {
-      printf_unfiltered (_("  Trying %s..."), link.c_str ());
+      printf_unfiltered (_("  Trying %s..."), orig_link.c_str ());
       gdb_flush (gdb_stdout);
     }
 
-  /* lrealpath() is expensive even for the usually non-existent files.  */
-  gdb::unique_xmalloc_ptr<char> filename;
-  if (access (link.c_str (), F_OK) == 0)
-    filename.reset (lrealpath (link.c_str ()));
-
-  if (filename == NULL)
+  for (unsigned seqno = 0;; seqno++)
     {
-      if (separate_debug_file_debug)
-	printf_unfiltered (_(" no, unable to compute real path\n"));
+      std::string link = orig_link;
 
-      return {};
-    }
+      if (seqno > 0)
+	{
+	  /* There can be multiple build-id symlinks pointing to real files
+	     with the same build-id (such as hard links).  Some of the real
+	     files may not be installed.  */
 
-  /* We expect to be silent on the non-existing files.  */
-  gdb_bfd_ref_ptr debug_bfd = gdb_bfd_open (filename.get (), gnutarget);
+	  string_appendf (link, ".%u", seqno);
+	}
 
-  if (debug_bfd == NULL)
-    {
-      if (separate_debug_file_debug)
-	printf_unfiltered (_(" no, unable to open.\n"));
+      link += suffix;
+
+      ret_link = link;
+
+      struct stat statbuf_trash;
+
+      /* `access' automatically dereferences LINK.  */
+      if (lstat (link.c_str (), &statbuf_trash) != 0)
+	{
+	  /* Stop increasing SEQNO.  */
+	  break;
+	}
+
+      /* lrealpath() is expensive even for the usually non-existent files.  */
+      gdb::unique_xmalloc_ptr<char> filename;
+
+      if (access (link.c_str (), F_OK) == 0)
+	filename.reset (lrealpath (link.c_str ()));
+
+      if (filename == NULL)
+	{
+	  if (separate_debug_file_debug)
+	    printf_unfiltered (_(" no, unable to compute real path\n"));
+
+	  continue;
+	}
+
+      /* We expect to be silent on the non-existing files.  */
+      gdb_bfd_ref_ptr debug_bfd = gdb_bfd_open (filename.get (), gnutarget);
 
-      return {};
+      if (debug_bfd == NULL)
+	{
+	  if (separate_debug_file_debug)
+	    printf_unfiltered (_(" no, unable to open.\n"));
+
+	  continue;
+	}
+
+      if (!build_id_verify (debug_bfd.get(), build_id_len, build_id))
+	{
+	  if (separate_debug_file_debug)
+	    printf_unfiltered (_(" no, build-id does not match.\n"));
+
+	  continue;
+	}
+
+      ret_bfd = debug_bfd;
+      break;
     }
 
-  if (!build_id_verify (debug_bfd.get(), build_id_len, build_id))
+  std::string link_all;
+
+  if (ret_bfd != NULL)
     {
       if (separate_debug_file_debug)
-	printf_unfiltered (_(" no, build-id does not match.\n"));
+	printf_unfiltered (_(" yes!\n"));
+    }
+  else
+    {
+      /* If none of the real files is found report as missing file
+	 always the non-.%u-suffixed file.  */
+      std::string link0 = orig_link;
+
+      link0 += suffix;
 
-      return {};
+      /* If the symlink has target request to install the target.
+	 BASE-debuginfo.rpm contains the symlink but BASE.rpm may be missing.
+	 https://bugzilla.redhat.com/show_bug.cgi?id=981154  */
+      std::string link0_resolved (link_resolve (link0.c_str (), 0));
+
+      if (link_all.empty ())
+	link_all = link0_resolved;
+      else
+	{
+	  /* Use whitespace instead of DIRNAME_SEPARATOR to be compatible with
+	     its possible use as an argument for installation command.  */
+	  link_all += " " + link0_resolved;
+	}
     }
 
-  if (separate_debug_file_debug)
-    printf_unfiltered (_(" yes!\n"));
+  if (link_return != NULL)
+    {
+      if (ret_bfd != NULL)
+	{
+	  *link_return = xstrdup (ret_link.c_str ());
+	}
+      else
+	{
+	  *link_return = xstrdup (link_all.c_str ());
+	}
+    }
 
-  return debug_bfd;
+  return ret_bfd;
 }
 
 /* Common code for finding BFDs of a given build-id.  This function
@@ -124,7 +632,7 @@ build_id_to_debug_bfd_1 (const std::string &link, size_t build_id_len,
 
 static gdb_bfd_ref_ptr
 build_id_to_bfd_suffix (size_t build_id_len, const bfd_byte *build_id,
-			const char *suffix)
+			char **link_return, const char *suffix)
 {
   /* Keep backward compatibility so that DEBUG_FILE_DIRECTORY being "" will
      cause "/.build-id/..." lookups.  */
@@ -147,16 +655,17 @@ build_id_to_bfd_suffix (size_t build_id_len, const bfd_byte *build_id,
       if (size > 0)
 	{
 	  size--;
-	  string_appendf (link, "%02x/", (unsigned) *data++);
+	  string_appendf (link, "%02x", (unsigned) *data++);
 	}
 
+      if (size > 0)
+	link += "/";
       while (size-- > 0)
 	string_appendf (link, "%02x", (unsigned) *data++);
 
-      link += suffix;
-
       gdb_bfd_ref_ptr debug_bfd
-	= build_id_to_debug_bfd_1 (link, build_id_len, build_id);
+	= build_id_to_debug_bfd_1 (link, build_id_len, build_id,
+				   link_return, suffix);
       if (debug_bfd != NULL)
 	return debug_bfd;
 
@@ -170,7 +679,8 @@ build_id_to_bfd_suffix (size_t build_id_len, const bfd_byte *build_id,
       if (strcmp (gdb_sysroot, TARGET_SYSROOT_PREFIX) != 0)
 	{
 	  link = gdb_sysroot + link;
-	  debug_bfd = build_id_to_debug_bfd_1 (link, build_id_len, build_id);
+	  debug_bfd = build_id_to_debug_bfd_1 (link, build_id_len, build_id,
+					       link_return, suffix);
 	  if (debug_bfd != NULL)
 	    return debug_bfd;
 	}
@@ -182,9 +692,10 @@ build_id_to_bfd_suffix (size_t build_id_len, const bfd_byte *build_id,
 /* See build-id.h.  */
 
 gdb_bfd_ref_ptr
-build_id_to_debug_bfd (size_t build_id_len, const bfd_byte *build_id)
+build_id_to_debug_bfd (size_t build_id_len, const bfd_byte *build_id,
+		       char **link_return)
 {
-  return build_id_to_bfd_suffix (build_id_len, build_id, ".debug");
+  return build_id_to_bfd_suffix (build_id_len, build_id, link_return, ".debug");
 }
 
 /* See build-id.h.  */
@@ -192,25 +703,192 @@ build_id_to_debug_bfd (size_t build_id_len, const bfd_byte *build_id)
 gdb_bfd_ref_ptr
 build_id_to_exec_bfd (size_t build_id_len, const bfd_byte *build_id)
 {
-  return build_id_to_bfd_suffix (build_id_len, build_id, "");
+  return build_id_to_bfd_suffix (build_id_len, build_id, NULL, "");
+}
+
+char *
+build_id_to_filename (const struct bfd_build_id *build_id, char **link_return)
+{
+  gdb_bfd_ref_ptr abfd;
+  char *result;
+  
+  abfd = build_id_to_bfd_suffix (build_id->size, build_id->data, link_return, "");
+  if (abfd == NULL)
+    return NULL;
+
+  result = xstrdup (bfd_get_filename (abfd.get ()));
+  return result;
+}
+
+/* This MISSING_FILEPAIR_HASH tracker is used only for the duplicite messages
+     Try to install the hash file ...
+   avoidance.  */
+
+struct missing_filepair
+  {
+    char *binary;
+    char *debug;
+    char data[1];
+  };
+
+static struct htab *missing_filepair_hash;
+static struct obstack missing_filepair_obstack;
+
+static void *
+missing_filepair_xcalloc (size_t nmemb, size_t nmemb_size)
+{
+  void *retval;
+  size_t size = nmemb * nmemb_size;
+
+  retval = obstack_alloc (&missing_filepair_obstack, size);
+  memset (retval, 0, size);
+  return retval;
+}
+
+static hashval_t
+missing_filepair_hash_func (const struct missing_filepair *elem)
+{
+  hashval_t retval = 0;
+
+  retval ^= htab_hash_string (elem->binary);
+  if (elem->debug != NULL)
+    retval ^= htab_hash_string (elem->debug);
+
+  return retval;
+}
+
+static int
+missing_filepair_eq (const struct missing_filepair *elem1,
+		       const struct missing_filepair *elem2)
+{
+  return strcmp (elem1->binary, elem2->binary) == 0
+         && ((elem1->debug == NULL) == (elem2->debug == NULL))
+         && (elem1->debug == NULL || strcmp (elem1->debug, elem2->debug) == 0);
+}
+
+static void
+missing_filepair_change (void)
+{
+  if (missing_filepair_hash != NULL)
+    {
+      obstack_free (&missing_filepair_obstack, NULL);
+      /* All their memory came just from missing_filepair_OBSTACK.  */
+      missing_filepair_hash = NULL;
+    }
+}
+
+static void
+debug_print_executable_changed (void)
+{
+  missing_filepair_change ();
+}
+
+/* Notify user the file BINARY with (possibly NULL) associated separate debug
+   information file DEBUG is missing.  DEBUG may or may not be the build-id
+   file such as would be:
+     /usr/lib/debug/.build-id/dd/b1d2ce632721c47bb9e8679f369e2295ce71be.debug
+   */
+
+void
+debug_print_missing (const char *binary, const char *debug)
+{
+  size_t binary_len0 = strlen (binary) + 1;
+  size_t debug_len0 = debug ? strlen (debug) + 1 : 0;
+  struct missing_filepair missing_filepair_find;
+  struct missing_filepair *missing_filepair;
+  struct missing_filepair **slot;
+
+  if (build_id_verbose < BUILD_ID_VERBOSE_FILENAMES)
+    return;
+
+  if (missing_filepair_hash == NULL)
+    {
+      obstack_init (&missing_filepair_obstack);
+      missing_filepair_hash = htab_create_alloc (64,
+	(hashval_t (*) (const void *)) missing_filepair_hash_func,
+	(int (*) (const void *, const void *)) missing_filepair_eq, NULL,
+	missing_filepair_xcalloc, NULL);
+    }
+
+  /* Use MISSING_FILEPAIR_FIND first instead of calling obstack_alloc with
+     obstack_free in the case of a (rare) match.  The problem is ALLOC_F for
+     MISSING_FILEPAIR_HASH allocates from MISSING_FILEPAIR_OBSTACK maintenance
+     structures for MISSING_FILEPAIR_HASH.  Calling obstack_free would possibly
+     not to free only MISSING_FILEPAIR but also some such structures (allocated
+     during the htab_find_slot call).  */
+
+  missing_filepair_find.binary = (char *) binary;
+  missing_filepair_find.debug = (char *) debug;
+  slot = (struct missing_filepair **) htab_find_slot (missing_filepair_hash,
+						      &missing_filepair_find,
+						      INSERT);
+
+  /* While it may be still printed duplicitely with the missing debuginfo file
+   * it is due to once printing about the binary file build-id link and once
+   * about the .debug file build-id link as both the build-id symlinks are
+   * located in the debuginfo package.  */
+
+  if (*slot != NULL)
+    return;
+
+  missing_filepair = (struct missing_filepair *) obstack_alloc (&missing_filepair_obstack,
+								sizeof (*missing_filepair) - 1
+								+ binary_len0 + debug_len0);
+  missing_filepair->binary = missing_filepair->data;
+  memcpy (missing_filepair->binary, binary, binary_len0);
+  if (debug != NULL)
+    {
+      missing_filepair->debug = missing_filepair->binary + binary_len0;
+      memcpy (missing_filepair->debug, debug, debug_len0);
+    }
+  else
+    missing_filepair->debug = NULL;
+
+  *slot = missing_filepair;
+
+  /* We do not collect and flush these messages as each such message
+     already requires its own separate lines.  */
+
+  fprintf_unfiltered (gdb_stdlog,
+		      _("Missing separate debuginfo for %s\n"), binary);
+  if (debug != NULL)
+    fprintf_unfiltered (gdb_stdlog, _("Try to install the hash file %s\n"),
+			debug);
 }
 
 /* See build-id.h.  */
 
 std::string
-find_separate_debug_file_by_buildid (struct objfile *objfile)
+find_separate_debug_file_by_buildid (struct objfile *objfile,
+			gdb::unique_xmalloc_ptr<char> *build_id_filename_return)
 {
   const struct bfd_build_id *build_id;
 
-  build_id = build_id_bfd_get (objfile->obfd);
+  if (build_id_filename_return)
+    *build_id_filename_return = NULL;
+
+  build_id = build_id_bfd_shdr_get (objfile->obfd);
   if (build_id != NULL)
     {
       if (separate_debug_file_debug)
 	printf_unfiltered (_("\nLooking for separate debug info (build-id) for "
 			     "%s\n"), objfile_name (objfile));
 
+      char *build_id_filename_cstr = NULL;
       gdb_bfd_ref_ptr abfd (build_id_to_debug_bfd (build_id->size,
-						   build_id->data));
+						   build_id->data,
+	      (!build_id_filename_return ? NULL : &build_id_filename_cstr)));
+      if (build_id_filename_return)
+	{
+	  if (!build_id_filename_cstr)
+	    gdb_assert (!*build_id_filename_return);
+	  else
+	    {
+	      *build_id_filename_return = gdb::unique_xmalloc_ptr<char> (build_id_filename_cstr);
+	      build_id_filename_cstr = NULL;
+	    }
+	}
+
       /* Prevent looping on a stripped .debug file.  */
       if (abfd != NULL
 	  && filename_cmp (bfd_get_filename (abfd.get ()),
@@ -223,3 +901,22 @@ find_separate_debug_file_by_buildid (struct objfile *objfile)
 
   return std::string ();
 }
+
+extern void _initialize_build_id (void);
+
+void
+_initialize_build_id (void)
+{
+  add_setshow_zinteger_cmd ("build-id-verbose", no_class, &build_id_verbose,
+			    _("\
+Set debugging level of the build-id locator."), _("\
+Show debugging level of the build-id locator."), _("\
+Level 1 (default) enables printing the missing debug filenames,\n\
+level 2 also prints the parsing of binaries to find the identificators."),
+			    NULL,
+			    show_build_id_verbose,
+			    &setlist, &showlist);
+
+  gdb::observers::executable_changed.attach (debug_print_executable_changed,
+					     "build-id");
+}
diff --git a/gdb/build-id.h b/gdb/build-id.h
index 42f8d57ede1..55c3517cb0c 100644
--- a/gdb/build-id.h
+++ b/gdb/build-id.h
@@ -23,9 +23,10 @@
 #include "gdb_bfd.h"
 #include "gdbsupport/rsp-low.h"
 
-/* Locate NT_GNU_BUILD_ID from ABFD and return its content.  */
+/* Separate debuginfo files have corrupted PHDR but SHDR is correct there.
+   Locate NT_GNU_BUILD_ID from ABFD and return its content.  */
 
-extern const struct bfd_build_id *build_id_bfd_get (bfd *abfd);
+extern const struct bfd_build_id *build_id_bfd_shdr_get (bfd *abfd);
 
 /* Return true if ABFD has NT_GNU_BUILD_ID matching the CHECK value.
    Otherwise, issue a warning and return false.  */
@@ -38,7 +39,8 @@ extern int build_id_verify (bfd *abfd,
    can be found, return NULL.  */
 
 extern gdb_bfd_ref_ptr build_id_to_debug_bfd (size_t build_id_len,
-					      const bfd_byte *build_id);
+					      const bfd_byte *build_id,
+					      char **link_return);
 
 /* Find and open a BFD for an executable file given a build-id.  If no BFD
    can be found, return NULL.  The returned reference to the BFD must be
@@ -47,12 +49,15 @@ extern gdb_bfd_ref_ptr build_id_to_debug_bfd (size_t build_id_len,
 extern gdb_bfd_ref_ptr build_id_to_exec_bfd (size_t build_id_len,
 					     const bfd_byte *build_id);
 
+extern char *build_id_to_filename (const struct bfd_build_id *build_id,
+				   char **link_return);
+
 /* Find the separate debug file for OBJFILE, by using the build-id
    associated with OBJFILE's BFD.  If successful, returns the file name for the
    separate debug file, otherwise, return an empty string.  */
 
-extern std::string find_separate_debug_file_by_buildid
-  (struct objfile *objfile);
+extern std::string find_separate_debug_file_by_buildid (struct objfile *objfile,
+		       gdb::unique_xmalloc_ptr<char> *build_id_filename_return);
 
 /* Return an hex-string representation of BUILD_ID.  */
 
diff --git a/gdb/coffread.c b/gdb/coffread.c
index 0135363bc5a..37e3f1e6aa7 100644
--- a/gdb/coffread.c
+++ b/gdb/coffread.c
@@ -710,7 +710,8 @@ coff_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
   /* Try to add separate debug file if no symbols table found.   */
   if (!objfile->has_partial_symbols ())
     {
-      std::string debugfile = find_separate_debug_file_by_buildid (objfile);
+      std::string debugfile = find_separate_debug_file_by_buildid (objfile,
+								   NULL);
 
       if (debugfile.empty ())
 	debugfile = find_separate_debug_file_by_debuglink (objfile);
diff --git a/gdb/corelow.c b/gdb/corelow.c
index eb785a08633..134c09c988c 100644
--- a/gdb/corelow.c
+++ b/gdb/corelow.c
@@ -22,6 +22,10 @@
 #include <signal.h>
 #include <fcntl.h>
 #include "frame.h"		/* required by inferior.h */
+#include "auxv.h"
+#include "build-id.h"
+#include "elf/common.h"
+#include "gdbcmd.h"
 #include "inferior.h"
 #include "infrun.h"
 #include "symtab.h"
@@ -356,6 +360,49 @@ add_to_thread_list (asection *asect, asection *reg_sect)
     switch_to_thread (thr);			/* Yes, make it current.  */
 }
 
+static bool build_id_core_loads = true;
+
+static void
+build_id_locate_exec (int from_tty)
+{
+  CORE_ADDR at_entry;
+  gdb::unique_xmalloc_ptr<struct bfd_build_id> build_id;
+  gdb::unique_xmalloc_ptr<char> execfilename;
+  char *build_id_filename;
+
+  if (exec_bfd != NULL || symfile_objfile != NULL)
+    return;
+
+  if (target_auxv_search (current_top_target (), AT_ENTRY, &at_entry) <= 0)
+    return;
+
+  build_id.reset (build_id_addr_get (at_entry));
+  if (build_id == NULL)
+    return;
+
+  /* SYMFILE_OBJFILE should refer to the main executable (not only to its
+     separate debug info file).  gcc44+ keeps .eh_frame only in the main
+     executable without its duplicate .debug_frame in the separate debug info
+     file - such .eh_frame would not be found if SYMFILE_OBJFILE would refer
+     directly to the separate debug info file.  */
+
+  execfilename.reset (build_id_to_filename (build_id.get (),
+					    &build_id_filename));
+
+  if (execfilename != NULL)
+    {
+      exec_file_attach (execfilename.get (), from_tty);
+      symbol_file_add_main (execfilename.get (),
+			    symfile_add_flag (!from_tty ? 0 : SYMFILE_VERBOSE));
+      if (symfile_objfile != NULL)
+        symfile_objfile->flags |= OBJF_BUILD_ID_CORE_LOADED;
+    }
+  else
+    debug_print_missing (_("the main executable file"), build_id_filename);
+
+  /* No automatic SOLIB_ADD as the libraries would get read twice.  */
+}
+
 /* Issue a message saying we have no core to debug, if FROM_TTY.  */
 
 static void
@@ -392,7 +439,7 @@ core_file_command (const char *filename, int from_tty)
 static void
 locate_exec_from_corefile_build_id (bfd *abfd, int from_tty)
 {
-  const bfd_build_id *build_id = build_id_bfd_get (abfd);
+  const bfd_build_id *build_id = build_id_bfd_shdr_get (abfd);
   if (build_id == nullptr)
     return;
 
@@ -513,6 +560,14 @@ core_target_open (const char *arg, int from_tty)
   if (current_program_space->exec_bfd () == nullptr)
     locate_exec_from_corefile_build_id (core_bfd, from_tty);
 
+  /* Find the build_id identifiers.  If it gets executed after
+     POST_CREATE_INFERIOR we would clash with asking to discard the already
+     loaded VDSO symbols.  If it gets executed before bfd_map_over_sections
+     INFERIOR_PTID is still not set and libthread_db initialization crashes on
+     PID == 0 in ps_pglobal_lookup.  */
+  if (build_id_core_loads != false)
+    build_id_locate_exec (from_tty);
+
   post_create_inferior (from_tty);
 
   /* Now go through the target stack looking for threads since there
@@ -1208,4 +1263,11 @@ _initialize_corelow ()
 	   maintenance_print_core_file_backed_mappings,
 	   _("Print core file's file-backed mappings."),
 	   &maintenanceprintlist);
+
+  add_setshow_boolean_cmd ("build-id-core-loads", class_files,
+			   &build_id_core_loads, _("\
+Set whether CORE-FILE loads the build-id associated files automatically."), _("\
+Show whether CORE-FILE loads the build-id associated files automatically."),
+			   NULL, NULL, NULL,
+			   &setlist, &showlist);
 }
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index a16a3825ebb..6bb716ab94f 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -21415,6 +21415,27 @@ information files.
 
 @end table
 
+You can also adjust the current verbosity of the @dfn{build id} locating.
+
+@table @code
+
+@kindex set build-id-verbose
+@item set build-id-verbose 0
+No additional messages are printed.
+
+@item set build-id-verbose 1
+Missing separate debug filenames are printed.
+
+@item set build-id-verbose 2
+Missing separate debug filenames are printed and also all the parsing of the
+binaries to find their @dfn{build id} content is printed.
+
+@kindex show build-id-verbose
+@item show build-id-verbose
+Show the current verbosity value for the @dfn{build id} content locating.
+
+@end table
+
 @cindex @code{.gnu_debuglink} sections
 @cindex debug link sections
 A debug link is a special section of the executable file named
diff --git a/gdb/dwarf2/dwz.c b/gdb/dwarf2/dwz.c
index f9d5db6b48a..a89767b5d03 100644
--- a/gdb/dwarf2/dwz.c
+++ b/gdb/dwarf2/dwz.c
@@ -234,7 +234,7 @@ dwarf2_get_dwz_file (dwarf2_per_bfd *per_bfd, bool require)
     }
 
   if (dwz_bfd == NULL)
-    dwz_bfd = build_id_to_debug_bfd (buildid_len, buildid);
+    dwz_bfd = build_id_to_debug_bfd (buildid_len, buildid, NULL);
 
   if (dwz_bfd == nullptr)
     {
diff --git a/gdb/dwarf2/index-cache.c b/gdb/dwarf2/index-cache.c
index c3decf16ead..86472a7458b 100644
--- a/gdb/dwarf2/index-cache.c
+++ b/gdb/dwarf2/index-cache.c
@@ -95,7 +95,7 @@ index_cache::store (dwarf2_per_objfile *per_objfile)
     return;
 
   /* Get build id of objfile.  */
-  const bfd_build_id *build_id = build_id_bfd_get (obj->obfd);
+  const bfd_build_id *build_id = build_id_bfd_shdr_get (obj->obfd);
   if (build_id == nullptr)
     {
       if (debug_index_cache)
@@ -113,7 +113,8 @@ index_cache::store (dwarf2_per_objfile *per_objfile)
 
   if (dwz != nullptr)
     {
-      const bfd_build_id *dwz_build_id = build_id_bfd_get (dwz->dwz_bfd.get ());
+      const bfd_build_id *dwz_build_id
+	= build_id_bfd_shdr_get (dwz->dwz_bfd.get ());
 
       if (dwz_build_id == nullptr)
 	{
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 760d4319c29..2b30ff13161 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -5378,7 +5378,7 @@ get_gdb_index_contents_from_section (objfile *obj, T *section_owner)
 static gdb::array_view<const gdb_byte>
 get_gdb_index_contents_from_cache (objfile *obj, dwarf2_per_bfd *dwarf2_per_bfd)
 {
-  const bfd_build_id *build_id = build_id_bfd_get (obj->obfd);
+  const bfd_build_id *build_id = build_id_bfd_shdr_get (obj->obfd);
   if (build_id == nullptr)
     return {};
 
@@ -5391,7 +5391,7 @@ get_gdb_index_contents_from_cache (objfile *obj, dwarf2_per_bfd *dwarf2_per_bfd)
 static gdb::array_view<const gdb_byte>
 get_gdb_index_contents_from_cache_dwz (objfile *obj, dwz_file *dwz)
 {
-  const bfd_build_id *build_id = build_id_bfd_get (dwz->dwz_bfd.get ());
+  const bfd_build_id *build_id = build_id_bfd_shdr_get (dwz->dwz_bfd.get ());
   if (build_id == nullptr)
     return {};
 
diff --git a/gdb/elfread.c b/gdb/elfread.c
index 1dea226242d..84583423b85 100644
--- a/gdb/elfread.c
+++ b/gdb/elfread.c
@@ -1272,7 +1272,9 @@ elf_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
 	   && objfile->separate_debug_objfile == NULL
 	   && objfile->separate_debug_objfile_backlink == NULL)
     {
-      std::string debugfile = find_separate_debug_file_by_buildid (objfile);
+      gdb::unique_xmalloc_ptr<char> build_id_filename;
+      std::string debugfile
+	= find_separate_debug_file_by_buildid (objfile, &build_id_filename);
 
       if (debugfile.empty ())
 	debugfile = find_separate_debug_file_by_debuglink (objfile);
@@ -1284,10 +1286,14 @@ elf_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
 	  symbol_file_add_separate (debug_bfd.get (), debugfile.c_str (),
 				    symfile_flags, objfile);
 	}
+      /* Check if any separate debug info has been extracted out.  */
+      else if (bfd_get_section_by_name (objfile->obfd, ".gnu_debuglink")
+	       != NULL)
+	debug_print_missing (objfile_name (objfile), build_id_filename.get ());
       else
 	{
 	  has_dwarf2 = false;
-	  const struct bfd_build_id *build_id = build_id_bfd_get (objfile->obfd);
+	  const struct bfd_build_id *build_id = build_id_bfd_shdr_get (objfile->obfd);
 
 	  if (build_id != nullptr)
 	    {
diff --git a/gdb/exec.c b/gdb/exec.c
index 35bf7bd4506..4b9f143fe77 100644
--- a/gdb/exec.c
+++ b/gdb/exec.c
@@ -237,7 +237,7 @@ validate_exec_file (int from_tty)
   current_exec_file = get_exec_file (0);
 
   const bfd_build_id *exec_file_build_id
-    = build_id_bfd_get (current_program_space->exec_bfd ());
+    = build_id_bfd_shdr_get (current_program_space->exec_bfd ());
   if (exec_file_build_id != nullptr)
     {
       /* Prepend the target prefix, to force gdb_bfd_open to open the
@@ -250,7 +250,7 @@ validate_exec_file (int from_tty)
       if (abfd != nullptr)
 	{
 	  const bfd_build_id *target_exec_file_build_id
-	    = build_id_bfd_get (abfd.get ());
+	    = build_id_bfd_shdr_get (abfd.get ());
 
 	  if (target_exec_file_build_id != nullptr)
 	    {
diff --git a/gdb/objfiles.h b/gdb/objfiles.h
index 766c4b409df..b5f5c190cb9 100644
--- a/gdb/objfiles.h
+++ b/gdb/objfiles.h
@@ -867,6 +867,10 @@ struct obj_section
   int ovly_mapped;
 };
 
+/* This file was loaded according to the BUILD_ID_CORE_LOADS rules.  */
+
+#define OBJF_BUILD_ID_CORE_LOADED static_cast<enum objfile_flag>(1 << 12)
+
 /* Declarations for functions defined in objfiles.c */
 
 extern int entry_point_address_query (CORE_ADDR *entry_p);
diff --git a/gdb/python/py-objfile.c b/gdb/python/py-objfile.c
index 626f2d3e18c..caec3499223 100644
--- a/gdb/python/py-objfile.c
+++ b/gdb/python/py-objfile.c
@@ -132,7 +132,7 @@ objfpy_get_build_id (PyObject *self, void *closure)
 
   try
     {
-      build_id = build_id_bfd_get (objfile->obfd);
+      build_id = build_id_bfd_shdr_get (objfile->obfd);
     }
   catch (const gdb_exception &except)
     {
@@ -600,7 +600,7 @@ objfpy_lookup_objfile_by_build_id (const char *build_id)
       /* Don't return separate debug files.  */
       if (objfile->separate_debug_objfile_backlink != NULL)
 	continue;
-      obfd_build_id = build_id_bfd_get (objfile->obfd);
+      obfd_build_id = build_id_bfd_shdr_get (objfile->obfd);
       if (obfd_build_id == NULL)
 	continue;
       if (objfpy_build_id_matches (obfd_build_id, build_id))
diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
index a8a7d1171dc..9f1c648d8ae 100644
--- a/gdb/solib-svr4.c
+++ b/gdb/solib-svr4.c
@@ -45,6 +45,7 @@
 #include "auxv.h"
 #include "gdb_bfd.h"
 #include "probe.h"
+#include "build-id.h"
 
 static struct link_map_offsets *svr4_fetch_link_map_offsets (void);
 static int svr4_have_link_map_offsets (void);
@@ -1348,9 +1349,51 @@ svr4_read_so_list (svr4_info *info, CORE_ADDR lm, CORE_ADDR prev_lm,
 	  continue;
 	}
 
-      strncpy (newobj->so_name, buffer.get (), SO_NAME_MAX_PATH_SIZE - 1);
-      newobj->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
-      strcpy (newobj->so_original_name, newobj->so_name);
+      {
+	struct bfd_build_id *build_id;
+
+	strncpy (newobj->so_original_name, buffer.get (), SO_NAME_MAX_PATH_SIZE - 1);
+	newobj->so_original_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
+	/* May get overwritten below.  */
+	strcpy (newobj->so_name, newobj->so_original_name);
+
+	build_id = build_id_addr_get (((lm_info_svr4 *) newobj->lm_info)->l_ld);
+	if (build_id != NULL)
+	  {
+	    char *name, *build_id_filename;
+
+	    /* Missing the build-id matching separate debug info file
+	       would be handled while SO_NAME gets loaded.  */
+	    name = build_id_to_filename (build_id, &build_id_filename);
+	    if (name != NULL)
+	      {
+		strncpy (newobj->so_name, name, SO_NAME_MAX_PATH_SIZE - 1);
+		newobj->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
+		xfree (name);
+	      }
+	    else
+	      {
+		debug_print_missing (newobj->so_name, build_id_filename);
+
+		/* In the case the main executable was found according to
+		   its build-id (from a core file) prevent loading
+		   a different build of a library with accidentally the
+		   same SO_NAME.
+
+		   It suppresses bogus backtraces (and prints "??" there
+		   instead) if the on-disk files no longer match the
+		   running program version.  */
+
+		if (symfile_objfile != NULL
+		    && (symfile_objfile->flags
+			& OBJF_BUILD_ID_CORE_LOADED) != 0)
+		  newobj->so_name[0] = 0;
+	      }
+
+	    xfree (build_id_filename);
+	    xfree (build_id);
+	  }
+      }
 
       /* If this entry has no name, or its name matches the name
 	 for the main executable, don't include it in the list.  */
diff --git a/gdb/source.c b/gdb/source.c
index c993e25a892..731e10cdc86 100644
--- a/gdb/source.c
+++ b/gdb/source.c
@@ -1178,7 +1178,7 @@ open_source_file (struct symtab *s)
 	      srcpath += s->filename;
 	    }
 
-	  const struct bfd_build_id *build_id = build_id_bfd_get (ofp->obfd);
+	  const struct bfd_build_id *build_id = build_id_bfd_shdr_get (ofp->obfd);
 
 	  /* Query debuginfod for the source file.  */
 	  if (build_id != nullptr && !srcpath.empty ())
diff --git a/gdb/symfile.h b/gdb/symfile.h
index 22b091182aa..35d8eb133f0 100644
--- a/gdb/symfile.h
+++ b/gdb/symfile.h
@@ -338,6 +338,10 @@ void map_symbol_filenames (gdb::function_view<symbol_filename_ftype> fun,
    optional offset to apply to each section.  */
 extern void generic_load (const char *args, int from_tty);
 
+/* build-id support.  */
+extern struct bfd_build_id *build_id_addr_get (CORE_ADDR addr);
+extern void debug_print_missing (const char *binary, const char *debug);
+
 /* From minidebug.c.  */
 
 extern gdb_bfd_ref_ptr find_separate_debug_file_in_section (struct objfile *);
diff --git a/gdb/testsuite/gdb.base/corefile.exp b/gdb/testsuite/gdb.base/corefile.exp
index 828e6121701..89825161745 100644
--- a/gdb/testsuite/gdb.base/corefile.exp
+++ b/gdb/testsuite/gdb.base/corefile.exp
@@ -343,3 +343,33 @@ gdb_test_multiple "core-file $corefile" $test {
 	pass $test
     }
 }
+
+
+# Test auto-loading of binary files through build-id from the core file.
+set buildid [build_id_debug_filename_get $binfile]
+set wholetest "binfile found by build-id"
+if {$buildid == ""} {
+    untested "$wholetest (binary has no build-id)"
+} else {
+    gdb_exit
+    gdb_start
+
+    regsub {\.debug$} $buildid {} buildid
+    set debugdir [standard_output_file ${testfile}-debugdir]
+    file delete -force -- $debugdir
+    file mkdir $debugdir/[file dirname $buildid]
+    file copy $binfile $debugdir/$buildid
+
+    set test "show debug-file-directory"
+    gdb_test_multiple $test $test {
+	-re "The directory where separate debug symbols are searched for is \"(.*)\"\\.\r\n$gdb_prompt $" {
+	    set debugdir_orig $expect_out(1,string)
+	    pass $test
+	}
+    }
+    gdb_test_no_output "set debug-file-directory $debugdir:$debugdir_orig" "set debug-file-directory"
+    gdb_test "show build-id-core-loads" {Whether CORE-FILE loads the build-id associated files automatically is on\.}
+    gdb_test "core-file $corefile" "\r\nProgram terminated with .*" "core-file without executable"
+    gdb_test "info files" "Local exec file:\r\n\[ \t\]*`[string_to_regexp $debugdir/$buildid]', file type .*"
+    pass $wholetest
+}
diff --git a/gdb/testsuite/gdb.base/new-ui-pending-input.exp b/gdb/testsuite/gdb.base/new-ui-pending-input.exp
index 4853f951e86..639bc82a5f0 100644
--- a/gdb/testsuite/gdb.base/new-ui-pending-input.exp
+++ b/gdb/testsuite/gdb.base/new-ui-pending-input.exp
@@ -62,6 +62,7 @@ proc test_command_line_new_ui_pending_input {} {
     set options ""
     append options " -iex \"set height 0\""
     append options " -iex \"set width 0\""
+    append options " -iex \"set build-id-verbose 0\""
     append options " -iex \"new-ui console $extra_tty_name\""
     append options " -ex \"b $bpline\""
     append options " -ex \"run\""
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 38f40fdddb5..297a566e44c 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -2130,6 +2130,17 @@ proc default_gdb_start { } {
 	}
     }
 
+    # Turn off the missing warnings as the testsuite does not expect it.
+    send_gdb "set build-id-verbose 0\n"
+    gdb_expect 10 {
+	-re "$gdb_prompt $" {
+	    verbose "Disabled the missing debug infos warnings." 2
+	}
+	timeout {
+	    warning "Could not disable the missing debug infos warnings.."
+	}
+    }
+
     gdb_debug_init
     return 0
 }
diff --git a/gdb/testsuite/lib/mi-support.exp b/gdb/testsuite/lib/mi-support.exp
index d1c87dc7517..5faa50e4725 100644
--- a/gdb/testsuite/lib/mi-support.exp
+++ b/gdb/testsuite/lib/mi-support.exp
@@ -322,6 +322,16 @@ proc default_mi_gdb_start { args } {
 	    warning "Couldn't set the width to 0."
 	}
     }
+    # Turn off the missing warnings as the testsuite does not expect it.
+    send_gdb "190-gdb-set build-id-verbose 0\n"
+    gdb_expect 10 {
+	-re ".*190-gdb-set build-id-verbose 0\r\n190\\\^done\r\n$mi_gdb_prompt$" {
+	    verbose "Disabled the missing debug infos warnings." 2
+	}
+	timeout {
+	    warning "Could not disable the missing debug infos warnings.."
+	}
+    }
 
     if { $separate_inferior_pty } {
 	mi_create_inferior_pty
-- 
2.32.0

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File gdb-6.6-buildid-locate.patch of Package gdb (Revision b14e3ea05919fa8bab2669f9bc0d280d)

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