readelf: Support --dynamic with --use-dynamic

Currently, eu-readelf is using section headers to dump the dynamic
segment information (print_dynamic -> handle_dynamic).

This patch adds new options to eu-readelf (-D, --use-dynamic)
for (-d, --dynamic).

https://sourceware.org/bugzilla/show_bug.cgi?id=28873

Signed-off-by: Di Chen <dichen@redhat.com>

7 files changed, 280 insertions, 27 deletions

diff --git a/ChangeLog b/ChangeLog
index 0ececcc9..5421f5b8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2022-04-28  Di Chen  <dichen@redhat.com>
+
+	* NEWS: Add readefl -D, --use-dynamic.
+
 2022-07-28  Di Chen  <dichen@redhat.com>
 
 	* NEWS: Add dwfl_frame_reg.
diff --git a/NEWS b/NEWS
index 82c86cb6..156f78df 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,7 @@
 Version 0.188 some time after 0.187
 
+readelf: Add -D, --use-dynamic option.
+
 debuginfod: Add --disable-source-scan option.
 
 libdwfl: Add new function dwfl_get_debuginfod_client.
diff --git a/src/ChangeLog b/src/ChangeLog
index 8c9f5ddd..db20a6ef 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,16 @@
+2022-04-28  Di Chen  <dichen@redhat.com>
+
+	* readelf.c (options): Add use-dynamic 'D'.
+	(use_dynamic_segment): New static bool.
+	(enum dyn_idx): New.
+	(get_dynscn_strtab): New function.
+	(get_dynscn_addrs): Likewise.
+	(find_offsets): Likewise.
+	(parse_opt): Handle 'D'.
+	(handle_dynamic): New argument phdr. Get data either through the shdr
+	or phdr.  Print segment info when use_dynamic_segment. Use
+	get_dynscn_strtab. Get library name and paths through strtab_data.
+
 2022-05-09  Mark Wielaard  <mark@klomp.org>
 
 	* strip.c (remove_debug_relocations): Check gelf_getshdr, gelf_getrela,
diff --git a/src/readelf.c b/src/readelf.c
index 4b6aab2b..f4d973da 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -137,6 +137,8 @@ static const struct argp_option options[] =
   { "string-dump", 'p', NULL, OPTION_ALIAS | OPTION_HIDDEN, NULL, 0 },
   { "archive-index", 'c', NULL, 0,
     N_("Display the symbol index of an archive"), 0 },
+  { "use-dynamic", 'D', NULL, 0,
+    N_("Use the dynamic segment when possible for displaying info"), 0 },
 
   { NULL, 0, NULL, 0, N_("Output control:"), 0 },
   { "numeric-addresses", 'N', NULL, 0,
@@ -195,6 +197,9 @@ static bool print_symbol_table;
 /* True if (only) the dynsym table should be printed.  */
 static bool print_dynsym_table;
 
+/* True if reconstruct dynamic symbol table from the PT_DYNAMIC segment.  */
+static bool use_dynamic_segment;
+
 /* A specific section name, or NULL to print all symbol tables.  */
 static char *symbol_table_section;
 
@@ -318,6 +323,24 @@ static void dump_strings (Ebl *ebl);
 static void print_strings (Ebl *ebl);
 static void dump_archive_index (Elf *, const char *);
 
+enum dyn_idx
+{
+  i_strsz,
+  i_verneed,
+  i_verdef,
+  i_versym,
+  i_symtab,
+  i_strtab,
+  i_hash,
+  i_gnu_hash,
+  i_max
+};
+
+/* Declarations of local functions for use-dynamic.  */
+static Elf_Data *get_dynscn_strtab (Elf *elf, GElf_Phdr *phdr);
+static void get_dynscn_addrs (Elf *elf, GElf_Phdr *phdr, GElf_Addr addrs[i_max]);
+static void find_offsets (Elf *elf, GElf_Addr main_bias, size_t n,
+			  GElf_Addr addrs[n], GElf_Off offs[n]);
 
 /* Looked up once with gettext in main.  */
 static char *yes_str;
@@ -429,6 +452,9 @@ parse_opt (int key, char *arg,
       print_dynamic_table = true;
       any_control_option = true;
       break;
+    case 'D':
+      use_dynamic_segment = true;
+      break;
     case 'e':
       print_debug_sections |= section_exception;
       any_control_option = true;
@@ -1791,7 +1817,7 @@ get_dyn_ents (Elf_Data * dyn_data)
 
 
 static void
-handle_dynamic (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr)
+handle_dynamic (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr, GElf_Phdr *phdr)
 {
   int class = gelf_getclass (ebl->elf);
   GElf_Shdr glink_mem;
@@ -1802,34 +1828,64 @@ handle_dynamic (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr)
   size_t dyn_ents;
 
   /* Get the data of the section.  */
-  data = elf_getdata (scn, NULL);
+  if (use_dynamic_segment)
+    data = elf_getdata_rawchunk(ebl->elf, phdr->p_offset,
+				phdr->p_filesz, ELF_T_DYN);
+  else
+    data = elf_getdata (scn, NULL);
+
   if (data == NULL)
     return;
 
   /* Get the dynamic section entry number */
   dyn_ents = get_dyn_ents (data);
 
-  /* Get the section header string table index.  */
-  if (unlikely (elf_getshdrstrndx (ebl->elf, &shstrndx) < 0))
-    error_exit (0, _("cannot get section header string table index"));
+  if (!use_dynamic_segment)
+    {
+      /* Get the section header string table index.  */
+      if (unlikely (elf_getshdrstrndx (ebl->elf, &shstrndx) < 0))
+	error_exit (0, _("cannot get section header string table index"));
 
-  glink = gelf_getshdr (elf_getscn (ebl->elf, shdr->sh_link), &glink_mem);
-  if (glink == NULL)
-    error_exit (0, _("invalid sh_link value in section %zu"),
-		elf_ndxscn (scn));
+      glink = gelf_getshdr (elf_getscn (ebl->elf, shdr->sh_link), &glink_mem);
+      if (glink == NULL)
+	error_exit (0, _("invalid sh_link value in section %zu"),
+		    elf_ndxscn (scn));
 
-  printf (ngettext ("\
+      printf (ngettext ("\
 \nDynamic segment contains %lu entry:\n Addr: %#0*" PRIx64 "  Offset: %#08" PRIx64 "  Link to section: [%2u] '%s'\n",
 		    "\
 \nDynamic segment contains %lu entries:\n Addr: %#0*" PRIx64 "  Offset: %#08" PRIx64 "  Link to section: [%2u] '%s'\n",
-		    dyn_ents),
-	  (unsigned long int) dyn_ents,
-	  class == ELFCLASS32 ? 10 : 18, shdr->sh_addr,
-	  shdr->sh_offset,
-	  (int) shdr->sh_link,
-	  elf_strptr (ebl->elf, shstrndx, glink->sh_name));
+			dyn_ents),
+	      (unsigned long int) dyn_ents,
+	      class == ELFCLASS32 ? 10 : 18, shdr->sh_addr,
+	      shdr->sh_offset,
+	      (int) shdr->sh_link,
+	      elf_strptr (ebl->elf, shstrndx, glink->sh_name));
+    }
+  else
+    {
+      printf (ngettext ("\
+\nDynamic segment contains %lu entry:\n Addr: %#0*" PRIx64 "  Offset: %#08" PRIx64 "\n",
+		    "\
+\nDynamic segment contains %lu entries:\n Addr: %#0*" PRIx64 "  Offset: %#08" PRIx64 "\n",
+			dyn_ents),
+	      (unsigned long int) dyn_ents,
+	      class == ELFCLASS32 ? 10 : 18, phdr->p_paddr,
+	      phdr->p_offset);
+    }
+
   fputs_unlocked (_("  Type              Value\n"), stdout);
 
+  /* if --use-dynamic option is enabled,
+     use the string table to get the related library info.  */
+  Elf_Data *strtab_data = NULL;
+  if (use_dynamic_segment)
+    {
+      strtab_data = get_dynscn_strtab(ebl->elf, phdr);
+      if (strtab_data == NULL)
+	error_exit (0, _("cannot get string table by using dynamic segment"));
+    }
+
   for (cnt = 0; cnt < dyn_ents; ++cnt)
     {
       GElf_Dyn dynmem;
@@ -1841,6 +1897,20 @@ handle_dynamic (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr)
       printf ("  %-17s ",
 	      ebl_dynamic_tag_name (ebl, dyn->d_tag, buf, sizeof (buf)));
 
+      char *name = NULL;
+      if (dyn->d_tag == DT_NEEDED
+	  || dyn->d_tag == DT_SONAME
+	  || dyn->d_tag == DT_RPATH
+	  || dyn->d_tag == DT_RUNPATH)
+	{
+	  if (! use_dynamic_segment)
+	    name = elf_strptr (ebl->elf, shdr->sh_link, dyn->d_un.d_val);
+	  else if (dyn->d_un.d_ptr < strtab_data->d_size
+		   && memrchr (strtab_data->d_buf + strtab_data->d_size - 1, '\0',
+			       strtab_data->d_size - 1 - dyn->d_un.d_ptr) != NULL)
+	    name = ((char *) strtab_data->d_buf) + dyn->d_un.d_ptr;
+	}
+
       switch (dyn->d_tag)
 	{
 	case DT_NULL:
@@ -1852,23 +1922,19 @@ handle_dynamic (Ebl *ebl, Elf_Scn *scn, GElf_Shdr *shdr)
 	  break;
 
 	case DT_NEEDED:
-	  printf (_("Shared library: [%s]\n"),
-		  elf_strptr (ebl->elf, shdr->sh_link, dyn->d_un.d_val));
+	  printf (_("Shared library: [%s]\n"), name);
 	  break;
 
 	case DT_SONAME:
-	  printf (_("Library soname: [%s]\n"),
-		  elf_strptr (ebl->elf, shdr->sh_link, dyn->d_un.d_val));
+	  printf (_("Library soname: [%s]\n"), name);
 	  break;
 
 	case DT_RPATH:
-	  printf (_("Library rpath: [%s]\n"),
-		  elf_strptr (ebl->elf, shdr->sh_link, dyn->d_un.d_val));
+	  printf (_("Library rpath: [%s]\n"), name);
 	  break;
 
 	case DT_RUNPATH:
-	  printf (_("Library runpath: [%s]\n"),
-		  elf_strptr (ebl->elf, shdr->sh_link, dyn->d_un.d_val));
+	  printf (_("Library runpath: [%s]\n"), name);
 	  break;
 
 	case DT_PLTRELSZ:
@@ -1942,8 +2008,9 @@ print_dynamic (Ebl *ebl)
 	  Elf_Scn *scn = gelf_offscn (ebl->elf, phdr->p_offset);
 	  GElf_Shdr shdr_mem;
 	  GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
-	  if (shdr != NULL && shdr->sh_type == SHT_DYNAMIC)
-	    handle_dynamic (ebl, scn, shdr);
+	  if ((use_dynamic_segment && phdr != NULL)
+	      || (shdr != NULL && shdr->sh_type == SHT_DYNAMIC))
+	    handle_dynamic (ebl, scn, shdr, phdr);
 	  break;
 	}
     }
@@ -4801,6 +4868,99 @@ print_ops (Dwfl_Module *dwflmod, Dwarf *dbg, int indent, int indentrest,
 }
 
 
+/* Turn the addresses into file offsets by using the phdrs.  */
+static void
+find_offsets(Elf *elf, GElf_Addr main_bias, size_t n,
+                  GElf_Addr addrs[n], GElf_Off offs[n])
+{
+  size_t unsolved = n;
+  for (size_t i = 0; i < phnum; ++i) {
+    GElf_Phdr phdr_mem;
+    GElf_Phdr *phdr = gelf_getphdr(elf, i, &phdr_mem);
+    if (phdr != NULL && phdr->p_type == PT_LOAD && phdr->p_memsz > 0)
+      for (size_t j = 0; j < n; ++j)
+        if (offs[j] == 0 && addrs[j] >= phdr->p_vaddr + main_bias &&
+            addrs[j] - (phdr->p_vaddr + main_bias) < phdr->p_filesz) {
+          offs[j] = addrs[j] - (phdr->p_vaddr + main_bias) + phdr->p_offset;
+          if (--unsolved == 0)
+            break;
+        }
+  }
+}
+
+/* The dynamic segment (type PT_DYNAMIC), contains the .dynamic section.
+   And .dynamic section contains an array of the dynamic structures.
+   We use the array to get:
+    DT_STRTAB: the address of the string table
+    DT_SYMTAB: the address of the symbol table
+    DT_STRSZ: the size, in bytes, of the string table
+    ...  */
+static void
+get_dynscn_addrs(Elf *elf, GElf_Phdr *phdr, GElf_Addr addrs[i_max])
+{
+  Elf_Data *data = elf_getdata_rawchunk(
+    elf, phdr->p_offset, phdr->p_filesz, ELF_T_DYN);
+
+  int dyn_idx = 0;
+  for (;; ++dyn_idx) {
+    GElf_Dyn dyn_mem;
+    GElf_Dyn *dyn = gelf_getdyn(data, dyn_idx, &dyn_mem);
+    /* DT_NULL Marks end of dynamic section.  */
+    if (dyn->d_tag == DT_NULL)
+      break;
+
+    switch (dyn->d_tag) {
+    case DT_SYMTAB:
+      addrs[i_symtab] = dyn->d_un.d_ptr;
+      break;
+
+    case DT_HASH:
+      addrs[i_hash] = dyn->d_un.d_ptr;
+      break;
+
+    case DT_GNU_HASH:
+      addrs[i_gnu_hash] = dyn->d_un.d_ptr;
+      break;
+
+    case DT_STRTAB:
+      addrs[i_strtab] = dyn->d_un.d_ptr;
+      break;
+
+    case DT_VERSYM:
+      addrs[i_versym] = dyn->d_un.d_ptr;
+      break;
+
+    case DT_VERDEF:
+      addrs[i_verdef] = dyn->d_un.d_ptr;
+      break;
+
+    case DT_VERNEED:
+      addrs[i_verneed] = dyn->d_un.d_ptr;
+      break;
+
+    case DT_STRSZ:
+      addrs[i_strsz] = dyn->d_un.d_val;
+      break;
+    }
+  }
+}
+
+
+/* Use dynamic segment to get data for the string table section.  */
+static Elf_Data *
+get_dynscn_strtab(Elf *elf, GElf_Phdr *phdr)
+{
+  Elf_Data *strtab_data;
+  GElf_Addr addrs[i_max] = {0,};
+  GElf_Off offs[i_max] = {0,};
+  get_dynscn_addrs(elf, phdr, addrs);
+  find_offsets(elf, 0, i_max, addrs, offs);
+  strtab_data = elf_getdata_rawchunk(
+          elf, offs[i_strtab], addrs[i_strsz], ELF_T_BYTE);
+  return strtab_data;
+}
+
+
 struct listptr
 {
   Dwarf_Off offset:(64 - 3);
diff --git a/tests/ChangeLog b/tests/ChangeLog
index e65ea09b..fb573d80 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,3 +1,9 @@
+2022-04-28  Di Chen  <dichen@redhat.com>
+
+	* run-readelf-Dd.sh: New test.
+	* Makefile.am (TESTS): Add run-readelf-Dd.sh.
+	(EXTRA_DIST): Likewise.
+
 2022-06-01  Mark Wielaard  <mark@klomp.org>
 
 	* testfile-arm-flags.bz2: New test file.
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 07851594..87988fb9 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -198,7 +198,8 @@ TESTS = run-arextract.sh run-arsymtest.sh run-ar.sh newfile test-nlist \
 	msg_tst system-elf-libelf-test \
 	$(asm_TESTS) run-disasm-bpf.sh run-low_high_pc-dw-form-indirect.sh \
 	run-nvidia-extended-linemap-libdw.sh run-nvidia-extended-linemap-readelf.sh \
-	run-readelf-dw-form-indirect.sh run-strip-largealign.sh
+	run-readelf-dw-form-indirect.sh run-strip-largealign.sh \
+	run-readelf-Dd.sh
 
 if !BIARCH
 export ELFUTILS_DISABLE_BIARCH = 1
@@ -381,6 +382,7 @@ EXTRA_DIST = run-arextract.sh run-arsymtest.sh run-ar.sh \
 	     testfile56.bz2 testfile57.bz2 testfile58.bz2 \
 	     run-typeiter.sh testfile59.bz2 \
 	     run-readelf-d.sh testlib_dynseg.so.bz2 \
+	     run-readelf-Dd.sh \
 	     testfile-s390x-hash-both.bz2 \
 	     run-readelf-gdb_index.sh testfilegdbindex5.bz2 \
 	     testfilegdbindex7.bz2 \
diff --git a/tests/run-readelf-Dd.sh b/tests/run-readelf-Dd.sh
new file mode 100755
index 00000000..8c699937
--- /dev/null
+++ b/tests/run-readelf-Dd.sh
@@ -0,0 +1,66 @@
+#! /bin/sh
+# Copyright (C) 2022 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 the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# 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 a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. $srcdir/test-subr.sh
+
+# #include <stdio.h>
+#
+# __thread int i;
+#
+# void print_i ()
+# {
+#   printf("%d\n", i);
+# }
+#
+# gcc -fPIC -shared -o testlib_dynseg.so testlib_dynseg.c
+# With ld --version
+# GNU gold (GNU Binutils 2.22.52.20120402) 1.11
+
+# The same testfile is used in run-readelf-d.sh
+testfiles testlib_dynseg.so
+
+testrun_compare ${abs_top_builddir}/src/readelf -Dd testlib_dynseg.so <<\EOF
+
+Dynamic segment contains 23 entries:
+ Addr: 0x00000000000017e0  Offset: 0x0007e0
+  Type              Value
+  PLTGOT            0x00000000000019c8
+  PLTRELSZ          72 (bytes)
+  JMPREL            0x0000000000000568
+  PLTREL            RELA
+  RELA              0x00000000000004d8
+  RELASZ            144 (bytes)
+  RELAENT           24 (bytes)
+  RELACOUNT         1
+  SYMTAB            0x0000000000000228
+  SYMENT            24 (bytes)
+  STRTAB            0x0000000000000360
+  STRSZ             190 (bytes)
+  GNU_HASH          0x0000000000000420
+  NEEDED            Shared library: [libc.so.6]
+  NEEDED            Shared library: [ld-linux-x86-64.so.2]
+  INIT              0x00000000000005b0
+  FINI              0x0000000000000748
+  VERSYM            0x0000000000000460
+  VERDEF            0x000000000000047c
+  VERDEFNUM         1
+  VERNEED           0x0000000000000498
+  VERNEEDNUM        2
+  NULL              
+EOF
+
+exit 0