readelf: print_attributes (-A) robustify and handle non-gnu attributes.

print_attributes wasn't robust against empty or broken attribute sections.
It also only handled GNU attributes. But the arm backend contains some
none-GNU attributes. The difference is in how to handle the tag arguments.

Adds a new test run-readelf-A.sh for both gnu (ppc32) and non-gnu (arm)
attributes.

Signed-off-by: Mark Wielaard <mjw@redhat.com>

6 files changed, 118 insertions, 10 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index bace91d5..aa16b67c 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,10 @@
+2014-11-21  Mark Wielaard  <mjw@redhat.com>
+
+	* readelf.c (print_attributes): Guard against empty section.
+	Document attribute format. Break when vendor name isn't terminated.
+	Add overflow check for subsection_len. Handle both gnu and non-gnu
+	attribute tags.
+
 2014-11-22  Mark Wielaard  <mjw@redhat.com>
 
 	* elflint.c (check_sections): Call ebl_bss_plt_p without ehdr.
diff --git a/src/readelf.c b/src/readelf.c
index 3b1f035a..529af5a4 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -3309,11 +3309,12 @@ print_attributes (Ebl *ebl, const GElf_Ehdr *ehdr)
 	      shdr->sh_size, shdr->sh_offset);
 
       Elf_Data *data = elf_rawdata (scn, NULL);
-      if (data == NULL)
+      if (unlikely (data == NULL || data->d_size == 0))
 	return;
 
       const unsigned char *p = data->d_buf;
 
+      /* There is only one 'version', A.  */
       if (unlikely (*p++ != 'A'))
 	return;
 
@@ -3324,8 +3325,10 @@ print_attributes (Ebl *ebl, const GElf_Ehdr *ehdr)
 	return (const unsigned char *) data->d_buf + data->d_size - p;
       }
 
+      /* Loop over the sections.  */
       while (left () >= 4)
 	{
+	  /* Section length.  */
 	  uint32_t len;
 	  memcpy (&len, p, sizeof len);
 
@@ -3335,19 +3338,23 @@ print_attributes (Ebl *ebl, const GElf_Ehdr *ehdr)
 	  if (unlikely (len > left ()))
 	    break;
 
+	  /* Section vendor name.  */
 	  const unsigned char *name = p + sizeof len;
 	  p += len;
 
 	  unsigned const char *q = memchr (name, '\0', len);
 	  if (unlikely (q == NULL))
-	    continue;
+	    break;
 	  ++q;
 
 	  printf (gettext ("  %-13s  %4" PRIu32 "\n"), name, len);
 
+	  bool gnu_vendor = (q - name == sizeof "gnu"
+			     && !memcmp (name, "gnu", sizeof "gnu"));
+
+	  /* Loop over subsections.  */
 	  if (shdr->sh_type != SHT_GNU_ATTRIBUTES
-	      || (q - name == sizeof "gnu"
-		  && !memcmp (name, "gnu", sizeof "gnu")))
+	      || gnu_vendor)
 	    while (q < p)
 	      {
 		const unsigned char *const sub = q;
@@ -3366,7 +3373,10 @@ print_attributes (Ebl *ebl, const GElf_Ehdr *ehdr)
 		if (MY_ELFDATA != ehdr->e_ident[EI_DATA])
 		  CONVERT (subsection_len);
 
-		if (unlikely (p - sub < (ptrdiff_t) subsection_len))
+		/* Don't overflow, ptrdiff_t might be 32bits, but signed.  */
+		if (unlikely (subsection_len == 0
+			      || subsection_len >= (uint32_t) PTRDIFF_MAX
+			      || p - sub < (ptrdiff_t) subsection_len))
 		  break;
 
 		const unsigned char *r = q + sizeof subsection_len;
@@ -3375,6 +3385,7 @@ print_attributes (Ebl *ebl, const GElf_Ehdr *ehdr)
 		switch (subsection_tag)
 		  {
 		  default:
+		    /* Unknown subsection, print and skip.  */
 		    printf (gettext ("    %-4u %12" PRIu32 "\n"),
 			    subsection_tag, subsection_len);
 		    break;
@@ -3390,16 +3401,30 @@ print_attributes (Ebl *ebl, const GElf_Ehdr *ehdr)
 			if (unlikely (r >= q))
 			  break;
 
+			/* GNU style tags have either a uleb128 value,
+			   when lowest bit is not set, or a string
+			   when the lowest bit is set.
+			   "compatibility" (32) is special.  It has
+			   both a string and a uleb128 value.  For
+			   non-gnu we assume 6 till 31 only take ints.
+			   XXX see arm backend, do we need a separate
+			   hook?  */
 			uint64_t value = 0;
 			const char *string = NULL;
-			if (tag == 32 || (tag & 1) == 0)
+			if (tag == 32 || (tag & 1) == 0
+			    || (! gnu_vendor && (tag > 5 && tag < 32)))
 			  {
 			    get_uleb128 (value, r);
 			    if (r > q)
 			      break;
 			  }
-			if (tag == 32 || (tag & 1) != 0)
+			if (tag == 32
+			    || ((tag & 1) != 0
+				&& (gnu_vendor
+				    || (! gnu_vendor && tag > 32)))
+			    || (! gnu_vendor && tag > 3 && tag < 6))
 			  {
+			    string = (const char *) r;
 			    r = memchr (r, '\0', q - r);
 			    if (r == NULL)
 			      break;
@@ -3426,7 +3451,10 @@ print_attributes (Ebl *ebl, const GElf_Ehdr *ehdr)
 			  }
 			else
 			  {
-			    assert (tag != 32);
+			    /* For "gnu" vendor 32 "compatibility" has
+			       already been handled above.  */
+			    assert (tag != 32
+				    || strcmp ((const char *) name, "gnu"));
 			    if (string == NULL)
 			      printf (gettext ("      %u: %" PRId64 "\n"),
 				      tag, value);
diff --git a/tests/ChangeLog b/tests/ChangeLog
index 798bb7ae..909a61e1 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,3 +1,10 @@
+2014-11-21  Mark Wielaard  <mjw@redhat.com>
+
+	* run-readelf-A.sh: New test.
+	* testfileppc32attrs.o.bz2: New test file.
+	* Makefile.am (TESTS): Add run-readelf-A.sh.
+	(EXTRA_DIST): Add run-readelf-A.sh and testfileppc32attrs.o.bz2.
+
 2014-11-10  Mark Wielaard  <mjw@redhat.com>
 
 	* vdsosyms.c: New test.
diff --git a/tests/Makefile.am b/tests/Makefile.am
index dcaf4f65..5b381130 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -110,7 +110,7 @@ TESTS = run-arextract.sh run-arsymtest.sh newfile test-nlist \
 	run-backtrace-core-aarch64.sh \
 	run-backtrace-demangle.sh run-stack-d-test.sh run-stack-i-test.sh \
 	run-readelf-dwz-multi.sh run-allfcts-multi.sh run-deleted.sh \
-	run-linkmap-cut.sh run-aggregate-size.sh vdsosyms
+	run-linkmap-cut.sh run-aggregate-size.sh vdsosyms run-readelf-A.sh
 
 if !BIARCH
 export ELFUTILS_DISABLE_BIARCH = 1
@@ -276,7 +276,8 @@ EXTRA_DIST = run-arextract.sh run-arsymtest.sh \
 	     run-deleted.sh run-linkmap-cut.sh linkmap-cut-lib.so.bz2 \
 	     linkmap-cut.bz2 linkmap-cut.core.bz2 \
 	     run-aggregate-size.sh testfile-sizes1.o.bz2 testfile-sizes2.o.bz2 \
-	     testfile-sizes3.o.bz2
+	     testfile-sizes3.o.bz2 \
+	     run-readelf-A.sh testfileppc32attrs.o.bz2
 
 if USE_VALGRIND
 valgrind_cmd='valgrind -q --error-exitcode=1 --run-libc-freeres=no'
diff --git a/tests/run-readelf-A.sh b/tests/run-readelf-A.sh
new file mode 100755
index 00000000..6ca9be89
--- /dev/null
+++ b/tests/run-readelf-A.sh
@@ -0,0 +1,65 @@
+#! /bin/sh
+# Copyright (C) 2014 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
+
+# See run-addrcfi.sh for testfilearm.
+
+# = testfileppc32attrs.s =
+# .gnu_attribute 8,1
+# .gnu_attribute 12,1
+#
+# gcc -m32 -c testfileppc32attrs.s
+
+testfiles testfilearm testfileppc32attrs.o
+
+testrun_compare ${abs_top_builddir}/src/readelf -A testfilearm <<\EOF
+
+Object attributes section [27] '.ARM.attributes' of 53 bytes at offset 0x718:
+  Owner          Size
+  aeabi            52
+    File:          42
+      CPU_name: 7-A
+      CPU_arch: v7
+      CPU_arch_profile: Application
+      ARM_ISA_use: Yes
+      THUMB_ISA_use: Thumb-2
+      VFP_arch: VFPv3-D16
+      ABI_PCS_wchar_t: 4
+      ABI_FP_rounding: Needed
+      ABI_FP_denormal: Needed
+      ABI_FP_exceptions: Needed
+      ABI_FP_number_model: IEEE 754
+      ABI_align8_needed: Yes
+      ABI_align8_preserved: Yes, except leaf SP
+      ABI_enum_size: int
+      ABI_HardFP_use: SP and DP
+      ABI_VFP_args: VFP registers
+      CPU_unaligned_access: v6
+EOF
+
+testrun_compare ${abs_top_builddir}/src/readelf -A testfileppc32attrs.o <<\EOF
+
+Object attributes section [ 4] '.gnu.attributes' of 18 bytes at offset 0x34:
+  Owner          Size
+  gnu              17
+    File:           9
+      GNU_Power_ABI_Vector: Generic
+      GNU_Power_ABI_Struct_Return: r3/r4
+EOF
+
+exit 0
diff --git a/tests/testfileppc32attrs.o.bz2 b/tests/testfileppc32attrs.o.bz2
new file mode 100644
index 00000000..c8d80a99
--- /dev/null
+++ b/tests/testfileppc32attrs.o.bz2