BFD error message suppression test case

This commit adds a GDB test case which tests GDB's BFD error handler
hook for suppressing output of all but the first identical messages.

See the comment at the beginning of bfd-errors.exp for details about
this new test.

I've tested this test for both 32- and 64-bit ELF files and also
on both little endian and big endian machines.  It also works for
both native and remote targets.  The only major restriction is that
it only works for ELF targets.

diff --git a/gdb/testsuite/gdb.base/bfd-errors-lib.c b/gdb/testsuite/gdb.base/bfd-errors-lib.c
new file mode 100644 (file)
index 0000000..2b582d1
--- /dev/null
+++ b/gdb/testsuite/gdb.base/bfd-errors-lib.c
@@ -0,0 +1,44 @@
+/* Copyright 2022 Free Software Foundation, Inc.
+   This program 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.
+
+   This program 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/>.
+*/
+
+#include <stdio.h>
+
+void
+foo1 ()
+{
+  printf ("foo1 in lib\n");
+  return;
+}
+
+void
+foo2()
+{
+  printf ("foo2 in lib\n");
+  return;
+}
+
+void
+foo3()
+{
+  printf ("foo3 in lib\n");
+  return;
+}
+
+void
+foo4()
+{
+  printf ("foo4 in lib\n");
+  return;
+}

diff --git a/gdb/testsuite/gdb.base/bfd-errors.exp b/gdb/testsuite/gdb.base/bfd-errors.exp
new file mode 100644 (file)
index 0000000..e436e40
--- /dev/null
+++ b/gdb/testsuite/gdb.base/bfd-errors.exp
@@ -0,0 +1,185 @@
+# Copyright 2022 Free Software Foundation, Inc.
+# This program 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.
+#
+# This program 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/>.
+
+# Tools which use the BFD library will output error messages of the
+# form "BFD: some messsage" when a problem with the file upon which it
+# operating is found.  E.g. an actual message (modulo some shortening
+# of the pathname) from this test is:
+#
+# BFD: bfd-errors-lib.so: invalid string offset 1154 >= 154 for section `.dynstr'
+#
+# For some problems with executable files or libraries, BFD will
+# attempt to output many identical messages.  Code has been added to
+# GDB to suppress messages which are identical to earlier messages
+# that have already been printed.
+#
+# This test makes sure that (all but the first) identical BFD messages
+# are suppresssed and also that differing messages are output at least
+# once.
+#
+# To accomplish this, a shared object with at least four symbols is
+# created.  The .dynsym section is extracted and offsets which should
+# refer to strings in the .dynstr section are changed to be
+# larger than the size of the .dynstr section.  Only two (different)
+# offsets are used; thus BFD will attempt to output at least two pairs
+# of identical messages.  (And it would do this too if not intercepted
+# by the hook placed by GDB.)  After modifying the extracted section,
+# the mangled section is placed back into the shared object.
+#
+# This test then loads the shared library's symbol table (and other
+# debug info) using the 'add-symbol-file' command.  While doing this,
+# the test observes and records the BFD errors that were output. 
+# Finally, data collected while adding the shared library symbols are
+# examined to make sure that identical messages were suppressed while
+# also making sure that at least two messages have been printed.
+
+# This test can't be run on targets lacking shared library support
+# or for non-ELF targets.
+if { [skip_shlib_tests] || ![is_elf_target] } {
+    return 0
+}
+
+# Library file names and flags:
+set lib_basename ${::gdb_test_file_name}-lib
+set srcfile_lib ${srcdir}/${subdir}/${lib_basename}.c
+set binfile_lib [standard_output_file ${lib_basename}.so]
+set lib_flags debug
+
+# Compile shared library:
+if { [gdb_compile_shlib ${srcfile_lib} ${binfile_lib} $lib_flags] != "" } {
+    untested "failed to compile"
+    return -1
+}
+
+# Open the shared library and determine some basic facts.  The key
+# things that we need to learn are 1) whether the solib is 32-bit or
+# 64-bit ELF file, and 2) the endianness.
+set solib_fp [open ${binfile_lib} r]
+fconfigure $solib_fp -translation binary
+
+# Read and check EI_MAG to verify that it's really an ELF file.
+set data [read $solib_fp 4]
+if { ![string equal $data "\x7fELF"] } {
+    close $solib_fp
+    untested "shared library is not an ELF file"
+    return -1
+}
+
+# Read EI_CLASS for ELF32 versus ELF64.
+set data [read $solib_fp 1]
+set is_elf64 [string equal $data "\x02"]
+
+# Read EI_DATA to determine data encoding (byte order).
+set data [read $solib_fp 1]
+set is_big_endian [string equal $data "\x02"]
+
+close $solib_fp
+
+set objcopy_program [gdb_find_objcopy]
+
+# Extract the .dynsym and .dynstr section from the shared object.
+if { [catch "exec $objcopy_program \
+              --dump-section .dynsym=${binfile_lib}.dynsym \
+             --dump-section .dynstr=${binfile_lib}.dynstr \
+             ${binfile_lib}" output] } {
+    untested "failed objcopy dump-section"
+    verbose -log "objcopy output: $output"
+    return -1
+}
+
+# Determine length of .dynstr.  We'll use the length for creating invalid
+# offsets into .dynstr.
+set dynstr_len [file size ${binfile_lib}.dynstr]
+
+# Open the file containing .dynsym and determine its length.  In this
+# case, we want to know the length in order to compute the total number
+# of symbols that it contains.  We also leave the file open for a
+# while so that we can write invalid offsets to it.
+set dynsym_fp [open ${binfile_lib}.dynsym r+]
+fconfigure $dynsym_fp -translation binary
+set dynsym_len [string length [read $dynsym_fp]]
+
+# SZ is the size of the Elf32_Sym / Elf64_Sym struct.  OFF is the
+# offset into the file.  CNT is one greater than the number of symbols
+# left to mangle.  Note that, in the loop below, the first symbol is
+# skipped.  This is intentional since the first symbol is defined by
+# the ELF specification to be the undefined symbol.
+set off 0
+if { $is_elf64 } {
+    set sz 24
+} else {
+    set sz 16
+}
+set cnt [expr $dynsym_len / $sz]
+
+# Create 32-bit patterns (bad offsets) to write into the st_name area.
+if { $is_big_endian } {
+    set pat(0) [binary format I [expr $dynstr_len + 1000]]
+    set pat(1) [binary format I [expr $dynstr_len + 2000]]
+} else {
+    set pat(0) [binary format i [expr $dynstr_len + 1000]]
+    set pat(1) [binary format i [expr $dynstr_len + 2000]]
+}
+
+# Mangle st_name for the symbols following the first (STN_UNDEF) entry.
+while { [incr cnt -1] > 0 } {
+    seek $dynsym_fp [incr off $sz]
+    puts $dynsym_fp $pat([expr $cnt % 2])
+}
+
+close $dynsym_fp
+
+# Replace .dynsym section in shared object with the mangled version.
+if { [catch "exec $objcopy_program \
+               --update-section .dynsym=${binfile_lib}.dynsym \
+              ${binfile_lib}" output] } {
+    untested "failed objcopy update-section"
+    verbose -log "objcopy output: $output"
+    return -1
+}
+
+clean_restart
+
+# Count number of distinct BFD error messages via 'bfd_error_count'
+# array while using add-symbol-file to "load" the shared library.
+gdb_test_multiple "add-symbol-file -readnow $binfile_lib" \
+                  "load library with add-symbol-file" {
+    -re "add symbol table from file.*\(y or n\)" {
+       send_gdb "y\n" answer
+       exp_continue
+    }
+    -re "(BFD:\[^\r\n\]*)\[\r\n\]+" {
+       incr bfd_error_count($expect_out(1,string))
+       exp_continue
+    }
+    -re "Expanding full symbols from.*$gdb_prompt $" {
+       pass $gdb_test_name
+    }
+}
+
+# Examine counts recorded in the 'bfd_error_count' array to see if any
+# message was printed multiple times.
+set more_than_one 0
+foreach index [array names bfd_error_count] {
+    if { $bfd_error_count($index) > 1 } {
+       incr more_than_one
+    }
+}
+gdb_assert { $more_than_one == 0 } "consolidated bfd errors"
+
+# There should have been at least two distinct BFD errors printed.
+gdb_assert { [array size bfd_error_count] >= 2 } "print all unique bfd errors"
+
+gdb_exit
+return 0