Extend GNU ifunc testcases

This patch extends/rewrites the gdb.base/gnu-ifunc.exp testcase to
cover the many different fixes in earlier patches.  (This was actually
what encovered most of the problems.)

The current testcase uses an ifunc symbol with the same name as the
ifunc resolver symbol and makes sure to compile the ifunc resolver
without debug info.  That does not model how ifuncs are implemented in
gcc/ifunc nowadays.  Instead, what we have is that the glibc ifunc
resolvers nowadays are written in C and end up with debug info.

Also, in some cases the ifunc target is written in assembly, but in
other cases it's written in C.  In the case of target function written
in C, if the target function has debug info, when we set a break on
the ifunc, we want to set it past the prologue of the target function.
Currently GDB gets that wrong.

To make sure we cover all the different scenarios, the testcase is
tweaked to cover all the different combinations of

 - An ifunc resolver with the same name as the user-visible symbol vs
   an ifunc resolver with a different name as the user-visible symbol.

 - ifunc resolver compiled with and without debug info.

 - ifunc target function compiled with and without debug info.

The testcase currently sets breakpoints on ifuncs, calls ifunc
functions, steps into ifunc functions, etc.  After this series, this
all works and the testcase passes cleanly.

While working on this, I noticed that "b gnu_ifunc" before and after
the inferior resolved the ifunc would end up with a breakpoint with
different locations.  That's now covered by new tests inside the new
"set-break" procedure.

It also tests other things like making sure we can't call an ifunc
without a return-type case if we don't know the type of the target.
And making sure that we pass enough arguments when we do know the
type.

gdb/testsuite/ChangeLog:
2018-04-26  Pedro Alves  <palves@redhat.com>

	* gdb.base/gnu-ifunc-final.c: New file.
	* gdb.base/gnu-ifunc.c (final): Delete, moved to gnu-ifunc-final.c.
	* gdb.base/gnu-ifunc.exp (executable): Delete.
	(staticexecutable): Adjust.
	(lib_opts, exec_opts): Delete.
	(make_binsuffix, build, set-break): New procedures.
	(misc_tests): New, with tests factored out from the top level.
	(top level): Test different combinations of ifunc resolver name,
	resolver with and with debug info, and ifunc target with and
	without debug info.  Wrap static tests with with_target_prefix.

gdb/testsuite/ChangeLog

@@ -1,3 +1,16 @@
+2018-04-26  Pedro Alves  <palves@redhat.com>
+
+	* gdb.base/gnu-ifunc-final.c: New file.
+	* gdb.base/gnu-ifunc.c (final): Delete, moved to gnu-ifunc-final.c.
+	* gdb.base/gnu-ifunc.exp (executable): Delete.
+	(staticexecutable): Adjust.
+	(lib_opts, exec_opts): Delete.
+	(make_binsuffix, build, set-break): New procedures.
+	(misc_tests): New, with tests factored out from the top level.
+	(top level): Test different combinations of ifunc resolver name,
+	resolver with and with debug info, and ifunc target with and
+	without debug info.  Wrap static tests with with_target_prefix.
+
 2018-04-26  Pedro Alves  <palves@redhat.com>
 
 	* gdb.compile/compile-ifunc.exp: Also expect "function has unknown

gdb/testsuite/gdb.base/gnu-ifunc-final.c

@@ -0,0 +1,22 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2009-2018 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/>.  */
+
+int
+final (int arg)
+{
+  return arg + 1;
+}

gdb/testsuite/gdb.base/gnu-ifunc-lib.c

@@ -22,10 +22,14 @@ extern int final (int arg);
 
 typedef int (*final_t) (int arg);
 
+#ifndef IFUNC_RESOLVER_ATTR
 asm (".type gnu_ifunc, %gnu_indirect_function");
-
 final_t
 gnu_ifunc (unsigned long hwcap)
+#else
+final_t
+gnu_ifunc_resolver (unsigned long hwcap)
+#endif
 {
   resolver_hwcap = hwcap;
   if (! gnu_ifunc_initialized)
@@ -33,3 +37,9 @@ gnu_ifunc (unsigned long hwcap)
   else
     return final;
 }
+
+#ifdef IFUNC_RESOLVER_ATTR
+extern int gnu_ifunc (int arg);
+
+__typeof (gnu_ifunc) gnu_ifunc __attribute__ ((ifunc ("gnu_ifunc_resolver")));
+#endif

gdb/testsuite/gdb.base/gnu-ifunc.c

@@ -23,12 +23,6 @@ init_stub (int arg)
   return 0;
 }
 
-int
-final (int arg)
-{
-  return arg + 1;
-}
-
 /* Make differentiation of how the gnu_ifunc call resolves before and after
    calling gnu_ifunc_pre.  This ensures the resolved function address is not
    being cached anywhere for the debugging purposes.  */

gdb/testsuite/gdb.base/gnu-ifunc.exp

@@ -18,139 +18,371 @@ if {[skip_shlib_tests]} {
 }
 
 standard_testfile .c
-set executable ${testfile}
+set staticexecutable ${testfile}-static
-set staticexecutable ${executable}-static
 set staticbinfile [standard_output_file ${staticexecutable}]
 
 set libfile "${testfile}-lib"
 set libsrc ${libfile}.c
-set lib_so [standard_output_file ${libfile}.so]
-# $lib_o must not have {debug}, it would override the STT_GNU_IFUNC ELF markers.
-set lib_o [standard_output_file ${libfile}.o]
 
-# We need DWARF for the "final" function as we "step" into the function and GDB
+set final_file "${testfile}-final"
-# would step-over the "final" function if there would be no line number debug
+set final_src ${final_file}.c
-# information (DWARF) available.
-#
-# We must not have DWARF for the "gnu_ifunc" function as DWARF has no way to
-# express the STT_GNU_IFUNC type and it would be considered as a regular
-# function due to DWARF by GDB.  In ELF gnu-ifunc is expressed by the
-# STT_GNU_IFUNC type.
-#
-# Both functions need to be in the same shared library file but
-# gdb_compile_shlib has no way to specify source-specific compilation options.
-#
-# Therefore $libfile contains only the STT_GNU_IFUNC function with no DWARF
-# referencing all the other parts from the main executable with DWARF.
-
-set lib_opts {}
-set exec_opts [list debug shlib=$lib_so]
 
 if [get_compiler_info] {
     return -1
 }
 
-if { [gdb_compile_shlib ${srcdir}/${subdir}/$libsrc $lib_so $lib_opts] != ""
+# Return the binary suffix appended to program and library names to
-     || [gdb_compile ${srcdir}/${subdir}/$srcfile $binfile executable $exec_opts] != ""} {
+# make each testcase variant unique.
-    untested "failed to compile first testcase"
+proc make_binsuffix {resolver_attr resolver_debug final_debug} {
-    return -1
+    return "$resolver_attr-$resolver_debug-$final_debug"
 }
 
-# Start with a fresh gdb.
+# Compile the testcase.  RESOLVER_ATTR is true if we're testing with
+# an ifunc resolver that has a different name from the user symbol,
+# specified with GCC's __attribute__ ifunc.  RESOLVER_DEBUG is true
+# iff the resolver was compiled with debug info.  FINAL_DEBUG is true
+# iff the target function was compiled with debug info.
+proc build {resolver_attr resolver_debug final_debug} {
+    global srcdir subdir srcfile binfile
+    global libsrc lib_so libfile
+    global exec_opts executable
+    global hex gdb_prompt
+    global final_file final_src
 
-clean_restart $executable
+    set suffix [make_binsuffix $resolver_attr $resolver_debug $final_debug]
-gdb_load_shlib ${lib_so}
+
+    set lib_so [standard_output_file ${libfile}-$suffix.so]
+    # $lib_o must not have {debug}, it would override the STT_GNU_IFUNC ELF markers.
+    set lib_o [standard_output_file ${libfile}-$suffix.o]
+
+    set exec_opts [list debug shlib=$lib_so]
+
+    set lib_opts {}
+    set final_opts {}
+
+    if {$resolver_attr} {
+	lappend lib_opts "additional_flags=-DIFUNC_RESOLVER_ATTR"
+    }
+
+    if {$resolver_debug} {
+	lappend lib_opts "debug"
+    }
+
+    if {$final_debug} {
+	lappend final_opts "debug"
+    }
+
+    set final_o $final_file-$suffix.o
+
+    if { [gdb_compile_shlib ${srcdir}/${subdir}/$libsrc \
+	      $lib_so $lib_opts] != ""
+	 || [gdb_compile ${srcdir}/${subdir}/$final_src \
+		 $final_o object $final_opts] != ""
+	 || [gdb_compile [list ${srcdir}/${subdir}/$srcfile $final_o] \
+		 $binfile-$suffix executable $exec_opts] != ""} {
+	untested "failed to compile testcase"
+	return 0
+    }
 
-if ![runto_main] then {
-    fail "can't run to main"
     return 1
 }
 
-# The "if" condition is artifical to test regression of a former patch.
+# Test setting a breakpoint on a ifunc function before and after the
-gdb_breakpoint "[gdb_get_line_number "break-at-nextcall"] if i && gnu_ifunc (i) != 42"
+# ifunc is resolved.  For the description of RESOLVER_ATTR,
+# RESOLVER_DEBUG and FINAL_DEBUG, see the "build" procedure above.
+proc_with_prefix set-break {resolver_attr resolver_debug final_debug} {
+    global binfile libfile lib_so
+    global hex decimal
+    global gdb_prompt
 
-gdb_breakpoint [gdb_get_line_number "break-at-call"]
+    set suffix [make_binsuffix $resolver_attr $resolver_debug $final_debug]
-gdb_continue_to_breakpoint "break-at-call" ".*break-at-call.*"
 
-# Test GDB will automatically indirect the call.
+    set lib_so [standard_output_file ${libfile}-$suffix.so]
+    clean_restart $binfile-$suffix
+    gdb_load_shlib ${lib_so}
 
-gdb_test "p gnu_ifunc (3)" " = 4"
+    if ![runto_main] then {
-
+	fail "can't run to main"
-# Test that the resolver received its argument.
+	return 1
-
-set actual_hwcap "0x0"
-set test "info auxv"
-gdb_test_multiple $test $test {
-    -re "\r\n\\d+\\s+AT_HWCAP\[^\r\n\]+($hex)\r\n.*$gdb_prompt $" {
-	set actual_hwcap $expect_out(1,string)
     }
-    -re ".*$gdb_prompt $" {
+
-	pass "$test (no HWCAP)"
+    set ws "\[ \t\]+"
+    set dot "\\.?"
+
+    if {$resolver_attr} {
+	set gnu_ifunc_resolver "gnu_ifunc_resolver"
+    } else {
+	set gnu_ifunc_resolver "gnu_ifunc"
+    }
+
+    if {!$resolver_debug} {
+	set gnu_ifunc_resolver "${dot}${gnu_ifunc_resolver}"
+    }
+
+    if {!$final_debug} {
+	set final "${dot}final"
+    } else {
+	set final "final"
+    }
+
+    with_test_prefix "before resolving" {
+	delete_breakpoints
+	gdb_test "break gnu_ifunc" \
+	    "Breakpoint $decimal at gnu-indirect-function resolver at $hex"
+	gdb_test "info breakpoints" \
+	    "$decimal${ws}STT_GNU_IFUNC resolver${ws}keep${ws}y${ws}$hex <${gnu_ifunc_resolver}>"
+    }
+
+    global final_src
+
+    with_test_prefix "resolve" {
+	delete_breakpoints
+	gdb_breakpoint [gdb_get_line_number "break-at-exit"]
+	gdb_continue_to_breakpoint "break-at-exit" ".*break-at-exit.*"
+    }
+
+    with_test_prefix "after resolving" {
+	delete_breakpoints
+
+	if {!$final_debug} {
+	    # Set a breakpoint both at the ifunc, and at the ifunc's
+	    # target.  GDB should resolve both to the same address.
+	    # Start with the ifunc's target.
+	    set addr "-"
+	    set test "break final"
+	    # Extract the address without the leading "0x", because
+	    # addresses in "info break" output include leading 0s
+	    # (like "0x0000ADDR").
+	    set hex_number {[0-9a-fA-F][0-9a-fA-F]*}
+	    gdb_test_multiple $test $test {
+		-re "Breakpoint .* at 0x($hex_number)\r\n$gdb_prompt $" {
+		    set addr $expect_out(1,string)
+		    pass $test
+		}
+	    }
+
+	    # Now set a break at the ifunc.
+	    gdb_test "break gnu_ifunc" "Breakpoint .* at 0x$addr"
+	    set location "$decimal${ws}breakpoint${ws}keep${ws}y${ws}0x0*$addr${ws}<${final}\\+.*>"
+	} else {
+	    set lineno -1
+	    set test "break final"
+	    gdb_test_multiple $test $test {
+		-re "Breakpoint .* at $hex: file .*$final_src, line ($decimal)\\.\r\n$gdb_prompt $" {
+		    set lineno $expect_out(1,string)
+		    pass $test
+		}
+	    }
+	    gdb_test "break gnu_ifunc" "Breakpoint .* at $hex: file .*$final_src, line $lineno\\."
+	    set location "$decimal${ws}breakpoint${ws}keep${ws}y${ws}$hex in final at .*$final_src:$lineno"
+	}
+	gdb_test "info breakpoints" "$location\r\n$location"
     }
 }
 
-gdb_test "p/x resolver_hwcap" "= $actual_hwcap" "resolver received HWCAP"
+# Misc GNU ifunc tests.  For the description of RESOLVER_ATTR,
+# RESOLVER_DEBUG and FINAL_DEBUG, see the "build" procedure above.
+proc misc_tests {resolver_attr resolver_debug final_debug} {
+    global srcdir subdir srcfile binfile
+    global libsrc lib_so libfile
+    global exec_opts executable
+    global hex gdb_prompt
+    global final_file final_src
 
-# Test GDB will skip the gnu_ifunc resolver on first call.
+    set suffix [make_binsuffix $resolver_attr $resolver_debug $final_debug]
 
-gdb_test "step" "\r\nfinal .*"
+    if {$resolver_attr} {
+	set gnu_ifunc_resolver "gnu_ifunc_resolver"
+    } else {
+	set gnu_ifunc_resolver "gnu_ifunc"
+    }
 
-# Test GDB will not break before the final chosen implementation.
+    set dot "\\.?"
 
-# Also test a former patch regression:
+    if {!$resolver_debug} {
-# Continuing.
+	set gnu_ifunc_resolver "${dot}${gnu_ifunc_resolver}"
-# Error in testing breakpoint condition:
+    }
-# Attempt to take address of value not located in memory.
-# 
-# Breakpoint 2, main () at ./gdb.base/gnu-ifunc.c:33
 
-gdb_test "continue" "Continuing.\r\n\r\nBreakpoint .* (at|in) .*break-at-nextcall.*" \
+    if {!$final_debug} {
-	 "continue to break-at-nextcall"
+	set final "${dot}final"
+    } else {
+	set final "final"
+    }
 
-gdb_breakpoint "gnu_ifunc"
+    # Start with a fresh gdb.
 
-gdb_continue_to_breakpoint "nextcall gnu_ifunc"
+    clean_restart $binfile-$suffix
+    gdb_load_shlib ${lib_so}
 
-gdb_test "frame" "#0 +(0x\[0-9a-f\]+ in +)?final \\(.*" "nextcall gnu_ifunc skipped"
+    if ![runto_main] then {
+	fail "can't run to main"
+	return 1
+    }
 
+    # The "if" condition is artifical to test regression of a former patch.
+    gdb_breakpoint "[gdb_get_line_number "break-at-nextcall"] if i && (int) gnu_ifunc (i) != 42"
 
-# Check any commands not doing an inferior call access the address of the
+    gdb_breakpoint [gdb_get_line_number "break-at-call"]
-# STT_GNU_IFUNC resolver, not the target function.
+    gdb_continue_to_breakpoint "break-at-call" ".*break-at-call.*"
 
-if {[istarget powerpc64-*] && [is_lp64_target]} {
+    # Test GDB will automatically indirect the call.
-    # With only minimal symbols GDB provides the function descriptors.  With
-    # full debug info the function code would be displayed.
-    set func_prefix {\.}
-} else {
-    set func_prefix {}
-}
 
-gdb_test "p gnu_ifunc" " = {<text gnu-indirect-function variable, no debug info>} 0x\[0-9a-f\]+ <${func_prefix}gnu_ifunc>" "p gnu_ifunc executing"
+    if {!$resolver_debug && !$final_debug} {
-gdb_test "info sym gnu_ifunc" "gnu_ifunc in section .*" "info sym gnu_ifunc executing"
+	gdb_test "p gnu_ifunc()" \
+	    "'${dot}final' has unknown return type; cast the call to its declared return type"
+	gdb_test "p gnu_ifunc (3)" \
+	    "'${dot}final' has unknown return type; cast the call to its declared return type"
+	gdb_test "p (int) gnu_ifunc (3)" " = 4"
+    } else {
+	gdb_test "p gnu_ifunc()" "Too few arguments in function call\\."
+	gdb_test "p gnu_ifunc (3)" " = 4"
+    }
 
-set test "info addr gnu_ifunc"
+    # Test that the resolver received its argument.
-gdb_test_multiple $test $test {
+
-    -re "Symbol \"gnu_ifunc\" is at (0x\[0-9a-f\]+) in .*$gdb_prompt $" {
+    set actual_hwcap "0x0"
-	pass $test
+    set test "info auxv"
+    gdb_test_multiple $test $test {
+	-re "\r\n\\d+\\s+AT_HWCAP\[^\r\n\]+($hex)\r\n.*$gdb_prompt $" {
+	    set actual_hwcap $expect_out(1,string)
+	}
+	-re ".*$gdb_prompt $" {
+	    pass "$test (no HWCAP)"
+	}
+    }
+
+    gdb_test "p/x resolver_hwcap" "= $actual_hwcap" "resolver received HWCAP"
+
+    # Test GDB will skip the gnu_ifunc resolver on first call.
+
+    # Even if the resolver has debug info, stepping into an ifunc call
+    # should skip the resolver.
+    if {!$final_debug} {
+	# Make GDB stop stepping even if it steps into a function with
+	# no debug info.
+	gdb_test_no_output "set step-mode on"
+	gdb_test "step" "$hex in ${dot}final \\\(\\\)"
+    } else {
+	gdb_test "step" "\r\nfinal .*"
+    }
+
+    # Test GDB will not break before the final chosen implementation.
+
+    # Also test a former patch regression:
+    # Continuing.
+    # Error in testing breakpoint condition:
+    # Attempt to take address of value not located in memory.
+    #
+    # Breakpoint 2, main () at ./gdb.base/gnu-ifunc.c:33
+
+    gdb_test "continue" \
+	"Continuing.\r\n\r\nBreakpoint .* (at|in) .*break-at-nextcall.*" \
+	"continue to break-at-nextcall"
+
+    gdb_breakpoint "gnu_ifunc"
+
+    gdb_continue_to_breakpoint "nextcall gnu_ifunc"
+
+    gdb_test "frame" \
+	"#0 +(0x\[0-9a-f\]+ in +)?${final} \\(.*" "nextcall gnu_ifunc skipped"
+
+    # Check any commands not doing an inferior call access the address of the
+    # STT_GNU_IFUNC resolver, not the target function.
+
+    if {[istarget powerpc64-*] && [is_lp64_target]} {
+	# With only minimal symbols GDB provides the function descriptors.  With
+	# full debug info the function code would be displayed.
+    }
+
+    gdb_test "p gnu_ifunc" \
+	" = {<text gnu-indirect-function variable, no debug info>} 0x\[0-9a-f\]+ <${gnu_ifunc_resolver}>" \
+	"p gnu_ifunc executing"
+    gdb_test "info sym gnu_ifunc" \
+	"${gnu_ifunc_resolver} in section .*" \
+	"info sym gnu_ifunc executing"
+
+    set test "info addr gnu_ifunc"
+    if {!$resolver_attr && $resolver_debug} {
+	gdb_test_multiple $test $test {
+	    -re "Symbol \"gnu_ifunc\" is a function at address (0x\[0-9a-f\]+).*$gdb_prompt $" {
+		pass $test
+	    }
+	}
+    } else {
+	gdb_test_multiple $test $test {
+	    -re "Symbol \"gnu_ifunc\" is at (0x\[0-9a-f\]+) in .*$gdb_prompt $" {
+		pass $test
+	    }
+	}
+    }
+    gdb_test "info sym $expect_out(1,string)" \
+	"${gnu_ifunc_resolver} in section .*" \
+	"info sym <gnu_ifunc-address>"
+
+    # Test calling the resolver directly instead of the ifunc symbol.
+    # Can only do that if the ifunc and the ifunc resolver have
+    # different names.
+    if {$resolver_attr} {
+	if {$resolver_debug} {
+	    if {[istarget powerpc64-*] && [is_lp64_target]} {
+		gdb_test "p gnu_ifunc_resolver(0)" \
+		    " = \\(int \\(\\*\\)\\(int\\)\\) @$hex: $hex <${final}>"
+	    } else {
+		gdb_test "p gnu_ifunc_resolver(0)" \
+		    " = \\(int \\(\\*\\)\\(int\\)\\) $hex <final>"
+	    }
+	} else {
+	    gdb_test "p gnu_ifunc_resolver(0)" \
+		"'${gnu_ifunc_resolver}' has unknown return type; cast the call to its declared return type"
+	    gdb_test "p (void *) gnu_ifunc_resolver(0)" \
+		" = \\(void \\*\\) $hex <${final}>"
+	}
     }
 }
-gdb_test "info sym $expect_out(1,string)" "gnu_ifunc in section .*" "info sym <gnu_ifunc-address>"
 
+# Test all the combinations of:
+#
+# - An ifunc resolver with the same name as the ifunc symbol vs an
+#   ifunc resolver with a different name as the ifunc symbol.
+#
+# - ifunc resolver compiled with and without debug info.  This ensures
+#   that GDB understands that a function not a regular function by
+#   looking at the STT_GNU_IFUNC type in the elf symbols.  DWARF has
+#   no way to express the STT_GNU_IFUNC type.
+#
+# - ifunc target function (resolved) compiled with and without debug
+#   info.
+foreach_with_prefix resolver_attr {0 1} {
+    foreach_with_prefix resolver_debug {0 1} {
+	foreach_with_prefix final_debug {0 1} {
+	    build $resolver_attr $resolver_debug $final_debug
+	    misc_tests $resolver_attr $resolver_debug $final_debug
+	    set-break $resolver_attr $resolver_debug $final_debug
+	}
+    }
+}
 
 # Test statically linked ifunc resolving during inferior start.
 # https://bugzilla.redhat.com/show_bug.cgi?id=624967
 
-# Compile $staticbinfile separately as it may exit on error (ld/12595).
+with_test_prefix "static" {
+    # Compile $staticbinfile separately as it may exit on error
+    # (ld/12595).
 
-if { [gdb_compile ${srcdir}/${subdir}/$libsrc $lib_o object {}] != ""
+    set lib_o [standard_output_file ${libfile}.o]
-     || [gdb_compile "${srcdir}/${subdir}/$srcfile $lib_o" $staticbinfile executable {debug}] != "" } {
+    set final_o [standard_output_file ${final_file}.o]
-    untested "failed to compile second testcase"
+    if { [gdb_compile ${srcdir}/${subdir}/$libsrc $lib_o object {}] != ""
-    return -1
+	 || [gdb_compile ${srcdir}/${subdir}/$final_src $final_o object {}] != ""
+	 || [gdb_compile "${srcdir}/${subdir}/$srcfile $lib_o $final_o" \
+		 $staticbinfile executable {debug}] != "" } {
+	untested "failed to compile second testcase"
+	return -1
+    }
+
+    clean_restart $staticexecutable
+
+    gdb_breakpoint "gnu_ifunc"
+    gdb_breakpoint "main"
+    gdb_run_cmd
+    gdb_test "" "Breakpoint \[0-9\]*, main .*" "static gnu_ifunc"
 }
-
-clean_restart $staticexecutable
-
-gdb_breakpoint "gnu_ifunc"
-gdb_breakpoint "main"
-gdb_run_cmd
-gdb_test "" "Breakpoint \[0-9\]*, main .*" "static gnu_ifunc"