[binutils-gdb] gdb: Preserve IFUNC marker when finding inferior functions

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=de930032d883219559d1dba575f2c0f5359e80fc

commit de930032d883219559d1dba575f2c0f5359e80fc
Author: Muhammad Kamran <[email protected]>
Date:   Tue Aug 11 13:12:18 2026 +0000

    gdb: Preserve IFUNC marker when finding inferior functions
    
    GDB calls find_function_in_inferior ("malloc") when expression
    evaluation needs to allocate memory in the inferior, e.g. for string
    literal arguments.
    
    The minimal-symbol fallback created a synthetic ordinary function
    pointer from msymbol.value_address ().  If the symbol was a GNU IFUNC,
    this discarded the IFUNC marker, so call_function_by_hand did not
    resolve the symbol before calling it.
    
    Check the minimal symbol kind directly and propagate the GNU IFUNC
    marker to the synthetic function type for mst_text_gnu_ifunc and
    mst_data_gnu_ifunc symbols.  This keeps the existing fallback address
    and return type while allowing inferior calls through IFUNC symbols to
    be resolved correctly.
    
    Extend gdb.base/gnu-ifunc.exp with an internal inferior-call test that
    uses an IFUNC malloc.  The test runs through the existing IFUNC matrix
    for resolver attr, resolver debug info, and resolved-target debug
    info.
    
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=34330
    Reviewed-By: Kevin Buettner <[email protected]>
    Approved-By: Andrew Burgess <[email protected]>

Diff:
---
 .../gdb.base/gnu-ifunc-inferior-call-final.c       |  27 ++++++
 .../gdb.base/gnu-ifunc-inferior-call-resolver.c    |  43 +++++++++
 gdb/testsuite/gdb.base/gnu-ifunc-inferior-call.c   |  37 ++++++++
 gdb/testsuite/gdb.base/gnu-ifunc.exp               | 105 +++++++++++++++++++++
 gdb/valops.c                                       |   5 +
 5 files changed, 217 insertions(+)

diff --git a/gdb/testsuite/gdb.base/gnu-ifunc-inferior-call-final.c b/gdb/testsuite/gdb.base/gnu-ifunc-inferior-call-final.c
new file mode 100644
index 00000000000..1a9ae6fdcba
--- /dev/null
+++ b/gdb/testsuite/gdb.base/gnu-ifunc-inferior-call-final.c
@@ -0,0 +1,27 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2026 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 <stddef.h>
+
+extern char arena[32];
+
+void *
+dummy_malloc (size_t size)
+{
+  (void) size;
+  return arena;
+}
diff --git a/gdb/testsuite/gdb.base/gnu-ifunc-inferior-call-resolver.c b/gdb/testsuite/gdb.base/gnu-ifunc-inferior-call-resolver.c
new file mode 100644
index 00000000000..217002968de
--- /dev/null
+++ b/gdb/testsuite/gdb.base/gnu-ifunc-inferior-call-resolver.c
@@ -0,0 +1,43 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2026 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 <stddef.h>
+
+extern void *dummy_malloc (size_t size);
+
+typedef void *(*malloc_t) (size_t size);
+
+#ifndef IFUNC_RESOLVER_ATTR
+asm (".type malloc, %gnu_indirect_function");
+malloc_t
+malloc (unsigned long hwcap)
+#else
+static malloc_t
+resolve_malloc (void)
+#endif
+{
+#ifndef IFUNC_RESOLVER_ATTR
+  (void) hwcap;
+#endif
+  return dummy_malloc;
+}
+
+#ifdef IFUNC_RESOLVER_ATTR
+extern void *malloc (size_t size);
+
+__typeof (malloc) malloc __attribute__ ((ifunc ("resolve_malloc")));
+#endif
diff --git a/gdb/testsuite/gdb.base/gnu-ifunc-inferior-call.c b/gdb/testsuite/gdb.base/gnu-ifunc-inferior-call.c
new file mode 100644
index 00000000000..67d195d25f0
--- /dev/null
+++ b/gdb/testsuite/gdb.base/gnu-ifunc-inferior-call.c
@@ -0,0 +1,37 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2026 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/>.  */
+
+char arena[32];
+const char *str;
+
+int
+str_in_arena (void)
+{
+  return str == arena;
+}
+
+void
+get_string (const char *s)
+{
+  str = s;
+}
+
+int
+main (void)
+{
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/gnu-ifunc.exp b/gdb/testsuite/gdb.base/gnu-ifunc.exp
index e6389102ae3..d146a197776 100644
--- a/gdb/testsuite/gdb.base/gnu-ifunc.exp
+++ b/gdb/testsuite/gdb.base/gnu-ifunc.exp
@@ -25,6 +25,13 @@ set libsrc ${libfile}.c
 set final_file "${testfile}-final"
 set final_src ${final_file}.c
 
+set infcall_file "${testfile}-inferior-call"
+set infcall_src ${infcall_file}.c
+set infcall_resolver_file "${testfile}-inferior-call-resolver"
+set infcall_resolver_src ${infcall_resolver_file}.c
+set infcall_final_file "${testfile}-inferior-call-final"
+set infcall_final_src ${infcall_final_file}.c
+
 # Return the binary suffix appended to program and library names to
 # make each testcase variant unique.
 proc make_binsuffix {resolver_attr resolver_debug final_debug} {
@@ -356,6 +363,103 @@ proc misc_tests {resolver_attr resolver_debug final_debug} {
     }
 }
 
+# Test that GDB resolves a GNU IFUNC minimal symbol when it uses
+# find_function_in_inferior to make an internal inferior call.  String
+# literals are copied into the inferior with a call to malloc, so an
+# IFUNC malloc exercises this path.
+
+proc_with_prefix test_inferior_call {resolver_attr resolver_debug final_debug} {
+    global srcdir subdir
+    global infcall_file infcall_src
+    global infcall_resolver_file infcall_resolver_src
+    global infcall_final_file infcall_final_src
+
+    set suffix [make_binsuffix $resolver_attr $resolver_debug $final_debug]
+    set executable ${infcall_file}-$suffix
+    set binfile [standard_output_file $executable]
+    set infcall_lib_so [standard_output_file ${infcall_file}-$suffix.so]
+    set resolver_obj [standard_output_file ${infcall_resolver_file}-$suffix.o]
+    set final_obj [standard_output_file ${infcall_final_file}-$suffix.o]
+
+    set resolver_opts {additional_flags=-fno-builtin-malloc additional_flags=-fpic}
+    set final_opts {additional_flags=-fpic}
+    set shlib_opts {ldflags=-Wl,-z,lazy}
+    set exec_opts [list debug shlib=$infcall_lib_so]
+    lappend exec_opts "ldflags=-Wl,-z,lazy"
+
+    if {$resolver_attr} {
+	lappend resolver_opts "additional_flags=-DIFUNC_RESOLVER_ATTR"
+    }
+
+    if {$resolver_debug} {
+	lappend resolver_opts "debug"
+    }
+
+    if {$final_debug} {
+	lappend final_opts "debug"
+    }
+
+    if { [gdb_compile ${srcdir}/${subdir}/${infcall_resolver_src} \
+	      $resolver_obj object $resolver_opts] != ""
+	 || [gdb_compile ${srcdir}/${subdir}/${infcall_final_src} \
+		 $final_obj object $final_opts] != ""
+	 || [gdb_compile_shlib [list $resolver_obj $final_obj] \
+		 $infcall_lib_so $shlib_opts] != ""
+	 || [gdb_compile ${srcdir}/${subdir}/${infcall_src} \
+		 $binfile executable $exec_opts] != "" } {
+	untested "failed to compile inferior call testcase"
+	return
+    }
+
+    clean_restart $executable
+    gdb_load_shlib $infcall_lib_so
+    if {![runto_main]} {
+	return
+    }
+
+    set malloc_addr {}
+    gdb_test_multiple "pipe maint print msymbols | grep \" malloc \"" \
+	"look for malloc msyms" {
+	-re "($::hex) malloc section \[^\r\n\]+\r\n" {
+	    lappend malloc_addr $expect_out(1,string)
+	    exp_continue
+	}
+
+	-re "$::gdb_prompt $" {
+	    gdb_assert {[llength $malloc_addr] > 0} \
+	       "found at least one malloc symbol"
+	}
+    }
+
+    set found_correct_malloc false
+    set first_addr [lindex $malloc_addr 0]
+    set infcall_lib_tail [file tail $infcall_lib_so]
+    gdb_test_multiple "info symbol $first_addr" "check first malloc symbol" {
+	-re -wrap " in section \[^\r\n\]+ of \[^\r\n\]+/$infcall_lib_tail" {
+	    set found_correct_malloc true
+	}
+
+	-re -wrap " in section \[^\r\n\]+" {
+	    # Nothing to do.
+	}
+    }
+    if { !$found_correct_malloc } {
+       unsupported "found some other malloc symbol"
+       return
+    }
+
+    # Without debug info for both the resolver and the resolved target,
+    # find_function_addr currently loses the synthetic return type after
+    # resolving the IFUNC.
+    if {!$resolver_debug && !$final_debug} {
+	unsupported "internal call resolves IFUNC malloc"
+	return
+    }
+    gdb_test "print (get_string (\"hello-ifunc\"), str_in_arena ())" \
+	" = 1" \
+	"internal call resolves IFUNC malloc"
+}
+
 # Test all the combinations of:
 #
 # - An ifunc resolver with the same name as the ifunc symbol vs an
@@ -374,6 +478,7 @@ foreach_with_prefix resolver_attr {0 1} {
 	    if { [build $resolver_attr $resolver_debug $final_debug] != 0 } {
 		misc_tests $resolver_attr $resolver_debug $final_debug
 		set-break $resolver_attr $resolver_debug $final_debug
+		test_inferior_call $resolver_attr $resolver_debug $final_debug
 	    }
 	}
     }
diff --git a/gdb/valops.c b/gdb/valops.c
index d2dc3d9e869..c478bdc3f15 100644
--- a/gdb/valops.c
+++ b/gdb/valops.c
@@ -138,6 +138,11 @@ find_function_in_inferior (const char *name, struct objfile **objf_p)
 	  type = lookup_function_type (type);
 	  type = lookup_pointer_type (type);
 	  maddr = msymbol.value_address ();
+	  minimal_symbol_type minsym_type = msymbol.minsym->type ();
+
+	  if (minsym_type == mst_text_gnu_ifunc
+	      || minsym_type == mst_data_gnu_ifunc)
+	    type->target_type ()->set_is_gnu_ifunc (true);
 
 	  if (objf_p)
 	    *objf_p = objfile;