[RFC PATCH glibc 1/8] Introduce <elf_machine_sym_no_match.h>

[Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>]

From: Florian Weimer <fweimer@redhat.com>

MIPS needs to ignore certain existing symbols during symbol lookup.
The old scheme uses the ELF_MACHINE_SYM_NO_MATCH macro, with an
inline function, within its own header, with a sysdeps override for
MIPS.  This allows re-use of the function from another file (without
having to include <dl-machine.h> or providing the default definition
for ELF_MACHINE_SYM_NO_MATCH).

Built with build-many-glibcs.py, with manual verification that
sysdeps/mips/elf_machine_sym_no_match.h is picked up on MIPS.  Tested
on aarch64-linux-gnu, i686-linux-gnu, powerpc64-linux-gnu,
s390x-linux-gnu, x86_64-linux-gnu.

	* elf/elf_machine_sym_no_match.h: New file.
	* elf/dl-lookip.c (ELF_MACHINE_SYM_NO_MATCH): Do not define.
	* elf/dl-lookup.c (check_match) Call elf_machine_sym_no_match
	instead of ELF_MACHINE_SYM_NO_MATCH.
	* sysdeps/mips/dl-machine.h (ELF_MACHINE_SYM_NO_MATCH): Remove
	definition.
	* sysdeps/mips/elf_machine_sym_no_match.h: New file.  Extracted
	from sysdeps/mips/dl-machine.h.
---
 elf/dl-lookup.c                         | 10 ++----
 elf/elf_machine_sym_no_match.h          | 34 +++++++++++++++++++
 sysdeps/mips/dl-machine.h               | 15 ---------
 sysdeps/mips/elf_machine_sym_no_match.h | 43 +++++++++++++++++++++++++
 4 files changed, 79 insertions(+), 23 deletions(-)
 create mode 100644 elf/elf_machine_sym_no_match.h
 create mode 100644 sysdeps/mips/elf_machine_sym_no_match.h

diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c
index 378f28fa7d..db9785ab75 100644
--- a/elf/dl-lookup.c
+++ b/elf/dl-lookup.c
@@ -28,18 +28,12 @@
 #include <libc-lock.h>
 #include <tls.h>
 #include <atomic.h>
+#include <elf_machine_sym_no_match.h>
 
 #include <assert.h>
 
-/* Return nonzero if check_match should consider SYM to fail to match a
-   symbol reference for some machine-specific reason.  */
-#ifndef ELF_MACHINE_SYM_NO_MATCH
-# define ELF_MACHINE_SYM_NO_MATCH(sym) 0
-#endif
-
 #define VERSTAG(tag)	(DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (tag))
 
-
 struct sym_val
   {
     const ElfW(Sym) *s;
@@ -78,7 +72,7 @@ check_match (const char *const undef_name,
   if (__glibc_unlikely ((sym->st_value == 0 /* No value.  */
 			 && sym->st_shndx != SHN_ABS
 			 && stt != STT_TLS)
-			|| ELF_MACHINE_SYM_NO_MATCH (sym)
+			|| elf_machine_sym_no_match (sym)
 			|| (type_class & (sym->st_shndx == SHN_UNDEF))))
     return NULL;
 
diff --git a/elf/elf_machine_sym_no_match.h b/elf/elf_machine_sym_no_match.h
new file mode 100644
index 0000000000..6e299e5ee8
--- /dev/null
+++ b/elf/elf_machine_sym_no_match.h
@@ -0,0 +1,34 @@
+/* Function to ignore certain symbol matches for machine-specific reasons.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _ELF_MACHINE_SYM_NO_MATCH_H
+#define _ELF_MACHINE_SYM_NO_MATCH_H
+
+#include <link.h>
+#include <stdbool.h>
+
+/* This can be customized to ignore certain symbols during lookup in
+   case there are machine-specific rules to disregard some
+   symbols.  */
+static inline bool
+elf_machine_sym_no_match (const ElfW(Sym) *sym)
+{
+  return false;
+}
+
+#endif /* _ELF_MACHINE_SYM_NO_MATCH_H */
diff --git a/sysdeps/mips/dl-machine.h b/sysdeps/mips/dl-machine.h
index 06021ea9ab..e3b11a4f21 100644
--- a/sysdeps/mips/dl-machine.h
+++ b/sysdeps/mips/dl-machine.h
@@ -467,21 +467,6 @@ elf_machine_plt_value (struct link_map *map, const ElfW(Rel) *reloc,
   return value;
 }
 
-/* The semantics of zero/non-zero values of undefined symbols differs
-   depending on whether the non-PIC ABI is in use.  Under the non-PIC
-   ABI, a non-zero value indicates that there is an address reference
-   to the symbol and thus it must always be resolved (except when
-   resolving a jump slot relocation) to the PLT entry whose address is
-   provided as the symbol's value; a zero value indicates that this
-   canonical-address behaviour is not required.  Yet under the classic
-   MIPS psABI, a zero value indicates that there is an address
-   reference to the function and the dynamic linker must resolve the
-   symbol immediately upon loading.  To avoid conflict, symbols for
-   which the dynamic linker must assume the non-PIC ABI semantics are
-   marked with the STO_MIPS_PLT flag.  */
-#define ELF_MACHINE_SYM_NO_MATCH(sym) \
-  ((sym)->st_shndx == SHN_UNDEF && !((sym)->st_other & STO_MIPS_PLT))
-
 #endif /* !dl_machine_h */
 
 #ifdef RESOLVE_MAP
diff --git a/sysdeps/mips/elf_machine_sym_no_match.h b/sysdeps/mips/elf_machine_sym_no_match.h
new file mode 100644
index 0000000000..f2be74caaf
--- /dev/null
+++ b/sysdeps/mips/elf_machine_sym_no_match.h
@@ -0,0 +1,43 @@
+/* MIPS-specific handling of undefined symbols.
+   Copyright (C) 2008-2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _ELF_MACHINE_SYM_NO_MATCH_H
+#define _ELF_MACHINE_SYM_NO_MATCH_H
+
+#include <link.h>
+#include <stdbool.h>
+
+/* The semantics of zero/non-zero values of undefined symbols differs
+   depending on whether the non-PIC ABI is in use.  Under the non-PIC
+   ABI, a non-zero value indicates that there is an address reference
+   to the symbol and thus it must always be resolved (except when
+   resolving a jump slot relocation) to the PLT entry whose address is
+   provided as the symbol's value; a zero value indicates that this
+   canonical-address behaviour is not required.  Yet under the classic
+   MIPS psABI, a zero value indicates that there is an address
+   reference to the function and the dynamic linker must resolve the
+   symbol immediately upon loading.  To avoid conflict, symbols for
+   which the dynamic linker must assume the non-PIC ABI semantics are
+   marked with the STO_MIPS_PLT flag.  */
+static inline bool
+elf_machine_sym_no_match (const ElfW(Sym) *sym)
+{
+  return sym->st_shndx == SHN_UNDEF && !(sym->st_other & STO_MIPS_PLT);
+}
+
+#endif /* _ELF_MACHINE_SYM_NO_MATCH_H */
-- 
2.17.1