[PATCH v2 1/2] dl-runtime: reloc_{offset, index} now functions arch overide'able

Vineet Gupta Vineet.Gupta1@synopsys.com
Mon Jun 1 22:18:22 GMT 2020


The existing macros are fragile and expect local variables with a
certain name. Fix this by defining them as functions with default
implementation in a new header dl-runtime.h which arches can override
if need be.

This came up during ARC port review, hence the need for argument pltgot
in reloc_index() which is not needed by existing ports.

This patch potentially only affects hppa/x86 ports,
build tested for both those configs and a few more.

Suggested-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
---
 elf/dl-runtime.c            | 28 +++++++++++++++++-----------
 elf/dl-runtime.h            | 30 ++++++++++++++++++++++++++++++
 sysdeps/hppa/dl-runtime.c   |  4 ----
 sysdeps/hppa/dl-runtime.h   | 31 +++++++++++++++++++++++++++++++
 sysdeps/x86_64/dl-runtime.c |  9 ---------
 sysdeps/x86_64/dl-runtime.h | 35 +++++++++++++++++++++++++++++++++++
 6 files changed, 113 insertions(+), 24 deletions(-)
 create mode 100644 elf/dl-runtime.h
 create mode 100644 sysdeps/hppa/dl-runtime.h
 delete mode 100644 sysdeps/x86_64/dl-runtime.c
 create mode 100644 sysdeps/x86_64/dl-runtime.h

diff --git a/elf/dl-runtime.c b/elf/dl-runtime.c
index cf5f1d3e82e1..85a229f6f019 100644
--- a/elf/dl-runtime.c
+++ b/elf/dl-runtime.c
@@ -27,6 +27,7 @@
 #include "dynamic-link.h"
 #include <tls.h>
 #include <dl-irel.h>
+#include <dl-runtime.h>
 
 
 #if (!ELF_MACHINE_NO_RELA && !defined ELF_MACHINE_PLT_REL) \
@@ -42,13 +43,6 @@
 # define ARCH_FIXUP_ATTRIBUTE
 #endif
 
-#ifndef reloc_offset
-# define reloc_offset reloc_arg
-# define reloc_index  reloc_arg / sizeof (PLTREL)
-#endif
-
-
-
 /* This function is called through a special trampoline from the PLT the
    first time each PLT entry is called.  We must perform the relocation
    specified in the PLT of the given shared object, and return the resolved
@@ -68,8 +62,11 @@ _dl_fixup (
     = (const void *) D_PTR (l, l_info[DT_SYMTAB]);
   const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
 
+  const uintptr_t pltgot = (uintptr_t) D_PTR (l, l_info[DT_PLTGOT]);
+
   const PLTREL *const reloc
-    = (const void *) (D_PTR (l, l_info[DT_JMPREL]) + reloc_offset);
+    = (const void *) (D_PTR (l, l_info[DT_JMPREL])
+		      + reloc_offset (pltgot, reloc_arg));
   const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)];
   const ElfW(Sym) *refsym = sym;
   void *const rel_addr = (void *)(l->l_addr + reloc->r_offset);
@@ -180,9 +177,12 @@ _dl_profile_fixup (
 			l, reloc_arg);
     }
 
+  const uintptr_t pltgot = (uintptr_t) D_PTR (l, l_info[DT_PLTGOT]);
+
   /* This is the address in the array where we store the result of previous
      relocations.  */
-  struct reloc_result *reloc_result = &l->l_reloc_result[reloc_index];
+  struct reloc_result *reloc_result
+    = &l->l_reloc_result[reloc_index (pltgot, reloc_arg, sizeof (PLTREL))];
 
  /* CONCURRENCY NOTES:
 
@@ -219,8 +219,11 @@ _dl_profile_fixup (
 	= (const void *) D_PTR (l, l_info[DT_SYMTAB]);
       const char *strtab = (const char *) D_PTR (l, l_info[DT_STRTAB]);
 
+      const uintptr_t pltgot = (uintptr_t) D_PTR (l, l_info[DT_PLTGOT]);
+
       const PLTREL *const reloc
-	= (const void *) (D_PTR (l, l_info[DT_JMPREL]) + reloc_offset);
+	= (const void *) (D_PTR (l, l_info[DT_JMPREL])
+			  + reloc_offset (pltgot, reloc_arg));
       const ElfW(Sym) *refsym = &symtab[ELFW(R_SYM) (reloc->r_info)];
       const ElfW(Sym) *defsym = refsym;
       lookup_t result;
@@ -485,11 +488,14 @@ _dl_call_pltexit (struct link_map *l, ElfW(Word) reloc_arg,
 		  const void *inregs, void *outregs)
 {
 #ifdef SHARED
+  const uintptr_t pltgot = (uintptr_t) D_PTR (l, l_info[DT_PLTGOT]);
+
   /* This is the address in the array where we store the result of previous
      relocations.  */
   // XXX Maybe the bound information must be stored on the stack since
   // XXX with bind_not a new value could have been stored in the meantime.
-  struct reloc_result *reloc_result = &l->l_reloc_result[reloc_index];
+  struct reloc_result *reloc_result =
+    &l->l_reloc_result[reloc_index (pltgot, reloc_arg, sizeof (PLTREL))];
   ElfW(Sym) *defsym = ((ElfW(Sym) *) D_PTR (reloc_result->bound,
 					    l_info[DT_SYMTAB])
 		       + reloc_result->boundndx);
diff --git a/elf/dl-runtime.h b/elf/dl-runtime.h
new file mode 100644
index 000000000000..dd87d799465e
--- /dev/null
+++ b/elf/dl-runtime.h
@@ -0,0 +1,30 @@
+/* Helpers for On-demand PLT fixup for shared objects. Generic version.
+   Copyright (C) 2020 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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+static inline uintptr_t
+reloc_offset (uintptr_t plt0, uintptr_t pltn)
+{
+  return pltn;
+}
+
+static inline uintptr_t
+reloc_index (uintptr_t plt0, uintptr_t pltn, size_t size)
+{
+  return pltn / size;
+}
diff --git a/sysdeps/hppa/dl-runtime.c b/sysdeps/hppa/dl-runtime.c
index 885a3f1837cb..2d061b150f06 100644
--- a/sysdeps/hppa/dl-runtime.c
+++ b/sysdeps/hppa/dl-runtime.c
@@ -17,10 +17,6 @@
    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
    02111-1307 USA.  */
 
-/* Clear PA_GP_RELOC bit in relocation offset.  */
-#define reloc_offset (reloc_arg & ~PA_GP_RELOC)
-#define reloc_index  (reloc_arg & ~PA_GP_RELOC) / sizeof (PLTREL)
-
 #include <elf/dl-runtime.c>
 
 /* The caller has encountered a partially relocated function descriptor.
diff --git a/sysdeps/hppa/dl-runtime.h b/sysdeps/hppa/dl-runtime.h
new file mode 100644
index 000000000000..be3bc929c74c
--- /dev/null
+++ b/sysdeps/hppa/dl-runtime.h
@@ -0,0 +1,31 @@
+/* Helpers for On-demand PLT fixup for shared objects. HPAA version.
+   Copyright (C) 2020 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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+/* Clear PA_GP_RELOC bit in relocation offset.  */
+static inline uintptr_t
+reloc_offset (uintptr_t plt0, uintptr_t pltn)
+{
+  return pltn & ~PA_GP_RELOC;
+}
+
+static inline uintptr_t
+reloc_index (uintptr_t plt0, uintptr_t pltn, size_t size)
+{
+  return (pltn & ~PA_GP_RELOC )/ size;
+}
diff --git a/sysdeps/x86_64/dl-runtime.c b/sysdeps/x86_64/dl-runtime.c
deleted file mode 100644
index b625d1e88257..000000000000
--- a/sysdeps/x86_64/dl-runtime.c
+++ /dev/null
@@ -1,9 +0,0 @@
-/* The ABI calls for the PLT stubs to pass the index of the relocation
-   and not its offset.  In _dl_profile_fixup and _dl_call_pltexit we
-   also use the index.  Therefore it is wasteful to compute the offset
-   in the trampoline just to reverse the operation immediately
-   afterwards.  */
-#define reloc_offset reloc_arg * sizeof (PLTREL)
-#define reloc_index  reloc_arg
-
-#include <elf/dl-runtime.c>
diff --git a/sysdeps/x86_64/dl-runtime.h b/sysdeps/x86_64/dl-runtime.h
new file mode 100644
index 000000000000..b82fdce8367d
--- /dev/null
+++ b/sysdeps/x86_64/dl-runtime.h
@@ -0,0 +1,35 @@
+/* Helpers for On-demand PLT fixup for shared objects. x86_64 version.
+   Copyright (C) 2020 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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+/* The ABI calls for the PLT stubs to pass the index of the relocation
+   and not its offset.  In _dl_profile_fixup and _dl_call_pltexit we
+   also use the index.  Therefore it is wasteful to compute the offset
+   in the trampoline just to reverse the operation immediately
+   afterwards.  */
+static inline uintptr_t
+reloc_offset (uintptr_t plt0, uintptr_t pltn)
+{
+  return pltn * sizeof (ElfW(Rela));
+}
+
+static inline uintptr_t
+reloc_index (uintptr_t plt0, uintptr_t pltn, size_t size)
+{
+  return pltn;
+}
-- 
2.20.1



More information about the Libc-alpha mailing list