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[PATCH] Implement x86 SIZE32/SIZE64 relocations
- From: "H.J. Lu" <hongjiu dot lu at intel dot com>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 15 Jan 2013 13:45:14 -0800
- Subject: [PATCH] Implement x86 SIZE32/SIZE64 relocations
- Reply-to: "H.J. Lu" <hjl dot tools at gmail dot com>
Hi
Back to 2005, Solaris added R_386_SIZE32, R_X86_64_SIZE32 and
R_X86_64_SIZE64, which are resolved to symbol size plus addend. But they
aren't implemented in glibc. This patch implements them. They can used
to improve address sanitizer for global common symbols:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55739
OK to install?
BTW, I will also implement them in binutils.
H.J.
---
elf/elf.h | 2 +-
sysdeps/i386/dl-machine.h | 9 +++++++++
sysdeps/x86_64/dl-machine.h | 25 +++++++++++++++++++++++++
4 files changed, 44 insertions(+), 1 deletion(-)
2013-01-15 H.J. Lu <hongjiu.lu@intel.com>
* elf/elf.h (R_386_SIZE32): New relocation.
* sysdeps/i386/dl-machine.h (elf_machine_rel): Handle
R_386_SIZE32.
(elf_machine_rela): Likewise.
* sysdeps/x86_64/dl-machine.h (R_X86_64_SIZE): New macro.
(elf_machine_rela): Handle R_X86_64_SIZE64, R_X86_64_SIZE
and R_X86_64_SIZE32.
diff --git a/elf/elf.h b/elf/elf.h
index 9a31373..9bc5004 100644
--- a/elf/elf.h
+++ b/elf/elf.h
@@ -1229,7 +1229,7 @@ typedef struct
#define R_386_TLS_DTPMOD32 35 /* ID of module containing symbol */
#define R_386_TLS_DTPOFF32 36 /* Offset in TLS block */
#define R_386_TLS_TPOFF32 37 /* Negated offset in static TLS block */
-/* 38? */
+#define R_386_SIZE32 38 /* 32-bit symbol size */
#define R_386_TLS_GOTDESC 39 /* GOT offset for TLS descriptor. */
#define R_386_TLS_DESC_CALL 40 /* Marker of call through TLS
descriptor for
diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h
index 9e36687..a1e40d8 100644
--- a/sysdeps/i386/dl-machine.h
+++ b/sysdeps/i386/dl-machine.h
@@ -348,6 +348,12 @@ elf_machine_rel (struct link_map *map, const Elf32_Rel *reloc,
switch (r_type)
{
+# ifndef RTLD_BOOTSTRAP
+ case R_386_SIZE32:
+ /* Set to symbol size plus addend. */
+ *reloc_addr += sym->st_size;
+ break;
+# endif
case R_386_GLOB_DAT:
case R_386_JMP_SLOT:
*reloc_addr = value;
@@ -507,6 +513,9 @@ elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
switch (ELF32_R_TYPE (reloc->r_info))
{
+ case R_386_SIZE32:
+ /* Set to symbol size plus addend. */
+ value = sym->st_size;
case R_386_GLOB_DAT:
case R_386_JMP_SLOT:
case R_386_32:
diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h
index 660f1aa..382caa4 100644
--- a/sysdeps/x86_64/dl-machine.h
+++ b/sysdeps/x86_64/dl-machine.h
@@ -190,6 +190,13 @@ _dl_start_user:\n\
/* The x86-64 never uses Elf64_Rel/Elf32_Rel relocations. */
#define ELF_MACHINE_NO_REL 1
+/* Size relocation. */
+#ifdef __ILP32__
+# define R_X86_64_SIZE R_X86_64_SIZE32
+#else
+# define R_X86_64_SIZE R_X86_64_SIZE64
+#endif
+
/* We define an initialization function. This is called very early in
_dl_sysdep_start. */
#define DL_PLATFORM_INIT dl_platform_init ()
@@ -286,6 +293,19 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
switch (r_type)
{
+# ifndef RTLD_BOOTSTRAP
+# ifdef __ILP32__
+ case R_X86_64_SIZE64:
+ /* Set to symbol size plus addend. */
+ *((Elf64_Addr *) (uintptr_t) reloc_addr)
+ = (Elf64_Addr) sym->st_size + reloc->r_addend;
+ break;
+# endif
+
+ case R_X86_64_SIZE:
+ /* Set to symbol size plus addend. */
+ value = sym->st_size;
+# endif
case R_X86_64_GLOB_DAT:
case R_X86_64_JUMP_SLOT:
*reloc_addr = value + reloc->r_addend;
@@ -394,6 +414,11 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
relocation updates the whole 64-bit entry. */
*(Elf64_Addr *) reloc_addr = (Elf64_Addr) value + reloc->r_addend;
break;
+# ifndef __ILP32__
+ case R_X86_64_SIZE32:
+ /* Set to symbol size plus addend. */
+ value = sym->st_size;
+# endif
case R_X86_64_32:
value += reloc->r_addend;
*(unsigned int *) reloc_addr = value;
--
1.7.11.7