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From bca0f5cbc9257c13322b99e55235c4f21ba0bd82 Mon Sep 17 00:00:00 2001
From: Fangrui Song <maskray@google.com>
Date: Wed, 18 Aug 2021 11:13:03 -0700
Subject: [PATCH] arm: Simplify elf_machine_{load_address,dynamic}
and drop reliance on _GLOBAL_OFFSET_TABLE_[0] being the link-time
address of _DYNAMIC. &__ehdr_start is a better way to get the load address.
This is similar to commits b37b75d269883a2c553bb7019a813094eb4e2dd1
(x86-64) and 43d06ed218fc8be58987bdfd00e21e5720f0b862 (aarch64).
Reviewed-by: Joseph Myers <joseph@codesourcery.com>
---
sysdeps/arm/dl-machine.h | 47 ++++++++++-------------------------------------
1 file changed, 10 insertions(+), 37 deletions(-)
diff --git a/sysdeps/arm/dl-machine.h b/sysdeps/arm/dl-machine.h
index ff5e09e..eb13cb8 100644
--- a/sysdeps/arm/dl-machine.h
+++ b/sysdeps/arm/dl-machine.h
@@ -37,48 +37,21 @@ elf_machine_matches_host (const Elf32_Ehdr *ehdr)
return ehdr->e_machine == EM_ARM;
}
-
-/* Return the link-time address of _DYNAMIC. Conveniently, this is the
- first element of the GOT. */
-static inline Elf32_Addr __attribute__ ((unused))
-elf_machine_dynamic (void)
-{
- /* Declaring this hidden ensures that a PC-relative reference is used. */
- extern const Elf32_Addr _GLOBAL_OFFSET_TABLE_[] attribute_hidden;
- return _GLOBAL_OFFSET_TABLE_[0];
-}
-
-
/* Return the run-time load address of the shared object. */
-static inline Elf32_Addr __attribute__ ((unused))
+static inline ElfW(Addr) __attribute__ ((unused))
elf_machine_load_address (void)
{
- Elf32_Addr pcrel_addr;
-#ifdef SHARED
- extern Elf32_Addr __dl_start (void *) asm ("_dl_start");
- Elf32_Addr got_addr = (Elf32_Addr) &__dl_start;
- asm ("adr %0, _dl_start" : "=r" (pcrel_addr));
-#else
- extern Elf32_Addr __dl_relocate_static_pie (void *)
- asm ("_dl_relocate_static_pie") attribute_hidden;
- Elf32_Addr got_addr = (Elf32_Addr) &__dl_relocate_static_pie;
- asm ("adr %0, _dl_relocate_static_pie" : "=r" (pcrel_addr));
-#endif
-#ifdef __thumb__
- /* Clear the low bit of the function address.
-
- NOTE: got_addr is from GOT table whose lsb is always set by linker if it's
- Thumb function address. PCREL_ADDR comes from PC-relative calculation
- which will finish during assembling. GAS assembler before the fix for
- PR gas/21458 was not setting the lsb but does after that. Always do the
- strip for both, so the code works with various combinations of glibc and
- Binutils. */
- got_addr &= ~(Elf32_Addr) 1;
- pcrel_addr &= ~(Elf32_Addr) 1;
-#endif
- return pcrel_addr - got_addr;
+ extern const ElfW(Ehdr) __ehdr_start attribute_hidden;
+ return (ElfW(Addr)) &__ehdr_start;
}
+/* Return the link-time address of _DYNAMIC. */
+static inline ElfW(Addr) __attribute__ ((unused))
+elf_machine_dynamic (void)
+{
+ extern ElfW(Dyn) _DYNAMIC[] attribute_hidden;
+ return (ElfW(Addr)) _DYNAMIC - elf_machine_load_address ();
+}
/* Set up the loaded object described by L so its unrelocated PLT
entries will jump to the on-demand fixup code in dl-runtime.c. */
--
1.8.3.1
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