[glibc] riscv: Drop reliance on _GLOBAL_OFFSET_TABLE_[0]

[glibc] riscv: Drop reliance on _GLOBAL_OFFSET_TABLE_[0]

[Fangrui Song]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=34b4624b04fc8f038b2c329ca7560197320615b4

commit 34b4624b04fc8f038b2c329ca7560197320615b4
Author: Fangrui Song <maskray@google.com>
Date:   Wed Aug 18 10:01:31 2021 -0700

    riscv: Drop reliance on _GLOBAL_OFFSET_TABLE_[0]
    
    &__ehdr_start is a better way to get the load address.
    
    This is similar to commits b37b75d269883a2c553bb7019a813094eb4e2dd1
    (x86-64) and 43d06ed218fc8be58987bdfd00e21e5720f0b862 (aarch64).
    
    Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>

Diff:
---
 sysdeps/riscv/dl-machine.h | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/sysdeps/riscv/dl-machine.h b/sysdeps/riscv/dl-machine.h
index aedf69fcdd..5b0746175c 100644
--- a/sysdeps/riscv/dl-machine.h
+++ b/sysdeps/riscv/dl-machine.h
@@ -76,27 +76,26 @@ elf_machine_matches_host (const ElfW(Ehdr) *ehdr)
   return 1;
 }
 
+/* Return the run-time load address of the shared object.  */
+static inline ElfW(Addr)
+elf_machine_load_address (void)
+{
+  extern const ElfW(Ehdr) __ehdr_start attribute_hidden;
+  return (ElfW(Addr)) &__ehdr_start;
+}
+
 /* Return the link-time address of _DYNAMIC.  */
 static inline ElfW(Addr)
 elf_machine_dynamic (void)
 {
-  extern ElfW(Addr) _GLOBAL_OFFSET_TABLE_ __attribute__ ((visibility ("hidden")));
-  return _GLOBAL_OFFSET_TABLE_;
+  extern ElfW(Dyn) _DYNAMIC[] attribute_hidden;
+  return (ElfW(Addr)) _DYNAMIC - elf_machine_load_address ();
 }
 
 #define STRINGXP(X) __STRING (X)
 #define STRINGXV(X) STRINGV_ (X)
 #define STRINGV_(...) # __VA_ARGS__
 
-/* Return the run-time load address of the shared object.  */
-static inline ElfW(Addr)
-elf_machine_load_address (void)
-{
-  ElfW(Addr) load_addr;
-  asm ("lla %0, _DYNAMIC" : "=r" (load_addr));
-  return load_addr - elf_machine_dynamic ();
-}
-
 /* Initial entry point code for the dynamic linker.
    The C function `_dl_start' is the real entry point;
    its return value is the user program's entry point.  */