| Message ID | 1483983079-28539-1-git-send-email-vgupta@synopsys.com |
|---|---|
| State | Superseded |
| Headers | show |
On 01/09/2017 09:31 AM, Vineet Gupta wrote: > Historically we've used a special construct _DYNAMIC@gotpc to refer to > base address of GOT This has been done with a special hack in binutils > which tools guys now wish to get rid off. > > So rewrite the 2 callers of this construct to use the simpler and more > obvious constructs. There's existing _GLOBAL_OFFSET_TABLE symbols > provided by linker which can be used for same purposes. > > Signed-off-by: Vineet Gupta <vgupta@synopsys.com> Please ignore this one - it is broken with current binutils ! Assembler is also converting _DYNAMIC@pcl into _GLOBAL_OFFSET_TABLE v2 to follow ! -Vineet > --- > ldso/ldso/arc/dl-sysdep.h | 35 ++++++++++++----------------------- > 1 file changed, 12 insertions(+), 23 deletions(-) > > diff --git a/ldso/ldso/arc/dl-sysdep.h b/ldso/ldso/arc/dl-sysdep.h > index c6086e68e5c6..361a9bb9c0c3 100644 > --- a/ldso/ldso/arc/dl-sysdep.h > +++ b/ldso/ldso/arc/dl-sysdep.h > @@ -119,37 +119,26 @@ extern unsigned __udivmodsi4(unsigned, unsigned) attribute_hidden; > | (((type) == R_ARC_COPY) * ELF_RTYPE_CLASS_COPY)) > > /* > - * Get the runtime address of GOT[0] > + * Get build time address of .dynamic as setup in GOT[0] > + * This is called very early in _dl_start() so it has not been relocated to > + * runtime value > */ > static __always_inline Elf32_Addr elf_machine_dynamic(void) > { > - Elf32_Addr dyn; > - > - __asm__("ld %0,[pcl,_DYNAMIC@gotpc]\n\t" : "=r" (dyn)); > - return dyn; > + /* 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 __always_inline Elf32_Addr elf_machine_load_address(void) > { > - /* To find the loadaddr we subtract the runtime addr of a non-local symbol > - * say _DYNAMIC from it's build-time addr. > - * N.B., gotpc loads get optimized by the linker if it finds the symbol > - * is resolved locally. > - * A more robust - and efficient - solution would be to use a symbol > - * set by the linker. To make it actually save space, we'd have to > - * suppress the unwanted text relocation in the linked dso, though. > - * (I.e. in ldso.so.*, though it's just another dso as far as bfd/ld > - * are concerned.) > - */ > - Elf32_Addr addr, tmp; > - __asm__ ( > - "ld %1, [pcl, _DYNAMIC@gotpc] ;build addr of _DYNAMIC" "\n" > - "add %0, pcl, _DYNAMIC@pcl ;runtime addr of _DYNAMIC" "\n" > - "sub %0, %0, %1 ;delta" "\n" > - : "=&r" (addr), "=r"(tmp) > - ); > - return addr; > + Elf32_Addr build_addr, run_addr; > + > + build_addr = elf_machine_dynamic(); > + __asm__ ("add %0, pcl, _DYNAMIC@pcl \n" : "=r" (run_addr)); > + > + return run_addr - build_addr; > } > > static __always_inline void
Hi, This came out as a precursor to removal of binutils hack which converts _DYNAMIC@ to _GLOBAL_OFFSET_TABLE_ More details in respective patches ! Thx, -Vineet Vineet Gupta (2): ARC: ldso: don't use _DYNAMIC@gotpc construct #1 ARC: ldso: don't use _DYNAMIC@gotpc construct #2 ldso/ldso/arc/dl-startup.h | 2 +- ldso/ldso/arc/dl-sysdep.h | 14 +++++++------- 2 files changed, 8 insertions(+), 8 deletions(-)
Hi, Vineet Gupta wrote, > Hi, > > This came out as a precursor to removal of binutils hack which converts > _DYNAMIC@ to _GLOBAL_OFFSET_TABLE_ > > More details in respective patches ! Applied and pushed, The missing testresults for 1.0.21 are done: http://tests.embedded-test.org/uClibc-ng/1.0.21/ best regards Waldemar
diff --git a/ldso/ldso/arc/dl-sysdep.h b/ldso/ldso/arc/dl-sysdep.h index c6086e68e5c6..361a9bb9c0c3 100644 --- a/ldso/ldso/arc/dl-sysdep.h +++ b/ldso/ldso/arc/dl-sysdep.h @@ -119,37 +119,26 @@ extern unsigned __udivmodsi4(unsigned, unsigned) attribute_hidden; | (((type) == R_ARC_COPY) * ELF_RTYPE_CLASS_COPY)) /* - * Get the runtime address of GOT[0] + * Get build time address of .dynamic as setup in GOT[0] + * This is called very early in _dl_start() so it has not been relocated to + * runtime value */ static __always_inline Elf32_Addr elf_machine_dynamic(void) { - Elf32_Addr dyn; - - __asm__("ld %0,[pcl,_DYNAMIC@gotpc]\n\t" : "=r" (dyn)); - return dyn; + /* 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 __always_inline Elf32_Addr elf_machine_load_address(void) { - /* To find the loadaddr we subtract the runtime addr of a non-local symbol - * say _DYNAMIC from it's build-time addr. - * N.B., gotpc loads get optimized by the linker if it finds the symbol - * is resolved locally. - * A more robust - and efficient - solution would be to use a symbol - * set by the linker. To make it actually save space, we'd have to - * suppress the unwanted text relocation in the linked dso, though. - * (I.e. in ldso.so.*, though it's just another dso as far as bfd/ld - * are concerned.) - */ - Elf32_Addr addr, tmp; - __asm__ ( - "ld %1, [pcl, _DYNAMIC@gotpc] ;build addr of _DYNAMIC" "\n" - "add %0, pcl, _DYNAMIC@pcl ;runtime addr of _DYNAMIC" "\n" - "sub %0, %0, %1 ;delta" "\n" - : "=&r" (addr), "=r"(tmp) - ); - return addr; + Elf32_Addr build_addr, run_addr; + + build_addr = elf_machine_dynamic(); + __asm__ ("add %0, pcl, _DYNAMIC@pcl \n" : "=r" (run_addr)); + + return run_addr - build_addr; } static __always_inline void
Historically we've used a special construct _DYNAMIC@gotpc to refer to base address of GOT This has been done with a special hack in binutils which tools guys now wish to get rid off. So rewrite the 2 callers of this construct to use the simpler and more obvious constructs. There's existing _GLOBAL_OFFSET_TABLE symbols provided by linker which can be used for same purposes. Signed-off-by: Vineet Gupta <vgupta@synopsys.com> --- ldso/ldso/arc/dl-sysdep.h | 35 ++++++++++++----------------------- 1 file changed, 12 insertions(+), 23 deletions(-)