* Andrew Burgess andrew.burgess@embecosm.com [2016-07-29 10:43:17 +0100]:

• Alexey Brodkin Alexey.Brodkin@synopsys.com [2016-07-29 08:49:22 +0000]:

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Hi Andrew, all,

On Thu, 2016-07-28 at 15:40 -0700, Vineet Gupta wrote:

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On 07/28/2016 03:04 PM, Bernhard Reutner-Fischer wrote:

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Indeed your 2/2 seems to be the most "past-proof" code change. So I

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would think it is indeed better and is something I should have done in the first place.

@Alexey, @Vlad what say you ?

uClibc traditionally supports the current stable release of binutils, which would make it patch #1 I think.

But 2/2 works for both and makes actual binutils version moot. FWIW, ARC tools don't as of last release didn't use the upstream/stable binutils, but we are pretty close to that now though.

Personally I'd prefer to not add more conditional defines in uClibc but make it a little-bit simpler.

I.e. either Vlad's patch or #1 from this series IMHO looks better. It's been quite some time since we updated our tools with PCL support and I'm not really sure if there's anybody interested in using ages old tools with today's uClibc. We don't test such combinations and there could be issues already in such combos.

BTW I noticed that Vlad's patch removes/reverts that thing as well: http://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/commit/ldso/ldso/arc/dl-sys... c5187

While Andrew just replaces ".&" construction with "@pcl". I'm wondering which is the correct approach here?

I left the second block in as the two blocks use different symbols, the native threads block uses _DYNAMIC, while the non-native uses _dl_start.

I wasn't sure if this was significant, so left the the split in place. If more knowledgeable folk believe these can be combined then that's fine with me (so long as we combine on @pcl).

Having looked at this a little more I think that we should merge the section Alexey mentioned above. In the second instance (the one I modified) we use the symbol _dl_start, while in the first we use _DYNAMIC.

However, the comment in the first block makes it clear the symbol used should be a global symbol, not a local, and _dl_start is a local symbol.

The consequence of using a local here is that we end up with a R_ARC_NONE relocation being generated again the .got.

[ The generation of the R_ARC_NONE is probably a bug, or at least a lack of optimisation, but it is what happens with the current upstream tools. ]

As the arc dynamic loader does not currently support patching R_ARC_NONE during the bootstrap phase, if uClibc(-ng) is configured without native threads, then currently we get a dynamic loader that does not work.

So, I think we should collapse both sections, and make use of the _DYNAMIC symbol instead of _dl_start. I've included a revised version of patch 1/2 that includes this latest change.

Thanks, Andrew

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[PATCH] ARC: Update relocation syntax for old-thread model code

This commit reverses a change introduced in commit 20554a78a9bba that split some of the ARC code into two based on whether uClibc was configured with native threads or not.

The native thread code was updated to use the relocation syntax of modern binutils, while the non-native code path used a syntax only accepted in older versions of binutils.

The problem with this is that the choice of old binutils or not is orthogonal to the choice of native threads or not, and so, inevitably a user with a recent version of binutils can make the choice to configure uClibc with non-native thread support, and run into code that will not assemble.

The solution is either to abandon support for the old tools completely, or to add a new compile time flag for ARC that is set when the version of binutils being used is old; this new flag would allow the old relocation structure to be selected.

In this commit I have simply dropped support for older versions of the tools. --- ldso/ldso/arc/dl-startup.h | 7 ------- ldso/ldso/arc/dl-sysdep.h | 10 ---------- 2 files changed, 17 deletions(-)

diff --git a/ldso/ldso/arc/dl-startup.h b/ldso/ldso/arc/dl-startup.h index ef89b53..664b860 100644 --- a/ldso/ldso/arc/dl-startup.h +++ b/ldso/ldso/arc/dl-startup.h @@ -34,15 +34,8 @@ __asm__( " ; skip the extra args calc by dl_start() \n" " ld_s r1, [sp] ; orig argc from aux-vec Tbl \n"

-#ifdef __UCLIBC_HAS_THREADS_NATIVE__ " ld r12, [pcl, _dl_skip_args@pcl] \n" - " add r2, pcl, _dl_fini@pcl ; finalizer \n" -#else - " add r12, pcl, _dl_skip_args-.+(.&2) \n" - " ld r12, [r12] \n" - " add r2, pcl, _dl_fini-.+(.&2) ; finalizer \n" -#endif

" add2 sp, sp, r12 ; discard argv entries from stack\n" " sub_s r1, r1, r12 ; adjusted argc, on stack \n" diff --git a/ldso/ldso/arc/dl-sysdep.h b/ldso/ldso/arc/dl-sysdep.h index caece99..c6086e6 100644 --- a/ldso/ldso/arc/dl-sysdep.h +++ b/ldso/ldso/arc/dl-sysdep.h @@ -132,7 +132,6 @@ static __always_inline Elf32_Addr elf_machine_dynamic(void) /* Return the run-time load address of the shared object. */ static __always_inline Elf32_Addr elf_machine_load_address(void) { -#ifdef __UCLIBC_HAS_THREADS_NATIVE__ /* 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 @@ -150,15 +149,6 @@ static __always_inline Elf32_Addr elf_machine_load_address(void) "sub %0, %0, %1 ;delta" "\n" : "=&r" (addr), "=r"(tmp) ); -#else - Elf32_Addr addr, tmp; - __asm__ ( - "ld %1, [pcl, _dl_start@gotpc] ;build addr of _dl_start \n" - "add %0, pcl, _dl_start-.+(.&2) ;runtime addr of _dl_start \n" - "sub %0, %0, %1 ;delta \n" - : "=&r" (addr), "=r"(tmp) - ); -#endif return addr; }