[PATCH v4 5/7] MIPS: Fix some ld testcases with compiler

[YunQiang Su]

Alan Modra via Binutils <binutils@sourceware.org> 于2023年6月19日周一 14:44写道：
>
> Hi YunQiang Su,
> I thought I'd take a detailed look at your patch modifying the generic
> ELF tests for mips, despite not really being familiar enough with mips
> to properly review mips changes.  Most of this review is not about
> details of the patch but rather questioning whether you have done the
> necessary analysis before xfailing tests.  It is reasonable to xfail a
> test if for some reason a problem cannot be fixed, or even if a
> problem is too difficult to be fixed.  On the other hand we don't want
> a clean testsuite result if there are problems that should be fixed.
>
> On Fri, Jun 16, 2023 at 02:34:10PM +0800, YunQiang Su wrote:
> > 1. config/default.exp:
> >       use -mabi=32 not for -gnuabi64;
> >       xfail_from_runlist: remove an element and mark it xfail.
>
> I dislike the use of xfail here.  xfail should only be used after
> running a test, to record an expected fail.  Don't use it when a test
> is not run.
>

Maybe, kfail is better?

> > 2. ld-elf/indirect.exp: xfail
> >       indirect5a, indirect5b, indirect6a, indirect6b,
> >       indirect5c, indirect5d, indirect6c, indirect6d.
>
> Can you explain why is it correct to xfail these for mips?  The first
> four pass for me on mips-linux.  Is there a reason why the last four
> must make "bar" dynamic on mips?
>

Do you have a cross compiler installed?
These tests won't even try to run without a  corresponding cross
compiler installed.

The real problem seems due to the output of nm -D.

objdump -D on aarch64:
Disassembly of section .bss:
0000000000011038 <completed.0>:
        ...
0000000000011040 <bar>:
        ...

objdump -D on mips32el:
Disassembly of section .bss:
00010a70 <completed.1>:
   10a70:       00000000        nop
00010a74 <dtor_idx.0>:
        ...
00010a80 <bar>:
        ...

While the outputs of NM -D are different. Let me have a more dig about it.


> > 3. ld-elf/pr23658-2: mips output is not common.
>
> The purpose of this test is to check the placement of orphan loaded
> note sections.  These ought to be placed near the start of the first
> PT_LOAD segment, so that they can be accessed by the kernel without
> reading many disk pages.  Ideally they would be placed in the same
> page as the file header.  This isn't happening for mips64, and I see
> the standard scripts don't even mention .interp, a section that also
> should be placed near the start of the first PT_LOAD.  Why not?!
>

Oh, yes. This tiny patch can solve this problem.
I have no idea why it doesn't like that.
Maybe somebody forgot this in history.

@Maciej W. Rozycki Any ideas?

```
diff --git a/ld/emulparams/elf64bmip-defs.sh b/ld/emulparams/elf64bmip-defs.sh
index 4165f51e9e5..19d782d8e7a 100644
--- a/ld/emulparams/elf64bmip-defs.sh
+++ b/ld/emulparams/elf64bmip-defs.sh
@@ -1,6 +1,10 @@
 source_sh ${srcdir}/emulparams/elf32bmipn32-defs.sh
 COMMONPAGESIZE="CONSTANT (COMMONPAGESIZE)"
-INITIAL_READONLY_SECTIONS="
+INITIAL_READONLY_SECTIONS=
+if test -z "${CREATE_SHLIB}"; then
+  INITIAL_READONLY_SECTIONS=".interp       ${RELOCATING-0} : { *(.interp) }"
+fi
+INITIAL_READONLY_SECTIONS="${INITIAL_READONLY_SECTIONS}
   .MIPS.abiflags      ${RELOCATING-0} : { *(.MIPS.abiflags) }
   .MIPS.xhash      ${RELOCATING-0} : { *(.MIPS.xhash) }
   .MIPS.options : { *(.MIPS.options) }
```

> > 4. ld-elf/shared.exp: non-run on mips: Build libpr16496b.so.
>
> OK, seems like we will actually generate a correct .so here for mips,
> so not much is lost by not running the testcase for mips.
>

Should we add a pr16496b-mips.od file?

> > 5. ld-elfvers/vers.exp:
> >       xfail vers4, vers4b;
>
> I see a ld segfault in _bfd_mips_elf_generic_reloc due to
> symbol->section->output_section being NULL prior to this patch series.
> I'd hope that someone making changes to the testsuite would have seen
> this, and not ignored it.  No one expects you to make linking
> non-native object files work, but not segfaulting it fairly important.
>

Maybe we should grep segfault in the log files on our CI system.
I will try to do so.

FYI: I run my test here:
https://oss.cipunited.com/ci/job/Toolchain/job/binutils-cross/

> >       no-run on mips: vers24a, vers24b, vers24c.
>
> OK, fair enough.  Mips is different enough that it isn't expected to
> pass these tests.
>
> > 6. ld-gc/gc.exp: add -KPIC into asflags for pr13683, pr14265, pr19161.
>
> OK.
>
> > 7. ld-mips-elf/mips-elf.exp:
> >       use noarch for mips16-local-stubs-1, since it use -mips4.
>
> I'll leave this for the mips maintainers to OK.
>
> > 8. ld-plugin/lto.exp:
> >       no-run on mips/linux: PR ld/12982;
>
> Please add a comment to lto.exp as to why mips requires an executable
> stack.
>
> >       add -KPIC into asflags for lto-3r, lto-5r, PR ld/19317 (2);
>
> OK.
>
> >       xfail PR ld/15323 (4), PR ld/19317 (3).
>
> Please explain why the lto plugin won't handle the objects.
>
> > 9. ld-plugin/plugin.exp: xfail
> >       plugin claimfile lost symbol,
> >       plugin claimfile replace symbol,
> >       plugin claimfile replace symbol,
> >       plugin claimfile lost symbol with source,
> >       plugin claimfile replace symbol with source,
> >       plugin claimfile resolve symbol with source,
> >       plugin 2 with source lib,
> >       load plugin 2 with source,
> >       plugin 3 with source lib,
> >       load plugin 3 with source.
>
> These all pass on mips-linux, and on mips64-linux.  Why disable them?
> Yes, I see fails on mips64-linux-gnuabi64 but that looks like a gcc
> problem to me.
>

Do you really install C/C++ compilers?

> > 11. ld-selective/selective.exp: add -fno-PIC, which is needed for -mno-abicalls.
>
> OK.
>
> > 12. ld-shared/shared.exp: xfail shared (non PIC), shared (PIC main, non PIC so).
>
> OK, and thanks for tweaking the xcoff test message.
>
> --
> Alan Modra
> Australia Development Lab, IBM



-- 
YunQiang Su