ÔÚ 2024/1/30 ÉÏÎç12:47, Rich Felker дµÀ:
> On Thu, Jan 25, 2024 at 12:43:54PM -0500, Rich Felker wrote:
>> I'm going through where everything was left on this topic and
>> preparing a patch for merge. This message/thread is to document what
>> I'm actually doing vs the various submitted versions of the patch
>> since v5/v6 where the major review took place.
>>
>>
>> Subsequent changes I'm reverting:
>>
>> - De-optimization of __get_tp. No motivation for removing the
>>    potentially in-place $tp was provided, and we generally use the
>>    arch's tp in-place unless there's a compiler bug to be worked
>>    around. See powerpc{,64} for an example where it's used, or1k where
>>    we have a probably-obsolete workaround for ancient clang being
>>    broken.
>>
>> - unsigned -> unsigned int, etc.
>>
>> - Gratuitous whitespace changes in headers that obscure the fact that
>>    a header is a complete duplicate that could eventually be shared
>>    between archs (e.g. bits/float.h, bits/posix.h) or just obscure
>>    what differs from other archs when running diff.
>>
>>
>> Fixes from previous review that were overlooked:
>>
>> - Removing SA_RESTORER -- its presence defined as 0 produces wrong
>>    sigaction ABI.
>>
>>
>> Additions:
>>
>> - Adding the reloc.h/configure case for single-only float.
>>
>> - The new member names for mcontext_t are all in reserved namespace,
>>    so there's no reason to have a separate namespace-clean version of
>>    mcontext_t, and I'm removing the latter.
>>
>> - Public member uc_flags with no __, macro for compat with any
>>    existing software using the __-prefixed name.
>>
>>
>> Still TODO:
>>
>> I don't think I ever reviewed the apparent rewrite of sigsetjmp and
>> possibly some other asm that changed between v5 and v8. I'm about to
>> start looking at that and will follow up.
> 
> OK, sigsetjmp appears to have been non-working in v5 (it failed to
> save the argument anywhere, so attempted it use it after it was
> clobbered in the code path after calling setjmp).
> 
> v8 fixes this and seems like it should work, but I don't understand
> the offsets used.
> 
> The loongarch64 __jmp_buf has 23 slots, but only appears to use 21 of
> them, with sigsetjmp storing its extra data in the last 2 unused
> slots. The contract here is supposed to be that the entirety of
> __jmp_buf belongs to setjmp/longjmp, with sigsetjmp using the extra
> space in the full jmp_buf/sigjmp_buf type with signal mask and lots of
> extra space.
> 
> Were these slots added just for sigsetjmp? If so, that was an ABI
> mistake, but I don't think it warrants a late change; it's probably
> better to just leave them there as extensibility.

Yes, the purpose of the last 2 slots of __jmp_buf just used for
sigsetjmp to storing its extra data.
Now leave them there as extensibility is OK.

Hongliang Wang

> 
> Either way, I think sigsetjmp should be modified not to rely on
> storage in space that setjmp is entitled to be able to modify, i.e. it
> should be using offsets 184 and 184+16, not 168 and 176.
> 
> Rich
> 
I understand. I attached a patch to fix this issue. please review it.

diff --git a/src/signal/loongarch64/sigsetjmp.s 
b/src/signal/loongarch64/sigsetjmp.s
index 992ab1a4..9c0e3ae2 100644
--- a/src/signal/loongarch64/sigsetjmp.s
+++ b/src/signal/loongarch64/sigsetjmp.s
@@ -5,8 +5,8 @@
  sigsetjmp:
  __sigsetjmp:
         beq     $a1, $zero, 1f
-       st.d    $ra, $a0, 168
-       st.d    $s0, $a0, 176
+       st.d    $ra, $a0, 184
+       st.d    $s0, $a0, 200  #184+8+8
         move    $s0, $a0

         la.global  $t0, setjmp
@@ -14,8 +14,8 @@ __sigsetjmp:

         move    $a1, $a0        # Return from 'setjmp' or 'longjmp'
         move    $a0, $s0
-       ld.d    $ra, $a0, 168
-       ld.d    $s0, $a0, 176
+       ld.d    $ra, $a0, 184
+       ld.d    $s0, $a0, 200 #184+8+8

  .hidden __sigsetjmp_tail
         la.global  $t0, __sigsetjmp_tail
(END)

Hongliang Wang