Re: [musl] add loongarch64 port v8.

[Jingyun Hua <huajingyun@loongson.cn>]

hi,

I have a suggestion regarding the musl dynamic linker name for the
LoongArch architecture:

The basic ABI types are specified in the ABI document of the LoongArch,
which can be seen:
https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html 

and the dynamic linker name of glibc distinguishes lp64d, lp64s and
lp64f with abi types.The v8 patch only defines the value of SUBARCH
as "-sf" for “__loongarch_soft_float”, which means that only
“ld-musl-loongarch64.so.1” or “ld-musl-loongarch64-sf.so.1” can be
generated when compiled with the v8 patch.

So I think the musl dynamic linker name for the LoongArch architecture
needs to be modified, maybe defined like glibc?

Regards,
Jingyun Hua

On 11/9/23 9:15 PM, Jingyun Hua wrote:
> Hi all,
> 
> Thank you for taking the time to check this email. I'm very interested
> in musl and alpine, and I'd like to know the current status of this
> patch and what we can do for it next.
> 
> After Hongliang updated this patch from v7 to v8, in order to verify it,
> I built the alpine linux from scratch base on this musl v8 patch on the
> LoongArch64 machine, and successfully compiled projects such as gcc,
> rust, llvm, go, etc.. Currently, more than 8,500 packages have been
> built and running normally in my local repository.
> 
> The patch has indeed been on hold for a long time. Is it in the
> immediate plans? Is there anything that needs to be modified and
> improved?
> 
> Looking forward to your reply, thanks!
> 
> Regards,
> Jingyun Hua
> 
> 在 2023/9/26 上午11:28, Hongliang Wang 写道:
>> Hi,
>>
>> I have fixed the issues listed below, and post
>> 0001-add-loongarch64-port-v8.patch,as shown in the attachment.
>> please review again, if there are anything that need to be modified,
>> please point out, thank you.
>>
>> Hongliang Wang
>>
>> 在 2023/9/22 上午9:37, Hongliang Wang 写道:
>>> Hi,
>>>
>>> Thank you for your review, I will modify it according to the review
>>> suggestions and post v8 patch later.
>>>
>>> Hongliang Wang
>>>
>>> 在 2023/9/20 下午9:16, Szabolcs Nagy 写道:
>>>> * Jianmin Lv <lvjianmin@loongson.cn> [2023-09-20 15:45:39 +0800]:
>>>>> Sorry to bother you, but I just want to know if there is any 
>>>>> progress on
>>>>> this, because Alpine is blocking by this patch for a long time. As 
>>>>> Hongliang
>>>>> has explained questions you mentioned one by one, if any question 
>>>>> need to be
>>>>> discussed, please point them out, so that the patch can be handled 
>>>>> further.
>>>>
>>>> i think you should post a v8 patch to move
>>>> this forward. (not on github, but here)
>>>>
>>>>> On 2023/8/15 下午4:17, Hongliang Wang wrote:
>>>>>> 在 2023/8/13 上午9:41, Rich Felker 写道:
>>>>>>> On Sat, Aug 05, 2023 at 11:43:08AM -0400, Rich Felker wrote:
>>>>>>>> On Sat, Aug 05, 2023 at 02:18:35PM +0800, 翟小娟 wrote:
>>>>>>>> -+#define __BYTE_ORDER 1234
>>>>>>>> ++#define __BYTE_ORDER  __LITTLE_ENDIAN
>>>>>>>
>>>>>>> This is gratuitous, mismatches what is done on other archs, and is
>>>>>>> less safe.
>>>>>>>
>>>>>> The modification is based on the following review suggestion(
>>>>>> WANG Xuerui <i@xen0n.name> reviewed in
>>>>>> https://www.openwall.com/lists/musl/2022/10/12/1):
>>>>>>
>>>>>> `#define __BYTE_ORDER __LITTLE_ENDIAN` could be more consistent
>>>>>> with other arches.
>>>>
>>>> please use 1234.
>>
>> --- a/arch/loongarch64/bits/alltypes.h.in
>> +++ b/arch/loongarch64/bits/alltypes.h.in
>> @@ -2,7 +2,7 @@
>>   #define _Int64 long
>>   #define _Reg   long
>>
>> -#define __BYTE_ORDER  __LITTLE_ENDIAN
>> +#define __BYTE_ORDER  1234
>>   #define __LONG_MAX    0x7fffffffffffffffL
>>
>>
>>>>
>>>>>>>> -+TYPEDEF unsigned nlink_t;
>>>>>>>> ++TYPEDEF unsigned int nlink_t;
>>>>>>>
>>>>>>> Gratuitous and in opposite direction of coding style used 
>>>>>>> elsewhere in
>>>>>>> musl. There are a few other instances of this too.
>>>>>>>
>>>>>> Based on the following review question(WANG Xuerui <i@xen0n.name>
>>>>>> reviewed in https://www.openwall.com/lists/musl/2022/10/12/1):
>>>>>>
>>>>>> `unsigned int`? Same for other bare `unsigned` usages.
>>>>>>
>>>>>> I fixed it to a explicit definition.
>>>>
>>>> please use plain unsigned, not unsigned int.
>>
>> --- a/arch/loongarch64/bits/alltypes.h.in
>> +++ b/arch/loongarch64/bits/alltypes.h.in
>> @@ -2,7 +2,7 @@
>>
>> -TYPEDEF unsigned int nlink_t;
>> +TYPEDEF unsigned nlink_t;
>>   TYPEDEF int blksize_t;
>>
>>>>
>>>>>>>> -+      register uintptr_t tp __asm__("tp");
>>>>>>>> -+      __asm__ ("" : "=r" (tp) );
>>>>>>>> ++      uintptr_t tp;
>>>>>>>> ++      __asm__ __volatile__("move %0, $tp" : "=r"(tp));
>>>>>>>>    +      return tp;
>>>>>>>
>>>>>>> Not clear what the motivation is here. Is it working around a 
>>>>>>> compiler
>>>>>>> bug? The original form was more optimal.
>>>>>>
>>>>>> The modification is based on the following review suggestion(
>>>>>> WANG Xuerui <i@xen0n.name> reviewed in
>>>>>> https://www.openwall.com/lists/musl/2022/10/12/1):
>>>>>>
>>>>>> While the current approach works, it's a bit fragile [1], and
>>>>>> the simple and plain riscv version works too:
>>>>>>
>>>>>> uintptr_t tp;
>>>>>> __asm__ ("move %0, $tp" : "=r"(tp));
>>>>>>
>>>>>> [1]:https://gcc.gnu.org/onlinedocs/gcc/Local-Register-Variables.html#Local-Register-Variables 
>>>>>>
>>>>
>>>> this looks ok to me.
>>>>
>>>> (original code looks sketchy to me.)
>>>>
>>>>>>>>    +#define CRTJMP(pc,sp) __asm__ __volatile__( \
>>>>>>>> -+      "move $sp,%1 ; jr %0" : : "r"(pc), "r"(sp) : "memory" )
>>>>>>>> -+
>>>>>>>> -+#define GETFUNCSYM(fp, sym, got) __asm__ ( \
>>>>>>>> -+      ".hidden " #sym "\n" \
>>>>>>>> -+      ".align 8 \n" \
>>>>>>>> -+      "       la.local $t1, "#sym" \n" \
>>>>>>>> -+      "       move %0, $t1 \n" \
>>>>>>>> -+      : "=r"(*(fp)) : : "memory" )
>>>>>>>> ++      "move $sp, %1 ; jr %0" : : "r"(pc), "r"(sp) : "memory" )
>>>>>>>
>>>>>>> Not clear why this was changed. It was never discussed afaik. It 
>>>>>>> looks
>>>>>>> somewhat dubious removing GETFUNCSYM and using the maybe-unreliable
>>>>>>> default definition.
>>>>>>>
>>>>>> Based on the following review question(
>>>>>> WANG Xuerui <i@xen0n.name> reviewed
>>>>>> in https://www.openwall.com/lists/musl/2022/10/12/1):
>>>>>>
>>>>>> Does the generic version residing in ldso/dlstart.c not work?
>>>>>>
>>>>>> I found the code logic is consistent with the generic version, So
>>>>>> I removed the definition here and replaced it with generic version.
>>>>
>>>> i would change it back to the asm.
>>>>
>>>> generic version should work, but maybe we don't
>>>> want to trust the compiler here (there may be
>>>> ways to compile the generic code that is not
>>>> compatible with incompletely relocated libc.so)
>>>> the asm is safer.
>>>>
>> --- a/arch/loongarch64/reloc.h
>> +++ b/arch/loongarch64/reloc.h
>> @@ -18,3 +18,10 @@
>>
>>   #define CRTJMP(pc,sp) __asm__ __volatile__( \
>>          "move $sp, %1 ; jr %0" : : "r"(pc), "r"(sp) : "memory" )
>> +
>> +#define GETFUNCSYM(fp, sym, got) __asm__ ( \
>> +       ".hidden " #sym "\n" \
>> +       ".align 8 \n" \
>> +       "       la.local $t1, "#sym" \n" \
>> +       "       move %0, $t1 \n" \
>> +       : "=r"(*(fp)) : : "memory" )
>>
>>>>>>> It also looks like v5->v6 rewrote sigsetjmp.
>>>>>>>
>>>>>> Based on the following review question(
>>>>>> WANG Xuerui <i@xen0n.name> reviewed
>>>>>> in https://www.openwall.com/lists/musl/2022/10/12/1):
>>>>>>
>>>>>> This is crazy complicated compared to the riscv port, why is the
>>>>>> juggling between a0/a1 and t5/t6 necessary?
>>>>>>
>>>>>> I optimized the code implementations.
>>>>
>>>> this should be ok.
>>>>
>>>>>>> v6->v7:
>>>>>>>
>>>>>>> sigcontext/mcontext_t change mostly makes sense, but the
>>>>>>> namespace-safe and full mcontext_t differ in their use of the 
>>>>>>> aligned
>>>>>>> attribute and it's not clear that the attribute is needed (since the
>>>>>>> offset is naturally aligned and any instance of the object is 
>>>>>>> produced
>>>>>>> by the kernel, not by userspace).
>>>>>>>
>>>>>>>> -+      long               __uc_pad;
>>>>>>>
>>>>>>> This change to ucontext_t actually makes the struct ABI-incompatible
>>>>>>> in the namespace-safe version without the alignment attribute. 
>>>>>>> IIRC I
>>>>>>> explicitly requested the explicit padding field to avoid this 
>>>>>>> kind of
>>>>>>> footgun. Removing it does not seem like a good idea.
>>>>>>>
>>>>>> Initially, we add __uc_pad to ensure uc_mcontext is 16 byte 
>>>>>> alignment.
>>>>>> Now, we added __attribute__((__aligned__(16))) to
>>>>>> uc_mcontext.__extcontext[],this can ensure uc_mcontext is also 16 
>>>>>> byte
>>>>>> alignment. so __uc_pad is not used.
>>>>>>
>>>>>> Remove __uc_pad, from the point of struct layout, musl and kernel are
>>>>>> consistent. otherwise, I think it may bring a sense of inconsistency
>>>>>> between kernel and musl. Due to Loongarch is not merged into musl 
>>>>>> now,
>>>>>> Remove it no compatibility issues.
>>>>
>>>> please add back the padding field.
>>
>> --- a/arch/loongarch64/bits/signal.h
>> +++ b/arch/loongarch64/bits/signal.h
>> @@ -40,6 +40,7 @@ typedef struct __ucontext
>>          struct __ucontext  *uc_link;
>>          stack_t            uc_stack;
>>          sigset_t           uc_sigmask;
>> +       long               __uc_pad;
>>          mcontext_t         uc_mcontext;
>>   } ucontext_t;
>>
>>>>
>>>>>>> In stat.h:
>>>>>>>
>>>>>>>> -+      unsigned long __pad;
>>>>>>>> ++      unsigned long __pad1;
>>>>>>>
>>>>>>> This is gratuitous and makes the definition gratuitously mismatch 
>>>>>>> what
>>>>>>> will become the "generic" version of bits/stat.h. There is no 
>>>>>>> contract
>>>>>>> for applications to be able to access these padding fields by 
>>>>>>> name, so
>>>>>>> no motivation to make their names match glibc's names or the 
>>>>>>> kernel's.
>>>>>>>
>>>>>> OK.
>>>>
>>>> please fix it.
>>
>> --- a/arch/loongarch64/bits/stat.h
>> +++ b/arch/loongarch64/bits/stat.h
>> @@ -6,7 +6,7 @@ struct stat {
>>          uid_t st_uid;
>>          gid_t st_gid;
>>          dev_t st_rdev;
>> -       unsigned long __pad1;
>> +       unsigned long __pad;
>>          off_t st_size;
>>          blksize_t st_blksize;
>>          int __pad2;
>>
>>>>
>>>>>>> In fenv.S:
>>>>>>>
>>>>>>>> ++#ifdef __clang__
>>>>>>>> ++#define FCSR $fcsr0
>>>>>>>> ++#else
>>>>>>>> ++#define FCSR $r0
>>>>>>>> ++#endif
>>>>>>>
>>>>>>> It's not clear to me what's going on here. Is there a clang
>>>>>>> incompatibility in the assembler language you're working around? Or
>>>>>>> what? If so that seems like a tooling bug that should be fixed.
>>>>>>>
>>>>>> The GNU assembler cannot correctly recognize $fcsr0, but the
>>>>>> LLVM IAS does not have this issue, so make a distinction.
>>>>>> This issue has been fixed in GNU assembler 2.41. but for compatible
>>>>>> with GNU assembler 2.40 and below, $r0 need reserved.
>>>>
>>>> it sounds like the correct asm is $fcsr0, so that's
>>>> what should be used on all assemblers, not just on
>>>> clang as.
>>>>
>>>> only broken old gnu as should use different syntax.
>>>> for this a configure test is needed that adds a
>>>> CFLAG like -DBROKEN_LOONGARCH_FCSR_ASM when fails.
>>>> and use that for the ifdef.
>>>>
>> --- a/configure
>> +++ b/configure
>>
>> if test "$ARCH" = "loongarch64" ; then
>> trycppif __loongarch_soft_float "$t" && SUBARCH=${SUBARCH}-sf
>> +printf "checking whether compiler support FCSRs... "
>> +echo "__asm__(\"movfcsr2gr \$t0,\$fcsr0\");" > "$tmpc"
>> +if $CC -c -o /dev/null "$tmpc" >/dev/null 2>&1 ; then
>> +printf "yes\n"
>> +else
>> +printf "no\n"
>> +CFLAGS_AUTO="$CFLAGS_AUTO -DBROKEN_LOONGARCH_FCSR_ASM"
>> +fi
>> fi
>>
>> --- a/src/fenv/loongarch64/fenv.S
>> +++ b/src/fenv/loongarch64/fenv.S
>> @@ -1,9 +1,9 @@
>>   #ifndef __loongarch_soft_float
>>
>> -#ifdef __clang__
>> -#define FCSR $fcsr0
>> -#else
>> +#ifdef BROKEN_LOONGARCH_FCSR_ASM
>>   #define FCSR $r0
>> +#else
>> +#define FCSR $fcsr0
>>   #endif
>>
>>   .global        feclearexcept
>>
>>>>>>
>>>>>> The linux kernel also has a similar distinction:
>>>>>>
>>>>>> commit 38bb46f94544c5385bc35aa2bfc776dcf53a7b5d
>>>>>> Author: WANG Xuerui <git@xen0n.name>
>>>>>> Date:   Thu Jun 29 20:58:43 2023 +0800
>>>>>>
>>>>>>      LoongArch: Prepare for assemblers with proper FCSR class support
>>>>>>
>>>>>>      The GNU assembler (as of 2.40) mis-treats FCSR operands as 
>>>>>> GPRs, but
>>>>>>      the LLVM IAS does not. Probe for this and refer to FCSRs 
>>>>>> as"$fcsrNN"
>>>>>>      if support is present.
>>>>>>
>>>>>>      Signed-off-by: WANG Xuerui <git@xen0n.name>
>>>>>>      Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
>>>>>>
>>>>>>> Otherwise, everything looks as expected, I think. I'm okay with 
>>>>>>> making
>>>>>>> any fixups for merging rather than throwing this back on your 
>>>>>>> team for
>>>>>>> more revisions, but can you please follow up and clarify the above?
>>>>
>>>> all issues look minor.
>>>>
>>>> if you post a v8 it likely gets into a release faster.
>>>>
> 

-- 
Jingyun Hua