Re: [AArch64] nosys.specs and printf

[Alexander Fedotov <alfedotov at gmail dot com>]

So can we have approach in aarch64 the same ARM already has? To
simplify further support.
I know that aarch64 is more preferable with Linux to use. But some
customers want to have baremetal with newlib like for ARM.

Alex

On Tue, Sep 19, 2017 at 5:43 PM, Tamar Christina
<Tamar.Christina@arm.com> wrote:
> Hi Alex,
>
> It's not that ARM is working, in the sense it does anything useful,
>
> It's just that the warnings don't seem to be emitted because the conftests in libgloss/libnosys/configure.in are too simplistic,
> for instance it tests for elf platforms by seeing if the target triple ends with "-elf".
>
> However, just like aarch64, using nosys gives you stubs and not actual code.
>
> /d/t/g/s/gcc (master ↩☡=) ../../build-arm-none-eabi/install/bin/arm-none-eabi-gcc test.c --specs=nosys.specs
> /d/t/g/s/gcc (master ↩☡=) ../../build-arm-none-eabi/install/bin/arm-none-eabi-objdump -d a.out
>
> ...
> 0000b0b4 <_lseek>:
>     b0b4:       e3a02058        mov     r2, #88 ; 0x58
>     b0b8:       e59f3008        ldr     r3, [pc, #8]    ; b0c8 <_lseek+0x14>
>     b0bc:       e3e00000        mvn     r0, #0
>     b0c0:       e5832000        str     r2, [r3]
>     b0c4:       e12fff1e        bx      lr
>     b0c8:       0001b9fc        .word   0x0001b9fc
>
> 0000b0cc <_read>:
>     b0cc:       e3a02058        mov     r2, #88 ; 0x58
>     b0d0:       e59f3008        ldr     r3, [pc, #8]    ; b0e0 <_read+0x14>
>     b0d4:       e3e00000        mvn     r0, #0
>     b0d8:       e5832000        str     r2, [r3]
>     b0dc:       e12fff1e        bx      lr
>     b0e0:       0001b9fc        .word   0x0001b9fc
> ...
>
> They all just return -1 and set ERRNO just as expected. https://github.com/eblot/newlib/blob/master/libgloss/libnosys/read.c
>
> So Aarch64 is actually working as intended, it's ARM that's missing the warnings. And yeah, in order to suppress the warnings
> you need to provide an alternate implementation.
>
> Tamar.
> ________________________________________
> From: Alexander Fedotov <alfedotov@gmail.com>
> Sent: Tuesday, September 19, 2017 2:15 PM
> To: Tamar Christina
> Subject: Re: [AArch64] nosys.specs and printf
>
> Hello Tamar
>
> Well that's sounds to me like newlib completely useless for aarch64 in
> current state.
> So if I want to use nosys in my way I need to implement empty stubs to
> suppress these warnings ? Right ?
>
> How nosys ARM port is working in such case ?
>
> BR,
> Alex
>
>
> On Tue, Sep 19, 2017 at 2:08 PM, Tamar Christina
> <Tamar.Christina@arm.com> wrote:
>> Hi Alexander,
>>
>> I believe your changes to libnosys are correct. We don't actually support nosys on AArch64, enough stuff has been committed for particular use cases but that's about it.
>>
>> The warnings you get with your libnosys changes are correct in that libnosys doesn't provide any IO functionality, so you don't have open, close, read and write. Which means your printf example won't work and it's just warning you ahead of time.
>>
>> Kind regards,
>> Tamar
>> ________________________________________
>> From: newlib-owner@sourceware.org <newlib-owner@sourceware.org> on behalf of Alexander Fedotov <alfedotov@gmail.com>
>> Sent: Friday, September 15, 2017 11:43:23 AM
>> To: newlib@sourceware.org
>> Subject: [AArch64] nosys.specs and printf
>>
>> Hello all
>>
>> I'm trying to compile following simple program for aarch64 with nosys specs
>>
>> #include <stdio.h>
>> int main(void) {
>>   printf("hello");
>>   return 0;
>> }
>>
>> But I've got:
>> d:\gcc-6.3-arm64-eabi\bin>aarch64-none-elf-gcc --specs=nosys.specs test.c
>> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-sbrkr.o):
>> In function `_sbrk_r':
>> sbrkr.c:(.text._sbrk_r+0x1c): undefined reference to `_sbrk'
>> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-writer.o):
>> In function `_write_r':
>> writer.c:(.text._write_r+0x24): undefined reference to `_write'
>> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-closer.o):
>> In function `_close_r':
>> closer.c:(.text._close_r+0x1c): undefined reference to `_close'
>> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-fstatr.o):
>> In function `_fstat_r':
>> fstatr.c:(.text._fstat_r+0x20): undefined reference to `_fstat'
>> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-isattyr.o):
>> In function `_isatty_r':
>> isattyr.c:(.text._isatty_r+0x1c): undefined reference to `_isatty'
>> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-lseekr.o):
>> In function `_lseek_r':
>> lseekr.c:(.text._lseek_r+0x24): undefined reference to `_lseek'
>> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-readr.o):
>> In function `_read_r':
>> readr.c:(.text._read_r+0x24): undefined reference to `_read'
>> collect2.exe: error: ld returned 1 exit status
>>
>> d:\gcc-6.3-arm64-eabi\bin>aarch64-none-elf-gcc --specs=rdimon.specs test.c
>>
>> d:\gcc-6.3-arm64-eabi\bin>
>>
>>
>> I tried to reconfigure libnosys  in the same way as ARM port:
>>
>> diff -ruN newlib-2.5.0/libgloss/libnosys/configure
>> newlib-2.5.0/libgloss/libnosys/configure
>> --- newlib-2.5.0/libgloss/libnosys/configure    2016-12-23
>> 05:33:54.000000000 +0300
>> +++ newlib-2.5.0/libgloss/libnosys/configure    2017-09-15
>> 13:14:56.412457618 +0300
>> @@ -2009,6 +2009,8 @@
>>      ;;
>>    a29k-amd-udi)
>>      ;;
>> +  aarch64*-*-*)
>> +    ;;
>>    arc-*-*)
>>      ;;
>>    arm*-*-*)
>> diff -ruN newlib-2.5.0/libgloss/libnosys/configure.in
>> newlib-2.5.0/libgloss/libnosys/configure.in
>> --- newlib-2.5.0/libgloss/libnosys/configure.in    2016-12-23
>> 05:33:54.000000000 +0300
>> +++ newlib-2.5.0/libgloss/libnosys/configure.in    2017-09-14
>> 18:32:27.330466884 +0300
>> @@ -43,6 +43,8 @@
>>      ;;
>>    a29k-amd-udi)
>>      ;;
>> +  aarch64*-*-*)
>> +    ;;
>>    arc-*-*)
>>      ;;
>>    arm*-*-*)
>>
>> It now compiles so I get final elf, but with warnings:
>> d:\gcc-6.3-arm64-eabi\bin>aarch64-none-elf-gcc --specs=nosys.specs test.c
>> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-closer.o):
>> In function `_close_r':
>> /home/af/GIT/BG/build_gnu/opt/freescale/Earmv8/obj_newlib/aarch64-none-elf/newlib/libc/reent/../../../../../src_newlib/newlib/libc/reent/closer.c:53:
>> warning: _close is not impl
>> emented and will always fail
>> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-fstatr.o):
>> In function `_fstat_r':
>> /home/af/GIT/BG/build_gnu/opt/freescale/Earmv8/obj_newlib/aarch64-none-elf/newlib/libc/reent/../../../../../src_newlib/newlib/libc/reent/fstatr.c:62:
>> warning: _fstat is not impl
>> emented and will always fail
>> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-isattyr.o):
>> In function `_isatty_r':
>> /home/af/GIT/BG/build_gnu/opt/freescale/Earmv8/obj_newlib/aarch64-none-elf/newlib/libc/reent/../../../../../src_newlib/newlib/libc/reent/isattyr.c:58:
>> warning: _isatty is not im
>> plemented and will always fail
>> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-lseekr.o):
>> In function `_lseek_r':
>> /home/af/GIT/BG/build_gnu/opt/freescale/Earmv8/obj_newlib/aarch64-none-elf/newlib/libc/reent/../../../../../src_newlib/newlib/libc/reent/lseekr.c:58:
>> warning: _lseek is not impl
>> emented and will always fail
>> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-readr.o):
>> In function `_read_r':
>> /home/af/GIT/BG/build_gnu/opt/freescale/Earmv8/obj_newlib/aarch64-none-elf/newlib/libc/reent/../../../../../src_newlib/newlib/libc/reent/readr.c:58:
>> warning: _read is not implem
>> ented and will always fail
>> d:/gcc-6.3-arm64-eabi/bin/../lib/gcc/aarch64-none-elf/6.3.1/../../../../aarch64-none-elf/lib\libc.a(lib_a-writer.o):
>> In function `_write_r':
>> /home/af/GIT/BG/build_gnu/opt/freescale/Earmv8/obj_newlib/aarch64-none-elf/newlib/libc/reent/../../../../../src_newlib/newlib/libc/reent/writer.c:58:
>> warning: _write is not impl
>> emented and will always fail
>>
>>
>> Hi do I correctly to configure AArch64 nosys ?
>
>
>
> --
> Best regards,
> AF



-- 
Best regards,
AF