ARM semihosting issue

ARM semihosting issue

[Bruno Prado]

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Hi,

I was able to use stdout, stderr for output and files for both input and
output in qemu-system-arm, but stdin is not working (always returns -1 from
syscall). I found no information and have already checked the code for
possible hints.

I am on Arch Linux LTS + QEMU 5.1.0.

Thanks,
----
Bruno Prado

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Re: ARM semihosting issue

[Peter Maydell]

On Thu, 1 Oct 2020 at 21:33, Bruno Prado <bruno@dcomp.ufs.br> wrote:
> I was able to use stdout, stderr for output and files for
> both input and output in qemu-system-arm, but stdin is not
> working (always returns -1 from syscall). I found no
> information and have already checked the code for possible hints.

Rather hard to say what might be going on with this little
information... what semihosting calls are you making, what
do you expect them to do and what do they actually do?
Do you have a minimal test case we can reproduce with?

thanks
-- PMM

Re: ARM semihosting issue

[Bruno Prado]

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Thanks for the reply... I am attaching some code and output:

#include <stdio.h>
int main() {
       char name[50] = "Nobody";
       FILE* file = fopen("name", "r");
       printf("What is your name?\n");
       fprintf(stdout, "Reading from file...\n");
       fscanf(file, "%s", name);
       fscanf(stdin, "%s", name);
       printf("My name is %s\n", name);
       fprintf(stderr, "I am alive!!!\n");
       fclose(file);
       return 0;
}

$ cat name
Turing
$ qemu-system-arm -M netduino2 -nographic -semihosting -kernel vp2.bin
What is your name?
Reading from file...
My name is Turing
I am alive!!!
$

Basically the scanf call has no effect. I was expecting a pause in
execution to input a string, but nothing happens.

Regards,
----
Bruno Prado


On Thu, Oct 1, 2020 at 5:38 PM Peter Maydell <peter.maydell@linaro.org>
wrote:

> On Thu, 1 Oct 2020 at 21:33, Bruno Prado <bruno@dcomp.ufs.br> wrote:
> > I was able to use stdout, stderr for output and files for
> > both input and output in qemu-system-arm, but stdin is not
> > working (always returns -1 from syscall). I found no
> > information and have already checked the code for possible hints.
>
> Rather hard to say what might be going on with this little
> information... what semihosting calls are you making, what
> do you expect them to do and what do they actually do?
> Do you have a minimal test case we can reproduce with?
>
> thanks
> -- PMM
>

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Re: ARM semihosting issue

[Peter Maydell]

On Thu, 1 Oct 2020 at 22:21, Bruno Prado <bruno@dcomp.ufs.br> wrote:
> Thanks for the reply... I am attaching some code and output:
>
> #include <stdio.h>
> int main() {
>        char name[50] = "Nobody";
>        FILE* file = fopen("name", "r");
>        printf("What is your name?\n");
>        fprintf(stdout, "Reading from file...\n");
>        fscanf(file, "%s", name);
>        fscanf(stdin, "%s", name);
>        printf("My name is %s\n", name);
>        fprintf(stderr, "I am alive!!!\n");
>        fclose(file);
>        return 0;
> }

This is not making direct semihosting calls. The behaviour
of these function calls will depend on whatever the C
standard library implementation you're linking with is doing.

You're not checking for errors from any of your function
calls, incidentally.

thanks
-- PMM

Re: ARM semihosting issue

[Bruno Prado]

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I am including some syscall functions:

int _fstat(int file, struct stat* st) {
       register int value asm("r0");
       uint32_t p[] = { file };
       R0(0x0C);
       R1(p);
       BKPT();
       return value;
}

int _read(int file, char* ptr, int len) {
       register int value asm("r0");
       uint32_t p[] = { file, (uint32_t)(ptr), len };
       R0(0x06);
       R1(p);
       BKPT();
       return value;
}

int _write(int file, char* ptr, int len) {
       register int value asm("r0");
       uint32_t p[] = { file, (uint32_t)(ptr), len };
       R0(0x05);
       R1(p);
       BKPT();
       return value;
}

Also the interruption output from execution:

$ qemu-system-arm -M netduino2 -nographic -semihosting -kernel vp2.bin -d
int
Taking exception 16 [Semihosting call]
...handling as semihosting call 0x1
Taking exception 16 [Semihosting call]
...handling as semihosting call 0x1
Taking exception 16 [Semihosting call]
...handling as semihosting call 0x1
Taking exception 16 [Semihosting call]
...handling as semihosting call 0x1
Taking exception 16 [Semihosting call]
...handling as semihosting call 0xc
Taking exception 16 [Semihosting call]
...handling as semihosting call 0x5
What is your name?
Taking exception 16 [Semihosting call]
...handling as semihosting call 0x5
Reading from file...
Taking exception 16 [Semihosting call]
...handling as semihosting call 0xc
Taking exception 16 [Semihosting call]
...handling as semihosting call 0x6
Taking exception 16 [Semihosting call]
...handling as semihosting call 0xc
Taking exception 16 [Semihosting call]
...handling as semihosting call 0x6
Taking exception 16 [Semihosting call]
...handling as semihosting call 0x5
My name is Turing
Taking exception 16 [Semihosting call]
...handling as semihosting call 0x5
I am alive!!!
Taking exception 16 [Semihosting call]
...handling as semihosting call 0xa
Taking exception 16 [Semihosting call]
...handling as semihosting call 0xa
Taking exception 16 [Semihosting call]
...handling as semihosting call 0x2
Taking exception 16 [Semihosting call]
...handling as semihosting call 0x20

Could you please provide any working example using ARM semihosting on stdin?

Thanks,
----
Bruno Prado


On Fri, Oct 2, 2020 at 7:25 AM Peter Maydell <peter.maydell@linaro.org>
wrote:

> On Thu, 1 Oct 2020 at 22:21, Bruno Prado <bruno@dcomp.ufs.br> wrote:
> > Thanks for the reply... I am attaching some code and output:
> >
> > #include <stdio.h>
> > int main() {
> >        char name[50] = "Nobody";
> >        FILE* file = fopen("name", "r");
> >        printf("What is your name?\n");
> >        fprintf(stdout, "Reading from file...\n");
> >        fscanf(file, "%s", name);
> >        fscanf(stdin, "%s", name);
> >        printf("My name is %s\n", name);
> >        fprintf(stderr, "I am alive!!!\n");
> >        fclose(file);
> >        return 0;
> > }
>
> This is not making direct semihosting calls. The behaviour
> of these function calls will depend on whatever the C
> standard library implementation you're linking with is doing.
>
> You're not checking for errors from any of your function
> calls, incidentally.
>
> thanks
> -- PMM
>

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Re: ARM semihosting issue

[Bruno Prado]

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Hello, is it really a bug?

----
Bruno Prado


On Fri, Oct 2, 2020 at 8:09 AM Bruno Prado <bruno@dcomp.ufs.br> wrote:

> I am including some syscall functions:
>
> int _fstat(int file, struct stat* st) {
>        register int value asm("r0");
>        uint32_t p[] = { file };
>        R0(0x0C);
>        R1(p);
>        BKPT();
>        return value;
> }
>
> int _read(int file, char* ptr, int len) {
>        register int value asm("r0");
>        uint32_t p[] = { file, (uint32_t)(ptr), len };
>        R0(0x06);
>        R1(p);
>        BKPT();
>        return value;
> }
>
> int _write(int file, char* ptr, int len) {
>        register int value asm("r0");
>        uint32_t p[] = { file, (uint32_t)(ptr), len };
>        R0(0x05);
>        R1(p);
>        BKPT();
>        return value;
> }
>
> Also the interruption output from execution:
>
> $ qemu-system-arm -M netduino2 -nographic -semihosting -kernel vp2.bin -d
> int
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0x1
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0x1
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0x1
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0x1
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0xc
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0x5
> What is your name?
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0x5
> Reading from file...
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0xc
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0x6
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0xc
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0x6
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0x5
> My name is Turing
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0x5
> I am alive!!!
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0xa
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0xa
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0x2
> Taking exception 16 [Semihosting call]
> ...handling as semihosting call 0x20
>
> Could you please provide any working example using ARM semihosting on
> stdin?
>
> Thanks,
> ----
> Bruno Prado
>
>
> On Fri, Oct 2, 2020 at 7:25 AM Peter Maydell <peter.maydell@linaro.org>
> wrote:
>
>> On Thu, 1 Oct 2020 at 22:21, Bruno Prado <bruno@dcomp.ufs.br> wrote:
>> > Thanks for the reply... I am attaching some code and output:
>> >
>> > #include <stdio.h>
>> > int main() {
>> >        char name[50] = "Nobody";
>> >        FILE* file = fopen("name", "r");
>> >        printf("What is your name?\n");
>> >        fprintf(stdout, "Reading from file...\n");
>> >        fscanf(file, "%s", name);
>> >        fscanf(stdin, "%s", name);
>> >        printf("My name is %s\n", name);
>> >        fprintf(stderr, "I am alive!!!\n");
>> >        fclose(file);
>> >        return 0;
>> > }
>>
>> This is not making direct semihosting calls. The behaviour
>> of these function calls will depend on whatever the C
>> standard library implementation you're linking with is doing.
>>
>> You're not checking for errors from any of your function
>> calls, incidentally.
>>
>> thanks
>> -- PMM
>>
>

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Re: ARM semihosting issue

[Alex Bennée]

Bruno Prado <bruno@dcomp.ufs.br> writes:

> Hello, is it really a bug?
>
> ----
> Bruno Prado
>
>
> On Fri, Oct 2, 2020 at 8:09 AM Bruno Prado <bruno@dcomp.ufs.br> wrote:
>
>> I am including some syscall functions:
>>
>> int _fstat(int file, struct stat* st) {
>>        register int value asm("r0");
>>        uint32_t p[] = { file };
>>        R0(0x0C);
>>        R1(p);
>>        BKPT();
>>        return value;
>> }
>>
>> int _read(int file, char* ptr, int len) {
>>        register int value asm("r0");
>>        uint32_t p[] = { file, (uint32_t)(ptr), len };
>>        R0(0x06);
>>        R1(p);
>>        BKPT();
>>        return value;
>> }
>>
>> int _write(int file, char* ptr, int len) {
>>        register int value asm("r0");
>>        uint32_t p[] = { file, (uint32_t)(ptr), len };
>>        R0(0x05);
>>        R1(p);
>>        BKPT();
>>        return value;
>> }
>>
>> Also the interruption output from execution:
>>
>> $ qemu-system-arm -M netduino2 -nographic -semihosting -kernel vp2.bin -d
>> int
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0x1
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0x1
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0x1
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0x1
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0xc
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0x5
>> What is your name?
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0x5
>> Reading from file...
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0xc
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0x6
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0xc
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0x6
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0x5
>> My name is Turing
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0x5
>> I am alive!!!
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0xa
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0xa
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0x2
>> Taking exception 16 [Semihosting call]
>> ...handling as semihosting call 0x20
>>
>> Could you please provide any working example using ARM semihosting on
>> stdin?

We have a test which you can run by hand:

   ./tests/tcg/arm-linux-user/semiconsole

>>
>> Thanks,
>> ----
>> Bruno Prado
>>
>>
>> On Fri, Oct 2, 2020 at 7:25 AM Peter Maydell <peter.maydell@linaro.org>
>> wrote:
>>
>>> On Thu, 1 Oct 2020 at 22:21, Bruno Prado <bruno@dcomp.ufs.br> wrote:
>>> > Thanks for the reply... I am attaching some code and output:
>>> >
>>> > #include <stdio.h>
>>> > int main() {
>>> >        char name[50] = "Nobody";
>>> >        FILE* file = fopen("name", "r");
>>> >        printf("What is your name?\n");
>>> >        fprintf(stdout, "Reading from file...\n");
>>> >        fscanf(file, "%s", name);
>>> >        fscanf(stdin, "%s", name);
>>> >        printf("My name is %s\n", name);
>>> >        fprintf(stderr, "I am alive!!!\n");
>>> >        fclose(file);
>>> >        return 0;
>>> > }
>>>
>>> This is not making direct semihosting calls. The behaviour
>>> of these function calls will depend on whatever the C
>>> standard library implementation you're linking with is doing.
>>>
>>> You're not checking for errors from any of your function
>>> calls, incidentally.
>>>
>>> thanks
>>> -- PMM
>>>
>>


-- 
Alex Bennée

Re: ARM semihosting issue

[Bruno Prado]

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Thanks a lot! I will check it out.

----
Bruno Prado


On Wed, Oct 21, 2020 at 12:45 PM Alex Bennée <alex.bennee@linaro.org> wrote:

>
> Bruno Prado <bruno@dcomp.ufs.br> writes:
>
> > Hello, is it really a bug?
> >
> > ----
> > Bruno Prado
> >
> >
> > On Fri, Oct 2, 2020 at 8:09 AM Bruno Prado <bruno@dcomp.ufs.br> wrote:
> >
> >> I am including some syscall functions:
> >>
> >> int _fstat(int file, struct stat* st) {
> >>        register int value asm("r0");
> >>        uint32_t p[] = { file };
> >>        R0(0x0C);
> >>        R1(p);
> >>        BKPT();
> >>        return value;
> >> }
> >>
> >> int _read(int file, char* ptr, int len) {
> >>        register int value asm("r0");
> >>        uint32_t p[] = { file, (uint32_t)(ptr), len };
> >>        R0(0x06);
> >>        R1(p);
> >>        BKPT();
> >>        return value;
> >> }
> >>
> >> int _write(int file, char* ptr, int len) {
> >>        register int value asm("r0");
> >>        uint32_t p[] = { file, (uint32_t)(ptr), len };
> >>        R0(0x05);
> >>        R1(p);
> >>        BKPT();
> >>        return value;
> >> }
> >>
> >> Also the interruption output from execution:
> >>
> >> $ qemu-system-arm -M netduino2 -nographic -semihosting -kernel vp2.bin
> -d
> >> int
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0x1
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0x1
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0x1
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0x1
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0xc
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0x5
> >> What is your name?
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0x5
> >> Reading from file...
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0xc
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0x6
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0xc
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0x6
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0x5
> >> My name is Turing
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0x5
> >> I am alive!!!
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0xa
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0xa
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0x2
> >> Taking exception 16 [Semihosting call]
> >> ...handling as semihosting call 0x20
> >>
> >> Could you please provide any working example using ARM semihosting on
> >> stdin?
>
> We have a test which you can run by hand:
>
>    ./tests/tcg/arm-linux-user/semiconsole
>
> >>
> >> Thanks,
> >> ----
> >> Bruno Prado
> >>
> >>
> >> On Fri, Oct 2, 2020 at 7:25 AM Peter Maydell <peter.maydell@linaro.org>
> >> wrote:
> >>
> >>> On Thu, 1 Oct 2020 at 22:21, Bruno Prado <bruno@dcomp.ufs.br> wrote:
> >>> > Thanks for the reply... I am attaching some code and output:
> >>> >
> >>> > #include <stdio.h>
> >>> > int main() {
> >>> >        char name[50] = "Nobody";
> >>> >        FILE* file = fopen("name", "r");
> >>> >        printf("What is your name?\n");
> >>> >        fprintf(stdout, "Reading from file...\n");
> >>> >        fscanf(file, "%s", name);
> >>> >        fscanf(stdin, "%s", name);
> >>> >        printf("My name is %s\n", name);
> >>> >        fprintf(stderr, "I am alive!!!\n");
> >>> >        fclose(file);
> >>> >        return 0;
> >>> > }
> >>>
> >>> This is not making direct semihosting calls. The behaviour
> >>> of these function calls will depend on whatever the C
> >>> standard library implementation you're linking with is doing.
> >>>
> >>> You're not checking for errors from any of your function
> >>> calls, incidentally.
> >>>
> >>> thanks
> >>> -- PMM
> >>>
> >>
>
>
> --
> Alex Bennée
>

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