Re: ARM semihosting issue

[Bruno Prado <bruno@dcomp.ufs.br>]

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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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