Re: ARM semihosting issue

[Bruno Prado]

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