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