need some help with my screen of death

[Pyrofan1]

my screen of death is invoked by exceptions
my regs struct

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struct regs
{
    unsigned int gs, fs, es, ds;      /* pushed the segs last */
    unsigned int edi, esi, ebp, esp, ebx, edx, ecx, eax;  /* pushed by 'pusha' */
    unsigned int int_no, err;    /* our 'push byte #' and ecodes do this */
    unsigned int eip, cs, eflags, useresp, ss;   /* pushed by the processor automatically */ 
};

my isr_common

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.type isr_common,@function
isr_common:
pusha
push %ds
push %es
push %fs
push %gs
call RSOD
sti
iret

RSOD

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void RSOD(struct regs r)
{
	text_color(WHITE,RED);
	clrscr();

	Puts("ChaoS has encounted a problem\n");
	if(r.int_no<19)
	{
		Printf("%s, interrupt %d, error %d\n",messages[r.int_no],r.int_no,r.err);
	}
	Puts("Registers:\n");
	Printf("eax: %d ebx: %d ecx: %d\n",r.eax,r.ebx,r.ecx);
	Printf("edx: %d esi: %d edi: %d\n",r.edx,r.esi,r.edi);
	Printf("ebp: %d esp: %d gs: %d\n",r.ebp,r.esp,r.gs);
	Printf("fs: %d es: %d ds: %d\n\n",r.fs,r.es,r.ds);
	Printf("EFLAGS: %d\neip: %d\ncs: %d\n",r.eflags,r.eip,r.cs);
	Printf("ss: %d\n",r.ss);
	asm("hlt");
}

this prints the contents of the rodata section of my executable.

[Bughunter]

Why do a 'sti' and 'iret' after 'call RSOD', it won't ever return.

As for the rest of your post, what exactly is your question? Where do you want help?

[Pyrofan1]

Why do a 'sti' and 'iret' after 'call RSOD', it won't ever return.

that was just left over code

Where do you want help?

well i'd like it to do what it's suppose to do instead of doing this

this prints the contents of the rodata section of my executable.

[os64dev]

well in your assembly you don't push the the struct r parameter of the c function. so that would be pointing anywhere producing the garbage you discribe.

insert a push %esp before the call. if this doesn't work then your c function should be void RSOD(struct regs * r)

[AJ]

I would also suggest that for debugging it would be a lot more useful to have hex numbers rather than decimal - it will tend to flag up bits that should be set but aren't in e.g. the EFLAGS register.

Cheers,
Adam

[Pyrofan1]

insert a push %esp before the call. if this doesn't work then your c function should be void RSOD(struct regs * r)

nope, didn't work

useful to have hex numbers

i know that

[t0xic]

@Pyrofan1

Try and use:

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struct regs *r

I found the same problem you did when regs wasn't a pointer

--t0xic

[Pyrofan1]

nope

[AJ]

It should work if you are correctly passing the pointer. Could we see your source files, please? Also, is the value of ESP in Bochs what you would expect?

Just one thought - if an exception has occurred, you should think about loading your segment registers with known "good values" in case they are scrapped.

Cheers,
Adam

[t0xic]

Here's my common stub... my gsod works perfectly so try this:
Try using an indirect push of esp, and load the segments like AJ said
Notice the following:

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mov eax, esp
push eax

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_isrcommonstub:
    pusha
    push ds
    push es
    push fs
    push gs
    mov ax, 0x10
    mov ds, ax
    mov es, ax
    mov fs, ax
    mov gs, ax
    mov eax, esp
    push eax
    mov eax, _fault_handler
    call eax
    pop eax
    pop gs
    pop fs
    pop es
    pop ds
    popa
    add esp, 8
    iret

--t0xic

[Pyrofan1]

Also, is the value of ESP in Bochs what you would expect?

I don't use bochs or qemu. also i'm not triggering any exceptions (purposfully)
RSOD

Code: Select all

void RSOD(struct regs *r)
{
	text_color(WHITE,RED);
	clrscr();

	Puts("ChaoS has encounted a problem\n");
	if(r->int_no<19)
	{
		Printf("%s, interrupt %d, error %d\n",messages[r->int_no],r->int_no,r->err);
	}
	else
	{
		Printf("Reserved, interrupt %d, error %d\n",r->int_no,r->err);
	} 

	Puts("Registers:\n");
	Printf("eax: %x ebx: %x ecx: %x\n",r->eax,r->ebx,r->ecx);
	Printf("edx: %x esi: %x edi: %x\n",r->edx,r->esi,r->edi);
	Printf("ebp: %x esp: %x gs: %x\n",r->ebp,r->esp,r->gs);
	Printf("fs: %x es: %x ds: %x\n",r->fs,r->es,r->ds);
	Printf("EFLAGS: %x\neip: %x\ncs: %x\n",r->eflags,r->eip,r->cs);
	Printf("ss: %x\n",r->ss);
	asm("hlt");
}

[AJ]

I don't use bochs or qemu.

Please do. It will make debugging this much easier.

I can't see any glaringly obvious mistakes in your code, although the syntax is not one I'm familiar with - I assume it's AT&T.

You might still try to put known good segments in to the segment registers. Out of interest, if you aren't causing any exceptions, how do you know that your exception handlers aren't working

Cheers,
Adam

[Pyrofan1]

Please do. It will make debugging this much easier.

I tried to, but qemu wouldn't run it

You might still try to put known good segments in to the segment registers.

i tried that, didn't work

Out of interest, if you aren't causing any exceptions, how do you know that your exception handlers aren't working

because when i boot, i get a red screen

[os64dev]

so it could be your Puts that fails in case of an exeption handler. or do you see white text also.

edit: hmm you told this already. can we see the linker script?

[Pyrofan1]

I do see white text.