Superleaf1995
Joined 8 June 2024
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Hello I'm Superleaf1995, a C and Assembly coder that has build a
Userpages:
* [[User:Superleaf1995/Explaining the architectures|Explaining the architectures]]
* [[User:Superleaf1995/AFPFS|Arbitrary File Position File System]]
* [[User:Superleaf1995/PCI in assembly|Code of PCI article translated into Intel Assembly]]
* [[User:Superleaf1995/lowFS|lowFS specification]]
* [[User:Superleaf1995/Compile GCCMVS under MVS3.8j|Compile GCCMVS under MVS3.8j]]
Send a happy face to COM1:
<syntaxhighlight lang="c">
typedef int i;typedef void v;typedef char c;i z(){return inb(0x3F8+5)&32;}w(c a){while(!z()){}outb(0x3F8,a);}u(){w(':');w(')');}
</syntaxhighlight>
== 390 Bits ==
stack preparation for thread switching:
<syntaxhighlight lang="c">
/* follows MVS calling convention (used by gccmvs) */
void SchedPrepareThreadStack(struct thread* thread)
{
/* R13 is used as a stack pointer, now we have to setup a few things up */
thread->context.r15 = (unsigned int)thread->stack + stack_size;
/* stack+76 should point to stack+180 (because this would be the next frame!) */
*((uint32_t *)(&((uint8_t *)thread->stack)[76])) = (&((uint8_t *)thread->stack)[180]);
*((uint32_t *)(&((uint8_t *)thread->stack)[8])) = (&((uint8_t *)thread->stack)[180]);
/* Set backchain to 0 for stack unwinding */
*((uint32_t *)(&((uint8_t *)thread->stack)[4])) = NULL;
*((uint32_t *)(&((uint8_t *)thread->stack)[8])) = NULL;
return;
}
</syntaxhighlight>
stack unwinding:
<syntaxhighlight lang="c">
int DbgUnwindStack(cpu_context *ctx_frame)
{
extern uint32_t __stack[1024]; /* your kernel stack*/
uint8_t *frame = (uint8_t *)ctx_frame->r13;
/* Corrupt stack pointer? */
if((ptrdiff_t)frame < (ptrdiff_t)&__stack) {
KeDebugPrint("Potentially corrupt stack, (SP=%x)\r\n", (unsigned int)frame);
frame = (uint8_t *)&__stack;
}
/* Pointer to top of the stack */
while(frame != NULL) {
/* R14 is stored on frame+12; and holds the address of the return point of the caller */
uint32_t retaddr = *((uint32_t *)&frame[12]);
struct DebugSymData *retsym = DbgGetSymbol((void *)retaddr);
/* And R15 is also stored on frame+16, and contains the branching/base address of the callee */
uint32_t calladdr = *((uint32_t *)&frame[16]);
struct DebugSymData *callsym = DbgGetSymbol((void *)calladdr);
if(retsym != NULL) {
KeDebugPrint("RET=(%i=%s:%i)\r\n", (unsigned int)retaddr, retsym->name, (int)((ptrdiff_t)retaddr - (ptrdiff_t)retsym->addr));
}
if(callsym != NULL) {
KeDebugPrint("CALL=(%x=%s:%i)\r\n", (unsigned int)calladdr, callsym->name, (int)((ptrdiff_t)calladdr - (ptrdiff_t)callsym->addr));
}
/* Get the forward chain */
KeDebugPrint("%p\r\n", (unsigned int)frame);
frame = *((uint8_t **)(&frame[8]));
}
return 0;
}
</syntaxhighlight>
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