Triple Fault after adding declarations to kernel

[ajmoritz]

Hello all,

While writing some of my kernel, after just creating another function in the code, without even executing the function, I started triple faulting. Using qemu, having it dump interupts (although my idt doesn't have the chance to get initialized when I TF), I get this

Code: Select all

check_exception old: 0xffffffff new 0xe
     0: v=0e e=0000 i=0 cpl=0 IP=0010:c01044ca pc=c01044ca SP=0018:c010eab8 CR2=c010f570
EAX=c010f570 EBX=0010f570 ECX=c010ea30 EDX=000000a1
ESI=0010f000 EDI=0010943c EBP=c010eae0 ESP=c010eab8
EIP=c01044ca EFL=00200082 [--S----] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0018 00000000 ffffffff 00cf9300 DPL=0 DS   [-WA]
CS =0010 00000000 ffffffff 00cf9a00 DPL=0 CS32 [-R-]
SS =0018 00000000 ffffffff 00cf9300 DPL=0 DS   [-WA]
DS =0018 00000000 ffffffff 00cf9300 DPL=0 DS   [-WA]
FS =0018 00000000 ffffffff 00cf9300 DPL=0 DS   [-WA]
GS =0018 00000000 ffffffff 00cf9300 DPL=0 DS   [-WA]
LDT=0000 00000000 0000ffff 00008200 DPL=0 LDT
TR =0000 00000000 0000ffff 00008b00 DPL=0 TSS32-busy
GDT=     000010b0 00000020
IDT=     00000000 00000000
CR0=80000011 CR2=c010f570 CR3=00108000 CR4=00000000
DR0=00000000 DR1=00000000 DR2=00000000 DR3=00000000 
DR6=ffff0ff0 DR7=00000400
CCS=00000010 CCD=c010eaa8 CCO=ADDL
EFER=0000000000000000
check_exception old: 0xe new 0xd
     1: v=08 e=0000 i=0 cpl=0 IP=0010:c01044ca pc=c01044ca SP=0018:c010eab8 env->regs[R_EAX]=c010f570
EAX=c010f570 EBX=0010f570 ECX=c010ea30 EDX=000000a1
ESI=0010f000 EDI=0010943c EBP=c010eae0 ESP=c010eab8
EIP=c01044ca EFL=00200082 [--S----] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0018 00000000 ffffffff 00cf9300 DPL=0 DS   [-WA]
CS =0010 00000000 ffffffff 00cf9a00 DPL=0 CS32 [-R-]
SS =0018 00000000 ffffffff 00cf9300 DPL=0 DS   [-WA]
DS =0018 00000000 ffffffff 00cf9300 DPL=0 DS   [-WA]
FS =0018 00000000 ffffffff 00cf9300 DPL=0 DS   [-WA]
GS =0018 00000000 ffffffff 00cf9300 DPL=0 DS   [-WA]
LDT=0000 00000000 0000ffff 00008200 DPL=0 LDT
TR =0000 00000000 0000ffff 00008b00 DPL=0 TSS32-busy
GDT=     000010b0 00000020
IDT=     00000000 00000000
CR0=80000011 CR2=c010f570 CR3=00108000 CR4=00000000
DR0=00000000 DR1=00000000 DR2=00000000 DR3=00000000 
DR6=ffff0ff0 DR7=00000400
CCS=00000010 CCD=c010eaa8 CCO=ADDL
EFER=0000000000000000
check_exception old: 0x8 new 0xd

Now so far what I've found is this happens for all extra declarations such as global variables. I also realize this is a page fault as cr2 has that address in it, and looking through the page table I can see my kernel only maps through 0xc010e000. Now the part which I am confused on is my kernel WILL map past 0xc010f570 as long as I don't go over the "allotted" symbol amount. Another thing I've noticed is if I comment out a few lines of my code, it will work fine. It doesn't really matter what lines.

I've been able to trace this to just calling the function pg_init in my code, but it never gets the chance to execute any code.
Looking at the instruction, it is just

Code: Select all

mov %eax, (%eax)

, which is why the value is eax is the same as cr0.

The only reason I can see is my kernel being too big, and the code going over the 4mb initial paging, although checking the size of the kernel when a triple fault happens (I logged by stopping the page fault by using an inline infinite loop) and when one doesn't yields the same size of 0xeaf0. I have tried increasing and decreasing the stack size, but that has made no noticeable effect.

Any ideas of what this could be? Or are my suspicions correct and I need to somehow increase the available memory to load in my kernel (Not super sure on how I'd do this yet).

This is a 32-bit kernel and my first attempt, so things are not optimal.
Github link: https://github.com/ajmoritz2/wordOS
(Hopefully my code is readable enough, I apologize for any troubles)

[MichaelPetch]

Your `programs`directory is missing in the git repo?

[ajmoritz]

All should be pushed onto the github now. Sorry about that, I'm not very good at git yet.

[ajmoritz]

Another thing I should add after snooping around a bit more: I've been able to get the code to execute farther by changing around the order of objs in the makefile. From that I've found my kernel page directory is getting corrupted, which is causing the issue. Now I'm not so sure why that happens yet.