Kernel Crashes after C main call

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thestew42
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Kernel Crashes after C main call

Post by thestew42 »

So I have a boot loader that loads a second stage, then the second stage loads the kernel and jumps to it in pmode. The kernel has an assembly entry point that calls a C main function. I'm having a problem with the C code though. If the C main is empty or just has an infinite loop, it works fine, but when I add code to copy data to the video memory, it crashes and restarts.

The bochs log shows a 3rd exception (13) at the instruction that copies data to the video memory. I DAFS looking for the exception, but I couldn't find any information, and I don't know why this is happening because I've had programs with similar C code work.

This is the C code (I just took code from the barebones to make sure it wasn't my C code that was the problem):

Code: Select all

int main(void)
{
unsigned char *videoram = (unsigned char *) 0xb8000;
videoram[0] = 65; /* character 'A' */
videoram[1] = 0x07; /* forground, background color. */

return 0;
}
then this is the linker script:

Code: Select all

OUTPUT_FORMAT("binary")
ENTRY(start)
phys = 0x00100000;
SECTIONS
{
.text phys : AT(phys) {
code = .;
*(.text)
. = ALIGN(4096);
}
.rodata : AT(phys + (rodata - code))
{
rodata = .;
*(.rodata)
. = ALIGN(4096);
}
.data : AT(phys + (data - code))
{
data = .;
*(.data)
. = ALIGN(4096);
}
.bss : AT(phys + (bss - code))
{
bss = .;
*(.bss)
. = ALIGN(4096);
}
end = .;
}
Any suggestions would be appreciated. Thanks
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Combuster
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Re: Kernel Crashes after C main call

Post by Combuster »

Could you post the entire bochs log?
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thestew42
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Re: Kernel Crashes after C main call

Post by thestew42 »

I'm not on my dev machine but I will later this afternoon
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Re: Kernel Crashes after C main call

Post by Firestryke31 »

Also, did you set up the data segments before jumping to the kernel? I've had that one bite me before.
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thestew42
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Re: Kernel Crashes after C main call

Post by thestew42 »

Combuster wrote:Could you post the entire bochs log?
sure

Code: Select all

00000000000i[     ] Bochs x86 Emulator 2.3.7
00000000000i[     ]   Build from CVS snapshot, on June 3, 2008
00000000000i[     ] System configuration
00000000000i[     ]   processors: 1 (cores=1, HT threads=1)
00000000000i[     ]   A20 line support: yes
00000000000i[     ]   APIC support: yes
00000000000i[     ] CPU configuration
00000000000i[     ]   level: 6
00000000000i[     ]   SMP support: no
00000000000i[     ]   FPU support: yes
00000000000i[     ]   MMX support: yes
00000000000i[     ]   SSE support: 2
00000000000i[     ]   CLFLUSH support: yes
00000000000i[     ]   VME support: yes
00000000000i[     ]   3dnow! support: no
00000000000i[     ]   PAE support: yes
00000000000i[     ]   PGE support: yes
00000000000i[     ]   PSE support: yes
00000000000i[     ]   x86-64 support: yes
00000000000i[     ]   SEP support: yes
00000000000i[     ]   MWAIT support: no
00000000000i[     ]   XSAVE support: no
00000000000i[     ]   AES support: no
00000000000i[     ] Optimization configuration
00000000000i[     ]   Guest2HostTLB support: yes
00000000000i[     ]   RepeatSpeedups support: yes
00000000000i[     ]   Icache support: yes
00000000000i[     ]   Trace cache support: yes
00000000000i[     ]   Fast function calls: yes
00000000000i[     ] Devices configuration
00000000000i[     ]   ACPI support: yes
00000000000i[     ]   NE2000 support: yes
00000000000i[     ]   PCI support: yes
00000000000i[     ]   SB16 support: yes
00000000000i[     ]   USB support: yes
00000000000i[     ]   VGA extension support: vbe cirrus
00000000000i[MEM0 ] allocated memory at 024C0020. after alignment, vector=024C1000
00000000000i[MEM0 ] 32.00MB
00000000000i[MEM0 ] rom at 0xfffe0000/131072 ('BIOS-bochs-latest')
00000000000i[MEM0 ] rom at 0xc0000/38400 ('VGABIOS-lgpl-latest')
00000000000i[APIC?] set APIC ID to 0
00000000000i[APIC0] 80686
00000000000i[APIC0] local apic in CPU apicid=00 initializing
00000000000i[IOAP ] initializing I/O APIC
00000000000i[IOAP ] set APIC ID to 1
00000000000i[MEM0 ] Register memory access handlers: 0xfec00000 - 0xfec00fff
00000000000i[CMOS ] Using local time for initial clock
00000000000i[CMOS ] Setting initial clock to: Thu Mar 19 17:22:14 2009 (time0=1237497734)
00000000000i[DMA  ] channel 4 used by cascade
00000000000i[DMA  ] channel 2 used by Floppy Drive
00000000000i[FDD  ] fd0: 'floppy.img' ro=0, h=2,t=80,spt=18
00000000000i[PCI  ] 440FX Host bridge present at device 0, function 0
00000000000i[PCI  ] PIIX3 PCI-to-ISA bridge present at device 1, function 0
00000000000i[MEM0 ] Register memory access handlers: 0x000a0000 - 0x000bffff
00000000000i[WGUI ] Desktop Window dimensions: 1680 x 1050
00000000000i[WGUI ] Number of Mouse Buttons = 8
00000000000i[WGUI ] IME disabled
00000000000i[MEM0 ] Register memory access handlers: 0xe0000000 - 0xe07fffff
00000000000i[CLVGA] VBE Bochs Display Extension Enabled
00000000000i[CLVGA] interval=300000
00000000000i[     ] init_mem of 'harddrv' plugin device by virtual method
00000000000i[     ] init_mem of 'keyboard' plugin device by virtual method
00000000000i[     ] init_mem of 'serial' plugin device by virtual method
00000000000i[     ] init_mem of 'parallel' plugin device by virtual method
00000000000i[     ] init_mem of 'extfpuirq' plugin device by virtual method
00000000000i[     ] init_mem of 'gameport' plugin device by virtual method
00000000000i[     ] init_mem of 'speaker' plugin device by virtual method
00000000000i[     ] init_mem of 'pci_ide' plugin device by virtual method
00000000000i[     ] init_mem of 'acpi' plugin device by virtual method
00000000000i[     ] init_dev of 'harddrv' plugin device by virtual method
00000000000i[HD   ] Using boot sequence floppy, none, none
00000000000i[HD   ] Floppy boot signature check is enabled
00000000000i[     ] init_dev of 'keyboard' plugin device by virtual method
00000000000i[KBD  ] will paste characters every 1000 keyboard ticks
00000000000i[     ] init_dev of 'serial' plugin device by virtual method
00000000000i[SER  ] com1 at 0x03f8 irq 4
00000000000i[     ] init_dev of 'parallel' plugin device by virtual method
00000000000i[PAR  ] parallel port 1 at 0x0378 irq 7
00000000000i[     ] init_dev of 'extfpuirq' plugin device by virtual method
00000000000i[     ] init_dev of 'gameport' plugin device by virtual method
00000000000i[     ] init_dev of 'speaker' plugin device by virtual method
00000000000i[     ] init_dev of 'pci_ide' plugin device by virtual method
00000000000i[PCI  ] PIIX3 PCI IDE controller present at device 1, function 1
00000000000i[     ] init_dev of 'acpi' plugin device by virtual method
00000000000i[PCI  ] ACPI Controller present at device 1, function 3
00000000000i[     ] register state of 'harddrv' plugin device by virtual method
00000000000i[     ] register state of 'keyboard' plugin device by virtual method
00000000000i[     ] register state of 'serial' plugin device by virtual method
00000000000i[     ] register state of 'parallel' plugin device by virtual method
00000000000i[     ] register state of 'extfpuirq' plugin device by virtual method
00000000000i[     ] register state of 'gameport' plugin device by virtual method
00000000000i[     ] register state of 'speaker' plugin device by virtual method
00000000000i[     ] register state of 'pci_ide' plugin device by virtual method
00000000000i[     ] register state of 'acpi' plugin device by virtual method
00000000000i[SYS  ] bx_pc_system_c::Reset(HARDWARE) called
00000000000i[CPU0 ] cpu hardware reset
00000000000i[APIC0] local apic in CPU 0 initializing
00000000000i[     ] reset of 'harddrv' plugin device by virtual method
00000000000i[     ] reset of 'keyboard' plugin device by virtual method
00000000000i[     ] reset of 'serial' plugin device by virtual method
00000000000i[     ] reset of 'parallel' plugin device by virtual method
00000000000i[     ] reset of 'extfpuirq' plugin device by virtual method
00000000000i[     ] reset of 'gameport' plugin device by virtual method
00000000000i[     ] reset of 'speaker' plugin device by virtual method
00000000000i[     ] reset of 'pci_ide' plugin device by virtual method
00000000000i[     ] reset of 'acpi' plugin device by virtual method
00000003302i[BIOS ] $Revision: 1.209 $ $Date: 2008/06/02 20:08:10 $
00000320071i[KBD  ] reset-disable command received
00000443645i[VBIOS] VGABios $Id: vgabios.c,v 1.67 2008/01/27 09:44:12 vruppert Exp $

00000443716i[CLVGA] VBE known Display Interface b0c0
00000443748i[CLVGA] VBE known Display Interface b0c4
00000446673i[VBIOS] VBE Bios $Id: vbe.c,v 1.60 2008/03/02 07:47:21 vruppert Exp $
00000769674i[BIOS ] Starting rombios32
00000770501i[BIOS ] ram_size=0x02000000
00000870157i[BIOS ] Found 1 cpu(s)
00000886458i[BIOS ] bios_table_addr: 0x000fb778 end=0x000fcc00
00000886525i[PCI  ] 440FX PMC write to PAM register 59 (TLB Flush)
00001345332i[PCI  ] 440FX PMC write to PAM register 59 (TLB Flush)
00001804819i[P2I  ] PCI IRQ routing: PIRQA# set to 0x0b
00001804866i[P2I  ] PCI IRQ routing: PIRQB# set to 0x09
00001804913i[P2I  ] PCI IRQ routing: PIRQC# set to 0x0b
00001804960i[P2I  ] PCI IRQ routing: PIRQD# set to 0x09
00001804976i[P2I  ] write: ELCR2 = 0x0a
00001805913i[BIOS ] PIIX3 init: elcr=00 0a
00001826168i[BIOS ] PCI: bus=0 devfn=0x00: vendor_id=0x8086 device_id=0x1237
00001829405i[BIOS ] PCI: bus=0 devfn=0x08: vendor_id=0x8086 device_id=0x7000
00001832138i[BIOS ] PCI: bus=0 devfn=0x09: vendor_id=0x8086 device_id=0x7010
00001832599i[PIDE ] new BM-DMA address: 0xc000
00001833482i[BIOS ] region 4: 0x0000c000
00001836058i[BIOS ] PCI: bus=0 devfn=0x0b: vendor_id=0x8086 device_id=0x7113
00001836558i[ACPI ] new irq line = 11
00001836595i[ACPI ] new PM base address: 0xb000
00001836657i[ACPI ] new SM base address: 0xb100
00001837125i[CPU0 ] Enter to System Management Mode
00001837135i[CPU0 ] RSM: Resuming from System Management Mode
00001837169i[PCI  ] setting SMRAM control register to 0x4a
00001837451i[PCI  ] setting SMRAM control register to 0x0a
00001860732i[BIOS ] MP table addr=0x000fb850 MPC table addr=0x000fb780 size=0xd0
00001862935i[BIOS ] SMBIOS table addr=0x000fb860
00001865979i[BIOS ] ACPI tables: RSDP addr=0x000fb970 ACPI DATA addr=0x01ff0000 size=0x9d8
00001885512i[PCI  ] 440FX PMC write to PAM register 59 (TLB Flush)
00001886524i[BIOS ] bios_table_cur_addr: 0x000fb994
00003000000i[WGUI ] dimension update x=720 y=400 fontheight=16 fontwidth=9 bpp=8
00032315724i[BIOS ] Booting from 0000:7c00
00040924907e[CPU0 ] write_virtual_checks(): write beyond limit, r/w
00040924907e[CPU0 ] fetch_raw_descriptor: GDT: index (f007)1e00 > limit (17)
00040924907i[CPU0 ] CPU is in protected mode (active)
00040924907i[CPU0 ] CS.d_b = 32 bit
00040924907i[CPU0 ] SS.d_b = 16 bit
00040924907i[CPU0 ] EFER   = 0x00000000
00040924907i[CPU0 ] | RAX=0000000000000000  RBX=0000000000000007
00040924907i[CPU0 ] | RCX=000000000000000d  RDX=0000000000000fff
00040924907i[CPU0 ] | RSP=0000000000102ff0  RBP=0000000000102ff8
00040924907i[CPU0 ] | RSI=00000000ffff08c7  RDI=0000000000080005
00040924907i[CPU0 ] |  R8=0000000000000000   R9=0000000000000000
00040924907i[CPU0 ] | R10=0000000000000000  R11=0000000000000000
00040924907i[CPU0 ] | R12=0000000000000000  R13=0000000000000000
00040924907i[CPU0 ] | R14=0000000000000000  R15=0000000000000000
00040924907i[CPU0 ] | IOPL=0 id vip vif ac vm RF nt of df if tf sf zf af PF cf
00040924907i[CPU0 ] | SEG selector     base    limit G D
00040924907i[CPU0 ] | SEG sltr(index|ti|rpl)     base    limit G D
00040924907i[CPU0 ] |  CS:0008( 0001| 0|  0) 00000000 000fffff 1 1
00040924907i[CPU0 ] |  DS:0010( 0002| 0|  0) 00000000 000fffff 1 1
00040924907i[CPU0 ] |  SS:0000( 0005| 0|  0) 00000000 0000ffff 0 0
00040924907i[CPU0 ] |  ES:0010( 0002| 0|  0) 00000000 000fffff 1 1
00040924907i[CPU0 ] |  FS:07c0( 0005| 0|  0) 00007c00 0000ffff 0 0
00040924907i[CPU0 ] |  GS:07c0( 0005| 0|  0) 00007c00 0000ffff 0 0
00040924907i[CPU0 ] |  MSR_FS_BASE:0000000000007c00
00040924907i[CPU0 ] |  MSR_GS_BASE:0000000000007c00
00040924907i[CPU0 ] | RIP=0000000000003050 (0000000000003050)
00040924907i[CPU0 ] | CR0=0x60000011 CR1=0x0 CR2=0x0000000000000000
00040924907i[CPU0 ] | CR3=0x00000000 CR4=0x00000000
00040924907i[CPU0 ] >> mov dword ptr ss:[ebp+0xfffffffc], 0x000b8000 : C745FC00800B00
00040924907e[CPU0 ] exception(): 3rd (13) exception with no resolution, shutdown status is 00h, resetting
00040924907i[SYS  ] bx_pc_system_c::Reset(SOFTWARE) called
00040924907i[CPU0 ] cpu software reset
00040924907i[APIC0] local apic in CPU 0 initializing
00040928210i[BIOS ] $Revision: 1.209 $ $Date: 2008/06/02 20:08:10 $
00041245055i[KBD  ] reset-disable command received
After that it just repeats
Firestryke31 wrote:Also, did you set up the data segments before jumping to the kernel? I've had that one bite me before.
Like in the linker file? I have them there. This is the entry assembly file. I'm now using one from Bran's

Code: Select all

; This is the kernel's entry point. We could either call main here,
; or we can use this to setup the stack or other nice stuff, like
; perhaps setting up the GDT and segments. Please note that interrupts
; are disabled at this point: More on interrupts later!
[BITS 32]
global start
start:
    mov esp, _sys_stack     ; This points the stack to our new stack area
	mov ax, 10h
	mov ds, ax
	mov es, ax
    jmp stublet

; This part MUST be 4byte aligned, so we solve that issue using 'ALIGN 4'
ALIGN 4
mboot:
    ; Multiboot macros to make a few lines later more readable
    MULTIBOOT_PAGE_ALIGN	equ 1<<0
    MULTIBOOT_MEMORY_INFO	equ 1<<1
    MULTIBOOT_AOUT_KLUDGE	equ 1<<16
    MULTIBOOT_HEADER_MAGIC	equ 0x1BADB002
    MULTIBOOT_HEADER_FLAGS	equ MULTIBOOT_PAGE_ALIGN | MULTIBOOT_MEMORY_INFO | MULTIBOOT_AOUT_KLUDGE
    MULTIBOOT_CHECKSUM	equ -(MULTIBOOT_HEADER_MAGIC + MULTIBOOT_HEADER_FLAGS)
    EXTERN code, bss, end

    ; This is the GRUB Multiboot header. A boot signature
    dd MULTIBOOT_HEADER_MAGIC
    dd MULTIBOOT_HEADER_FLAGS
    dd MULTIBOOT_CHECKSUM
    
    ; AOUT kludge - must be physical addresses. Make a note of these:
    ; The linker script fills in the data for these ones!
    dd mboot
    dd code
    dd bss
    dd end
    dd start

; This is an endless loop here. Make a note of this: Later on, we
; will insert an 'extern _main', followed by 'call _main', right
; before the 'jmp $'.
stublet:
	extern _main
    call _main
	jmp $


; Shortly we will add code for loading the GDT right here!


; In just a few pages in this tutorial, we will add our Interrupt
; Service Routines (ISRs) right here!



; Here is the definition of our BSS section. Right now, we'll use
; it just to store the stack. Remember that a stack actually grows
; downwards, so we declare the size of the data before declaring
; the identifier '_sys_stack'
SECTION .bss
    resb 8192               ; This reserves 8KBytes of memory here
_sys_stack:
berkus wrote:You are sure "return 0;" is ok there? You have the hlt/jmp $ after call to main to handle that?
I do:

Code: Select all

stublet:
	extern _main
    call _main
	jmp $
and the error is

Code: Select all

00040924907i[CPU0 ] >> mov dword ptr ss:[ebp+0xfffffffc], 0x000b8000 : C745FC00800B00
00040924907e[CPU0 ] exception(): 3rd (13) exception with no resolution, shutdown status is 00h, resetting
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neonek
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Re: Kernel Crashes after C main call

Post by neonek »

You don't have IRQ handling code in your kernel, so try adding cli instruction before

Code: Select all

mov esp, _sys_stack
It'll help, I think.

Regards,
Mark
Please correct my English. If you'll find mistake please tell me about it so I can improve my English.
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thestew42
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Re: Kernel Crashes after C main call

Post by thestew42 »

neonek wrote:You don't have IRQ handling code in your kernel, so try adding cli instruction before

Code: Select all

mov esp, _sys_stack
It'll help, I think.

Regards,
Mark
Hmmmm. Thanks, well that's probably a good idea. I tried it though and I still get the same error :(
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Combuster
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Re: Kernel Crashes after C main call

Post by Combuster »

So your code is saying that it uses GRUB, and you say you're using your own bootloader...

Anyway, your segment registers have not been reloaded with their correct 4G limit versions - check your bootloader for that.
00040924907e[CPU0 ] write_virtual_checks(): write beyond limit, r/w
(...)
00040924907i[CPU0 ] | SS:0000( 0005| 0| 0) 00000000 0000ffff 0 0
"Certainly avoid yourself. He is a newbie and might not realize it. You'll hate his code deeply a few years down the road." - Sortie
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