I'm not especially familiar with the 4xx cpus, but on the 74xx cpus the MSR register has the "privilege level" bit, which determines if the processor can execute both user- and supervisor-level instructions, or only user-level instructions.
This needs to be setup by the bootloader to allow supervisor-level instructions to be executed, else you'll see some errors. > The early code needs to perform many privileged instructions; make sure that > you aren't restricting the cpu to only user instructions. > > > I found the correct exception guys. It means > > Privileged Instruction Exception. > > > > --- Prakash kanthi <pkanthi at yahoo.com> wrote: > > > > > > Folks, > > > > > > I just wanted to provide more info on my env. I have > > > PPC405 based board with no network support forcing > > > me > > > to use zImage.initrd.elf. > > > > > > Can you suggest more on my problem described below? > > > I > > > saw the memory values at 0x00000000 onwards after > > > uncompressing linux and they have changed. But when > > > the control jumps to 0x0, my board hangs. I see that > > > ESR is showing a value of 0x80000000, meaning either > > > illegal instruction or Machine Check. > > > > > > Can you tell what's going on? What happens next > > > after > > > uncompressing? I am thinking it executes > > > start_kernel > > > function which calls lock_kernel. Let me know if i > > > am > > > wrong. > > > > > > thanks, > > > Prakash > > > > > > > > > > > > > > > --- James Don <JDon at spacebridge.com> wrote: > > > > I just went thru this myself ... ;-) > > > > > > > > 1.) Get a BDM/JTAG tool look halt the processor > > > > after you see " Now booting > > > > the kernel" and look for valid asm at 0x0 ... make > > > > sure it mathes your > > > > start.s file ... > > > > > > > > 2.) Veryfy you have your mem map from ppcboot > > > > matching requirements for the > > > > kernel i.e ram (physical=0x0, virtual=0xc0000000) > > > > and immr (phys 0xff000000 > > > > virtual 0xff000000) ... I had my immr in ppc boot > > > at > > > > 0x02200000 this screwed > > > > me for quite a while ... otherwise you have no > > > > printk ... the memory map is > > > > very important not to screw with some things > > > depend > > > > on it (unless your > > > > careful) ... > > > > > > > > 3.) verify you SMC1 (uart) is getting proper > > > > clocking config ... i.e > > > > bus->brg1 and brg1 is 16 times baud rate ... > > > > otherwise you have no printk > > > > > > > > 4.) and always always keep in mind your RAM refesh > > > > could be wrong ... > > > > everyone will tell you this even when it has > > > nothing > > > > to do with your problem > > > > ... try not to ignore them if you are still stuck > > > > ;-) But verifying step 1 > > > > should prove your ok ... > > > > > > > > Best of luck, > > > > Jim > > > > > > > > > > > > -----Original Message----- > > > > From: Prakash kanthi [mailto:pkanthi at yahoo.com] > > > > Sent: Wednesday, December 18, 2002 7:14 PM > > > > To: LinuxPPC > > > > Subject: After Uncompresseing Linux..., what's > > > next > > > > > > > > > > > > Hi there, > > > > > > > > I was trying to load linuxppc_2_4_devel onto my > > > > board. > > > > It goes through the board info read, UART init and > > > > Uncompressing the linux kernel. But after that, i > > > do > > > > not see any messages and board hangs. > > > > > > > > Here is the UART output: > > > > ------------------------------------ > > > > OS Booting... > > > > > > > > loaded at: 00400000 0060D1CC > > > > board data at: 00000030 00000044 > > > > relocated to: 00405C24 00405C38 > > > > zimage at: 00406290 004A08FF > > > > initrd at: 004A1000 006097CA > > > > avail ram: 0060E000 007F8000 > > > > > > > > Linux/PPC load: console=ttyS0,9600 console=tty1 > > > > ip=on > > > > root=/dev/xsysace/disc0/pa > > > > rt3 rw > > > > Uncompressing Linux...done. > > > > Now booting the kernel > > > > ------------------------------------------- > > > > > > > > After the last line, it hangs. I get a feeling > > > that, > > > > the uncompressing process is not writing in the > > > > memory > > > > starting from 0x00000000 and, after uncompressing, > > > > it > > > > is jumping into 0x00000000 and is not able to find > > > > anything. > > > > > > > > My questions are, > > > > 1. How can i make sure that, the uncompressing > > > > process > > > > is going to start writing the data from > > > 0x00000000. > > > > > > > > 2. How big a space this uncompressing process > > > needs? > > > > And also how much overall memory is required for > > > > running linux. I just have 8MB SDRAM. > > > > > > > > 3. What is the next step in the booting process? > > > > Which > > > > Device (eth, pci, ide, ???) Initialization? > > > > > > > > Your help is appreciated. > > > > > > > > thanks, > > > > Prakash > > > > > > > > > > > > > > > > > > > > > -- > Sincerely, > > Jim Potter > 45th Parallel Processing > > Firefighting: Bustin' ours, Savin' yours. > -- Sincerely, Jim Potter 45th Parallel Processing Firefighting: Bustin' ours, Savin' yours. ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
