Difference between revisions of "Oops, Linux crashes"
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==ARM registers== | ==ARM registers== | ||
| + | To understand a kernel Oops you must understand how the underlaying processor architecture is working (here ARM one). | ||
| + | ARM processors has a set of 32 bits registers: | ||
| + | * general purposes one: '''r0 -> r10''' | ||
| + | * '''pc''': program counter, which handles the currently executed instruction address in memory | ||
| + | * '''lr''': link register, which handles the address to which the program counter should be set when it will reach a "return from subroutine" instruction. To summarize lr holds the address of the function which called the currently executing code. | ||
| + | * '''sp''': stack pointer, holds the current position in stack | ||
| + | |||
| + | You can see the registers content when the error occured at the beginning of the Oops. | ||
==System.map== | ==System.map== | ||
Revision as of 19:17, 21 October 2007
You've just started kernel development and got something like that:
Unable to handle kernel NULL pointer dereference at virtual address 00000000 pgd = c0004000 [00000000] *pgd=00000000 Internal error: Oops: 817 [#1] PREEMPT Modules linked in: CPU: 0 Not tainted (2.6.23.1 #14) pc : [<c0025720>] lr : [<c019dca0>] psr: 20000013 sp : c037dcfc ip : c037dd0c fp : c037dd08 r10: 00000000 r9 : 003c0000 r8 : 003c0000 r7 : c029eccc r6 : 00000002 r5 : 00020000 r4 : 000fa000 r3 : 00000000 r2 : 00000002 r1 : c33e0000 r0 : c33c0000 Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel Control: c000717f Table: 08e2c000 DAC: 00000017 Process pdflush (pid: 64, stack limit = 0xc037c258) Stack: (0xc037dcfc to 0xc037e000) dce0: c037dd18 dd00: c037dd0c c019dca0 c00256f0 c037dd9c c037dd1c c0199950 c019dc90 c037dd48 ... dfe0: 00000000 00000000 00000000 c037dff8 c00347dc c004711c e58d7000 e51b303c Backtrace: Function entered at [<c00256e0>] from [<c019dca0>] Function entered at [<c019dc80>] from [<c0199950>] Function entered at [<c019983c>] from [<c019c0b0>] Function entered at [<c019bdb4>] from [<c0197dd0>] ...
Well don't worry we will try to look at how to interpret this beast.
ARM registers
To understand a kernel Oops you must understand how the underlaying processor architecture is working (here ARM one). ARM processors has a set of 32 bits registers:
- general purposes one: r0 -> r10
- pc: program counter, which handles the currently executed instruction address in memory
- lr: link register, which handles the address to which the program counter should be set when it will reach a "return from subroutine" instruction. To summarize lr holds the address of the function which called the currently executing code.
- sp: stack pointer, holds the current position in stack
You can see the registers content when the error occured at the beginning of the Oops.
