The wiki is being retired!
Documentation is now handled by the same processes we use for code: Add something to the Documentation/ directory in the coreboot repo, and it will be rendered to https://doc.coreboot.org/. Contributions welcome!
Let begin by example and dissect it. An example Coreboot crash dump is shown:
PCI: 00:18.7: enabled 1 Mainboard NF81-T56N-LF Enable. Unexpected Exception: 6 @ 10:00246faa - Halting Code: 0 eflags: 00010402 eax: fdb01c7c ebx: 0027c4a4 ecx: 000c34b1 edx: 000045fd edi: 00000002 esi: 00000078 ebp: 00287ff0 esp: 00287f6d 00246f68: 0d 26 00 c7 04 24 06 00 00246f70: 00 00 e8 a9 c5 00 00 c6 00246f78: 05 00 0e d8 fe ff c6 05 00246f80: 01 0e d8 fe 00 fd 05 02 00246f88: 0e d8 fe 00 c6 00 03 0e 00246f90: d8 fe 00 c6 05 83 0e d8 00246f98: fe 00 c7 44 24 66 80 00 00246fa0: 00 00 c7 04 24 fd 00 00 00246fa8: 00 e8 fe d8 ff 00 c7 44 00246fb0: 24 04 61 00 00 83 c7 04 00246fb8: 24 28 00 00 00 66 ea d8 00246fc0: ff ff 83 c4 1c c3 c3 c3 00246fc8: 57 bf 00 0c 00 00 56 53 00246fd0: 83 ec 30 8b 44 24 40 c7 00246fd8: 44 24 04 00 00 00 00 89 00246fe0: 04 24 e8 a3 fb 00 00 8d
Here the line, Unexpected Exception: 6 @ 10:00246faa - Halting, is key to understanding the dump. In this example an Exception: 6 signifies an unknown Opcode was attempt to execute and 10:00246faa has two components, the segment selector (0x10) and address (e000_0001).
x86 Exception Summary
The following chart lists the exceptions that can be generated by the Intel 80286, 80386, 80486, and Pentium processors:
Exception | Description (dec/hex) | ----------|------------------------------------------------- 0 00h | Divide error: | Occurs during a DIV or an IDIV instruction when the | divisor is zero or a quotient overflow occurs. 1 01h | Single-step/debug exception: | Occurs for any of a number of conditions: | - Instruction address breakpoint fault | - Data address breakpoint trap | - General detect fault | - Single-step trap | - Task-switch breakpoint trap 2 02h | Nonmaskable interrupt: | Occurs because of a nonmaskable hardware interrupt. 3 03h | Breakpoint: | Occurs when the processor encounters an INT 3 instruction. 4 04h | Overflow: | Occurs when the processor encounters an INTO instruction | and the OF (overflow) flag is set. 5 05h | Bounds check (BOUND instruction): | Occurs when the processor, while executing a BOUND | instruction, finds that the operand exceeds the specified | limit. 6 06h | Invalid opcode: | Occurs when an invalid opcode is detected. 7 07h | Coprocessor not available: | Occurs for one of two conditions: | - The processor encounters an ESC (escape) instruction | and the EM (emulate) bit of CR0 (control register zero) | is set. | - The processor encounters either the WAIT instruction or | an ESC instruction and both the MP (monitor | coprocessor) and TS (task switched) bits of CR0 are set. 8 08h | Double fault: | Occurs when the processor detects an exception while | trying to invoke the handler for a prior exception. 9 09h | Coprocessor segment overrun: | Occurs when a page or segment violation is detected while | transferring the middle portion of a coprocessor operand | to the NPX. 10 0Ah | Invalid TSS: | Occurs if, during a task switch, the new TSS is invalid. 11 0Bh | Segment not present: | Occurs when the processor detects that the present bit of | a descriptor is zero. 12 0Ch | Stack exception: | Occurs for one of two conditions: | - As a result of a limit violation in any operation that | refers to SS (stack segment register) | - When attempting to load SS with a descriptor that is | marked as not-present but is otherwise valid 13 0Dh | General protection violation: | Each protection violation that does not cause another | exception causes a general protection exception. | - Exceeding segment limit when using CS, DS, ES, FS, or GS | - Exceeding segment limit when referencing a descriptor | table | - Transferring control to a segment that is not executable | - Writing to a read-only data segment or a code segment | - Reading from an execute-only segment | - Loading SS with a read-only descriptor | - Loading SS, DS, ES, FS, or GS with a descriptor of a system | segment | - Loading DS, ES, FS, or GS with the descriptor of an | executable segment that is also not readable | - Loading SS with the descriptor of an executable segment | - Accessing memory through DS, ES, FS, or GS when the segment | register contains a NULL selector | - Switching to a busy task | - Violating privilege rules | - Loading CR0 with PG=1 and PE=0 | - Interrupt or exception through trap or interrupt gate from | V86 mode to a privilege level other than 0 14 0Eh | Page fault: | Occurs when paging is enabled (PG=1) and the processor | detects one of the following conditions while translating | a linear address to a physical address: | - The page-directory or page-table entry needed for the | address translation has 0 in its present bit. | - The current procedure does not have sufficient privilege | to access the indicated page. 15 0Fh | (Reserved) 16 10h | Coprocessor error: | Occurs when the processor detects a signal from the | coprocessor on the ERROR# input pin. 17 11h | (Reserved) through | 31 1Fh |
See Intel 80386 Programmer's Reference Manual for further detail.