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Booting/linux-bootstrap-1.md: update to the latest coreboot code

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Iru Cai 2018-03-16 10:46:01 +08:00
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Booting/linux-bootstrap-1.md
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@ -76,26 +76,28 @@ The starting address is formed by adding the base address to the value in the EI
We get `0xfffffff0`, which is 16 bytes below 4GB. This point is called the [Reset vector](https://en.wikipedia.org/wiki/Reset_vector). This is the memory location at which the CPU expects to find the first instruction to execute after reset. It contains a [jump](https://en.wikipedia.org/wiki/JMP_%28x86_instruction%29) (`jmp`) instruction that usually points to the BIOS entry point. For example, if we look in the [coreboot](https://www.coreboot.org/) source code (`src/cpu/x86/16bit/reset16.inc`), we will see:
```assembly
.section ".reset"
.section ".reset", "ax", %progbits
.code16
.globl reset_vector
reset_vector:
.globl _start
_start:
.byte 0xe9
.int _start - ( . + 2 )
.int _start16bit - ( . + 2 )
...
```
Here we can see the `jmp` instruction [opcode](http://ref.x86asm.net/coder32.html#xE9), which is `0xe9`, and its destination address at `_start - ( . + 2)`.
Here we can see the `jmp` instruction [opcode](http://ref.x86asm.net/coder32.html#xE9), which is `0xe9`, and its destination address at `_start16bit - ( . + 2)`.
We can also see that the `reset` section is `16` bytes and that is compiled to start from `0xfffffff0` address (`src/cpu/x86/16bit/reset16.lds`):
We can also see that the `reset` section is `16` bytes and that is compiled to start from `0xfffffff0` address (`src/cpu/x86/16bit/reset16.ld`):
```
SECTIONS {
/* Trigger an error if I have an unuseable start address */
_bogus = ASSERT(_start16bit >= 0xffff0000, "_start16bit too low. Please report.");
_ROMTOP = 0xfffffff0;
. = _ROMTOP;
.reset . : {
*(.reset)
. = 15 ;
*(.reset);
. = 15;
BYTE(0x00);
}
}