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Merge pull request #296 from ruthgrace/bootstrap_1_bss_setup

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fixed grammar in linux-bootstrap-1.md, BSS Setup section
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0xAX 2015-12-03 15:38:10 +06:00
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Booting/linux-bootstrap-1.md
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@ -458,7 +458,7 @@ The BSS section is used to store statically allocated, uninitialized data. Linux
rep; stosl
```
First of all the [__bss_start](https://github.com/torvalds/linux/blob/master/arch/x86/boot/setup.ld#L47) address is moved into `di` and the `_end + 3` address (+3 - aligns to 4 bytes) is moved into `cx`. The `eax` register is cleared (using an `xor` instruction), and the bss section size (`cx`-`di`) is calculated and put into `cx`. Then, `cx` is divided by four (the size of a 'word'), and the `stosl` instruction is repeatedly used, storing the value of `eax` (zero) into the address pointed to by `di`, automatically increasing `di` by four (this occurs until `cx` reaches zero). The net effect of this code is that zeros are written through all words in memory from `__bss_start` to `_end`:
First of all the [__bss_start](https://github.com/torvalds/linux/blob/master/arch/x86/boot/setup.ld#L47) address is moved into `di` and the `_end + 3` address (+3 - aligns to 4 bytes) is moved into `cx`. The `eax` register is cleared (using a `xor` instruction), and the bss section size (`cx`-`di`) is calculated and put into `cx`. Then, `cx` is divided by four (the size of a 'word'), and the `stosl` instruction is repeatedly used, storing the value of `eax` (zero) into the address pointed to by `di`, automatically increasing `di` by four (this occurs until `cx` reaches zero). The net effect of this code is that zeros are written through all words in memory from `__bss_start` to `_end`:
![bss](http://oi59.tinypic.com/29m2eyr.jpg)