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Merge pull request #255 from ruthgrace/bootstrap_4_32_bit_entry

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fixed grammar in linux-bootstrap-4.md, 32-bit entry point section
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0xAX 2015-10-17 00:24:47 +06:00
commit e0f87ad2bd
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Booting/linux-bootstrap-4.md
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@ -46,7 +46,7 @@ We can see here that `cs` register contains - `0x10` (as you can remember from t
32-bit entry point
--------------------------------------------------------------------------------
We can find definition of the 32-bit entry point in the [arch/x86/boot/compressed/head_64.S](https://github.com/torvalds/linux/blob/master/arch/x86/boot/compressed/head_64.S):
We can find the definition of the 32-bit entry point in [arch/x86/boot/compressed/head_64.S](https://github.com/torvalds/linux/blob/master/arch/x86/boot/compressed/head_64.S):
```assembly
__HEAD
@ -58,14 +58,14 @@ ENTRY(startup_32)
ENDPROC(startup_32)
```
First of all why `compressed` directory? Actually `bzimage` is a gzipped `vmlinux + header + kernel setup code`. We saw the kernel setup code in the all of previous parts. So, the main goal of the `head_64.S` is to prepare for entering long mode, enter into it and decompress the kernel. We will see all of these steps besides kernel decompression in this part.
First of all why `compressed` directory? Actually `bzimage` is a gzipped `vmlinux + header + kernel setup code`. We saw the kernel setup code in all of the previous parts. So, the main goal of the `head_64.S` is to prepare for entering long mode, enter into it and decompress the kernel. We will see all of these steps besides kernel decompression in this part.
Also you can note that there are two files in the `arch/x86/boot/compressed` directory:
* head_32.S
* head_64.S
We will see only `head_64.S` because we are learning linux kernel for `x86_64`. `head_32.S` even not compiled in our case. Let's look on the [arch/x86/boot/compressed/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/boot/compressed/Makefile), we can see there following target:
We will see only `head_64.S` because we are learning linux kernel for `x86_64`. `head_32.S` even not compiled in our case. Let's look at [arch/x86/boot/compressed/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/boot/compressed/Makefile). We can see there the following target:
```Makefile
vmlinux-objs-y := $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o \