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Merge pull request #364 from relip/patch-1

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bootstrap-1: help readers not to confuse segment and physical address
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0xAX 2016-04-03 20:24:22 +06:00
commit 556a2d3c4d
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Booting/linux-bootstrap-1.md
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@ -313,6 +313,7 @@ Here we can see a `jmp` instruction opcode - `0xeb` to the `start_of_setup-1f` p
Actually this is the first code that runs (aside from the previous jump instruction of course). After the kernel setup got the control from the bootloader, the first `jmp` instruction is located at `0x200` (first 512 bytes) offset from the start of the kernel real mode. This we can read in the Linux kernel boot protocol and also see in the grub2 source code: Actually this is the first code that runs (aside from the previous jump instruction of course). After the kernel setup got the control from the bootloader, the first `jmp` instruction is located at `0x200` (first 512 bytes) offset from the start of the kernel real mode. This we can read in the Linux kernel boot protocol and also see in the grub2 source code:
```C ```C
segment = grub_linux_real_target >> 4;
state.gs = state.fs = state.es = state.ds = state.ss = segment; state.gs = state.fs = state.es = state.ds = state.ss = segment;
state.cs = segment + 0x20; state.cs = segment + 0x20;
``` ```
@ -324,7 +325,7 @@ gs = fs = es = ds = ss = 0x1000
cs = 0x1020 cs = 0x1020
``` ```
in my case when the kernel is loaded at `0x10000`. In my case when the kernel is loaded at `0x10000`.
After the jump to `start_of_setup`, it needs to do the following: After the jump to `start_of_setup`, it needs to do the following: