arno
/
linux-insides
mirror of https://github.com/0xAX/linux-insides.git
1
0
Fork 0
Code Issues Releases Wiki Activity

fixed grammar mistakes in linux-bootstrap-4.md, Stack setup and CPU verification section

Browse Source
pull/257/head
ruthgrace 9 years ago
parent 3616c8e78a
commit 796c21c171
1 changed files with 7 additions and 7 deletions
Show Stats Download Patch File Download Diff File

14
Booting/linux-bootstrap-4.md
Unescape View File

@ -175,7 +175,7 @@ Now we can setup the stack and verify CPU that it has support of the long mode a
Stack setup and CPU verification Stack setup and CPU verification
-------------------------------------------------------------------------------- --------------------------------------------------------------------------------
The next we can see assembly code which setups new stack for kernel decompression: Next we can see assembly code which sets up a new stack for kernel decompression:
```assembly ```assembly
movl $boot_stack_end, %eax movl $boot_stack_end, %eax
@ -183,7 +183,7 @@ The next we can see assembly code which setups new stack for kernel decompressio
movl %eax, %esp movl %eax, %esp
``` ```
`boots_stack_end` is in the `.bss` section, we can see definition of it in the end of `head_64.S`: `boots_stack_end` is in the `.bss` section. We can see the definition of it in the end of `head_64.S`:
```assembly ```assembly
.bss .bss
@ -195,9 +195,9 @@ boot_stack:
boot_stack_end: boot_stack_end:
``` ```
First of all we put address of the `boot_stack_end` into `eax` register and add to it value of the `ebp` (remember that `ebp` now contains address where we loaded - `0x100000`). In the end we just put `eax` value into `esp` and that's all, we have correct stack pointer. First of all we put the address of `boot_stack_end` into the `eax` register and add to it value of `ebp` (remember that `ebp` now contains the address where we loaded - `0x100000`). In the end we just put the `eax` value into `esp` and that's all, we have a correct stack pointer.
The next step is CPU verification. Need to check that CPU has support of `long mode` and `SSE`: The next step is CPU verification. We need to check that the CPU supports `long mode` and `SSE`:
```assembly ```assembly
call verify_cpu call verify_cpu
@ -205,9 +205,9 @@ The next step is CPU verification. Need to check that CPU has support of `long m
jnz no_longmode jnz no_longmode
``` ```
It just calls `verify_cpu` function from the [arch/x86/kernel/verify_cpu.S](https://github.com/torvalds/linux/blob/master/arch/x86/kernel/verify_cpu.S) which contains a couple of calls of the `cpuid` instruction. `cpuid` is instruction which is used for getting information about processor. In our case it checks long mode and SSE support and returns `0` on success or `1` on fail in the `eax` register. It just calls `verify_cpu` function from [arch/x86/kernel/verify_cpu.S](https://github.com/torvalds/linux/blob/master/arch/x86/kernel/verify_cpu.S) which contains a couple of calls to the `cpuid` instruction. `cpuid` is the instruction which is used for getting information about the processor. In our case it checks long mode and SSE support and returns `0` on success or `1` on fail in the `eax` register.
If `eax` is not zero, we jump to the `no_longmode` label which just stops the CPU with `hlt` instruction while any hardware interrupt will not happen. If `eax` is not zero, we jump to the `no_longmode` label which just stops the CPU with a `hlt` instruction while any hardware interrupt will not happen.
```assembly ```assembly
no_longmode: no_longmode:
@ -216,7 +216,7 @@ no_longmode:
jmp 1b jmp 1b
``` ```
We set stack, checked CPU and now can move on the next step. We set stack, checked CPU and now can move on to the next step.
Calculate relocation address Calculate relocation address
-------------------------------------------------------------------------------- --------------------------------------------------------------------------------

Write Preview
Loading…
Cancel
Save