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Merge pull request #268 from ruthgrace/bootstrap_3_heap_api

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fixed grammar in linux-bootstrap-3.md, Heap API section
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0xAX 2015-10-26 00:15:52 +06:00
commit b2732a0157
1 changed files with 5 additions and 5 deletions
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Booting/linux-bootstrap-3.md
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@ -58,7 +58,7 @@ If you the read source code of the kernel, you'll see these very often and so it
Heap API
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After we have `vid_mode` from the `boot_params.hdr` in the `set_video` function we can see call to `RESET_HEAP` function. `RESET_HEAP` is a macro which defined in the [boot.h](https://github.com/torvalds/linux/blob/master/arch/x86/boot/boot.h#L199). It is defined as:
After we get `vid_mode` from `boot_params.hdr` in the `set_video` function, we can see the call to the `RESET_HEAP` function. `RESET_HEAP` is a macro which is defined in [boot.h](https://github.com/torvalds/linux/blob/master/arch/x86/boot/boot.h#L199). It is defined as:
```C
#define RESET_HEAP() ((void *)( HEAP = _end ))
@ -70,9 +70,9 @@ If you have read the second part, you will remember that we initialized the heap
#define RESET_HEAP()
```
As we saw just above it resets the heap by setting the `HEAP` variable equal to `_end`, where `_end` is just `extern char _end[];`
As we saw just above, it resets the heap by setting the `HEAP` variable equal to `_end`, where `_end` is just `extern char _end[];`
Next is `GET_HEAP` macro:
Next is the `GET_HEAP` macro:
```C
#define GET_HEAP(type, n) \
@ -105,7 +105,7 @@ and further we will see its usage, something like:
saved.data = GET_HEAP(u16, saved.x * saved.y);
```
Let's try to understand how `__get_heap` works. We can see here that `HEAP` (which is equal to `_end` after `RESET_HEAP()`) is the address of aligned memory according to `a` parameter. After it we save memory address from `HEAP` to the `tmp` variable, move `HEAP` to the end of allocated block and return `tmp` which is start address of allocated memory.
Let's try to understand how `__get_heap` works. We can see here that `HEAP` (which is equal to `_end` after `RESET_HEAP()`) is the address of aligned memory according to the `a` parameter. After this we save the memory address from `HEAP` to the `tmp` variable, move `HEAP` to the end of the allocated block and return `tmp` which is the start address of allocated memory.
And the last function is:
@ -118,7 +118,7 @@ static inline bool heap_free(size_t n)
which subtracts value of the `HEAP` from the `heap_end` (we calculated it in the previous [part](linux-bootstrap-2.md)) and returns 1 if there is enough memory for `n`.
That's all. Now we have simple API for heap and can setup video mode.
That's all. Now we have a simple API for heap and can setup video mode.
Setup video mode
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