diff --git a/Booting/linux-bootstrap-2.md b/Booting/linux-bootstrap-2.md index cd02e62..a3df557 100644 --- a/Booting/linux-bootstrap-2.md +++ b/Booting/linux-bootstrap-2.md @@ -4,7 +4,7 @@ Kernel booting process. Part 2. First steps in the kernel setup -------------------------------------------------------------------------------- -We started to dive into linux kernel internals in the previous [part](https://github.com/0xAX/linux-insides/blob/master/Booting/linux-bootstrap-1.md) and saw the initial part of the kernel setup code. We stopped at the first call of the `main` function (which is the first function written in C) from [arch/x86/boot/main.c](https://github.com/torvalds/linux/blob/master/arch/x86/boot/main.c). Here we will continue to research of the kernel setup code and see what is `protected mode`, some preparation for transition to it, the heap and console initialization, memory detection and many many more. So... Let's go ahead. +We started to dive into linux kernel internals in the previous [part](linux-bootstrap-1.md) and saw the initial part of the kernel setup code. We stopped at the first call of the `main` function (which is the first function written in C) from [arch/x86/boot/main.c](https://github.com/torvalds/linux/blob/master/arch/x86/boot/main.c). Here we will continue to research of the kernel setup code and see what is `protected mode`, some preparation for transition to it, the heap and console initialization, memory detection and many many more. So... Let's go ahead. Protected mode -------------------------------------------------------------------------------- @@ -266,7 +266,7 @@ After that `biosregs` structure filled with `memset`, `bios_putchar` calls [0x10 Heap initialization -------------------------------------------------------------------------------- -After the stack and bss section were prepared in the [header.S](https://github.com/torvalds/linux/blob/master/arch/x86/boot/header.S) (see previous [part](https://github.com/0xAX/linux-insides/blob/master/Booting/linux-bootstrap-1.md)), need to initialize the [heap](https://github.com/torvalds/linux/blob/master/arch/x86/boot/main.c#L116) with the [init_heap](https://github.com/torvalds/linux/blob/master/arch/x86/boot/main.c#L116) function. +After the stack and bss section were prepared in the [header.S](https://github.com/torvalds/linux/blob/master/arch/x86/boot/header.S) (see previous [part](linux-bootstrap-1.md)), need to initialize the [heap](https://github.com/torvalds/linux/blob/master/arch/x86/boot/main.c#L116) with the [init_heap](https://github.com/torvalds/linux/blob/master/arch/x86/boot/main.c#L116) function. First of all `init_heap` checks `CAN_USE_HEAP` flag from the `loadflags` kernel setup header and calculates end of the stack if this flag was set: @@ -464,4 +464,4 @@ Links * [Intel SpeedStep](http://en.wikipedia.org/wiki/SpeedStep) * [APM](https://en.wikipedia.org/wiki/Advanced_Power_Management) * [EDD specification](http://www.t13.org/documents/UploadedDocuments/docs2004/d1572r3-EDD3.pdf) -* [Previous part](https://github.com/0xAX/linux-insides/blob/master/Booting/linux-bootstrap-1.md) +* [Previous part](linux-bootstrap-1.md) diff --git a/Booting/linux-bootstrap-3.md b/Booting/linux-bootstrap-3.md index 376c5f7..8cc25ac 100644 --- a/Booting/linux-bootstrap-3.md +++ b/Booting/linux-bootstrap-3.md @@ -4,9 +4,9 @@ Kernel booting process. Part 3. Video mode initialization and transition to protected mode -------------------------------------------------------------------------------- -This is the third part of the `Kernel booting process` series. In the previous [part](https://github.com/0xAX/linux-insides/blob/master/Booting/linux-bootstrap-2.md#kernel-booting-process-part-2), we stopped right before the call of the `set_video` routine from the [main.c](https://github.com/torvalds/linux/blob/master/arch/x86/boot/main.c#L181). We will see video mode initialization in the kernel setup code, preparation before switching into the protected mode and transition into it in this part. +This is the third part of the `Kernel booting process` series. In the previous [part](linux-bootstrap-2.md#kernel-booting-process-part-2), we stopped right before the call of the `set_video` routine from the [main.c](https://github.com/torvalds/linux/blob/master/arch/x86/boot/main.c#L181). We will see video mode initialization in the kernel setup code, preparation before switching into the protected mode and transition into it in this part. -**NOTE** If you don't know anything about protected mode, you can find some information about it in the previous [part](https://github.com/0xAX/linux-insides/blob/master/Booting/linux-bootstrap-2.md#protected-mode). Also there are a couple of [links](https://github.com/0xAX/linux-insides/blob/master/Booting/linux-bootstrap-2.md#links) which can help you. +**NOTE** If you don't know anything about protected mode, you can find some information about it in the previous [part](linux-bootstrap-2.md#protected-mode). Also there are a couple of [links](linux-bootstrap-2.md#links) which can help you. As i wrote above, we will start from the `set_video` function which defined in the [arch/x86/boot/video.c](https://github.com/torvalds/linux/blob/master/arch/x86/boot/video.c#L315) source code file. We can see that it starts with getting of video mode from the `boot_params.hdr` structure: @@ -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](https://github.com/0xAX/linux-insides/blob/master/Booting/linux-bootstrap-2.md)) and returns 1 if there is enough memory for `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. @@ -351,7 +351,7 @@ where we can see - 16-bit length of IDT and 32-bit pointer to it (More details a Setup Global Descriptor Table -------------------------------------------------------------------------------- -The next point is setup of the Global Descriptor Table (GDT). We can see `setup_gdt` function which setups GDT (you can read about it in the [Kernel booting process. Part 2.](https://github.com/0xAX/linux-insides/blob/master/Booting/linux-bootstrap-2.md#protected-mode)). There is definition of the `boot_gdt` array in this function, which contains definition of the three segments: +The next point is setup of the Global Descriptor Table (GDT). We can see `setup_gdt` function which setups GDT (you can read about it in the [Kernel booting process. Part 2.](linux-bootstrap-2.md#protected-mode)). There is definition of the `boot_gdt` array in this function, which contains definition of the three segments: ```C static const u64 boot_gdt[] __attribute__((aligned(16))) = { @@ -389,7 +389,7 @@ int main(void) Technically structure which contains one `int` field, must be 4 bytes, but here `aligned` structure will be 16 bytes: ``` -$ gcc test.c -o test && ./test +$ gcc test.c -o test && test Not aligned - 4 Aligned - 16 ``` @@ -421,7 +421,7 @@ in binary. Let's try to understand what every bit means. We will go through all * 101 - segment type execute/read/ * 1 - accessed bit -You can know more about every bit in the previous [post](https://github.com/0xAX/linux-insides/blob/master/Booting/linux-bootstrap-2.md) or in the [Intel® 64 and IA-32 Architectures Software Developer’s Manuals 3A](http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html). +You can know more about every bit in the previous [post](linux-bootstrap-2.md) or in the [Intel® 64 and IA-32 Architectures Software Developer’s Manuals 3A](http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html). After this we get length of GDT with: @@ -538,4 +538,4 @@ Links * [A20](http://en.wikipedia.org/wiki/A20_line) * [GCC designated inits](https://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Designated-Inits.html) * [GCC type attributes](https://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html) -* [Previous part](https://github.com/0xAX/linux-insides/blob/master/Booting/linux-bootstrap-2.md) +* [Previous part](linux-bootstrap-2.md)