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Update linux-bootstrap-5.md

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Ródgger Bruno 2021-05-05 03:00:36 -04:00 committed by GitHub
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@ -231,7 +231,7 @@ boot_heap:
.fill BOOT_HEAP_SIZE, 1, 0 .fill BOOT_HEAP_SIZE, 1, 0
``` ```
where `BOOT_HEAP_SIZE` is a macro which expands to `0x10000` (`0x400000` in thecase of a `bzip2` kernel) and represents the size of the heap. where `BOOT_HEAP_SIZE` is a macro which expands to `0x10000` (`0x400000` in the case of a `bzip2` kernel) and represents the size of the heap.
After we initialize the heap pointers, the next step is to call the `choose_random_location` function from the [arch/x86/boot/compressed/kaslr.c](https://github.com/torvalds/linux/blob/v4.16/arch/x86/boot/compressed/kaslr.c) source code file. As we can guess from the function name, it chooses a memory location to write the decompressed kernel to. It may look weird that we need to find or even `choose` where to decompress the compressed kernel image, but the Linux kernel supports [kASLR](https://en.wikipedia.org/wiki/Address_space_layout_randomization) which allows decompression of the kernel into a random address, for security reasons. After we initialize the heap pointers, the next step is to call the `choose_random_location` function from the [arch/x86/boot/compressed/kaslr.c](https://github.com/torvalds/linux/blob/v4.16/arch/x86/boot/compressed/kaslr.c) source code file. As we can guess from the function name, it chooses a memory location to write the decompressed kernel to. It may look weird that we need to find or even `choose` where to decompress the compressed kernel image, but the Linux kernel supports [kASLR](https://en.wikipedia.org/wiki/Address_space_layout_randomization) which allows decompression of the kernel into a random address, for security reasons.