英文:
What is the grub/machine include directory in GRUB source code?
问题
我一直好奇 GRUB 2 是如何工作的。在阅读其源代码时，我看到了一些 #include 指令，其中包含了看似不存在的 "grub/machine/..."，例如在 grub-core/boot/i386/pc/boot.S 引导加载程序文件中有以下代码：
#include <grub/machine/boot.h>
看起来，它提供了一些与体系结构相关的宏，我目前的猜测是，在针对特定体系结构进行编译时，它是从 include/grub 中的文件和宏的混合物中创建的（例如，#include <grub/machine/boot.h> 可能直接从 include/grub/i386/pc/boot.h 复制而来，这可以通过在 boot.S 中查看宏引用和在 i386/pc/boot.h 中查看相应的定义来假设），但是我对我的假设非常不确定，因为我未能找到任何关于这方面的文档或文章。此外，我无法理解，如果我的假设至少在某种程度上是正确的，为什么 include/grub 中的一些目录不仅不相似（例如，没有一些共同的文件，如 arm/ 有其自己的 boot.h），而且在某些情况下完全不同，这从我的角度看似乎是违反直觉的。
我将很高兴得到关于这些幕后发生的真正情况的解释，因为我正试图自己学习内核开发。
英文:
I have always wondered how does GRUB 2 work. While reading it's source code, I saw that there are some #include directives which include seemingly nonexistent "grub/machine/...", for example in grub-core/boot/i386/pc/boot.S bootloader file there is
#include <grub/machine/boot.h>
As it seems, it provides some architecture-specific macros, and my current guess is that it is created from sort of a mixin of files and macros from include/grub when compiling for a specific architecture (e.g. #include <grub/machine/boot.h> might be directly copied from include/grub/i386/pc/boot.h, which I can assume by looking at macro references in boot.S and corresponding definitions in i386/pc/boot.h), but I am very unsure about my assumption as I have failed to find any documentation or article about that. Also I'm failing to understand, in case my assumptions are at least somewhat correct, why are some directories in include/grub not just not similar to eachother (with, for example, having some files in common, like arm/ having it's own boot.h), but, in some cases, completely different, which seems counterintuitive from my perspective.
I would be glad to get some explanation on what is really going on behind those curtains as I'm trying to learn kernel development myself.
答案1
得分: 1
在./configure.ac中，有这一行
AC_CONFIG_LINKS([include/grub/machine:include/grub/$cpudir/$platform])
这一行在我在我的机器上运行了./autogen.sh && ./configure && make之后，创建了一个符号链接到正确的CPU架构../../include/grub/i386/pc。在该目录中将包含依赖于架构的boot.h文件。
我发现运行一些本地构建命令可以更容易理解这样的存储库。
英文:
In ./configure.ac, there is this line
AC_CONFIG_LINKS([include/grub/machine:include/grub/$cpudir/$platform])
That line creates a symlink to the right CPU architecture ../../include/grub/i386/pc after I ran ./autogen.sh && ./configure && make on my machine. Inside of that directory will be the architecture dependent boot.h file.
I find it easier to understand repos like this running some of the build commands locally.
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