From 9b07bfc5982087d0be1ba480c38071311db0bdf0 Mon Sep 17 00:00:00 2001 From: hailin cai Date: Fri, 5 Feb 2016 12:56:17 -0500 Subject: [PATCH] Update Booting/linux-bootstrap-2md.md --- Booting/linux-bootstrap-2md.md | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/Booting/linux-bootstrap-2md.md b/Booting/linux-bootstrap-2md.md index 66058ce..5091453 100644 --- a/Booting/linux-bootstrap-2md.md +++ b/Booting/linux-bootstrap-2md.md @@ -207,6 +207,22 @@ GLOBAL(memcpy) ENDPROC(memcpy) ``` -Yeah, we just moved to C code and now assembly again :) First of all we can see that `memcpy` and other routines which are defined here, start and end with the two macros: `GLOBAL` and `ENDPROC`. `GLOBAL` is described in [arch/x86/include/asm/linkage.h](https://github.com/torvalds/linux/blob/master/arch/x86/include/asm/linkage.h) which defines `globl` directive and the label for it. `ENDPROC` is described in [include/linux/linkage.h](https://github.com/torvalds/linux/blob/master/include/linux/linkage.h) which marks the `name` symbol as a function name and ends with the size of the `name` symbol. +在`copy.S`文件中，你可以看到所有的方法都开始于`GLOBAL`宏定义，而结束于`ENDPROC`宏定义。 + +你可以在 [arch/x86/include/asm/linkage.h](https://github.com/torvalds/linux/blob/master/arch/x86/include/asm/linkage.h)中找到`GLOBAL`宏定义。这个宏给代码段分配了一个名字标签，并且让这个名字全局可用。 + +```assembly +#define GLOBAL(name) \ + .globl name; \ + name: +``` + +你可以在[include/linux/linkage.h](https://github.com/torvalds/linux/blob/master/include/linux/linkage.h)中找到`ENDPROC`宏的定义。 这个宏通过`END(name)`代码标识了汇编函数的结束，同时将函数名输出，从而静态分析工具可以找到这个函数。 + +```assembly +#define ENDPROC(name) \ + .type name, @function ASM_NL \ + END(name) +``` Implementation of `memcpy` is easy. At first, it pushes values from the `si` and `di` registers to the stack to preserve their values because they will change during the `memcpy`. `memcpy` (and other functions in copy.S) use `fastcall` calling conventions. So it gets its incoming parameters from the `ax`, `dx` and `cx` registers. Calling `memcpy` looks like this: \ No newline at end of file