On Tue, Aug 16, 2022 at 05:55:33PM +0800, shiyu chou wrote:
> In arch x86 directory I found two global variables with the same
> name(master branch):
> 1.arch/x86/boot/main.c
> near line 18: struct boot_params boot_params __attribute__((aligned(16)));
> 2.arch/x86/kernel/setup.c
> near line 75: struct boot_params boot_params;
> Is that wrong to define two global variables with the same name? And when
> use extern to reference the variable,which one did it reference?
Same name would be a problem if these two variables end up in the same
binary program. However, as the comment in arch/x86/boot/main.c suggests:
/*
* Main module for the real-mode kernel code
*/
first variable is part of a small real-mode kernel that runs first. It
finishes running by switching to the protected mode kernel that contains
the second variable:
protected_mode_jump(boot_params.hdr.code32_start,
(u32)&boot_params + (ds() << 4));
For more details see https://www.kernel.org/doc/html/latest/x86/boot.html
--
Valentin
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