On Tue, May 28, 2013 at 10:02 PM, lx <lxlenovostar@xxxxxxxxx> wrote:
> hi all:
> They are some asm codes in the kernel like:
>
> #define set_bit(nr,addr) ({\
> register int res __asm__("ax"); \
> __asm__ __volatile__("btsl %2,%3\n\tsetb %%al": \
> "=a" (res):"0" (0),"r" (nr),"m" (*(addr))); \
> res;})
>
>
> But, almost I can't understand this. So I want to understand asm in C,
> which book or website I should learn ?
Hi,
This is a C (preprocessor) macro called set_bit which use GCC
inline assembly in its body.
http://gcc.gnu.org/onlinedocs/cpp/Macros.html
http://wiki.osdev.org/Inline_Assembly
--
Augusto Mecking Caringi
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