On Wed, Jun 20, 2012 at 6:45 PM, sumeet linux [off-list ref] wrote:

Hi All,

What is the meaning of user_mode(regs) macro ???What does it do ?

I assume you were referring to:
http://lxr.linux.no/#linux+v3.4.3/arch/x86/include/asm/ptrace.h#L164

right?

let me paste the code here:
return !!(regs->cs & 3)

As you can see there, it retrieve the CS register and AND it with 3
(11 in binary). We know that 3 in CS (Code segment) means CPU is
currently operating in ring level 3 a.k.a user mode. Whereas if it is
0, then it is in kernel mode.

Hope it makes it clear for you :)

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
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