title: Linux kernel exported symbols
body: <p>I want to check the list of symbol exported by the Linux kernel. 
  So I fire the command,</p>
  
  <pre><code># cat /proc/kallsyms
  0000000000000000 D per_cpu__irq_stack_union
  0000000000000000 D __per_cpu_start
  0000000000004000 D per_cpu__gdt_page
  0000000000005000 d per_cpu__exception_stacks
  000000000000b000 d per_cpu__idt_desc
  000000000000b010 d per_cpu__xen_cr0_value
  000000000000b018 D per_cpu__xen_vcpu
  000000000000b020 D per_cpu__xen_vcpu_info
  000000000000b060 d per_cpu__mc_buffer
  000000000000c570 D per_cpu__xen_mc_irq_flags
  </code></pre>
  
  <p>This is the output I got.
  My question is that, what is the meaning of each field in this output?
  The first field looks like the address, I didn't get any reference for second field.
  Can anybody explain to me the meaning of the values, D,d,t,T,s in second field?</p>