c)lets say for a program a.c i use gcc -S a.c ...do we have some other 
command to generate
somewhat more clear assembly code, may be with some comments in english

Not sure if this is of any help, but the kernel build system (no idea 
how to do this for user space programs) offers to generate a listing 
that interleaves the c code into assembly making it better readable. So 
if your function is e.g. in kernel/rtmutex.c you could do the following:

andi at PC63:~/working_git/linux-next$ make kernel/rtmutex.lst
   SYSHDR arch/x86/syscalls/../include/generated/uapi/asm/unistd_32.h
   SYSHDR arch/x86/syscalls/../include/generated/uapi/asm/unistd_64.h
<SNIP>
   HOSTCC  scripts/asn1_compiler
   MKLST   kernel/rtmutex.lst
No System.map
andi at PC63:~/working_git/linux-next$

here is one function from the resulting rtmutex.lst file:

static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
{
   70:    e8 00 00 00 00           callq  75 <fixup_rt_mutex_waiters+0x5>
                                      71: R_X86_64_PC32 
__fentry__+0xfffffffffffffffc
   75:    55                       push   %rbp
   76:    48 ff 05 00 00 00 00     incq   0x0(%rip)        # 7d 
<fixup_rt_mutex_waiters+0xd>
                                       79: R_X86_64_PC32 .bss+0x6fc
   7d:    48 89 e5                 mov    %rsp,%rbp
   80:    53                       push   %rbx
   81:    48 89 fb                 mov    %rdi,%rbx
                                            if (!rt_mutex_has_waiters(lock))
   84:    e8 8e ff ff ff           callq  17 <rt_mutex_has_waiters>
   89:    48 ff 05 00 00 00 00     incq   0x0(%rip)        # 90 
<fixup_rt_mutex_waiters+0x20>
             8c: R_X86_64_PC32    .bss+0x704
   90:    85 c0                    test   %eax,%eax
   92:    75 0c                    jne    a0 <fixup_rt_mutex_waiters+0x30>
}

btw. you can for example generate the pre-processed code in the same way:

andi at PC63:~/working_git/linux-next$ make kernel/rtmutex.i

or the assembly code:

andi at PC63:~/working_git/linux-next$ make kernel/rtmutex.s

this is especially helpful, as it also contains a list of all the flags 
used for compiling.

regards,
andi

Any kind of help in understanding this will be appreciated ..

Thanks
Nidhi





-- 
Thanks & Regards
Nidhi Mittal Hada

http://nidhi-searchingmyself.blogspot.com/



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