Re: [Valgrind-users] Large amount of instructions when profiling an empty program?

[John R. <jr...@bi...>]

> Since none of these functions were called by the program above,

Those functions are the dynamic linker adding libc.so to your process address space.
'main' is moderately far removed from the beginning of execution.

$ readelf --headers test  |  grep Entry
   Entry point address:               0x400400
$ gdb test
(gdb) x/12i 0x400400
    0x400400 <_start>:	xor    %ebp,%ebp
    0x400402 <_start+2>:	mov    %rdx,%r9
    0x400405 <_start+5>:	pop    %rsi
    0x400406 <_start+6>:	mov    %rsp,%rdx
    0x400409 <_start+9>:	and    $0xfffffffffffffff0,%rsp
    0x40040d <_start+13>:	push   %rax
    0x40040e <_start+14>:	push   %rsp
    0x40040f <_start+15>:	mov    $0x400570,%r8
    0x400416 <_start+22>:	mov    $0x400500,%rcx
    0x40041d <_start+29>:	mov    $0x4004f0,%rdi
    0x400424 <_start+36>:	callq  0x4003e0 <__libc_start_main@plt>
    0x400429 <_start+41>:	hlt
(gdb) quit
$ LD_DEBUG=ALL ./test
       5360:	
       5360:	file=libc.so.6 [0];  needed by ./test [0]
       5360:	find library=libc.so.6 [0]; searching
       5360:	 search cache=/etc/ld.so.cache
       5360:	  trying file=/lib64/libc.so.6
       5360:	
       5360:	file=libc.so.6 [0];  generating link map
       5360:	  dynamic: 0x0000003ef37b8b80  base: 0x0000000000000000   size: 0x00000000003bf260
       5360:	    entry: 0x0000003ef3421c50  phdr: 0x0000003ef3400040  phnum:                 10
       5360:	
       5360:	checking for version `GLIBC_2.2.5' in file /lib64/libc.so.6 [0] required by file ./test [0]
       5360:	checking for version `GLIBC_2.3' in file /lib64/ld-linux-x86-64.so.2 [0] required by file /lib64/libc.so.6 [0]
       5360:	checking for version `GLIBC_PRIVATE' in file /lib64/ld-linux-x86-64.so.2 [0] required by file /lib64/libc.so.6 [0]
       5360:	
       5360:	Initial object scopes
       5360:	object=./test [0]
       5360:	 scope 0: ./a.out /lib64/libc.so.6 /lib64/ld-linux-x86-64.so.2
   [[snip]]