Prelink fails on ARM when use API CLOCK_GETTIME

[naveen yadav <yad.naveen@xxxxxxxxx>]

Dear All,


I was trying to prelink and run the below mentioned test case, cross
compiled with arm toolchain (gcc-4.7.3).

#include <stdio.h>

#include <unistd.h>

#include <stdlib.h>

#include <time.h>

#include <errno.h>



int main()

{

        int rst;

        struct timespec to;



        rst = clock_gettime(CLOCK_MONOTONIC, &to);

        if(rst != 0)

        {

                printf("Got some error and error code may be %d
%d\n",rst,errno);

        }

        else

        {

                printf("clock_gettime returned=%d", rst);

                printf("rst=%d to.to_sec=%d", rst, to.tv_sec);



        }

}



Compiled the above test case as:
$arm-linux-gnueabi-gcc -o time_with_rt time.c -lrt


On linking it with rt library, and after prelinking it on host (x86
machine), running on the ARM target, it gives output as:
$ ./time_with_rt

       624:                      number of relocations: 0

       624:           number of relocations from cache: 29

       624:             number of relative relocations: 0

Got some error and error code may be 1091638508 0

       624:

       624:     runtime linker statistics:

       624:                final number of relocations: 0

       624:     final number of relocations from cache: 29



I have a query:

Why the return value in 'rst' variable is some large non-zero number?
The function clock_gettime() ideally returns either 0 or -1, if I am
not wrong? Why and How this large value is returned?


Also, my another observation regarding the same test case is as shown below.

$ arm-linux-gnueabi-readelf -a  lib/libc.so.6 | grep clock_gettime

  783: 411114ec   108 FUNC    GLOBAL DEFAULT   11 __clock_gettime@@GLIBC_PRIVATE
  1628: 411114ec   108 FUNC    GLOBAL DEFAULT   11 clock_gettime@@GLIBC_2.17
 10080: 00000000     0 FILE    LOCAL  DEFAULT  ABS clock_gettime.c
 15736: 411114ec   108 FUNC    GLOBAL DEFAULT   11 __clock_gettime
 15890: 411114ec   108 FUNC    GLOBAL DEFAULT   11 clock_gettime


$ arm-linux-gnueabi-readelf -a   lib/librt.so.1 | grep clock_gettime

411ce124  00002b15 R_ARM_GLOB_DAT    00000000   __clock_gettime
    43: 00000000     0 FUNC    GLOBAL DEFAULT  UND
__clock_gettime@GLIBC_PRIVATE (5)
    84: 411c4b0c    28 IFUNC   GLOBAL DEFAULT   12 clock_gettime@@GLIBC_2.4
   497: 411c4b0c    28 IFUNC   GLOBAL DEFAULT   12 clock_gettime
   547: 00000000     0 FUNC    GLOBAL DEFAULT  UND __clock_gettime@@GLIBC_PR




While looking for symbol, clock_gettime in the ELF of libc and lrt, I
found that in librt.so.1, its function attribute is IFUNC. I am not
clear how the symbols are resolved with function attribute IFUNC. And,
do the latest prelink support IFUNC function types yet? It would be
great if you can explain the concept of how this type of symbols are
handled differently.

Thanks