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Prelink fails on ARM when use API CLOCK_GETTIME
- From: naveen yadav <yad dot naveen at gmail dot com>
- To: Ian Lance Taylor <iant at google dot com>, prelink at sourceware dot org, jacob at redhat dot com, binutils Development <binutils at sourceware dot org>, gcc-help at gnu dot org, gcc-help at gcc dot gnu dot org
- Date: Thu, 4 Jul 2013 10:44:30 +0530
- Subject: Prelink fails on ARM when use API CLOCK_GETTIME
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