Regarding segmantation violation

Fri Jun 1 11:21:09 UTC 2007

Plea find the attachment of the code . if u memset to 0 it fails where as to
nay other ascii it works. I m cross compiling and running on the PPC board.
Until 8109 bytes it works fine . I have even tried to see whats happening at
8110 byte I couldn't when I m running on the board .

The inputs to the program are chunck of bytes to be allocated and no of
times to allocate and free them . running the exe file at the command prompt
looks like :

  #./mem 100 1

  100 is chunk of bytes
  1   allocate and free 1 time .

 I m sending u two instances of the program when 100 bytes are allocated for
1 time ( does successfully for memset to 0) : (used strace )

# ./strace ./mem 100 1
execve("./mem", ["./mem", "100", "1"], [/* 15 vars */]) = 0
uname({sys="Linux", node="SBT-PXC ", ...}) = 0
brk(0)                                  = 0x10012000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0x30016000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or
directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=64, ...}) = 0
mmap(NULL, 64, PROT_READ, MAP_PRIVATE, 3, 0) = 0x30017000
close(3)                                = 0
open("/lib/ppc823/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or
directory)
stat64("/lib/ppc823", 0x7fe6e208)       = -1 ENOENT (No such file or
directory)
open("/lib/libc.so.6", O_RDONLY)        = 3
read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\24\0\0\0\1\0\1\317"..., 512)
= 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1500625, ...}) = 0
mmap(0xfeab000, 1330296, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3,
0) = 0xfeab000
mprotect(0xffd8000, 97400, PROT_NONE)   = 0
mmap(0xffe8000, 24576, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x12d000) = 0xf0
mmap(0xffee000, 7288, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xffee000
close(3)                                = 0
mprotect(0xffe8000, 8192, PROT_READ)    = 0
mprotect(0x30025000, 4096, PROT_READ)   = 0
munmap(0x30017000, 64)                  = 0
gettimeofday({18672, 446432}, NULL)     = 0
brk(0)                                  = 0x10012000
brk(0x10033000)                         = 0x10033000
gettimeofday({18672, 454484}, NULL)     = 0
fstat64(1, {st_mode=S_IFCHR|0600, st_rdev=makedev(204, 46), ...}) = 0
ioctl(1, TCGETS, {B115200 opost isig icanon echo ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0x30017000
write(1, "Total time taken  8052.000000 us"..., 37Total time taken
8052.000000 usecs
) = 37
write(1, "Time for 1 loop  8052.000000 use"..., 36Time for 1 loop
8052.000000 usecs
) = 36
munmap(0x30017000, 4096)                = 0
exit_group(0)                           = ?
Process 265 detached

When I allocate 10,000 bytes 1 time (fails on memeset to 0): (used strace)

# ./strace ./mem 10000 1
execve("./mem", ["./mem", "10000", "1"], [/* 15 vars */]) = 0
uname({sys="Linux", node="SBT-PXC ", ...}) = 0
brk(0)                                  = 0x10012000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0x30016000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or
directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=64, ...}) = 0
mmap(NULL, 64, PROT_READ, MAP_PRIVATE, 3, 0) = 0x30017000
close(3)                                = 0
open("/lib/ppc823/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or
directory)
stat64("/lib/ppc823", 0x7fd00208)       = -1 ENOENT (No such file or
directory)
open("/lib/libc.so.6", O_RDONLY)        = 3
read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\24\0\0\0\1\0\1\317"..., 512)
= 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1500625, ...}) = 0
mmap(0xfeab000, 1330296, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3,
0) = 0xfeab000
mprotect(0xffd8000, 97400, PROT_NONE)   = 0
mmap(0xffe8000, 24576, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x12d000) = 0xf0
mmap(0xffee000, 7288, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xffee000
close(3)                                = 0
mprotect(0xffe8000, 8192, PROT_READ)    = 0
mprotect(0x30025000, 4096, PROT_READ)   = 0
munmap(0x30017000, 64)                  = 0
gettimeofday({18755, 138465}, NULL)     = 0
brk(0)                                  = 0x10012000
brk(0x10033000)                         = 0x10033000
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
+++ killed by SIGSEGV +++
Process 267 detached

Is it due to mmap or memset function in my busy box. Any more details needed
I will send .

Thanks for u r response.

Thanks & Regards ,
Sekhar Pedamallu

-----Original Message-----
From: busybox-bounces at busybox.net [mailto:busybox-bounces at busybox.net] On
Behalf Of Jason Curl
Sent: Friday, June 01, 2007 3:53 PM
To: busybox at busybox.net
Subject: Re: Regarding segmantation violation

Sekhar Pedamallu wrote:
> 
>    I m working on MPC8XX powerpc  . when I allocate memory for more than
> 10000 bytes and memset to 0 . its giving segmentation fault . When i
memset
> to any other ascii character it works fine . is it a problem with busy box
I
> m using ?
> 
> Or what could be the source of the problem ? I m new to linux .any more
> details u want I can mail u.

Can you post a completely compilable example where the problem is shown? 
Maybe a code review with your colleagues where you work can identify a 
problem?

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