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ntp 4.2.6p5

    1:  Bug Id: 4095849
    2:  Category: kernel
    3:  Subcategory: syscall
    4:  State: evaluated
    5:  Synopsis: time_constant value >6 with PLL in use leads to integer divide
    6:            zero trap panic
    7:  Description:
    8: If the time_constant parameter is 7 or higher, and the phase-lock looping model
    9: is in use, the system will take a "integer divide zero trap" panic in
   10: the clock routine as soon as the time_offset becomes non-zero.
   11: 
   12: time_constant defaults to 0.  The only place it is set is in the ntp_adjtime
   13: system call, from the 'constant' element of the timex structure argument.
   14: 
   15:  Work around:
   16: Never set the constant element of the timex structure passed to ntp_adjtime to
   17: a value larger than 6.
   18: 
   19: satish.mynam@Eng 1998-04-30
   20: 1. Use Sun's version of NTP software instead of PD version. This problem
   21: is not seen with Sun's NTP version (which is mostly eqivalent to PD NTP 3.4
   22: plus some Sun's local functionality futures).
   23: 
   24: 2. Workaround for the public domain NTP version  ONLY:
   25:  =====================================================
   26: The workaround for public domain NTP version is to disable the
   27: KERNEL_PLL from the NTP code. This way ntp_Adjtime() system call is
   28: totally bypassed without sacrificing any of the functionality of the
   29: NTP. The only hit you might see is the way  kernel precision timminig
   30: is done without the PLL algorithm in the kernel.
   31: 
   32:     The easiest way to disable ntp_adjtime option is(without changing
   33:     any makefiles or other config files) to disable the KERNEL_PLL
   34:     value in the ./config.h file.
   35: 
   36: After doing a ./configure for probing for all the necessary tools(compilers,
   37: os version, libraries),  please comment out KERNEL_PLL macro in
   38: the ./config.h  file.  This will disable the KERNEL_PLL part of the source
   39: code and the newly obtained xntpd is just similar to the old one but it
   40: does not use ntp_adjtime() system call. This prevents it from panic'ng
   41: the kernel.
   42: 
   43: /*#define KERNEL_PLL 1*/
   44: 
   45: I complied a new xntpd binary this way and it does nothave any ntp_adjtime()
   46: related stuff.
   47: 
   48: Default:
   49: =======
   50: /net/divya/export/home/mynam/public_domain/ntp/xntp3-5.92/xntpd>strings
   51: xntpd |
   52: grep ntp_adjtime
   53: 354:adj_frequency: ntp_adjtime failed: %m
   54: 357:loop_config: ntp_adjtime() failed: %m
   55: 435:get_kernel_info: ntp_adjtime() failed: %m
   56: 
   57: With KERNEL_PLL disabled in config.h file
   58: -=======================
   59: 
   60: /net/divya/export/home/mynam/public_domain/ntp/xntp3-5.92/xntpd>strings
   61: xntpd.nopll | grep ntp_adjtime
   62: 
   63:         Integrated in releases:
   64:  Duplicate of:
   65:  Patch id:
   66:  See also: 4133517
   67:  Summary:
   68: If the time_constant parameter is 7 or higher, and the phase-lock looping model
   69: is in use, the system will take a "integer divide zero trap" panic in
   70: the clock routine as soon as the time_offset becomes non-zero.
   71: 
   72: time_constant defaults to 0.  The only place it is set is in the ntp_adjtime
   73: system call, from the 'constant' element of the timex structure argument.
   74: ----------------------------------------------------------------------------