[Bug tapsets/11388] New: syscall.mmap* probes versus 2.6.33+ kernels

["mjw at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

Recent kernels saw some cleanups of the mmap implementation code. The systemtap
syscall tapsets should be updated to match.

The mmap syscalls are traditionally architecture specific because different
architectures used different implementation strategies, so had different entry
points. So look for the tapset aliases under tapset/<arch>/syscall.stp. The main
differences were because on some architectures not all arguments could be passed
in registers, so the arguments were passed in as one argument to a struct. Some
architectures even had both variants of the syscall. i386 for example has
syscall number 90 mmap, which takes a struct, and syscall number 192 mmap2,
which takes 6 arguments).

On different architectures either variant might exist and mapped to different
implementation function names. Recent cleanups (some only in recent git, not yet
released) map them to more consistent names (sys_old_mmap and sys_mmap_pgoff)

The relevant kernel commits are:

unreleased kernel:

commit a4679373cf4ee0e7792dc56205365732b725c2c1
Author: Christoph Hellwig <hch@lst.de>
Date:   Wed Mar 10 15:21:15 2010 -0800

    Add generic sys_old_mmap()
    
    Add a generic implementation of the old mmap() syscall, which expects its
    argument in a memory block and switch all architectures over to use it.

2.6.33 kernel:

commit f8b7256096a20436f6d0926747e3ac3d64c81d24
Author: Al Viro <viro@zeniv.linux.org.uk>
Date:   Mon Nov 30 17:37:04 2009 -0500

    Unify sys_mmap*
    
    New helper - sys_mmap_pgoff(); switch syscalls to using it.
    
    Acked-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

-- 
           Summary: syscall.mmap* probes versus 2.6.33+ kernels
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: tapsets
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: mjw at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=11388

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