[Bug translator/23634] WARNING: Can't parse SDT_V3 operand for x86_64 qemu tapset probe points

["wcohen at redhat dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=23634

--- Comment #3 from William Cohen <wcohen at redhat dot com> ---
sdt.h makes a special case for powerpc:

# ifndef STAP_SDT_ARG_CONSTRAINT
# if defined __powerpc__
# define STAP_SDT_ARG_CONSTRAINT        nZr
# else
# define STAP_SDT_ARG_CONSTRAINT        nor
# endif
# endif

This was added by:

commit 50f2ef5be3c24b3fe9eb4c9abc386d8dbc3b953a
Author: Sandipan Das <sandipan@linux.vnet.ibm.com>
Date:   Thu Oct 5 14:39:41 2017 +0530

    powerpc: Change SDT argument constraint

    With the 'o' memory constraint, any memory operand which
    has an offsettable address is allowed. However, for some
    architectures such as powerpc, this allows operands like
    the ones shown below in the readelf output from Fedora 26
    to be generated.

      $ readelf -n /lib64/libc.so.6 | grep memory_mallopt_mmap_max -A2 -B2
        stapsdt              0x0000006c     NT_STAPSDT (SystemTap probe
descriptors)
          Provider: libc
          Name: memory_mallopt_mmap_max
          Location: 0x00000000000a0274, Base: 0x00000000001ccb90, Semaphore:
0x0000000000000000
          Arguments: -4@9 -4@.LANCHOR0+44@toc@l(8) -4@.LANCHOR0+52@toc@l(7)

    The second and third argument shown above are both having
    operands which are pointers to static data anchors. Since
    these static anchors are not included in the symbol table,
    they cannot be resolved from the binary itself. So, such
    arguments cannot be read via their corresponding markers.

    Using the 'Z' memory constraint instead solves this issue
    as it will only allow a memory operand that is an indexed
    or indirect from a register.

    So, for powerpc, we set STAP_SDT_ARG_CONSTRAINT to 'nZr'
    but keep it as 'nor' for all other architectures.

    Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>

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