The Linux ftrace subsystem style for comparing is:

  var == 1
  var > 0

and not:

  1 == var
  0 < var

It is considered that Linux developers are smart enough not to do the

  if (var = 1)

mistake.

Cc: John Reiser <jreiser@bitwagon.com>
Link: http://lkml.kernel.org/r/20110421023737.290712238@goodmis.orgSigned-off-by: NSteven Rostedt <rostedt@goodmis.org>

Depending on the compiler version, ARM GCC calls the mcount function
either __gnu_mcount_nc or mcount.
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NRabin Vincent <rabin@rab.in>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

It looks to me like the change which introduced "virtual functions"
forgot about cross-platform endianness.

Thank you to Arnaud for supplying before+after data files do_mounts*.o.

This fixes a MIPS build failure triggered by recordmcount.
Reported-by: NArnaud Lacombe <lacombar@gmail.com>
Tested-by: NArnaud Lacombe <lacombar@gmail.com>
Acked-by: NWu Zhangjin <wuzhangjin@gmail.com>
Acked-by: NRalf Baechle <ralf@linux-mips.org>
Signed-off-by: NJohn Reiser <jreiser@BitWagon.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

Since MIPS modules' address space differs from the core kernel space, to access
the _mcount in the core kernel, the kernel functions in modules must use long
call (-mlong-calls): load the _mcount address into one register and jump to the
address stored by the register:

 c:  3c030000        lui     v1,0x0  <-------->  b label
           c: R_MIPS_HI16  _mcount
           c: R_MIPS_NONE  *ABS*
           c: R_MIPS_NONE  *ABS*
10:  64630000        daddiu  v1,v1,0
          10: R_MIPS_LO16 _mcount
          10: R_MIPS_NONE *ABS*
          10: R_MIPS_NONE *ABS*
14:	03e0082d 	move	at,ra
18:	0060f809 	jalr	v1
label:

In the old Perl version of recordmcount, we only need to record the position of
the 1st R_MIPS_HI16 type of _mcount, and later, in ftrace_make_nop(), replace
the instruction in this position by a "b label" and in ftrace_make_call(),
replace it back.

But, the default C version of recordmcount records all of the _mcount symbols,
so, we must filter the 2nd _mcount like the Perl version of recordmcount does.

The C version of recordmcount copes with the symbols before they are linked, So
It doesn't know the type of the symbols and therefore can not filter the
symbols as the Perl version of recordmcount does. But as we can see above, the
2nd _mcount symbols of the long call alawys follows the 1st _mcount symbol of
the same long call, which means the offset from the 1st to the 2nd is fixed, it
is 0x10-0xc = 4 here, 4 is the length of the 1st load instruciton, for MIPS has
fixed length of instructions, this offset is always 4.

And as we know, the _mcount is inserted into the entry of every kernel
function, the offset between the other _mcount's is expected to be always
bigger than 4. So, to filter the 2ns _mcount symbol of the long call, we can
simply check the offset between two _mcount symbols, If it is 4, then, filter
the 2nd _mcount symbol.

To avoid touching too much code, an 'empty' function fn_is_fake_mcount() is
added for all of the archs, and the specific archs can override it via chaning
the function pointer: is_fake_mcount in do_file() with the e_machine. e.g. This
patch adds MIPS_is_fake_mcount() to override the default fn_is_fake_mcount()
pointed by is_fake_mcount.

This fn_is_fake_mcount() checks if the _mcount symbol is fake, e.g. the 2nd
_mcount symbol of the long call is fake, for there are 2 _mcount symbols mapped
to one real mcount call, so, one of them is fake and must be filtered.

This fn_is_fake_mcount() is called in sift_rel_mcount() after finding the
_mcount symbols and before adding the _mcount symbol into mrelp, so, it can
prevent the fake mcount symbol going into the last __mcount_loc table.
Signed-off-by: NWu Zhangjin <wuzhangjin@gmail.com>
LKML-Reference: <b866f0138224340a132d31861fa3f9300dee30ac.1288176026.git.wuzhangjin@gmail.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

MIPS64 has 'weird' Elf64_Rel.r_info[1,2], which must be used instead of
the generic Elf64_Rel.r_info, otherwise, the C version of recordmcount
will not work for "segmentation fault".

Usage of "union mips_r_info" and the functions MIPS64_r_sym() and
MIPS64_r_info() written by Maciej W. Rozycki <macro@linux-mips.org>

----
[1] http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
[2] arch/mips/include/asm/module.h
Tested-by: NWu Zhangjin <wuzhangjin@gmail.com>
Signed-off-by: NJohn Reiser <jreiser@BitWagon.com>
Signed-off-by: NMaciej W. Rozycki <macro@linux-mips.org>
LKML-Reference: <AANLkTinwXjLAYACUfhLYaocHD_vBbiErLN3NjwN8JqSy@mail.gmail.com>
LKML-Reference: <910dc2d5ae1ed042df4f96815fe4a433078d1c2a.1288176026.git.wuzhangjin@gmail.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

The elf reader for recordmcount.c had duplicate functions for both
32 bit and 64 bit elf handling. This was due to the need of using
the 32 and 64 bit elf structures.

This patch consolidates the two by using macros to define the 32
and 64 bit names in a recordmcount.h file, and then by just defining
a RECORD_MCOUNT_64 macro and including recordmcount.h twice we
create the funtions for both the 32 bit version as well as the
64 bit version using one code source.

Cc: John Reiser <jreiser@bitwagon.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>