• Steven Rostedt's avatar
    nds32/ftrace: Fix Error: invalid operands (*UND* and *UND* sections) for `^' · be358af1
    Steven Rostedt authored
    I received a build failure for a new patch I'm working on the nds32
    architecture, and when I went to test it, I couldn't get to my build error,
    because it failed to build with a bunch of:
      Error: invalid operands (*UND* and *UND* sections) for `^'
    issues with various files. Those files were temporary asm files that looked
    like:  kernel/.tmp_mc_fork.s
    I decided to look deeper, and found that the "mc" portion of that name
    stood for "mcount", and was created by the recordmcount.pl script. One that
    I wrote over a decade ago. Once I knew the source of the problem, I was
    able to investigate it further.
    The way the recordmcount.pl script works (BTW, there's a C version that
    simply modifies the ELF object) is by doing an "objdump" on the object
    file. Looks for all the calls to "mcount", and creates an offset of those
    locations from some global variable it can use (usually a global function
    name, found with <.*>:). Creates a asm file that is a table of references
    to these locations, using the found variable/function. Compiles it and
    links it back into the original object file. This asm file is called
    The problem here is that the objdump produced by the nds32 object file,
    contains things that look like:
     0000159a <.L3^B1>:
        159a:       c6 00           beqz38 $r6, 159a <.L3^B1>
                            159a: R_NDS32_9_PCREL_RELA      .text+0x159e
        159c:       84 d2           movi55 $r6, #-14
        159e:       80 06           mov55 $r0, $r6
        15a0:       ec 3c           addi10.sp #0x3c
    Where ".L3^B1 is somehow selected as the "global" variable to index off of.
    Then the assembly file that holds the mcount locations looks like this:
            .section __mcount_loc,"a",@progbits
            .align 2
            .long .L3^B1 + -5522
            .long .L3^B1 + -5384
            .long .L3^B1 + -5270
            .long .L3^B1 + -5098
            .long .L3^B1 + -4970
            .long .L3^B1 + -4758
            .long .L3^B1 + -4122
    And when it is compiled back to an object to link to the original object,
    the compile fails on the "^" symbol.
    Simple solution for now, is to have the perl script ignore using function
    symbols that have an "^" in the name.
    Link: https://lkml.kernel.org/r/20211014143507.4ad2c0f7@gandalf.local.home
    Cc: stable@vger.kernel.org
    Acked-by: default avatarGreentime Hu <green.hu@gmail.com>
    Fixes: fbf58a52
     ("nds32/ftrace: Add RECORD_MCOUNT support")
    Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>