Re: [PATCH bpf-next v3 10/10] tools: bpftool: add delimiters to multi-function JITed dumps

On 05/23/2018 12:37 PM, Sandipan Das wrote:
[...]

Other than that, for powerpc64, there is a problem with the way the
binutils disassembler code (in "opcodes/ppc-dis.c") passes arguments
to the callback fprintf_json().

In fprintf_json(), we always expect the va_list elements to resolve
to strings (char *). But for powerpc64, the register or immediate
operands are always passed as integers. So, when the code attempts
to resolve these operands using va_arg(ap, char *), bpftool crashes.
For now, I am using a workaround based on vsnprintf() but this does
not get the semantics correct for memory operands. You can probably
see that for the store instructions in the JSON dump above this.

Daniel,

Would it be okay if I send out a fix for this in a different series?

I'm fine either way with regards to the fix. Feels like a portability bug
in the binutils disassembler?

We could probably have a feature test like in test-disassembler-four-args
and select a workaround in bpftool based on that outcome.

Thanks Sandipan!

  [1] tools/build/feature/test-disassembler-four-args.c