Re: [PATCH 2/3] powerpc: Fix undefined static key

Joel Stanley [off-list ref] writes:

When CONFIG_PPC_BARRIER_NOSPEC=n, security.c is not built leading to a
missing definition of uaccess_flush_key.

  LD      vmlinux.o
  MODPOST vmlinux.symvers
  MODINFO modules.builtin.modinfo
  GEN     modules.builtin
  LD      .tmp_vmlinux.kallsyms1
powerpc64le-linux-gnu-ld: arch/powerpc/kernel/align.o:(.toc+0x0): undefined reference to `uaccess_flush_key'
powerpc64le-linux-gnu-ld: arch/powerpc/kernel/signal_64.o:(.toc+0x0): undefined reference to `uaccess_flush_key'
powerpc64le-linux-gnu-ld: arch/powerpc/kernel/process.o:(.toc+0x0): undefined reference to `uaccess_flush_key'
powerpc64le-linux-gnu-ld: arch/powerpc/kernel/traps.o:(.toc+0x0): undefined reference to `uaccess_flush_key'
powerpc64le-linux-gnu-ld: arch/powerpc/kernel/hw_breakpoint_constraints.o:(.toc+0x0): undefined reference to `uaccess_flush_key'
powerpc64le-linux-gnu-ld: arch/powerpc/kernel/ptrace/ptrace.o:(.toc+0x0): more undefined references to `uaccess_flush_key' follow
make[1]: *** [Makefile:1176: vmlinux] Error 1

Hack one in to fix the build.

Yeah sorry that is a bit of a hack :)

I think the root cause here is that we don't have a CONFIG for "want
security workaround stuff", because so far we haven't had a CPU that
wants to turn that all off.

The generic code uses CONFIG_GENERIC_CPU_VULNERABILITIES, so I guess we
should follow that example and add PPC_CPU_VULNERABILITIES.

Then we'd use that to disable all the security.c stuff, and
PPC_BARRIER_NOSPEC would depend on it also.

Then we could allow configuring that off for Microwatt, or possibly for
all platforms if people want to do that.

cheers