powerpc/lib/sstep: fix 'ptesync' build error

BugLink: https://bugs.launchpad.net/bugs/1963890
commit fe663df7825811358531dc2e8a52d9eaa5e3515e upstream.

Building tinyconfig with gcc (Debian 11.2.0-16) and assembler (Debian
2.37.90.20220207) the following build error shows up:

  {standard input}: Assembler messages:
  {standard input}:2088: Error: unrecognized opcode: `ptesync'
  make[3]: *** [/builds/linux/scripts/Makefile.build:287: arch/powerpc/lib/sstep.o] Error 1

Add the 'ifdef CONFIG_PPC64' around the 'ptesync' in function
'emulate_update_regs()' to like it is in 'analyse_instr()'. Since it looks like
it got dropped inadvertently by commit 3cdfcbfd32b9 ("powerpc: Change
analyse_instr so it doesn't modify *regs").

A key detail is that analyse_instr() will never recognise lwsync or
ptesync on 32-bit (because of the existing ifdef), and as a result
emulate_update_regs() should never be called with an op specifying
either of those on 32-bit. So removing them from emulate_update_regs()
should be a nop in terms of runtime behaviour.

Fixes: 3cdfcbfd32b9 ("powerpc: Change analyse_instr so it doesn't modify *regs")
Cc: stable@vger.kernel.org # v4.14+
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
[mpe: Add last paragraph of change log mentioning analyse_instr() details]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220211005113.1361436-1-anders.roxell@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
index dd496642618a230b7908a822f355dc0fef3402a1..18cf3109cd686022798cde22085fe6141015e16d 100644 (file)
--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -3182,12 +3182,14 @@ void emulate_update_regs(struct pt_regs *regs, struct instruction_op *op)
                case BARRIER_EIEIO:
                        eieio();
                        break;
+#ifdef CONFIG_PPC64
                case BARRIER_LWSYNC:
                        asm volatile("lwsync" : : : "memory");
                        break;
                case BARRIER_PTESYNC:
                        asm volatile("ptesync" : : : "memory");
                        break;
+#endif
                }
                break;